WO2024236079A1

WO2024236079A1 - Aerosol-generating system with increased aerosol-forming substrate length

Info

Publication number: WO2024236079A1
Application number: PCT/EP2024/063446
Authority: WO
Inventors: Guillaume Bastien BAUR; Alexandros Vassilios VASSILIOU
Original assignee: Philip Morris Products SA
Current assignee: Philip Morris Products SA
Priority date: 2023-05-18
Filing date: 2024-05-15
Publication date: 2024-11-21
Anticipated expiration: 2025-11-18
Also published as: CN121078995A; MX2025013422A

Abstract

An aerosol-generating system (100) and an aerosol-generating article (10). The aerosol-generating system (100) comprises: a heating element (15); and an aerosol-forming substrate (12), wherein: the heating element (15) is arranged to heat the aerosol-forming substrate (12); the heating element (15) has a heating element length (LH); the aerosol-forming substrate (12) has a substrate length (Ls), the aerosol-forming substrate length (Ls) being greater than the heating element length (LH); and the ratio of the aerosol-forming substrate length (Ls) to the heating element length (LH) is between about 1.1 and 3. The aerosol-generating article (10) comprises: an aerosol-forming substrate (12); and a heating element (15), wherein: the heating element (15) is arranged to heat the aerosol-forming substrate (12); the heating element (15) has a heating element length (LH); the aerosol-forming substrate (12) has a substrate length (Ls), the aerosol-forming substrate length (Ls) being greater than the heating element length (LH); and the ratio of the aerosol-forming substrate length (Ls) to the heating element length (LH) is between about 1.1 and 3.

Description

AEROSOL-GENERATING SYSTEM WITH INCREASED AEROSOL-FORMING SUBSTRATE LENGTH

The present invention relates to an aerosol-generating system comprising a heating element and an aerosol-generating article. In particular, the present invention relates to an aerosolgenerating system in which the heating element has a heating element length and the aerosolgenerating article comprises an aerosol-forming substrate having a substrate length that is greater than the heating element length.

Aerosol-generating systems comprising a heating element and a corresponding aerosolgenerating article are known in the art. For example, systems are known in which the aerosolgenerating article comprising an aerosol-forming substrate that is heated by a heating element. The aerosol-forming substrate may be a tobacco-containing substrate, which is heated by the heating element rather than combusted. Typically, in such systems an aerosol is generated by the transfer of heat from the heating element to the aerosol-forming substrate. The heating element may be part of an aerosol-generating device or part of the aerosol-forming article. In use, the aerosol-forming substrate may be located in contact with, within, around, or downstream of the heating element. During use of the aerosol-generating system, volatile compounds are released from the heated aerosol-forming substrate by heat transfer from the heating element and entrained in air drawn through the aerosol-generating article. As the released compounds cool, they condense to form an aerosol.

A number of documents disclose aerosol-generating devices for heating aerosol-generating articles. Such devices include, for example, electrically heated aerosol-generating devices in which an aerosol is generated by the transfer of heat from one or more electrical heating elements of the aerosol-generating device to the aerosol-forming substrate of a heated aerosol-generating article. For example, electrically heated aerosol-generating devices have been proposed that comprise an internal heater blade which is configured to be inserted into the aerosol-forming substrate.

It is also known to provide aerosol-generating systems in which an aerosol-generating article is configured to be used with a specific aerosol-generating device. Aerosol-generating articles of the prior art may include a downstream section, downstream of the aerosol-forming substrate, and an upstream element, upstream of the aerosol-forming substrate. The downstream section may comprise at least one of a mouthpiece element, such as a filter, and one or more hollow tubular elements. The upstream element may be present to prevent aerosol-forming substrate from falling out of the aerosol-generating article and to control the resistance to draw of the aerosol-generating article. In prior art articles comprising one or more of a downstream section and an upstream element, the aerosol-forming substrate does not extend the entire length of the aerosol-generating article, and so there is no need to heat the full length of the aerosol-generating article. Accordingly, the aerosol-generating system may comprise a heating element that is sized to match the length of the aerosol-forming substrate of the aerosol-generating article, such that the heating element heats the full length of the aerosol-forming substrate, without heating the full length of the aerosolgenerating article.

There remains a need to improve the amount of aerosol generated from a given mass of aerosol-forming substrate. There also remains a need to improve the duration of aerosol generation from a given mass of aerosol-forming substrate.

According to the present disclosure, there is provided an aerosol-generating system. The aerosol-generating system may comprise a heating element. The aerosol-generating system may comprise an aerosol-forming substrate. The heating element may be arranged to heat the aerosolforming substrate. The heating element may have a heating element length. The aerosol-forming substrate may have a substrate length, the substrate length being greater than the heating element length. The ratio of the substrate length to the heating element length may be between about 1.1 and 3.

According to the present disclosure, there is provided an aerosol-generating system comprising: a heating element; and an aerosol-forming substrate. The heating element is arranged to heat the aerosol-forming substrate. The heating element has a heating element length, and the aerosol-forming substrate has a substrate length, the substrate length being greater than the heating element length. The ratio of the substrate length to the heating element length is between about 1.1 and 3.

In some preferred embodiments, the aerosol-generating system further comprises an aerosol-generating article comprising the aerosol-forming substrate. The heating element may be provided in the aerosol-generating article.

In some preferred embodiments, the aerosol-generating system further comprises an aerosol-generating device. The aerosol-generating device may comprise a device cavity configured to receive at least a portion of the aerosol-forming substrate. The heating element may be provided in the aerosol-generating device.

The inventors have found that, advantageously, increasing the length of an aerosol-forming substrate that is to be heated by a heating element, such that the substrate length is greater than the heating element length, can increase the amount of aerosol that can be generated compared to an equivalent system in which the substrate length is equal to or less than the heating element length, without requiring a corresponding increase in the length of the heating element or an increase in the power supplied to the heating element. In particular, the inventors have found that providing an aerosol-generating system with a heating element and an aerosol-forming substrate in which the ratio of the substrate length to the heating element length is between about 1.1 and 3 generates a greater amount of aerosol than equivalent aerosol-generating systems in which the ratio of the substrate length to the heating element length is 1 or less than 1 .

The inventors have also found that, advantageously, such an increase in the length of the aerosol-forming substrate can enable the generation of aerosol for a longer period of time without compromising the rate of aerosol generation compared to equivalent aerosol-generating systems in which the substrate length is equal to or less than the heating element length. In particular, longer periods of aerosol generation are achievable when a portion of the aerosol-forming substrate is arranged downstream of the heating element. Positioning a portion of the aerosol-forming substrate downstream of the heating element enables the downstream portion of the aerosolforming substrate to be heated by convection with the heated gasses that are drawn through the aerosol-forming substrate, away from the heating element to a downstream end of the aerosolgenerating system.

Advantageously, the time required to pre-heat the aerosol-forming substrate before aerosol generation remains the same in aerosol-generating systems having an aerosol-generating substrate with a substrate length greater than the length of the heating element as in equivalent aerosol-generating systems in which the substrate length is equal to or less than the heating element length. This is because the amount of aerosol-forming substrate that is in direct contact with the heating element, or is directly adjacent to the heating element is the same for both systems.

In aerosol-generating systems in which the aerosol-forming substrate has a substrate length that is equal to or less than the length of the heating element, the aerosol-forming substrate is typically in direct contact with the heating element along the entire substrate length, or is at least arranged directly adjacent the heating element along the entire substrate length. This arrangement enables heat transfer from the heating element to the aerosol-forming substrate by conduction and radiation. However, by increasing the length of the aerosol-forming substrate such that the substrate length is longer than the heating element length, a portion of the aerosol-forming substrate is arranged away from the heating element, not in direct contact with the heating element, and not arranged directly adjacent the heating element. The inventors have found that it is possible to generate aerosol from a portion of an aerosol-forming substrate that is not in direct contact with a heating element and is arranged not directly adjacent to the heating element by making use of the hot gasses generated when heating the portion of the aerosol-forming substrate that is in direct contact with the heating element or arranged directly adjacent to the heating element to heat the portion of the aerosol-forming substrate that is not in direct contact with the heating element or arranged directly adjacent the heating element. Accordingly, the inventors have found a way to increase the amount of aerosol-forming substrate provided in an aerosol-generating system, by increasing the length of the aerosol-forming substrate, without requiring a larger heating element or providing a larger supply of power to the heating element.

According to the present disclosure, the substrate length is able to be increased compared to typical aerosol-generating systems in which the substrate length is the same as or less than a heating element length. Increasing the substrate length enables the mass of the aerosol-forming substrate to be increased compared to typical aerosol-generating systems. Advantageously, particularly where a portion of the aerosol-forming substrate is arranged downstream of the heating element, providing a larger mass of aerosol-forming substrate can reduce the temperature of the initial puff or initial puffs on the aerosol-generating system perceived by a user. Puffs with a higher water vapour content tend to be perceived by users as being hotter than puffs with a lower water vapour content, and an initial puff of initial puffs on such an aerosol-generating system typically comprises a higher water vapour content compared to later puffs, since the aerosol-forming substrate typically comprises a higher water content before the aerosol-forming substrate is heated and during preheating. Providing a larger mass of aerosol-forming substrate, particularly downstream of the heating element, can help to cool and condense some of the water vapour in the initial puff or initial puffs while it is in the aerosol-generating article, before it reaches the user, lowering the perceived temperature of the aerosol delivered to the user.

As used herein, “aerosol-forming substrate” refers to a substrate capable of releasing volatile compounds that can form an aerosol. Such volatile compounds may be released by heating the aerosol-forming substrate. An aerosol-forming substrate is typically part of an aerosol-generating article.

As used herein, “aerosol-generating article” refers to an article comprising an aerosol-forming substrate that is capable of releasing volatile compounds that can form an aerosol. For example, an aerosol-generating article may be an article that generates an aerosol that is directly inhalable by the user drawing or puffing on a mouthpiece at a mouth end or downstream end of the aerosol-generating article, an aerosol-generating device, or an aerosol-generating system. An aerosol-generating article may be disposable.

As used herein, “aerosol-generating device” refers to a device that interacts with an aerosolforming substrate to generate an aerosol. Preferably, the aerosol-generating device is a device that interacts with an aerosol-forming substrate to generate an inhalable aerosol that is directly inhalable into a user’s lungs thorough the user's mouth.

As used herein, “aerosol-generating system” typically refers to the combination of an aerosolgenerating device with an aerosol-forming substrate, preferably where the aerosol-forming substrate is comprised in an aerosol-generating article. In an aerosol-generating system, the aerosol-forming substrate and the aerosol-generating device cooperate to generate an aerosol.

As used herein, “length” refers to the maximum dimension of a feature in a longitudinal direction of the feature. The term “length” denotes the dimension of a component of the aerosol-generating system in the longitudinal direction, from the component’s furthest upstream point to the component’s furthest downstream point. For example, it may be used to denote the dimension of aerosol-forming substrate or of any elongate tubular elements in the longitudinal direction.

As used herein, “longitudinal” refers to the direction corresponding to the main axis of the aerosol-generating article or aerosol-generating device, which extends between the upstream and downstream ends of the aerosol-generating article or aerosol-generating device.

As used herein, “width” refers to the maximum dimension of a feature in a transverse direction of the feature. The transverse direction is perpendicular to the longitudinal direction.

As used herein, “thickness” and “depth” refer to the maximum dimension of a feature in a direction perpendicular to the longitudinal direction of the feature and perpendicular to the transverse direction of the feature.

As used herein, “upstream” and “downstream” describe the relative positions of elements, or portions of elements, of the aerosol-generating system in relation to the direction in which the aerosol is transported through the aerosol-generating article during use. During use, air is drawn through the aerosol-generating article in the longitudinal direction.

As used herein, “end” and “side” are used interchangeably to refer to extremities of a feature, such as an aerosol-generating device, a heating assembly, a heating element, or an aerosolgenerating article. Preferably, features described herein have two opposing ends and at least one side extending between the two opposing ends. Preferably, features described herein have a length extending in a longitudinal direction between opposing ends, and a width extending in a transverse direction between two opposing sides.

As used herein, “fully received” refers to the position when the aerosol-forming substrate or the aerosol-generating article comprising the aerosol-forming substrate is inserted into a device cavity of the aerosol-generating device to the greatest extent possible. This may be when the upstream end of the aerosol-forming substrate abuts the upstream end of the device cavity. Alternatively, this may be when the upstream end of the aerosol-forming substrate abuts another components within the device cavity to prevent the aerosol-forming substrate moving any further upstream. This may be when the upstream end of the aerosol-generating article abuts the upstream end of the device cavity. Alternatively, this may be when the upstream end of the aerosol-generating article abuts another components within the device cavity to prevent the aerosol-generating article moving any further upstream. When the aerosol-generating article is “fully received” in the device cavity, a portion of the aerosol-generating article may protrude out of the open downstream end of the aerosol-generating article. This may be the case where, for example, the length of the aerosol-generating article is greater than that of the device cavity, or when length of the aerosol-generating article is greater than the distance between the downstream end of the device cavity and the component within the device cavity to prevent the aerosol-generating article moving any further upstream, where present.

In some preferred embodiments, the aerosol-forming substrate is an aerosol-forming substrate segment or an aerosol-forming substrate element. In other words, preferably the aerosolforming substrate is a unitary body of aerosol-forming substrate. In some preferred embodiments, the aerosol-forming substrate is a plug of aerosol-forming substrate material. In some preferred embodiments, the aerosol-forming substrate is a rod of aerosol-forming substrate. In some preferred embodiments, the aerosol-forming substrate is a plug of tobacco material. In some preferred embodiments, the aerosol-forming substrate is a rod of tobacco material. Accordingly, preferably the aerosol-forming substrate does not comprise multiple segments. Where the aerosolforming substrate does comprise multiple segments, the substrate length refers to the length of the segment of aerosol-forming substrate that is in direct contact with, or is directly adjacent to, the heating element.

As used herein, the heating element length refers to the length of the heating element that is arranged in direct contact with, or directly adjacent to, the aerosol-forming substrate. Where the aerosol-generating system comprises an aerosol-generating device comprising the heating element and a device cavity for receiving the aerosol-forming substrate, the heating element length refers to the length of the heating element that is arranged in direct contact with, or directly adjacent the aerosol-forming substrate when the aerosol-forming substrate is fully received in the device cavity.

In some preferred embodiments, the aerosol-generating system comprises a single heating element. In other words, the aerosol-generating system comprises no more than one heating element. In these preferred embodiments, the heating element length is the length of the heating element that is arranged in direct contact with, or directly adjacent to, the aerosol-forming substrate.

In some embodiments, the heating element comprises a plurality of heating elements. In these embodiments where the heating element comprises a plurality of heating elements, the heating element length is the length between the furthest downstream end of a heating element of the plurality of heating elements that is arranged in direct contact with, or directly adjacent to, the aerosol-forming substrate and the furthest upstream end of a heating element of the plurality of heating elements that is arranged in direct contact with, or directly adjacent to, the aerosol-forming substrate.

Where the aerosol-generating system comprises a plurality of segments of aerosol-forming substrate and a plurality of heating elements, the substrate length refers to the length of a segment of aerosol-forming substrate that is in direct contact with, or is directly adjacent to, one or more of the plurality of heating elements, and the heating element length refers to the length between the furthest downstream end of a heating element of the plurality of heating elements that is arranged in direct contact with, or directly adjacent to, that segment of aerosol-forming substrate and the furthest upstream end of a heating element of the plurality of heating elements that is arranged in direct contact with, or directly adjacent to, that segment of aerosol-forming substrate.

The substrate length is greater than the heating element length. The ratio of the substrate length to the heating element length may be any suitable ratio. The ratio of the substrate length to the heating element length is between about 1.1 and 3. Preferably, the ratio of the aerosol-forming substrate length to the heating element length is between about 1.1 and 1.16. The ratio of the aerosol-forming substrate length to the heating element length may be between about 1.11 and 1 .16, or between about 1.12 and 1 .16, or between about 1.13 and 1 .16, or between about 1.14 and 1 .16, or between about 1.15 and 1.16. Preferably, the ratio of the aerosol-forming substrate length to the heating element length is about 1.16.

The substrate length may be greater than the heating element length by any suitable amount. For example, the substrate length may be greater than the heating element length by at least 0.5 millimetres, or at least 0.6 millimetres, or at least 0.7 millimetres, or at least 0.8 millimetres, or at least 0.9 millimetres, or at least 1 millimetre. For example, the aerosol-forming substrate length may be greater than the heating element length by no more than about 5 millimetres, or no more than about 4 millimetres, or no more than about 3 millimetres. For example, the substrate length may be greater than the heating element length by between about 0.5 millimetres and about 5 millimetres, or between about 1 millimetres and about 4 millimetres, or between about 1.5 millimetres and about 3 millimetres. For example, the substrate length may be greater than the heating element length by about 2 millimetres.

The substrate length may be any suitable length. For example, the substrate length may be between about 8 millimetres and about 20 millimetres, or between about 10 millimetres and about 18 millimetres, or between about 12 millimetres and about 16 millimetres. In some preferred embodiments, the substrate length is about 14 millimetres.

The heating element length may be any suitable length. For example, the heating element length may be between about 7 millimetres and about 19 millimetres, or between about 8 millimetres and about 18 millimetres, or between about 10 millimetres and about 16 millimetres, or about 12 millimetres.

In some preferred embodiments, the substrate length is about 14 millimetres and the heating element length is about 12 millimetres. In some of these preferred embodiments, it has been found to be possible to generate aerosol at a desired rate for a period of between about 7 minutes and about 10 minutes, compared to a period of around 4 minutes with a corresponding aerosolgenerating device in which the substrate length is the same as the heating element length, and both the substrate length and the heating element length are 12 millimetres.

According to the present disclosure, the substrate length is able to be increased compared to typical aerosol-generating systems in which the substrate length is the same as or less than a heating element length. Increasing the substrate length enables the mass of the aerosol-forming substrate to be increased compared to typical aerosol-generating systems. Preferably, the mass of the aerosol-forming substrate is at least 150 milligrams, or at least 200 milligrams, or at least 250 milligrams, or at least 300 milligrams. Particularly preferably, the mass of the aerosol-forming substrate is at least 250 milligrams, or at least 260 milligrams, or at least 270 milligrams, or at least 280 milligrams. Preferably, the mass of the aerosol-forming substrate is more than 260 milligrams. The mass of the aerosol-forming substrate may be between 150 milligrams and 400 milligrams, or between 200 milligrams and 400 milligrams, or between 250 milligrams and 400 milligrams, or between 260 milligrams and 400 milligrams, or between 270 milligrams and 400 milligrams. In some preferred embodiments, the mass of the aerosol-forming substrate is more than 260 milligrams. In some preferred embodiments, the mass of the aerosol-forming substrate is between about 290 milligrams and about 310 milligrams.

Preferably, the aerosol-generating system comprises an upstream end and a downstream end. The aerosol-generating device may have an upstream end and a downstream end. The aerosol-forming substrate may have an upstream end and a downstream end. Where the aerosolgenerating system comprises an aerosol-generating article comprising the aerosol-forming substrate, the aerosol-generating article may have an upstream end and a downstream end.

In some particularly preferred embodiments, a downstream portion of the aerosol-forming substrate extends beyond a downstream end of the heating element. The downstream portion of the aerosol-forming substrate may extend beyond the downstream end of the heating element in a longitudinal direction. Where the aerosol-generating device comprises a device cavity, and the aerosol-generating device comprises the heating element, the downstream portion of the aerosolforming substrate may extend beyond the downstream end of the heating element when the aerosol-forming substrate is fully received in the device cavity.

Extending a downstream portion of the aerosol-forming substrate beyond the heating element advantageously enables hot gases being drawn through the aerosol-forming substrate during use to be drawn through the downstream portion and heat the downstream portion, such that the downstream portion also releases volatile compounds that may condense to form an aerosol. As a result, the downstream portion of the aerosol-forming substrate is also able to contribute to aerosol generation, even though the downstream portion of the aerosol-forming substrate is not in direct contact with the heating element or arranged directly adjacent to the heating element.

The downstream portion of the aerosol-forming substrate may have any suitable length. For example, the downstream portion of the aerosol-forming substrate may extend beyond the downstream end of the heating element in a longitudinal direction by at least 0.5 millimetres, or at least 1 millimetre, or at least 1.5 millimetres. For example, the downstream portion of the aerosolforming substrate may extend beyond the downstream end of the heating element in a longitudinal direction by no more than 5 millimetres, or 4 millimetres or 3 millimetres. The downstream portion of the aerosol-forming substrate may extend beyond the downstream end of the heating element in a longitudinal direction by between about 0.5 millimetres and about 5 millimetres, or between about 1 millimetre and about 4 millimetres, or between about 1.5 millimetres and about 3 millimetres. In some preferred embodiments, the downstream portion of the aerosol-forming substrate may extend beyond the downstream end of the heating element in a longitudinal direction by about 2 millimetres.

In some particularly preferred embodiments, an upstream end of the heating element is aligned with an upstream end of the aerosol-forming substrate. In other words, in some embodiments the aerosol-forming substrate does not extend beyond the upstream end of the heating element in an upstream direction.

The aerosol-generating system comprises a heating element. The heating element may be any suitable type of heating element. In some embodiments, the heating element is a resistive heating element. In some embodiments, the heating element is a susceptor element. Where the heating element is a susceptor element, the aerosol-generating device further comprises an inductor coil configured to generate an alternating magnetic field for heating the susceptor element. In some embodiments, the heating element comprises one or more electrodes of a capacitor. Where the heating element comprises one or more electrodes of a capacitor, the aerosol-generating system may be configured to heat the aerosol-forming substrate by dielectric heating. In some embodiments, the aerosol-generating device comprises the heating element. In some embodiments, the aerosolgenerating article comprises the heating element. The heating element may be an external heating element. An external heating element is a heating element that is configured to heat the outer surface of the aerosol-forming substrate. The heating element may be an internal heating element. An internal heating element is a heating element that is configured to heat the aerosol-forming substrate from the inside.

The heating element may be arranged at any suitable location for heating the aerosol-forming substrate. In some embodiments, the aerosol-generating device comprises the heating element. Where the aerosol-generating device comprises a device cavity, the heating element may be arranged at or around the device cavity. The heating element may circumscribe the device cavity. The heating element may be configured to circumscribe the aerosol-forming substrate when the aerosol-forming substrate is received in the device cavity. The heating element may be configured to heat the outer surface of the aerosol-forming substrate. Such a heating element is an external heating element. The heating element may extend into the device cavity. The heating element may be configured to pierce the aerosol-forming substrate when the aerosol-forming substrate is received in the device cavity. Such a heating element is an internal heating element. The heating element may take the form of a pin, rod, strip, or blade.

The heating element may be a resistive heating element.

Suitable materials for forming the resistive heating element include but are not limited to: semiconductors such as doped ceramics, electrically ‘conductive’ ceramics (such as, for example, molybdenum disilicide), carbon, graphite, metals, metal alloys and composite materials made of a ceramic material and a metallic material. Such composite materials may comprise doped or undoped ceramics. Examples of suitable doped ceramics include doped silicon carbides. Examples of suitable metals include titanium, zirconium, tantalum, and metals from the platinum group. Examples of suitable metal alloys include stainless steel, nickel-, cobalt-, chromium-, aluminium- titaniumzirconium-, hafnium-, niobium-, molybdenum-, tantalum-, tungsten-, tin-, gallium-, manganese- and iron-containing alloys, and super-alloys based on nickel, iron, cobalt, stainless steel, Timetai® and iron-manganese-aluminium based alloys.

In some embodiments, the resistive heating element comprises one or more stamped portions of electrically resistive material, such as stainless steel. Alternatively, the resistive heating element may comprise a heating wire or filament, for example a Ni-Cr (Nickel-Chromium), platinum, tungsten, or alloy wire.

In some embodiments, the heating element comprises an electrically insulating substrate, and a resistive heating element is provided on the electrically insulating substrate.

The electrically insulating substrate may comprise any suitable material. For example, the electrically insulating substrate may comprise one or more of: paper, glass, ceramic, anodized metal, coated metal, and a polymer. The ceramic may comprise mica, Alumina (AI2O3) or Zirconia (ZrO2). The polymer may comprise a Polyamide. Preferably, the electrically insulating substrate has a thermal conductivity of less than or equal to about 40 Watts per metre Kelvin, preferably less than or equal to about 20 Watts per metre Kelvin and ideally less than or equal to about 2 Watts per metre Kelvin. The heating element may be a susceptor element. In some embodiments, the aerosolgenerating device comprises the susceptor element. In some embodiments, the aerosolgenerating device comprises the susceptor element.

As used herein, “susceptor element” refers to an element that is heatable by penetration with a varying magnetic field. A susceptor element is typically heatable by at least one of Joule heating through induction of eddy currents in the susceptor element, and hysteresis losses.

The susceptor element may comprise any suitable material. The susceptor element may be formed from any material that can be inductively heated to a temperature sufficient to release volatile compounds from the aerosol-forming substrate. Suitable materials for the susceptor element include graphite, molybdenum, silicon carbide, stainless steels, niobium, aluminium, nickel, nickel containing compounds, titanium, and composites of metallic materials. Some susceptor elements comprise a metal or carbon. Advantageously the susceptor element may comprise or consist of a ferromagnetic material, for example, ferritic iron, a ferromagnetic alloy, such as ferromagnetic steel or stainless steel, such as such as SAE 400 series stainless steels, SAE type 409, 410, 420 or 430 stainless steels, ferromagnetic particles, and ferrite. A suitable susceptor element may be, or may comprise, aluminium.

The susceptor element preferably comprises more than about 5 percent, preferably more than 20 percent, more preferably more than 50 percent or more than 90 percent of ferromagnetic or paramagnetic materials. Some suitable susceptor elements may be heated to a temperature in excess of 250 degrees Celsius.

The susceptor element may comprise a non-metallic core with a metal layer disposed on the non-metallic core. For example, the susceptor element may comprise metallic tracks formed on an outer surface of a ceramic core or substrate.

In embodiments in which the heating element is a susceptor element, the aerosol-generating device preferably comprises an inductor coil. Preferably, the inductor coil is arranged to generate a varying magnetic field that penetrates the susceptor element.

The inductor coil may generate a varying magnetic field when a varying current is supplied to the inductor coil. Where the aerosol-generating device comprises a device cavity, the inductor coil may be configured to generate a varying magnetic field in the device cavity. The inductor coil may be located in or around the device cavity. The inductor coil may circumscribe the device cavity.

As used herein, “varying current” refers to a current that varies with time. An inductor coil generates a varying magnetic field when a varying electric current is supplied to the inductor coil. The term “varying current” is intended to include alternating currents. Where the varying current is an alternating current, the alternating current generates an alternating magnetic field. The varying current may be an alternating current. As used herein, “alternating current” refers to a current that periodically reverses direction. The alternating current may have any suitable frequency. Suitable frequencies for the alternating current may be between 100 kilohertz (kHz) and 30 megahertz (MHz). Where the at least one inductor coil is a tubular inductor coil, the alternating current may have a frequency of between 500 kilohertz (kHz) and 30 megahertz (MHz). Where the at least one inductor coil is a flat coil, the alternating current may have a frequency of be-tween 100 kilohertz (kHz), and 1 megahertz (MHz).

Preferably, the inductor coil is capable of generating a varying magnetic field having a magnetic field strength (H-field strength) of between 1 and 5 kilo amperes per metre (kA m), preferably between 2 and 3 kA/m, for example about 2.5 kA/m. The electrically-operated aerosol-generating device is preferably capable of generating a varying magnetic field having a frequency of between 100 kilohertz (kHz) and 30 megahertz (MHz).

The inductor coil may have any suitable form. The inductor coil may be a tubular inductor coil. The inductor coil may be a planar inductor coil. The inductor coil may be a flat inductor coil. Preferably, the inductor coil is a tubular coil that circumscribes the substrate cavity.

The inductor coil may have any suitable number of turns.

The inductor coil may be formed from any suitable material. The inductor coil may be formed from at least one of: silver, gold, aluminium, brass, zinc, iron, nickel, and alloys of thereof, and electrically conductive ceramics, such as yttrium-doped zirconia, indium tin oxide, and yttrium doped titanate.

Where the aerosol-generating device comprises an inductor coil, the aerosol-generating device may comprise a power supply configured to provide an alternating current to the inductor coil. The alternating current may have a frequency of between about 500 kHz and about 30 MHz. The aerosol-generating device may advantageously comprise a DC/ AC inverter for converting a DC current supplied by a DC power supply to the alternating current. The inductor coil may be arranged to generate an alternating magnetic field on receiving an alternating current from the power supply. The inductor coil may be arranged to generate an alternating magnetic field in the device cavity. In some embodiments, the inductor coil may substantially circumscribe the device cavity. The inductor coil may extend at least partially along the length of the device cavity. The inductor coil may have a length that is equal to or less than the length of the susceptor element.

The susceptor element shape may be different to the inductor coil shape. Preferably, the susceptor element shape is substantially the same as the inductor coil shape.

The inductor coil size may be different to the inductor coil size. Preferably, the susceptor element size is substantially the same as the inductor coil size. In some embodiments, the aerosol-generating system is configured to heat the aerosol-forming substrate by dielectric heating. Where the aerosol-generating system is configured to heat the aerosol-forming substrate by dielectric heating, the aerosol-generating device may comprise a load capacitor. The heating element may comprise one or more electrodes of the load capacitor. The load capacitor may form part of a resonant circuit. An aerosol-generating article comprising an aerosol-forming substrate may form a part of the load capacitor when the aerosol-generating article is received by the aerosol-generating device. For example, the load capacitor may comprise a pair of electrodes, and the aerosol-generating article comprising the aerosol-forming substrate may form part of the load capacitor when it is arranged in close proximity to, or between, the electrodes. The aerosol-generating device may be configured to generate an alternating electric field across the load capacitor. When the aerosol-generating article comprising the aerosol-forming substrate is received by the aerosol-generating device and forms part of the load capacitor, the aerosol-generating article may be dielectrically heated by the alternating electric field.

Dielectric heating, which is also often referred to as microwave heating, electric heating, or radio-frequency heating, generally refers to heating that arises as a result of dipole rotation of a to- be-heated material or substrate that is subjected to an alternating electric field, and particularly a high-frequency alternating electric field. When an alternating electric field is applied to materials or substrates containing polar molecules (i.e. molecules having an electrical dipole moment), the polar molecules align themselves in the electric field and rotate when the electric field alternates to maintain alignment with the electric field. This rotation (dipole rotation) results in heating of the material or substrate in the alternating electric field.

In some of these embodiments, the load capacitor comprises a first electrode and a second electrode. The second electrode may be spaced apart from the first electrode. The first electrode and the second electrode may be arranged such that when the aerosol-forming substrate is receive in a device cavity of the aerosol-generating device, at least a portion of the aerosol-forming substrate is arranged between the first electrode and the second electrode. The load capacitor may be formed by the first electrode, the second electrode and the aerosol-forming substrate received in the article chamber between the first electrode and the second electrode. One or both of the first electrode and the second electrode may form the heating element.

The aerosol-generating system comprises an aerosol-forming substrate.

The aerosol-forming substrate may be any suitable aerosol-forming substrate capable of releasing volatile compounds that can form an aerosol. Preferably the aerosol-forming substrate is solid. Preferably the aerosol-forming substrate is solid at room temperature. As used herein, “room temperature” refers to 20 degrees Celsius. In some embodiments, the aerosol-forming substrate comprises solid components and liquid components. In some embodiments, the aerosol-forming substrate is liquid. In some embodiments, the aerosol-forming substrate is liquid at room temperature.

The aerosol-forming substrate may be formed of any suitable material for generating an aerosol when heated. Suitable types of materials for use in the aerosol-forming substrate include, for example, tobacco cut filler, homogenised tobacco material such as cast leaf and aerosol-forming films.

Preferably, the aerosol-forming substrate comprises tobacco material. In certain preferred embodiments, the aerosol-forming substrate comprises shredded tobacco material. For example, the shredded tobacco material may be in the form of cut filler, as described in more detail below. Alternatively, the shredded tobacco material may be in the form of a shredded sheet of homogenised tobacco material. Suitable homogenised tobacco materials for use in the aerosol-generating system of the present disclosure are described below.

As used herein, “cut filler” describes a blend of shredded plant material, such as tobacco plant material, including, in particular, one or more of leaf lamina, processed stems and ribs, homogenised plant material. The cut filler may also comprise other after-cut, filler tobacco or casing.

Preferably, the cut filler comprises at least 25 percent of plant leaf lamina, more preferably, at least 50 percent of plant leaf lamina, still more preferably at least 75 percent of plant leaf lamina and most preferably at least 90 percent of plant leaf lamina. Preferably, the plant material is one of tobacco, mint, tea, and cloves. Most preferably, the plant material is tobacco. However, the aerosolgenerating system of the present disclosure is equally applicable to other plant material that has the ability to release substances upon the application of heat that can subsequently form an aerosol.

Preferably, the cut filler comprises tobacco plant material comprising lamina of one or more of bright tobacco, dark tobacco, aromatic tobacco, and filler tobacco. As used herein, “tobacco” describes any plant member of the genus Nicotiana.

Suitable cut fillers generally may resemble cut filler used for conventional smoking articles. The cut width of the cut filler preferably is between 0.3 millimetres and 2.0 millimetres, more preferably, the cut width of the cut filler is between 0.5 millimetres and 1 .2 millimetres and most preferably, the cut width of the cut filler is between 0.6 millimetres and 0.9 millimetres. The cut width may play a role in the distribution of heat inside the aerosol-forming substrate. Also, the cut width may play a role in the resistance to draw (RTD) of the aerosol-generating article. Further, the cut width may impact the overall density of the aerosol-forming substrate as a whole.

The strand length of the cut-filler is to some extent a random value as the length of the strands will depend on the overall size of the object that the strand is cut off from. Nevertheless, by conditioning the material before cutting, for example by controlling the moisture content and the overall subtlety of the material, longer strands can be cut. Preferably, the strands have a length of between about 10 millimetres and about 40 millimetres before the strands are collated to form the aerosol-forming substrate. Obviously, if the strands are arranged in the aerosol-forming substrate in a longitudinal extension where the longitudinal extension of the section is below 40 millimetres, the aerosol-forming substrate may comprise strands that are on average shorter than the initial strand length. Preferably, the strand length of the cut-filler is such that between about 20 percent and 60 percent of the strands extend along the full length of the aerosol-forming substrate. This prevents the strands from dislodging easily from the aerosol-forming substrate.

In other preferred embodiments, the aerosol-forming substrate comprises homogenised plant material, preferably a homogenised tobacco material.

As used herein, “homogenised plant material” encompasses any plant material formed by the agglomeration of particles of plant. For example, sheets or webs of homogenised tobacco material may be formed by agglomerating particles of tobacco material obtained by pulverising, grinding or comminuting plant material and optionally one or more of tobacco leaf lamina and tobacco leaf stems to form the aerosol-forming substrate. The homogenised plant material may be produced by casting, extrusion, paper making processes or other any other suitable processes known in the art.

The homogenised plant material may be provided in any suitable form. In some embodiments, the homogenised plant material may be in the form of one or more sheets. As used herein, a “sheet” describes a laminar element having a width and length substantially greater than the thickness thereof.

The aerosol-forming substrate may comprise one or more aerosol formers. Suitable aerosol formers for inclusion in the aerosol-forming substrate are known in the art and include, but are not limited to: polyhydric alcohols, such as triethylene glycol, propylene glycol, 1 ,3-butanediol and glycerol; esters of polyhydric alcohols, such as glycerol mono-, di- or triacetate; and aliphatic esters of mono-, di- or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate.

The aerosol-forming substrate preferably has an aerosol former content of no more than 30 percent by weight on a dry weight basis. More preferably, the aerosol-forming substrate has an aerosol former content of no more than 25 percent by weight on a dry weight basis. More preferably, the aerosol-forming substrate has an aerosol former content of no more than 20 percent by weight on a dry weight basis.

Preferably, the aerosol-forming substrate has an aerosol former content of at least 5 percent by weight on a dry weight basis. More preferably, the aerosol-forming substrate has an aerosol former content of at least 10 percent by weight on a dry weight basis. More preferably, the aerosolforming substrate has an aerosol former content of at least 12 percent by weight on a dry weight basis. More preferably, the aerosol-forming substrate has an aerosol former content of at least 15 percent by weight on a dry weight basis.

For example, the aerosol former content of the aerosol-forming substrate may be between 5 percent and 30 percent by weight, or between 10 percent and 25 percent by weight, or between 12 percent and 20 percent by weight, or between about 15 percent and about 20 percent by weight, on a dry weight basis.

Preferably, the aerosol-forming substrate comprises glycerol as an aerosol former. For example, the aerosol-forming substrate may comprise between 5 percent and 30 percent by weight of glycerol, or between 10 percent and 25 percent by weight of glycerol, or between 12 percent and 20 percent by weight of glycerol, or between 15 percent and 20 percent by weight of glycerol, on a dry weight basis.

Preferably, the aerosol-forming substrate has a relatively high aerosol former content compared to typical aerosol-generating systems. This is because the downstream portion of the aerosol-forming substrate is able to cool the aerosol generated in the initial puffs, as described above, enabling a higher aerosol former content to be used in the aerosol-forming substrate without adversely affecting the user experience during the initial puffs by a user on the aerosol-generating system.

Preferably, the aerosol-forming substrate comprises an aerosol former content of at least 12 percent, at least 15 percent, at least 18 percent, at least 20 percent, at least 22 percent or at least 25 percent by weight, on a dry weight basis. Most preferably, the aerosol-forming substrate comprises an aerosol former content of at least 18 percent, or at least 20 percent, or between 20 percent and 30 percent by weight, on a dry weight basis. The aerosol-forming substrate may comprise an aerosol former content of more than 18 percent by weight, on a dry weight basis.

In some preferred embodiments, the aerosol former comprises glycerol, and the aerosolforming substrate comprises at least 12 percent, at least 15 percent, at least 18 percent, at least 20 percent, at least 22 percent or at least 25 percent by weight of glycerol, on a dry weight basis. Most preferably, the aerosol-forming substrate comprises at least 18 percent, or at least 20 percent, or between 20 percent and 30 percent glycerol by weight, on a dry weight basis.

The aerosol-forming substrate may comprise non-tobacco plant flavour particles. The nontobacco plant flavour particles may be selected from one or more of: ginger particles, rosemary particles, eucalyptus particles, clove particles and star anise particles.

In some preferred embodiments, the aerosol-forming substrate comprises clove. The aerosolforming substrate may comprise at least 1 percent by weight of clove, on a dry weight basis. The aerosol-forming substrate may comprise at least 2 percent by weight of clove, on a dry weight basis. The aerosol-forming substrate may comprise about 1 percent by weight of clove, or about 2 percent by weight of clove, on a dry weight basis.

In some embodiments, the aerosol-forming substrate may comprise an aerosol-forming film. The aerosol-forming film may comprise a cellulosic based film forming agent, nicotine, and an aerosol former.

As used herein, the term “film” is used to describe a solid laminar element having a thickness that is less than the width or length thereof. The film may be self-supporting. In other words, a film may have cohesion and mechanical properties such that the film, even if obtained by casting a filmforming formulation on a support surface, can be separated from the support surface. Alternatively, the film may be disposed on a support or sandwiched between other materials. This may enhance the mechanical stability of the film.

The aerosol-forming film may have an aerosol former comprising glycerol, and may have a glycerol content of at least 40 percent by weight on a dry weight basis.

The aerosol-forming film may further comprise water, preferably 30 percent by weight of less of water.

The aerosol-forming film may comprise a cellulosic based film forming agent. As used herein, the term “cellulose based film-forming agent” is used to describe a cellulosic polymer capable, by itself or in the presence of an auxiliary thickening agent, of forming a continuous film. Preferably, the cellulose based film-forming agent is selected from the group consisting of hydroxypropyl methylcellulose (HPMC), methylcellulose (MC), ethylcellulose (EC), hydroxyethyl methyl cellulose (HEMC), hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC), and combinations thereof. The aerosol-forming film may have a cellulose based film-forming agent content of between 10 percent and 40 percent by weight, or between 15 percent and 35 percent by weight, or between 20 percent and 30 percent by weight, on a dry weight basis.

Preferably, the aerosol-forming film further comprises a cellulose based strengthening agent. Preferably, the cellulose based strengthening agent is selected from the group consisting of cellulose fibres, microcrystalline cellulose (MCC), cellulose powder, and combinations thereof. The aerosolforming film may have a cellulose based strengthening agent content of between 0.5 percent and 40 percent by weight on a dry weight basis, or between 5 percent and 30 percent by weight on a dry weight basis, or between 10 percent and 25 percent by weight on a dry weight basis.

The aerosol-forming film may further comprise a carboxymethyl cellulose, preferably sodium carboxymethyl cellulose. The aerosol-forming film may have a carboxymethyl cellulose content of between 1 percent and 15 percent by weight, or between 2 percent and 12 percent by weight, or between 4 percent and 10 percent by weight on a dry weight basis. The aerosol-forming film comprises nicotine. As used herein, the term “nicotine” is used to describe nicotine, a nicotine base, or a nicotine salt. In embodiments in which the aerosol-forming film comprises a nicotine base or a nicotine salt, the amounts of nicotine recited herein are the amount of free base nicotine or amount of protonated nicotine, respectively. The aerosol-forming film may comprise natural nicotine or synthetic nicotine. The aerosol-forming film may comprise one or more monoprotic nicotine salts. As used herein, the term “monoprotic nicotine salt” is used to describe a nicotine salt of a monoprotic acid. The aerosol-forming film may comprise between 0.5 percent and 10 percent by weight of nicotine, or between 1 percent and 8 percent by weight of nicotine, or between 2 percent and 6 percent by weight of nicotine, on a dry weight basis.

In preferred embodiments, the aerosol-forming film comprises an acid. More preferably, the aerosol-forming film comprises one or more organic acids. Even more preferably, the aerosolforming film comprises one or more carboxylic acids. In particularly preferred embodiments, the acid is lactic acid, benzoic acid, fumaric acid or levulinic acid. The aerosol-forming film may comprise between 0.25 percent and 3.5 percent by weight of an acid, or between 0.5 percent and 3 percent by weight of an acid, or between 1 percent and 2.5 percent by weight of an acid, on a dry weight basis.

The aerosol-forming film may have a thickness from about 0.1 millimetres to about 1 millimetre, more preferably from about 0.1 millimetres to about 0.75 millimetres, even more preferably from about 0.1 millimetres to about 0.5 millimetres. In particularly preferred embodiments, a layer of the film-forming composition is formed that has a thickness from about 50 micrometres to 400 micrometres, more preferably from about 100 micrometres to 200 micrometres.

In some embodiments, the aerosol-forming substrate may comprise a gel composition that includes nicotine, at least one gelling agent and an aerosol former. The gel composition may be substantially tobacco free.

The preferred weight ranges for nicotine in the gel composition are the same as those defined above in relation to aerosol-forming films.

The gel composition may comprise comprises at least 50 percent by weight of aerosol former, more preferably at least 60 percent by weight, more preferably at least 70 percent by weight of aerosol former, on a dry weight basis. The gel composition may comprise up to 80 percent by weight of aerosol former. The aerosol former in the gel composition is preferably glycerol.

The gel composition preferably includes at least one gelling agent. Preferably, the gel composition includes a total amount of gelling agents in a range from about 0.4 percent by weight to about 10 percent by weight. More preferably, the composition includes the gelling agents in a range from about 0.5 percent by weight to about 8 percent by weight. More preferably, the composition includes the gelling agents in a range from about 1 percent by weight to about 6 percent by weight. More preferably, the composition includes the gelling agents in a range from about 2 percent by weight to about 4 percent by weight. More preferably, the composition includes the gelling agents in a range from about 2 percent by weight to about 3 percent by weight.

The term “gelling agent” refers to a compound that homogeneously, when added to a 50 percent by weight water I 50 percent by weight glycerol mixture, in an amount of about 0.3 percent by weight, forms a solid medium or support matrix leading to a gel. Gelling agents include, but are not limited to, hydrogen-bond crosslinking gelling agents, and ionic crosslinking gelling agents.

The term “hydrogen-bond crosslinking gelling agent” refers to a gelling agent that forms non- covalent crosslinking bonds or physical crosslinking bonds via hydrogen bonding. Hydrogen bonding is a type of electrostatic dipole-dipole attraction between molecules, not a covalent bond to a hydrogen atom. It results from the attractive force between a hydrogen atom covalently bonded to a very electronegative atom such as a N, O, or F atom and another very electronegative atom.

The hydrogen-bond crosslinking gelling agent may include one or more of a galactomannan, gelatin, agarose, or konjac gum, or agar. The hydrogen-bond crosslinking gelling agent may preferably include agar.

The term “ionic crosslinking gelling agent” refers to a gelling agent that forms non-covalent crosslinking bonds or physical crosslinking bonds via ionic bonding. Ionic crosslinking involves the association of polymer chains by noncovalent interactions. A crosslinked network is formed when multivalent molecules of opposite charges electrostatically attract each other giving rise to a crosslinked polymeric network.

The ionic crosslinking gelling agent may include low acyl gellan, pectin, kappa carrageenan, iota carrageenan or alginate. The ionic crosslinking gelling agent may preferably include low acyl gellan.

The gelling agent may include one or more biopolymers. The biopolymers may be formed of polysaccharides.

Biopolymers include, for example, gellan gums (native, low acyl gellan gum, high acyl gellan gums with low acyl gellan gum being preferred), xanthan gum, alginates (alginic acid), agar, guar gum, and the like. The composition may preferably include xanthan gum. The composition may include two biopolymers. The composition may include three biopolymers. The composition may include the two biopolymers in substantially equal weights. The composition may include the three biopolymers in substantially equal weights.

The gel composition may further include a viscosifying agent. The viscosifying agent combined with the hydrogen-bond crosslinking gelling agent and the ionic crosslinking gelling agent appears to surprisingly support the solid medium and maintain the gel composition even when the gel composition comprises a high level of glycerol. The term “viscosifying agent” refers to a compound that, when added homogeneously into a 25°C, 50 percent by weight water/50 percent by weight glycerol mixture, in an amount of 0.3 percent by weight., increases the viscosity without leading to the formation of a gel, the mixture staying or remaining fluid. Preferably the viscosifying agent refers to a compound that when added homogeneously into a 25°C 50 percent by weight water I 50 percent by weight glycerol mixture, in an amount of 0.3 percent by weight, increases the viscosity to at least 50 cPs, preferably at least 200 cPs, preferably at least 500 cPs, preferably at least 1000 cPs at a shear rate of 0.1 s-1 , without leading to the formation of a gel, the mixture staying or remaining fluid. Preferably the viscosifying agent refers to a compound that when added homogeneously into a 25°C 50 percent by weight water/50 percent by weight glycerol mixture, in an amount of 0.3 percent by weight, increases the viscosity at least 2 times, or at least 5 times, or at least 10 times, or at least 100 times higher than before addition, at a shear rate of 0.1 s-1 , without leading to the formation of a gel, the mixture staying or remaining fluid.

The viscosity values recited herein can be measured using a Brookfield RVT viscometer rotating a disc type RV#2 spindle at 25°C at a speed of 6 revolutions per minute (rpm).

The gel composition preferably includes the viscosifying agent in a range from about 0.2 percent by weight to about 5 percent by weight. Preferably the composition includes the viscosifying agent in a range from about 0.5 percent by weight to about 3 percent by weight. Preferably the composition includes the viscosifying agent in a range from about 0.5 percent by weight to about 2 percent by weight. Preferably the composition includes the viscosifying agent in a range from about 1 percent by weight to about 2 percent by weight.

The viscosifying agent may include one or more of xanthan gum, carboxymethyl-cellulose, microcrystalline cellulose, methyl cellulose, gum Arabic, guar gum, lambda carrageenan, or starch. The viscosifying agent may preferably include xanthan gum.

The gel composition may further include a divalent cation. Preferably the divalent cation includes calcium ions, such as calcium lactate in solution. Divalent cations (such as calcium ions) may assist in the gel formation of compositions that include gelling agents such as the ionic crosslinking gelling agent, for example. The ion effect may assist in the gel formation. The divalent cation may be present in the gel composition in a range from about 0.1 to about 1 percent by weight, or about 0.5 percent by weight.

The gel composition may further include an acid. The acid may comprise a carboxylic acid. The carboxylic acid may include a ketone group. Preferably the carboxylic acid may include a ketone group having less than about 10 carbon atoms, or less than about 6 carbon atoms or less than about 4 carbon atoms, such as levulinic acid or lactic acid. Preferably this carboxylic acid has three carbon atoms (such as lactic acid). The gel composition preferably comprises some water. The gel composition is more stable when the composition comprises some water. Preferably the gel composition comprises at least about 1 percent by weight, or at least about 2 percent by weight, or at least about 5 percent by weight of water. Preferably the gel composition comprises at least about 10 percent by weight or at least about 15 percent by weight water.

Preferably the gel composition comprises between about 8 percent by weight to about 32 percent by weight water. Preferably the gel composition comprises from about 15 percent by weight to about 25 percent by weight water. Preferably the gel composition comprises from about 18 percent by weight to about 22 percent by weight water. Preferably the gel composition comprises about 20 percent by weight water.

The aerosol-forming substrate has an external diameter. The “external diameter” of the aerosol-forming substrate may be calculated as the average of a plurality of measurements of the diameter of the aerosol-forming substrate taken at different locations along the length of the aerosolforming substrate.

Preferably, the aerosol-forming substrate has an external diameter of at least about 5 millimetres. More preferably the aerosol-forming substrate has an external diameter of at least about

6 millimetres. Even more preferably the aerosol-forming substrate has an external diameter of at least about 7 millimetres or is about 7.2 millimetres.

The aerosol-forming substrate preferably has an external diameter of less than or equal to about 12 millimetres. More preferably, the aerosol-forming substrate has an external diameter of less than or equal to about 10 millimetres. Even more preferably, the aerosol-forming substrate has an external diameter of less than or equal to about 8 millimetres, or is about 7.2 millimetres.

Preferably, the external diameter of the aerosol-forming substrate is between 5 millimetres and 12 millimetres, more preferably between 6 millimetres and 10 millimetres, more preferably between

7 millimetres and 8 millimetres. In some embodiments, the external diameter of the aerosol-forming substrate may be less than 7 millimetres, for example, between 5 millimetres and 7 millimetres, or between 6 millimetres and 7 millimetres.

In general, it has been observed that the smaller the diameter of the aerosol-forming substrate, the lower the temperature that is required to raise a core temperature of the aerosol-forming substrate such that sufficient amounts of vaporizable species are released from the aerosol-forming substrate to form a desired amount of aerosol.

The aerosol-forming substrate preferably has an external diameter that is approximately equal to the external diameter of the aerosol-generating article. Preferably, the external diameter of the aerosol-forming substrate is substantially constant along the length of the aerosol-forming substrate. The average cross-sectional area of the aerosol-forming substrate is preferably at least 50 percent of the average cross-sectional area of the aerosol-generating article, more preferably at least 80 percent of the average cross-sectional area of the aerosol-generating article, more preferably at least 90 percent of the average cross-sectional area of the aerosol-generating article.

The cross-sectional area of the aerosol-forming substrate at the upstream end is preferably at least 50 percent of the average cross-sectional area of the aerosol-generating article, more preferably at least 80 percent of the average cross-sectional area of the aerosol-generating article, more preferably at least 90 percent of the average cross-sectional area of the aerosol-generating article.

Preferably, the aerosol-generating system comprises an aerosol-generating article comprising the aerosol-forming substrate.

In some preferred embodiments, the aerosol-generating article comprises an airflow path between the upstream end and the downstream end. The aerosol-forming substrate may be arranged in the airflow path.

In some embodiments, the aerosol-generating article comprises the heating element.

According to the present disclosure, there is provided an aerosol-generating article comprising: an aerosol-forming substrate; and a heating element, wherein: the heating element is arranged to heat the aerosol-forming substrate; the heating element has a heating element length; the aerosol-forming substrate has a substrate length, the aerosol-forming substrate length being greater than the heating element length; and the ratio of the aerosol-forming substrate length to the heating element length is between about 1.1 and 3. Preferably, the ratio of the aerosol-forming substrate length to the heating element length is between about 1.1 and 1.16. The ratio of the aerosol-forming substrate length to the heating element length may be between about 1.11 and 1 .16, or between about 1.12 and 1 .16, or between about 1.13 and 1 .16, or between about 1.14 and 1 .16, or between about 1.15 and 1.16. In some preferred embodiments, the ratio of the aerosolforming substrate length to the heating element length is about 1.16. In some preferred embodiments, the aerosol-generating article comprises an upstream end and a downstream end, and a downstream portion of the aerosol-forming substrate extends beyond the downstream end of the heating element. In addition, in some preferred embodiments, the upstream end of the heating element is aligned with the upstream end of the aerosol-forming substrate.

According to the present disclosure, there is provided an aerosol-generating article comprising an aerosol-forming substrate, wherein the aerosol-forming substrate has a substrate length of at least 13 millimetres, a mass of at least 260 milligrams and an aerosol former content of at least about 18 percent by weight, on a dry weight basis.

According to the present disclosure, there is provided an aerosol-generating article comprising an aerosol-forming substrate, wherein the aerosol-forming substrate has a substrate length of at least 14 millimetres, a mass of at least 27 milligrams and an aerosol former content of at least 20 percent by weight, on a dry weight basis. In some preferred embodiments, the aerosol former is glycerol.

As described above, in some embodiments the aerosol-generating article comprises the heating element. In particular, the aerosol-generating article may comprise a susceptor element. Providing a susceptor element in an aerosol-generating article is typically preferable to providing a resistive heating element in an aerosol-generating article since a susceptor element does not require a direct physical connection to a power supply in order to generate heat. As such, an aerosolgenerating article comprises a susceptor element, rather than a resistive heating element, avoids the need for electrical contacts to be provided on the aerosol-generating article, which may require regular cleaning.

In some embodiments, the susceptor element in the aerosol-generating article circumscribes a portion of the aerosol-forming substrate. In these embodiments, the susceptor element heats an outer surface of the aerosol-forming substrate.

In some embodiments, the susceptor element in the aerosol-generating article is substantially surrounded by the aerosol-forming substrate. The susceptor element may be embedded in the aerosol-forming substrate. In these embodiments, the susceptor element heats the aerosol-forming substrate from the inside. In these embodiments, the susceptor element may take the form of a pin, rod, strip, or blade.

The susceptor element may extend along the aerosol-forming substrate in a longitudinal direction. The susceptor element may be elongate. The susceptor element may extend from an upstream end of the aerosol-forming substrate. The susceptor element may extend to an upstream end of a downstream portion of the aerosol-forming substrate.

The susceptor element may have a width between about 1 millimetre and about 5 millimetres.

The susceptor element may have a thickness between about 0.01 millimetres and about 2 millimetres, for example between 0.5 millimetres and 2 millimetres. In some embodiments, the susceptor element preferably has a thickness between about 10 micrometres and about 500 micrometres, more preferably between 10 micrometres and 100 micrometres.

Preferably, the susceptor element is arranged in thermal contact with the aerosol-forming substrate. Thus, when the susceptor element heats up the aerosol-forming substrate is heated up and volatile compounds are released, which may condense to form an aerosol. Preferably the susceptor element is arranged in direct physical contact with the aerosol-forming substrate.

Preferably, an overall length of the aerosol-generating article is at least 40 millimetres. More preferably, an overall length of the aerosol-generating article is at least 50 millimetres. Even more preferably, an overall length of the aerosol-generating article is at least 60 millimetres. An overall length of the aerosol-generating article is preferably less than or equal to 90 millimetres. More preferably, an overall length of the aerosol-generating article is preferably less than or equal to 85 millimetres. Even more preferably, an overall length of the aerosol-generating article is preferably less than or equal to 80 millimetres.

In some embodiments, an overall length of the aerosol-generating article is preferably from 40 millimetres to 70 millimetres, more preferably from 45 millimetres to 70 millimetres. In other embodiments, an overall length of the aerosol-generating article is preferably from 40 millimetres to 60 millimetres, more preferably from about 45 millimetres to about 60 millimetres. In further embodiments, an overall length of the aerosol-generating article is preferably from 40 millimetres to 50 millimetres, more preferably from 45 millimetres to 50 millimetres. In an exemplary embodiment, an overall length of the aerosol-generating article is about 45 millimetres.

In some embodiments, an overall length of the aerosol-generating article is preferably from 50 millimetres to 90 millimetres, more preferably from 60 millimetres to 90 millimetres, even more preferably from 70 millimetres to 90 millimetres. In some embodiments, an overall length of the aerosol-generating article is preferably from 50 millimetres to 85 millimetres, more preferably from 60 millimetres to 85 millimetres, even more preferably from 70 millimetres to 85 millimetres. In some embodiments, an overall length of the aerosol-generating article is preferably from 50 millimetres to 80 millimetres, more preferably from 60 millimetres to 80 millimetres, even more preferably from 70 millimetres to 80 millimetres. In an exemplary embodiment, an overall length of the aerosolgenerating article is 75 millimetres.

The aerosol-generating article has an external diameter of at least 5 millimetres. Preferably, the aerosol-generating article has an external diameter of at least 6 millimetres. More preferably, the aerosol-generating article has an external diameter of at least 7 millimetres.

Preferably, the aerosol-generating article has an external diameter of less than or equal to about 12 millimetres. More preferably, the aerosol-generating article has an external diameter of less than or equal to about 10 millimetres. Even more preferably, the aerosol-generating article has an external diameter of less than or equal to about 8 millimetres.

In some embodiments, the aerosol-generating article has an external diameter from about 5 millimetres to about 12 millimetres, preferably from about 6 millimetres to about 12 millimetres, more preferably from about 7 millimetres to about 12 millimetres. In some embodiments, the aerosolgenerating article has an external diameter from about 5 millimetres to about 10 millimetres, preferably from about 6 millimetres to about 10 millimetres, more preferably from about 7 millimetres to about 10 millimetres. In some embodiments, the aerosol-generating article has an external diameter from about 5 millimetres to about 8 millimetres, preferably from about 6 millimetres to about 8 millimetres, more preferably from about 7 millimetres to about 8 millimetres. In some embodiments, the aerosol-generating article has an external diameter of less than 7 millimetres.

Preferably, the external diameter of the aerosol-generating article is substantially constant over the whole length of the aerosol-generating article. As an alternative, different portions of the aerosolgenerating article may have different external diameters.

The aerosol-generating article has an overall resistance to draw (RTD). The overall RTD of the aerosol-generating article may be at least 10 millimetres of water (mm H2O). For example, the overall RTD of the aerosol-generating article may be at least 20 millimetres of water (mm H2O), at least 30 millimetres of water (mm H2O), at least 35 millimetres of water (mm H2O), or at least 40 millimetres of water (mm H2O).

Unless otherwise specified, the resistance to draw (RTD) of a component or the aerosolgenerating article is measured in accordance with ISO 6565-2015. The RTD refers the pressure required to force air through the full length of a component. The terms “pressure drop” or “draw resistance” of a component or article may also refer to the “resistance to draw”. Such terms generally refer to the measurements in accordance with ISO 6565-2015 are normally carried out at under test at a volumetric flow rate of 17.5 millilitres per second at the output or downstream end of the measured component at a temperature of 22 degrees Celsius, a pressure of 101 kPa (about 760 Torr) and a relative humidity of 60%. Conditions for smoking and smoking machine specifications are set out in ISO Standard 3308 (ISO 3308:2000). Atmosphere for conditioning and testing are set out in ISO Standard 3402 (ISO 3402:1999).

The overall RTD of the aerosol-generating article may be no more than 70 millimetres of water (mm H2O). For example, the overall RTD of the aerosol-generating article may be no more than 60 millimetres of water (mm H2O), no more than 55 millimetres of water (mm H2O), no more than 50 millimetres of water (mm H2O), or no more than 45 millimetres of water (mm H2O).

The overall RTD of the aerosol-generating article may be between 10 millimetres of water (mm H2O) and 70 millimetres of water (mm H2O). For example, the overall RTD of the aerosol-generating article may be between 20 millimetres of water (mm H2O) and 60 millimetres of water (mm H2O), between 30 millimetres of water (mm H2O) and 55 millimetres of water (mm H2O), between 35 millimetres of water (mm H2O) and 50 millimetres of water (mm H2O), or between 40 millimetres of water (mm H2O) and 45 millimetres of water (mm H2O).

The overall RTD of the aerosol-generating article may be between 40 millimetres of water (mm H2O) and 60 millimetres of water (mm H2O), between 35 millimetres of water (mm H2O) and 40 millimetres of water (mm H2O), between 45 millimetres of water (mm H2O) and 50 millimetres of water (mm H2O), or between 55 millimetres of water (mm H2O) and 65 millimetres of water (mm H2O). The overall RTD of the aerosol-generating article may be about 38 millimetres of water (mm H2O), about 48 millimetres of water (mm H2O), or about 60 millimetres of water (mm H2O).

An aerosol-generating article in accordance with the present disclosure may have a ventilation level of at least 25 percent.

The term “ventilation level” is used throughout the present specification to denote a volume ratio between of the airflow admitted into the aerosol-generating article via the ventilation zone (ventilation airflow) and the sum of the aerosol airflow and the ventilation airflow. The greater the ventilation level, the higher the dilution of the aerosol flow delivered to the consumer. The aerosolgenerating article preferably has a ventilation level of at least 25 percent, more preferably at least 30 percent, even more preferably at least 40 percent, even more preferably at least 50 percent.

An aerosol-generating article in accordance with the present disclosure may have a ventilation level of up to 90 percent. Preferably, an aerosol-generating article in accordance with the present disclosure has a ventilation level of less than or equal to 80 percent, more preferably less than or equal to 70 percent, even more preferably less than or equal to 60 percent.

In some embodiments, the upstream end of the aerosol-forming substrate may define the upstream end of the aerosol-generating article. Alternatively, in some embodiments the aerosolgenerating article may further comprise an upstream element.

The upstream element may be located upstream of and adjacent to the aerosol-forming substrate. The upstream element may advantageously prevent direct physical contact with the upstream end of the aerosol-forming substrate. For example, where the aerosol-forming substrate comprises a susceptor element, the upstream element may prevent direct physical contact with the upstream end of the susceptor element. This helps to prevent the displacement or deformation of the susceptor element during handling or transport of the aerosol-generating article. This in turn helps to secure the form and position of the susceptor element. Furthermore, the presence of an upstream element helps to prevent any loss of the aerosol-forming substrate, which may be advantageous, for example, if the aerosol-forming substrate contains particulate plant material.

Where the aerosol-forming substrate comprises shredded tobacco, such as tobacco cut filler, the upstream element thereof may additionally help to prevent the loss of loose particles of tobacco from the upstream end of the aerosol-generating article. This may be particularly important when the shredded tobacco has a relatively low density, for example.

The upstream element may also additionally provide a degree of protection to the aerosolforming substrate during storage, as it covers at least to some extent the upstream end of the aerosolforming substrate, which may otherwise be exposed.

For aerosol-generating articles that are intended to be inserted into a device cavity in an aerosol-generating device such that the aerosol-forming substrate can be externally heated within the device cavity, the upstream element may advantageously facilitate the insertion of the upstream end of the aerosol-generating article into the device cavity. The inclusion of the upstream element may additionally protect the end of the aerosol-forming substrate during the insertion of the aerosolgenerating article into the device cavity such that the risk of damage to the aerosol-forming substrate is minimised.

The upstream element may be a porous plug element. Preferably, the upstream element has a porosity of at least 50 percent in the longitudinal direction of the aerosol-generating article. More preferably, the upstream element may have a porosity of between 50 percent and 90 percent in the longitudinal direction. The porosity of the upstream element in the longitudinal direction is defined by the ratio of the cross-sectional area of material forming the upstream element and the internal cross-sectional area of the aerosol-generating article at the position of the upstream element.

The upstream element may be made of a porous material. The upstream element may comprise a plurality of openings. This may, for example, be achieved through laser perforation. Preferably, the plurality of openings is distributed homogeneously over the cross-section of the upstream element.

The porosity or permeability of the upstream element may advantageously be designed in order to provide the aerosol-generating article with a particular overall resistance to draw (RTD) without substantially impacting the filtration provided by other portions of the aerosol-generating article.

The upstream element may be formed from a material that is impermeable to air. In such embodiments, the aerosol-generating article may be configured such that air flows into the aerosolforming substrate through suitable ventilation means provided in a wrapper.

In certain preferred embodiments, it may be desirable to minimise the RTD of the upstream element. For example, this may be the case for articles that are intended to be inserted the device cavity of the aerosol-generating device such that an outer surface of the aerosol-forming substrate is heated. For such articles, it is desirable to provide the aerosol-generating article with as low an RTD as possible, so that the majority of the RTD experience by the consumer is provided by the aerosolgenerating device and not the aerosol-generating article.

In some embodiments, the aerosol-generating article further comprises a downstream section located downstream of the aerosol-forming substrate. The downstream section is preferably located immediately downstream of the aerosol-forming substrate. The downstream section of the aerosolgenerating article preferably extends between the aerosol-forming substrate and the downstream end of the aerosol-generating article. The downstream section may extend to a downstream end of the aerosol-generating article.

The downstream section may comprise one or more elements, each of which will be described in more detail below. The downstream section may have a length. The length of the downstream section may be at least 20 millimetres. The length of the downstream section may be at least 25 millimetres. The length of the downstream section may be at least 30 millimetres.

The length of the downstream section may be less than 70 millimetres. The length of the downstream section may be equal to or less than 60 millimetres. The length of the downstream section may be equal to or less than 50 millimetres.

For example, the length of the downstream section may be between 20 millimetres and 70 millimetres, or between 25 millimetres and 60 millimetres, or between 30 millimetres and 50 millimetres.

Providing a relatively long downstream section ensures that a suitable length of the aerosolgenerating article protrudes from the aerosol-generating device when the aerosol-generating article is received therein. Such a suitable protrusion length facilitates the ease of insertion and extraction of the aerosol-generating article from the aerosol-generating device, which also ensures that the upstream portions of the aerosol-generating article are suitably inserted into the aerosol-generating device with reduced risk of damage, particularly during insertion.

A ratio between a length of the downstream section and an overall length of the aerosolgenerating article may be less than 0.80. More preferably, a ratio between a length of the downstream section and an overall length of the aerosol-generating article may be less than 0.75. Even more preferably, a ratio between a length of the downstream section and an overall length of the aerosol-generating article may be less than 0.70.

A ratio between a length of the downstream section and an overall length of the aerosolgenerating article may be at least 0.30. Preferably, a ratio between a length of the downstream section and an overall length of the aerosol-generating article may be at least 0.40. More preferably, a ratio between a length of the downstream section and an overall length of the aerosol-generating article may be at least 0.50.

In some embodiments, a ratio between a length of the downstream section and an overall length of the aerosol-generating article is from 0.30 to 0.80, preferably from 0.40 to 0.75, more preferably from 0.50 to 0.70.

The resistance to draw (RTD) of the downstream section may be at least 0 millimetres H₂O. The RTD of the downstream section may be at least 3 millimetres H₂O. The RTD of the downstream section may be at least 6 millimetres H₂O.

The RTD of the downstream section may be no greater than 12 millimetres H₂O. The RTD of the downstream section may be no greater than 11 millimetres H₂O. The RTD of the downstream section may be no greater than 10 millimetres H₂O. The downstream section of the aerosol-generating article may comprise a hollow tubular cooling element. The hollow tubular cooling element may be provided downstream of the aerosolforming substrate. The hollow tubular cooling element may advantageously provide an aerosolcooling element for the aerosol-generating article.

The hollow tubular cooling element may be provided immediately downstream of the aerosolforming substrate. In other words, the hollow tubular cooling element may abut a downstream end of the aerosol-forming substrate. The hollow tubular cooling element may define an upstream end of the downstream section of the aerosol-generating article. The downstream end of the aerosolgenerating article may coincide with the downstream end of the downstream section. In some embodiments, the downstream section of the aerosol-generating article comprises a single hollow tubular element. In other words, the downstream section of the aerosol-generating article may comprise only one hollow tubular element. In some embodiments, the downstream section comprises two or more hollow tubular elements, as described in more detail below.

As used herein, the term "hollow tubular element" denotes a generally elongate element defining a lumen or airflow passage along a longitudinal axis. In particular, the term "tubular" in this disclosure with reference to a tubular element having a substantially cylindrical cross-section and defining at least one airflow conduit establishing an uninterrupted fluid communication between an upstream end of the tubular element and a downstream end of the tubular element. However, it will be understood that alternative geometries (for example, alternative cross-sectional shapes) of the tubular element may be possible.

In the present disclosure, a hollow tubular cooling element provides an unrestricted airflow path downstream of the aerosol-forming substrate. This means that the hollow tubular cooling element provides a negligible level of resistance to draw (RTD). The term “negligible level of RTD” is used to describe an RTD of less than 1 millimetres of water (mm H₂O) per 10 millimetres of length of the hollow tubular cooling element, preferably less than 0.4 millimetres of water (mm H₂O) per 10 millimetres of length of the hollow tubular cooling element, more preferably less than 0.1 millimetres of water (mm H₂O) per 10 millimetres of length of the hollow tubular cooling element.

The RTD of a hollow tubular cooling element in the downstream section is preferably less than or equal to 10 millimetres of water (mm H₂O). More preferably, the RTD of a hollow tubular cooling element is less than or equal to 5 millimetres of water (mm H₂O). Even more preferably, the RTD of a hollow tubular cooling element is less than or equal to 2.5 millimetres of water (mm H₂O). Even more preferably, the RTD of the hollow tubular cooling element is less than or equal to 2 millimetres of water (mm H₂O). Even more preferably, the RTD of the hollow tubular cooling element is less than or equal to 1 millimetre of water (mm H₂O). The RTD of a hollow tubular cooling element may be at least 0 millimetres of water (mm H₂O), or at least 0.25 millimetres of water (mm H₂O) or at least 0.5 millimetres of water (mm H₂O) or at least 1 millimetre of water (mm H₂O).

The overall RTD of an aerosol-generating article of the present disclosure depends essentially on the RTD of the aerosol-forming substrate and optionally on the RTD of the downstream section any upstream elements. This is because the hollow tubular cooling element is substantially empty and, as such, only marginally contributes to the overall RTD of the aerosol-generating article. The airflow path through the hollow tubular cooling element should therefore be free from any components that would obstruct the flow of air in a longitudinal direction. Preferably, the airflow path is substantially empty and particularly preferably the airflow path is empty.

The aerosol-generating article may comprise a ventilation zone. The aerosol-generating article may comprise a ventilation zone at a location along the downstream section. In some embodiments, the aerosol-generating article may comprise a ventilation zone at a location along the hollow tubular cooling element. Such, or any, ventilation zone may extend through the peripheral wall of the hollow tubular cooling element. As such, fluid communication is established between the airflow path internally defined by the hollow tubular cooling element and the outer environment.

Providing such ventilation downstream of the aerosol-forming substrate may achieve several potential technical benefits. First of all, the inventors have found that one such ventilated hollow tubular cooling element provides a particularly efficient cooling of the aerosol. Thus, a satisfactory cooling of the aerosol can be achieved even by means of a relatively short downstream section. Secondly, the inventors have surprisingly found that such rapid cooling of the volatile species released upon heating the aerosol-forming substrate promotes enhanced nucleation of aerosol particles. Without wishing to be bound by theory, the inventors have found that the temperature drop caused by the admission of cooler, external air into the hollow tubular cooling element via the ventilation zone may have an advantageous effect on the nucleation and growth of aerosol particles.

The ventilation zone may typically comprise a plurality of perforations through the peripheral wall of the hollow tubular cooling element. Preferably, the ventilation zone comprises at least one circumferential row of perforations. In some embodiments, the ventilation zone may comprise two circumferential rows of perforations. For example, the perforations may be formed online during manufacturing of the aerosol-generating article. Preferably, each circumferential row of perforations comprises from 8 to 30 perforations.

Preferably, the hollow tubular cooling element has a length of at least 15 millimetres. More preferably, the length of the hollow tubular cooling element is at least 20 millimetres. The length of the hollow tubular cooling element may be at least 25 millimetres. More preferably, the length of the hollow tubular cooling element is at least 30 millimetres. The length of the hollow tubular cooling element is preferably less than 50 millimetres. More preferably, the length of the hollow tubular cooling element is less than 45 millimetres. More preferably, the length of the hollow tubular cooling element is less than 40 millimetres.

A relatively long hollow tubular cooling element provides and defines a relatively long internal cavity within the aerosol-generating article and downstream of the aerosol-forming substrate. As previously discussed, providing an empty cavity downstream, and preferably immediately downstream, of the aerosol-forming substrate enhances nucleation of aerosol particles from the volatile compounds released from the aerosol-forming substrate when heated. Providing a relatively long cavity maximises such nucleation benefits, thereby improving aerosol formation and cooling in the aerosol-generating article.

The thickness of a peripheral wall (in other words, the wall thickness) of the hollow tubular cooling element may be at least 100 micrometres. The wall thickness of the hollow tubular cooling element may be at least 150 micrometres. The wall thickness of the hollow tubular cooling element may be at least 200 micrometres, preferably at least 250 micrometres and even more preferably at least 500 micrometres (or 0.5 millimetres).

The wall thickness of the hollow tubular cooling element may be less than or equal to 2 millimetres, preferably less than or equal to 1.5 millimetres and even more preferably less than or equal to 1 .25 millimetres. The wall thickness of the hollow tubular cooling element may be less than or equal to 1 millimetre. The wall thickness of the hollow tubular cooling element may be less than or equal to 500 micrometres.

The wall thickness of the hollow tubular cooling element may between 100 micrometres and 2 millimetres, preferably between 150 micrometres and 1 .5 millimetres, even more preferably between 200 micrometres and 1.25 millimetres.

The wall thickness of the hollow tubular cooling element may preferably be 250 micrometres (0.25 millimetres).

Providing the hollow tubular cooling element with a peripheral wall having a thickness that is relatively low ensures that the overall internal volume of the hollow tubular cooling element - which is made available for the aerosol to begin the nucleation process as soon as the volatile compounds are released from the aerosol-forming substrate - and the cross-sectional surface area of the hollow tubular cooling element are effectively maximised, whilst at the same time ensuring that the hollow tubular cooling element has the necessary structural strength to prevent a collapse of the aerosolgenerating article as well as to provide some support to the aerosol-forming substrate, and that the RTD of the hollow tubular cooling element is minimised. Greater values of cross-sectional surface area of the cavity of the hollow tubular cooling element are understood to be associated with a reduced speed of the aerosol travelling along the aerosol-generating article, which is also expected to favour aerosol nucleation. Further, it would appear that by utilising a hollow tubular cooling element having a relatively low thickness, it is possible to substantially prevent diffusion of the ventilation air prior to its contacting and mixing with the stream of aerosol, which is also understood to further favour nucleation phenomena. In practice, by providing a more controllably localised cooling of the stream of volatilised species, it is possible to enhance the effect of cooling on the formation of new aerosol particles.

The hollow tubular cooling element preferably has an external diameter that is approximately equal to the external diameter of the aerosol-forming substrate and to the external diameter of the aerosol-generating article.

The hollow tubular cooling element may have an internal diameter. Preferably, the hollow tubular cooling element may have a constant internal diameter along a length of the hollow tubular cooling element. However, the internal diameter of the hollow tubular cooling element may vary along the length of the hollow tubular cooling element.

The hollow tubular cooling element may have an internal diameter of at least 2 millimetres. For example, the hollow tubular cooling element may have an internal diameter of at least 3 millimetres, at least 4 millimetres, or at least 5 millimetres.

The provision of a hollow tubular cooling element having an internal diameter as set out above may advantageously provide sufficient rigidity and strength to the hollow tubular cooling element.

The hollow tubular cooling element may have an internal diameter of no more than 10 millimetres. For example, the hollow tubular cooling element may have an internal diameter of no more than 9 millimetres, no more than 8 millimetres, or no more than 7 millimetres.

The provision of a hollow tubular cooling element having an internal diameter as set out above may advantageously reduce the resistance to draw of the hollow tubular cooling element.

The hollow tubular cooling element may have an internal diameter of between 2 millimetres and 10 millimetres, between 3 millimetres and 9 millimetres, between 4 millimetres and 8 millimetres, or between 5 millimetres and 7 millimetres.

The hollow tubular cooling element may comprise any suitable material. The hollow tubular cooling element may comprise a paper-based material. The hollow tubular cooling element may comprise at least one layer of paper. The paper may be very rigid paper. The paper may be crimped paper, such as crimped heat resistant paper or crimped parchment paper. Preferably, the hollow tubular cooling element may comprise cardboard. The hollow tubular cooling element may be a cardboard tube. The hollow tubular cooling element may be formed from cardboard. The hollow tubular cooling element may comprise a polymeric material. For example, the hollow tubular cooling element may comprise a polymeric film. The polymeric film may comprise a cellulosic film. The hollow tubular cooling element may comprise low density polyethylene (LDPE) or polyhydroxyalkanoate (PHA) fibres. The hollow tube may comprise cellulose acetate tow.

The downstream section may comprise a downstream filter segment. The downstream filter segment may extend to a downstream end of the downstream section. The downstream filter segment may be located at the downstream end of the aerosol-generating article. The downstream end of the downstream filter segment may define the downstream end of the aerosol-generating article.

The downstream filter segment may be located downstream of a hollow tubular cooling element. The downstream filter segment may extend between the hollow tubular cooling element and the downstream end of the aerosol-generating article.

The downstream filter segment is preferably a solid plug, which may also be described as a ‘plain’ plug and is non-tubular. The downstream filter segment therefore preferably has a substantially uniform transverse cross section.

The downstream filter segment is preferably formed of a fibrous filtration material. The fibrous filtration material may be for filtering the aerosol that is generated from the aerosol-forming substrate. Suitable fibrous filtration materials would be known to the skilled person. Particularly preferably, the at least one downstream filter segment comprises a cellulose acetate filter segment formed of cellulose acetate tow.

In certain preferred embodiments, the downstream section includes a single downstream filter segment. In alternative embodiments, the downstream section includes two or more downstream filter segments axially aligned in an abutting end to end relationship with each other.

The downstream filter segment may optionally comprise a flavourant, which may be provided in any suitable form. For example, the downstream filter segment may comprise one or more capsules, beads, or granules of a flavourant, or one or more flavour loaded threads or filaments.

Preferably, the downstream filter segment has a low particulate filtration efficiency.

Preferably, the downstream filter segment is circumscribed by a plug wrap. Preferably, the downstream filter segment is unventilated such that air does not enter the aerosol-generating article along the downstream filter segment.

The downstream filter segment is preferably connected to one or more of the adjacent upstream components of the aerosol-generating article by means of a tipping wrapper.

The downstream filter segment preferably has an external diameter that is approximately equal to the external diameter of the aerosol-generating article. The external diameter of the downstream filter segment may be substantially the same as the external diameter of the hollow tubular cooling element. The external diameter of the downstream filter segment may be between 5 millimetres and 12 millimetres. The diameter of the downstream filter segment may be between 6 millimetres and 10 millimetres, between 7 millimetres and 8 millimetres. In certain embodiments, the diameter of the downstream filter segment may be less than 7 millimetres, for example, between 5 millimetres and 7 millimetres, or between 6 millimetres and 7 millimetres.

The length of the downstream filter segment may be at least 5 millimetres. The length of the downstream filter segment may be at least 10 millimetres. The length of the downstream filter segment may less than 25 millimetres. The length of the downstream filter segment may be less than 20 millimetres. For example, the length of the downstream filter segment may be between 5 millimetres and 25 millimetres, or between 10 millimetres and 25 millimetres, or between 5 millimetres and 20 millimetres, or between 10 millimetres and 20 millimetres.

In some particularly preferred embodiments, there is provided an aerosol-generating article comprising: an aerosol-forming substrate having a substrate length of about 14 millimetres; an upstream element provided upstream of the aerosol-forming substrate, the upstream element having an upstream element length of about 5 millimetres; a hollow tubular cooling element provided downstream of the aerosol-forming substrate, the hollow tubular cooling element having a hollow tubular cooling element length of about 19 millimetres; and a downstream filter segment provided downstream of the hollow tubular cooling element, the downstream filter segment having a filter segment length of about 7 millimetres.

The downstream section may further comprise one or more additional hollow tubular elements.

In certain embodiments, the downstream section may comprise a hollow tubular support element upstream of the hollow tubular cooling element described above. Preferably, the hollow tubular support element abuts the downstream end of the aerosol-forming substrate. Preferably, the hollow tubular support element abuts the upstream end of the hollow tubular cooling element. Preferably, the hollow tubular support element and the hollow tubular cooling element are adjacent to each other and together provide a hollow tubular section within the downstream section.

Alternatively or in addition to the hollow tubular support element, the downstream section may further comprise a downstream hollow tubular element downstream of the hollow tubular cooling element. The downstream hollow tubular element may be provided immediately adjacent to the hollow tubular cooling element. Where the downstream section further comprises an additional downstream hollow tubular element, as described above, the additional downstream hollow tubular element may be formed of the same material as the downstream hollow tubular element, or a different material.

In certain preferred embodiments, the downstream section may comprise a ventilation zone at a location on the downstream hollow tubular element. In one example, this ventilation zone at a location on the downstream hollow tubular element may be provided instead of a ventilation zone at a location on the hollow tubular cooling element. In another example, the ventilation zone at a location on the downstream hollow tubular element may be provided in addition to the ventilation zone provided at a location on the hollow tubular cooling element.

The ventilation zone at a location along the downstream hollow tubular element may comprise a plurality of perforations through the peripheral wall of the downstream hollow tubular element. Preferably, the ventilation zone at a location along the downstream hollow tubular element comprises at least one circumferential row of perforations. In some embodiments, the ventilation zone may comprise two circumferential rows of perforations. For example, the perforations may be formed online during manufacturing of the aerosol-generating article. Preferably, each circumferential row of perforations comprises from 8 to 30 perforations.

The downstream section may optionally further comprise an additional cooling element defining a plurality of longitudinally extending channels such as to make a high surface area available for heat exchange. In other words, one such additional cooling element is adapted to function substantially as a heat exchanger. The plurality of longitudinally extending channels may be defined by a sheet material that has been pleated, gathered, or folded to form the channels. The plurality of longitudinally extending channels may be defined by a single sheet that has been pleated, gathered, or folded to form multiple channels. The sheet may also have been crimped prior to being pleated, gathered, or folded. Alternatively, the plurality of longitudinally extending channels may be defined by multiple sheets that have been crimped, pleated, gathered, or folded to form multiple channels. In some embodiments, the plurality of longitudinally extending channels may be defined by multiple sheets that have been crimped, pleated, gathered, or folded together - that is by two or more sheets that have been brought into overlying arrangement and then crimped, pleated, gathered, or folded as one.

As used herein, “crimped” denotes a sheet having a plurality of substantially parallel ridges or corrugations. Preferably, when the aerosol-generating article has been assembled, the substantially parallel ridges or corrugations extend in a longitudinal direction. As used herein, “gathered”, “pleated”, or “folded” denote that a sheet of material is convoluted, folded, or otherwise compressed or constricted substantially transversely to the cylindrical axis of the aerosol-generating article. A sheet may be crimped prior to being gathered, pleated, or folded. A sheet may be gathered, pleated, or folded without prior crimping.

One such additional cooling element may have a total surface area of between about 300 square millimetre per millimetre length and about 1000 square millimetres per millimetre length.

The additional cooling element preferably offers a low resistance to the passage of air through additional cooling element. Preferably, the additional cooling element does not substantially affect the resistance to draw of the aerosol-generating article. To achieve this, it is preferred that the porosity in a longitudinal direction is greater than 50 percent and that the airflow path through the additional cooling element is relatively uninhibited. The longitudinal porosity of the additional cooling element may be defined by a ratio of the cross-sectional area of material forming the additional cooling element and an internal cross-sectional area of the aerosol-generating article at the portion containing the additional cooling element.

The additional cooling element preferably comprises a sheet material selected from the group comprising a metallic foil, a polymeric sheet, and a substantially non-porous paper or cardboard. In some embodiments, the aerosol-cooling element may comprise a sheet material selected from the group consisting of polyethylene (PE), polypropylene (PP), polyvinylchloride (PVC), polyethylene terephthalate (PET), polylactic acid (PLA), cellulose acetate (CA), and aluminium foil. In a particularly preferred embodiment, the additional cooling element comprises a sheet of PLA.

In particularly preferred embodiments, one or more of the components of the aerosolgenerating article are individually circumscribed by their own wrapper.

In an embodiment, the aerosol-forming substrate is individually wrapped. The upstream element (where present), the aerosol-forming substrate, and the downstream section are then combined together with an outer wrapper. Subsequently, they are combined with the downstream filter element - which has its own wrapper - by means of tipping paper.

Preferably, at least one of the components of the aerosol-generating article is wrapped in a hydrophobic wrapper. A used herein, the term “hydrophobic” refers to a surface exhibiting water repelling properties. One useful way to determine this is to measure the water contact angle. The “water contact angle” is the angle, conventionally measured through the liquid, where a liquid/vapour interface meets a solid surface. It quantifies the wettability of a solid surface by a liquid via the Young equation. Hydrophobicity or water contact angle may be determined by utilizing TAPPI T558 test method and the result is presented as an interfacial contact angle and reported in “degrees” and can range from near zero to near 180 degrees.

In preferred embodiments, the hydrophobic wrapper is one including a paper layer having a water contact angle of about 30 degrees or greater, and preferably about 35 degrees or greater, or about 40 degrees or greater, or about 45 degrees or greater.

By way of example, the paper layer may comprise PVOH (polyvinyl alcohol) or silicon. The PVOH may be applied to the paper layer as a surface coating, or the paper layer may comprise a surface treatment comprising PVOH or silicon, as described in more detail below.

The aerosol-forming substrate may be individually circumscribed by a wrapper. The wrapper circumscribing the aerosol-forming substrate may be a paper wrapper or a non-paper wrapper. Suitable paper wrappers for use in the aerosol-generating system of the present disclosure are known in the art and include, but are not limited to: cigarette papers; and filter plug wraps. Suitable non-paper wrappers are also known in the art and include, but are not limited to sheets of homogenised tobacco materials.

A paper wrapper may have a grammage of at least 15 gsm (grams per square metre), preferably at least 20 gsm. The paper wrapper may have a grammage of less than or equal to 35 gsm, preferably less than or equal to 30 gsm. The paper wrapper may have a grammage from 15 gsm to 35 gsm, preferably from 20 gsm to 30 gsm. In a preferred embodiment, the paper wrapper may have a grammage of 25 gsm. The paper wrapper may have a thickness of at least 25 micrometres, preferably at least 30 micrometres, more preferably at least 35 micrometres. The paper wrapper may have a thickness of less than or equal to 55 micrometres, preferably less than or equal to 50 micrometres, more preferably less than or equal to 45 micrometres. The paper wrapper may have a thickness from 25 micrometres to 55 micrometres, preferably from 30 micrometres to 50 micrometres, more preferably from 35 micrometres to 45 micrometres. In a preferred embodiment, the paper wrapper may have a thickness of 40 microns.

In certain preferred embodiments, the wrapper may be formed of a laminate material comprising a plurality of layers. Preferably, the wrapper is formed of an aluminium co-laminated sheet. The use of a co-laminated sheet comprising aluminium advantageously prevents combustion of the aerosol-forming substrate in the event that the aerosol-forming substrate should be ignited, rather than heated in the intended manner.

A paper layer of the co-laminated sheet may have a grammage of at least 35 gsm, preferably at least 40 gsm. The paper layer of the co-laminated sheet may have a grammage of less than or equal to 55 gsm, preferably less than or equal to 50 gsm. The paper layer of the co-laminated sheet may have a grammage from 35 gsm to 55 gsm, preferably from 40 gsm to 50 gsm. In a preferred embodiment, the paper layer of the co-laminated sheet may have a grammage of 45 gsm.

A paper layer of the co-laminated sheet may have a thickness of at least 50 micrometres, preferably at least 55 micrometres, more preferably at least 60 micrometres. The paper layer of the co-laminated sheet may have a thickness of less than or equal to 80 micrometres, preferably less than or equal to 75 micrometres, more preferably less than or equal to 70 micrometres.

The paper layer of the co-laminated sheet may have a thickness from 50 micrometres to 80 micrometres, preferably from 55 micrometres to 75 micrometres, more preferably from 60 micrometres to 70 micrometres. In a preferred embodiment, the paper layer of the co-laminated sheet may have a thickness of 65 microns.

A metallic layer of the co-laminated sheet may have a grammage of at least 12 gsm, preferably at least 15 gsm. The metallic layer of the co-laminated sheet may have a grammage of less than or equal to 25 gsm, preferably less than or equal to 20 gsm. The metallic layer of the co-laminated sheet may have a grammage from 12 gsm to 25 gsm, preferably from 15 gsm to 20 gsm. In a preferred embodiment, the metallic layer of the co-laminated sheet may have a grammage of 17 gsm.

A metallic layer of the co-laminated sheet may have a thickness of at least 2 micrometres, preferably at least 3 micrometres, more preferably at least 5 micrometres. The metallic layer of the co-laminated sheet may have a thickness of less than or equal to 15 micrometres, preferably less than or equal to 12 micrometres, more preferably less than or equal to 10 micrometres.

The metallic layer of the co-laminated sheet may have a thickness from 2 micrometres to 15 micrometres, preferably from 3 micrometres to 12 micrometres, more preferably from 5 micrometres to 10 micrometres. In a preferred embodiment, the metallic layer of the co-laminated sheet may have a thickness of 6 microns.

The wrapper circumscribing the aerosol-forming substrate may be a paper wrapper comprising PVOH (polyvinyl alcohol) or silicone (or polysiloxane) (or polysiloxane). Addition of PVOH (polyvinyl alcohol) or silicone (or polysiloxane) may improve the grease barrier properties of the wrapper.

The PVOH or silicone (or polysiloxane) may be applied to the paper layer as a surface coating, such as disposed on an exterior surface of the paper layer of the wrapper circumscribing the aerosolforming substrate. The PVOH or silicone (or polysiloxane) may be disposed on and form a layer on the exterior surface of the paper layer of the wrapper. The PVOH or silicone (or polysiloxane) may be disposed on an interior surface of the paper layer of the wrapper. The PVOH or silicone (or polysiloxane) may be disposed on and form a layer on the interior surface of the paper layer of the aerosol generating article.

The paper wrapper comprising PVOH or silicone (or polysiloxane) may have a grammage of at least 20 gsm, preferably at least 25 gsm, more preferably at least 30 gsm. The paper wrapper comprising PVOH or silicone (or polysiloxane) may have a grammage of less than or equal to 50 gsm, preferably less than or equal to 45 gsm, more preferably less than or equal to 40 gsm.

The paper wrapper comprising PVOH or silicone (or polysiloxane) may have a thickness of at least 25 micrometres, preferably at least 30 micrometres, more preferably at least 35 micrometres. The paper wrapper comprising PVOH or silicone (or polysiloxane) may have a thickness of less than or equal to 50 micrometres, preferably less than or equal to 45 micrometres, more preferably less than or equal to 40 micrometres.

The wrapper circumscribing the aerosol-forming substrate may comprise a flame retardant composition comprising one or more flame retardant compounds. The term “flame retardant compounds” is used herein to describe chemical compounds that, when added to or otherwise incorporated into a carrier substrate, such as paper or plastic compounds, provide the carrier substrate with varying degrees of flammability protection. In practice, flame retardant compounds may be activated by the presence of an ignition source and are adapted to prevent or slow the further development of ignition by a variety of different physical and chemical mechanisms.

A flame retardant composition may typically further comprise one of more non-flame retardant compounds, that is, one or more compound - such as a solvent, an excipient, a filler - that does not actively contribute to providing the carrier substrate with flammability protection, but is used to facilitate the application of the flame retardant compound or compounds onto or into the wrapper or both. Some of the non-flame retardant compounds of a flame retardant composition - such as solvents - are volatile and may evaporate from the wrapper upon drying after the flame retardant composition has been applied onto or into the wrapping base material or both. As such, although such non-flame retardant compounds form part of the formulation of the flame retardant composition, they may no longer be present or they may only be detectable in trace amounts in the wrapper of an aerosol-generating article.

For example, the flame retardant composition may comprise a polymer and a mixed salt based on at least one mono, di- and/or tri-carboxylic acid, at least one polyphosphoric, pyrophosphoric and/or phosphoric acid, and a hydroxide or a salt of an alkali or an alkaline earth metal, where the at least one mono, di- and/or tri-carboxylic acid and the hydroxide or salt form a carboxylate and the at least one polyphosphoric, pyrophosphoric and/or phosphoric acid and the hydroxide or salt form a phosphate. Preferably, the flame retardant composition may further comprise a carbonate of an alkali or an alkaline earth metal.

In some preferred embodiments, the aerosol-generating article may be a substantially flat aerosol-generating article or a substantially planar aerosol-generating article. In particular, a thickness of the aerosol-generating article may less than 50 percent of both a length and a width of the aerosol-generating article. Advantageously, a smaller thickness may provide a small temperature gradient or difference across the thickness of the aerosol-generating substrate during heating. Advantageously, this may allow heating of a greater proportion of the aerosol-generating substrate to a temperature at which an aerosol is released whilst minimising the risk of burning the hottest portion of the aerosol-generating substrate closest to the heater. Advantageously, this may also reduce a time required to heat the aerosol-generating substrate sufficiently to release an aerosol.

In some preferred embodiments, the aerosol-generating article comprises: a first planar external surface; a second planar external surface; a cavity; a frame positioned between the first planar external surface and the second planar external surface, the frame at least partially defining the cavity; and an air inlet and an air outlet, and an airflow passage extending between the air inlet and the air outlet through the cavity.

The frame may be a planar frame. The frame may define a frame aperture extending through the thickness of the frame. The frame aperture may define or form the airflow passage of the aerosol-generating article. The frame aperture may define or form the cavity of the aerosol-generating article. For example, the frame may have a hollow cuboid shape or a square hollow tube shape.

The aerosol-forming substrate may be arranged in any suitable location within the aerosolgenerating article. The aerosol-forming substrate may be positioned within the cavity. The aerosolgenerating substrate may be comprised in a layer positioned between the frame and one of the first planar external surface and the second planar external surface.

The aerosol-generating system may comprise an aerosol-generating device. The aerosolgenerating device may comprise a device cavity configured to receive at least a portion of the aerosolforming substrate. Where the aerosol-forming substrate is comprised in an aerosol-generating article, the device cavity may be configured to receive at least a portion of the aerosol-generating article. The device cavity may be configured to receive an upstream portion of the aerosol-generating article. The device cavity may be located at the downstream end of the aerosol-generating device.

The aerosol-generating device may comprise a housing. The housing of the aerosolgenerating device may define the device cavity for receiving at least a portion of the aerosol-forming substrate.

The length of the device cavity may be between about 15 millimetres and about 80 millimetres. Preferably, the length of the device cavity is between about 20 millimetres and about 70 millimetres. More preferably, the length of the device cavity is between about 25 millimetres and about 60 millimetres. More preferably, the length of the device cavity is between about 25 millimetres and about 50 millimetres.

The length of the device cavity may be between about 25 millimetres and about 29 millimetres. Preferably, the length of the device cavity is between about 25 millimetres and about 29 millimetres. More preferably, the length of the device cavity is between about 26 millimetres and about 29 millimetres. Even more preferably, the length of the device cavity is about 27 millimetres or about 28 millimetres.

The length of the device cavity may be such that the downstream section of the aerosolgenerating article, or a portion of the downstream section, is configured to protrude from the device cavity when the aerosol-generating article is fully received in device cavity. The length of the device cavity may be such that a portion of the downstream section (such as the hollow tubular cooling element or downstream filter segment) is configured to protrude from the device cavity when the aerosol-generating article is fully received in the device cavity. The length of the device cavity may be such that a portion of the downstream section (such as the hollow tubular cooling element or downstream filter segment) is configured to be received in the device cavity when the aerosolgenerating article is fully received in the device cavity.

At least 25 percent of the length of the downstream section of the aerosol-generating article may be received in the device cavity when the aerosol-generating article is fully received in the device cavity. At least 30 percent of the length of the downstream section of the aerosol-generating article may be inserted or received in the device cavity when the aerosol-generating article is fully received in the device cavity.

Where the aerosol-generating article is provided with a hollow tubular element, at least 30 percent of the length of the hollow tubular element may be inserted or received in the device cavity, when the aerosol-generating article is fully received in the device cavity. At least 40 percent of the length of the hollow tubular element may be inserted or received in the device cavity, when the aerosol-generating article is fully received in the device cavity. At least 50 percent of the length of the hollow tubular element may be inserted or received in the device cavity, when the aerosolgenerating article is fully received in the device cavity. Various lengths of the hollow tubular element are described in more detail below.

Optimising the amount or length of the aerosol-generating article that is inserted into the device cavity of the aerosol-generating device may enhance the resistance of the aerosol-generating article to inadvertently falling out during use. Particularly, during heating of the aerosol-forming substrate the aerosol-forming substrate size may decrease, such that the external diameter of the aerosolforming substrate may reduce, thereby reducing the extent to which the inserted portion of the aerosol-generating article inserted into the aerosol-generating device is able to frictionally engage with the device cavity. The inserted portion of the aerosol-generating article, or the portion of the aerosol-generating article configured to be received in the device cavity, may be the same length as the device cavity.

A diameter of the device cavity may be between 4 millimetres and 10 millimetres. A diameter of the device cavity may be between 5 millimetres and 9 millimetres. A diameter of the device cavity may be between 6 millimetres and 8 millimetres. A diameter of the device cavity may be between 6 millimetres and 7 millimetres.

A diameter of the device cavity may be substantially the same as or greater than a diameter of the aerosol-generating article. A diameter of the device cavity may be the same as a diameter of the aerosol-generating article in order to establish a tight fit with the aerosol-generating article.

The device cavity may be configured to establish a tight fit with an aerosol-generating article received in the device cavity. As used herein a “tight fit” may refer to a snug fit.

The aerosol-generating device may comprise a peripheral wall. Such a peripheral wall may define the device cavity. The peripheral wall defining the device cavity may be configured to engage with an aerosol-generating article received in the device cavity with a tight fit, so that there is substantially no gap or empty space between the peripheral wall defining the device cavity and the aerosol-generating article when received in device cavity.

Such a tight fit may establish an airtight fit between the device cavity and an aerosol-generating article received in the device cavity. With such an airtight fit, there would be substantially no gap or empty space between the peripheral wall defining the device cavity and the aerosol-generating article for air to flow through. The tight fit between the device cavity and the aerosol-generating article may be established along the entire length of the device cavity or along a portion of the length of the device cavity.

The aerosol-generating device may comprise an airflow path. The airflow path may extend between an inlet and an outlet. The airflow path may be configured to establish fluid communication between the interior of the device cavity and the exterior of the aerosol-generating device. In other words, the airflow path may enable ambient air to be drawn into the device cavity. The airflow path of the aerosol-generating device may be defined within the housing of the aerosol-generating device to enable fluid communication between the interior of the device cavity and the exterior of the aerosolgenerating device. When an aerosol-generating article is fully received in the device cavity, the airflow path may be configured to provide air flow into the aerosol-generating article in order to deliver generated aerosol to a user drawing on the aerosol-generating article from the downstream end of the aerosol-generating article.

The airflow path of the aerosol-generating device may be defined within, or by, a peripheral wall of the housing of the aerosol-generating device. In other words, the airflow path of the aerosolgenerating device may be defined within the thickness of the peripheral wall or by the inner surface of the peripheral wall, or a combination of both. The airflow path may partially be defined by the inner surface of the peripheral wall and may be partially defined within the thickness of the peripheral wall. The inner surface of the peripheral wall defines a peripheral boundary of the device cavity.

The airflow path of the aerosol-generating device may extend from an inlet located at the downstream end, or the mouth end, of the aerosol-generating device to an outlet located away from the downstream end or mouth end of the aerosol-generating device. The airflow path may extend substantially along a direction parallel to the longitudinal axis of the aerosol-generating device.

The aerosol-generating device may comprise a controller. The controller may be configured to control a supply of power to the heating element. Where the heating element is a susceptor element and the aerosol-generating device comprises an inductor coil, the controller may be configured to control a supply of power to the inductor coil. The controller may comprise a microprocessor, which may be a programmable microprocessor, a microcontroller, or an application specific integrated chip (ASIC) or other electronic circuitry capable of providing control. The control circuitry may comprise further electronic components. The control circuitry may be configured to regulate a supply of current to the inductor coil. Current may be supplied to the inductor coil continuously following activation of the aerosol-generating device or may be supplied intermittently, such as on a puff by puff basis. The control circuitry may advantageously comprise DC/AC inverter, which may comprise a Class-D or Class-E power amplifier.

The aerosol-generating device may further comprise a power supply. The power supply may be configured to supply power to the aerosol generator. The controller may be configured to control the supply of power from the power supply to the aerosol generator.

The power supply may be a DC power supply. The power supply may comprise at least one of a battery and a capacitor. In one embodiment, the power supply is a DC power supply having a DC supply voltage in the range of about 2.5 Volts to about 4.5 Volts and a DC supply current in the range of about 1 Amp to about 10 Amps (corresponding to a DC power supply in the range of about 2.5 Watts to about 45 Watts).

Where the aerosol-generating device comprises an inductor coil, the power supply and the controller may be configured to supply an alternating current to the inductor coil.

The aerosol-generating system of the present disclosure may be configured to generate aerosol over a relatively long period of time compared to other aerosol-generating systems, since the aerosol-generating article of the present disclosure comprises a greater volume or weight of aerosolforming substrate than typical aerosol-generating articles. The aerosol-generating device may be configured to provide at least 12 puffs, or at least 15 puffs, or at least 20 puffs, or at least 25 puffs in a single user experience. The aerosol-generating device may be configured to heat aerosol-forming substrate for a period of at least 4 minutes, at least 5 minutes, at least 6 minutes, at least 7 minutes, at least 8 minutes or at least 9 minutes in a single user experience. Where the aerosol-generating device comprises a rechargeable power supply, the rechargeable power supply may be configured to provide at least 12 puffs, or at least 15 puffs, or at least 20 puffs, or at least 25 puffs before the rechargeable power supply requires recharging. Where the aerosol-generating device comprises a rechargeable power supply, the rechargeable power supply may be configured to heat aerosolforming substrate for a period of at least 4 minutes, at least 5 minutes, at least 6 minutes, at least 7 minutes, at least 8 minutes or at least 9 minutes before the rechargeable power supply requires recharging.

The invention is defined in the claims. However, below there is provided a non-exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of another example, embodiment, or aspect described herein.

1. An aerosol-generating system comprising: a heating element; and an aerosol-forming substrate, wherein: the heating element is arranged to heat the aerosol-forming substrate; the heating element has a heating element length; the aerosol-forming substrate has a substrate length, the aerosol-forming substrate length being greater than the heating element length; and the ratio of the aerosol-forming substrate length to the heating element length is between about 1.1 and 3.

2. An aerosol-generating system according to example 1 , wherein the ratio of the aerosol-forming substrate length to the heating element length is between about 1 .1 and 1.16, and optionally is about 1.16.

3. An aerosol-generating system according to example 1 or example 2, wherein the aerosol-forming substrate length is greater than the heating element length by at least 0.5 millimetres, or at least 1 millimetre, or between about 0.5 millimetres and 5 millimetres, or between about 1 millimetres and about 4 millimetres, or between about 1.5 millimetres and about 3 millimetres, or about 2 millimetres.

4. An aerosol-generating system according to any one of examples 1 to 3, wherein the aerosol-forming substrate length is between about 8 millimetres and about 20 millimetres, or between about 10 millimetres and about 18 millimetres, or between about 12 millimetres and about 16 millimetres, or about 14 millimetres, and optionally wherein the length of the aerosol-forming substrate is more than about 12 millimetres.

5. An aerosol-generating system according to any one of examples 1 to 4, wherein the heating element length is between about 7 millimetres and about 19 millimetres, or between about 8 millimetres and about 18 millimetres, or between about 10 millimetres and about 16 millimetres, or about 12 millimetres.

6. An aerosol-generating system according to any one of examples 1 to 5, wherein the aerosol-generating system comprises an upstream end and a downstream end, and wherein a downstream portion of the aerosol-forming substrate extends beyond a downstream end of the heating element.

7. An aerosol-generating system according to example 6, wherein at least one of: an upstream end of the heating element is aligned with an upstream end of the aerosol-forming substrate; and the aerosol-forming substrate does not extend beyond the upstream end of the heating element. 8. An aerosol-generating system according to any one of examples 1 to 7, wherein the aerosol-generating system further comprises an aerosol-generating article comprising the aerosolforming substrate, wherein the aerosol-generating article comprises: a first planar external surface; a second planar external surface; a cavity; a frame positioned between the first planar external surface and the second planar external surface, the frame at least partially defining the cavity; and an air inlet and an air outlet, and an airflow passage extending between the air inlet and the air outlet through the cavity.

9. An aerosol-generating system according to any one of examples 6 to 8, wherein the aerosol-generating system comprises an aerosol-generating article comprising the aerosol-forming substrate, wherein the aerosol-generating article comprises an airflow path between the upstream end and the downstream end, and wherein the aerosol-forming substrate is arranged in the airflow path.

10. An aerosol-generating system according to any one of examples 1 to 9, wherein the aerosol-forming substrate is a segment of aerosol-forming substrate, or a plug of aerosol-forming substrate, or a rod of aerosol-forming substrate.

11. An aerosol-generating system according to any one of examples 1 to 10, further comprising an aerosol-generating device comprising a device cavity configured to receive at least a portion of the aerosol-forming substrate.

12. An aerosol-generating system according to example 11 , wherein the aerosolgenerating device comprises the heating element, and optionally wherein the heating element is arranged at or around the device cavity.

13. An aerosol-generating system according to example 12, wherein the heating element extends into the device cavity and is configured to pierce the aerosol-forming substrate when the aerosol-forming substrate is received in the device cavity.

14. An aerosol-generating system according to example 12, wherein the heating element circumscribes the device cavity, and wherein the heating element is configured to circumscribe the aerosol-forming substrate when the aerosol-forming substrate is received in the device cavity.

15. An aerosol-generating system according to any one of examples 12 to 14, wherein the heating element is a resistive heating element.

16. An aerosol-generating system according to any one of examples 12 to 14, wherein the heating element is a susceptor element. 17. An aerosol-generating system according to example 16, wherein the aerosolgenerating device further comprises an inductor coil, wherein the inductor coil is configured to generate a varying magnetic field that penetrates the susceptor element.

18. An aerosol-generating system according to any one of examples 1 to 11 , wherein the aerosol-generating system comprises an aerosol-generating article, and wherein the aerosolgenerating article comprises the heating element.

19. An aerosol-generating system according to example 18, wherein the heating element is a susceptor element.

20. An aerosol-generating system according to example 19, wherein the aerosolgenerating device further comprises an inductor coil, wherein the inductor coil is configured to generate a varying magnetic field that penetrates the susceptor element when a portion of the aerosol-generating article is received in the device cavity.

21 . An aerosol-generating system according to any one of examples 1 to 20, wherein the aerosol-forming substrate is a solid aerosol-forming substrate.

22. An aerosol-generating system according to any one of examples 1 to 21 , wherein the aerosol-forming substrate comprises tobacco material.

23. An aerosol-generating system according to any one of examples 1 to 22, wherein the aerosol-forming substrate comprises shredded tobacco material.

24. An aerosol-generating system according to any one of examples 1 to 23, wherein the aerosol-forming substrate comprises at least one of: tobacco cut filler; and a shredded sheet of homogenised tobacco material.

25. An aerosol-generating system according to any one of examples 1 to 24, wherein the aerosol-forming substrate comprises an aerosol former, and wherein the aerosol former comprises at least 18 percent by weight of the aerosol-forming substrate, on a dry weight basis, optionally more than 18 percent by weight, on a dry weight basis, and optionally wherein the aerosol former comprises glycerol.

26. An aerosol-generating system according to any one of examples 1 to 25, wherein the aerosol-forming substrate comprises an aerosol former content of at least 18 percent, at least 20 percent, at least 22 percent or at least 25 percent by weight, on a dry weight basis, or optionally wherein the aerosol-forming substrate comprises an aerosol former content of more than 18 percent by weight, on a dry weight basis, and optionally wherein the aerosol former comprises glycerol.

27. An aerosol-generating system according to any one of examples 1 to 26, wherein the aerosol-forming substrate comprises clove, and optionally wherein the aerosol-forming substrate comprises at least 1 percent by weight of clove or at least 2 percent by weight of clove, on a dry weight basis. 28. An aerosol-generating system according to any one of examples 1 to 27, wherein the mass of the aerosol-forming substrate is at least 250 milligrams, or at least 260 milligrams, or at least 270 milligrams, or at least 280 milligrams, and optionally wherein the mass of aerosol-forming substrate is more than 260 milligrams.

29. An aerosol-generating system according to any one of examples 1 to 28, wherein the aerosol-generating system comprises an aerosol-generating article comprising the aerosol-forming substrate, and wherein the aerosol-generating article further comprises a downstream section provided downstream of the aerosol-forming substrate.

30. An aerosol-generating system according to example 29, wherein the downstream section extends to a downstream end of the aerosol-generating article.

31. An aerosol-generating system according to example 29 or example 30, wherein the downstream section comprises a downstream filter segment.

32. An aerosol-generating system according to example 31 , wherein the downstream filter segment is a solid plug.

33. An aerosol-generating system according to example 31 or 32, wherein the downstream filter segment has a length of at least 5 millimetres.

34. An aerosol-generating system according to any one of examples 29 to 33, wherein the downstream section comprises a ventilation zone.

35. An aerosol-generating system according to any one of examples 29 to 34, wherein the downstream section comprises a hollow tubular cooling element.

36. An aerosol-generating system according to example 35, wherein the hollow tubular cooling element has a length of at least 20 millimetres.

37. An aerosol-generating system according to example 35 or 36, wherein the downstream section comprises a ventilation zone at a location along the hollow tubular cooling element.

38. An aerosol-generating system according to any one of examples 35 to 37, wherein the downstream section further comprises a hollow tubular support element upstream of the hollow tubular cooling element.

39. An aerosol-generating system according to any one of examples 35 to 38, wherein the downstream section further comprises a downstream hollow tubular element downstream of the hollow tubular cooling element.

40. An aerosol-generating system according to any one of examples 1 to 39, further comprising an upstream element provided upstream of the aerosol-forming substrate. 41 . An aerosol-generating system according to any one of examples 1 to 40, wherein the aerosol-generating system comprises an aerosol-generating article comprising the aerosol-forming substrate, and wherein the aerosol-generating article has a ventilation level of at least 40 percent.

42. An aerosol-generating system according to any one of examples 1 to 41 , wherein the aerosol-generating system comprises an aerosol-generating article comprising the aerosol-forming substrate, and wherein the length of the aerosol-generating article is between 40 millimetres and 50 millimetres.

43. An aerosol-generating system according to any one of examples 1 to 41 , wherein the aerosol-generating system comprises an aerosol-generating article comprising the aerosol-forming substrate, and wherein the length of the aerosol-generating article is between 70 millimetres and 80 millimetres.

44. An aerosol-generating article comprising an aerosol-forming substrate.

45. An aerosol-generating article according to example 44, wherein: the aerosol-generating article further comprises a heating element; the heating element is arranged to heat the aerosol-forming substrate; the heating element has a heating element length; the aerosol-forming substrate has a substrate length, the aerosol-forming substrate length being greater than the heating element length; and the ratio of the aerosol-forming substrate length to the heating element length is between about 1.1 and 3.

46. An aerosol-generating article according to example 45, wherein the ratio of the aerosol-forming substrate length to the heating element length is between about 1 .1 and 1.16, and optionally is about 1.16.

47. An aerosol-generating article according to example 45 or example 46, wherein the aerosol-forming substrate length is greater than the heating element length by between about 0.5 millimetres and 5 millimetres, or between about 1 millimetres and about 4 millimetres, or between about 1 .5 millimetres and about 3 millimetres, or about 2 millimetres.

48. An aerosol-generating article according to any one of examples 44 to 47, wherein the aerosol-forming substrate length is between about 8 millimetres and about 20 millimetres, or between about 10 millimetres and about 18 millimetres, or between about 12 millimetres and about 16 millimetres, or about 14 millimetres, and optionally wherein the length of the aerosol-forming substrate is more than about 12 millimetres.

49. An aerosol-generating article according to any one of examples 44 to 48, wherein the heating element length is between about 7 millimetres and about 19 millimetres, or between about 8 millimetres and about 18 millimetres, or between about 10 millimetres and about 16 millimetres, or about 12 millimetres.

50. An aerosol-generating article according to any one of examples 44 to 49, wherein the aerosol-generating article comprises: a first planar external surface; a second planar external surface; a cavity; a frame positioned between the first planar external surface and the second planar external surface, the frame at least partially defining the cavity; and an air inlet and an air outlet, and an airflow passage extending between the air inlet and the air outlet through the cavity.

51 . An aerosol-generating article according to any one of examples 44 to 49, wherein the aerosol-generating article comprises an upstream end and a downstream end, and wherein a downstream portion of the aerosol-forming substrate extends beyond the downstream end of the heating element, and optionally wherein at least one of: the upstream end of the heating element is aligned with the upstream end of the aerosol-forming substrate; and the aerosol-forming substrate does not extend beyond the upstream end of the heating element.

52. An aerosol-generating article according to example 51 , wherein the aerosolgenerating article comprises an airflow path between the upstream end and the downstream end, and wherein the aerosol-forming substrate is arranged in the airflow path.

53. An aerosol-generating article according to any one of examples 44 to 52, wherein the aerosol-forming substrate is a segment of aerosol-forming substrate, or a plug of aerosolforming substrate, or a rod of aerosol-forming substrate.

54. An aerosol-generating article according to any one of examples 44 to 53, wherein the heating element is a susceptor element.

55. An aerosol-generating article according to any one of examples 44 to 54, wherein the aerosol-forming substrate is a solid aerosol-forming substrate.

56. An aerosol-generating article according to any one of examples 44 to 55, wherein the aerosol-forming substrate comprises tobacco material.

57. An aerosol-generating article according to any one of examples 44 to 56, wherein the aerosol-forming substrate comprises shredded tobacco material.

58. An aerosol-generating article according to any one of examples 44 to 57, wherein the aerosol-forming substrate comprises at least one of: tobacco cut filler; and a shredded sheet of homogenised tobacco material. 59.. An aerosol-generating article according to any one of examples 44 to 58, wherein the aerosol-forming substrate comprises an aerosol former, and wherein the aerosol former comprises at least 18 percent by weight of the aerosol-forming substrate, on a dry weight basis, optionally more than 18 percent by weight, on a dry weight basis, and optionally wherein the aerosol former comprises glycerol.

60. An aerosol-generating article according to any one of examples 44 to 59, wherein the aerosol-forming substrate comprises an aerosol former content of at least 18 percent, at least 20 percent, at least 22 percent or at least 25 percent by weight, on a dry weight basis, or optionally wherein the aerosol-forming substrate comprises an aerosol former content of more than 18 percent by weight, on a dry weight basis, and optionally wherein the aerosol former comprises glycerol.

61 . An aerosol-generating article according to any one of examples 44 to 60, wherein the aerosol-forming substrate comprises clove, and optionally wherein the aerosol-forming substrate comprises at least 1 percent by weight of clove or at least 2 percent by weight of clove, on a dry weight basis.

62. An aerosol-generating article according to any one of examples 44 to 61 , wherein the mass of the aerosol-forming substrate is at least 250 milligrams, or at least 260 milligrams, or at least 270 milligrams, or at least 280 milligrams, and optionally wherein the mass of aerosol-forming substrate is more than 260 milligrams.

61. An aerosol-generating article according to example 60, wherein the aerosol-forming substrate comprises an aerosol-forming film, the aerosol-forming film comprising a cellulosic based film forming agent, nicotine, and glycerol, wherein the aerosol-forming film has a glycerol content of at least 40 percent by weight.

62. An aerosol-generating article according to any one of examples 44 to 61 , wherein the aerosol-forming substrate comprises a gel composition comprising nicotine, at least one gelling agent and, aerosol former.

63. An aerosol-generating article according to any one of examples 44 to 62, further comprising a downstream section provided downstream of the aerosol-forming substrate.

64. An aerosol-generating article according to example 63, wherein the downstream section extends to a downstream end of the aerosol-generating article.

65. An aerosol-generating article according to example 63 or example 64, wherein the downstream section comprises a downstream filter segment.

66. An aerosol-generating article according to example 65, wherein the downstream filter segment is a solid plug.

67. An aerosol-generating article according to example 65 or example 66, wherein the downstream filter segment has a length of at least 5 millimetres. 68. An aerosol-generating article according to any one of examples 63 to 67, wherein the downstream section comprises a ventilation zone.

69. An aerosol-generating article according to any one of examples 63 to 68, wherein the downstream section comprises a hollow tubular cooling element.

70. An aerosol-generating article according to example 69, wherein the hollow tubular cooling element has a length of at least 20 millimetres.

71. An aerosol-generating article according to example 69 or example 70, wherein the downstream section comprises a ventilation zone at a location along the hollow tubular cooling element.

72. An aerosol-generating article according to any one of examples 69 to 71 , wherein the downstream section further comprises a hollow tubular support element upstream of the hollow tubular cooling element.

73. An aerosol-generating article according to any one of examples 69 to 72, wherein the downstream section further comprises a downstream hollow tubular element downstream of the hollow tubular cooling element.

74. An aerosol-generating article according to any one of examples 44 to 73, further comprising an upstream element provided upstream of the aerosol-forming substrate.

75. An aerosol-generating article according to any one of examples 44 to 74, wherein the aerosol-generating article has a ventilation level of at least 40 percent.

76. An aerosol-generating article according to any one of examples 44 to 75, wherein the length of the aerosol-generating article is between 40 millimetres and 50 millimetres.

77. An aerosol-generating article according to any one of examples 44 to 76, wherein the length of the aerosol-generating article is between 70 millimetres and 80 millimetres.

78. An aerosol-generating article comprising: an aerosol-forming substrate having a substrate length of about 14 millimetres; an upstream element provided upstream of the aerosol-forming substrate, the upstream element having an upstream element length of about 5 millimetres; a hollow tubular element provided downstream of the aerosol-forming substrate, the hollow tubular element having a hollow tubular element length of about 19 millimetres; and a downstream filter segment provided downstream of the hollow tubular element, the downstream filter segment having a downstream filter segment length of about 7 millimetres.

79. An aerosol-generating article comprising an aerosol-forming substrate, wherein the aerosol-forming substrate has a substrate length of at least 13 millimetres, a substrate mass of at least 260 milligrams and an aerosol former content of at least about 18 percent by weight, on a dry weight basis. 80. An aerosol-generating article comprising an aerosol-forming substrate, wherein the aerosol-forming substrate has a substrate length of at least 14 millimetres, a mass of at least 27 milligrams and an aerosol former content of at least 20 percent by weight, on a dry weight basis.

81 . An aerosol-generating article according to example 79 or example 80, wherein the aerosol former is glycerol.

The invention is further described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 shows a schematic side perspective view of an aerosol-generating article for use in an aerosol-generating system according to the present disclosure;

Figure 2 shows a schematic side sectional view an aerosol-generating system according to the present disclosure, the aerosol-generating system comprising the aerosol-generating article of Figure 1 ;

Figure 3 shows a schematic side sectional view of another aerosol-generating system according to the present disclosure, the aerosol-generating system comprising the aerosolgenerating article of Figure 1 ;

Figure 4 shows a schematic side sectional view of another aerosol-generating system according to the present disclosure;

Figure 5 shows a schematic side sectional view of another aerosol-generating system according to the present disclosure;

Figure 6 shows a schematic side perspective view of another aerosol-generating article for use in an aerosol-generating system according to the present disclosure;

Figure 7 shows a schematic side sectional view of another aerosol-generating system according to the present disclosure, the aerosol-generating system comprising the aerosolgenerating article of Figure 6;

Figure 8 shows a perspective view of an aerosol-generating article according to the present disclosure;

Figure 9 shows an exploded perspective view of the aerosol-generating article of Figure 8; and

Figure 10 is a schematic illustration of an aerosol-generating system according to an embodiment of the disclosure, the aerosol-generating system being configured to dielectrically heat the aerosol-forming substrate of the aerosol-generating article of Figures 8 and 9.

Figure 1 shows an aerosol-generating article 10 comprising an aerosol-forming substrate 12 at an upstream end 16 of the aerosol-generating article 10, and a downstream section 14 at a downstream end 18 of the aerosol-generating article 10. In this embodiment, the upstream end of the aerosol-forming substrate 12 defines the upstream end 16 of the aerosol-generating article 10. The downstream section 14 is located immediately downstream of the aerosol-forming substrate 12 and abuts the downstream end of the aerosol-forming substrate 12. The downstream end of the downstream section 14 defines the downstream end 18 of the aerosol-generating article 10.

In this embodiment, the downstream section 14 comprises a hollow tubular cooling element 20 and a downstream filter segment 50.

The aerosol-generating article 10 has an overall length of about 45 millimetres and an external diameter of about 7.2 millimetres.

The aerosol-forming substrate 12 is in the form of a cylindrical rod, having a length, Ls, of about 14 millimetres and an external diameter of about 7.2 millimetres. The aerosol-forming substrate 12 comprises about 50 mg of shredded tobacco material comprising between 15 percent by weight and 20 percent by weight of glycerol, and is wrapped in a plug wrap (not shown).

The hollow tubular cooling element 20 of the downstream section 14 is located immediately downstream of the aerosol-forming substrate, the hollow tubular cooling element 20 being in longitudinal alignment with the aerosol-forming substrate 12. The upstream end of the hollow tubular cooling element 20 abuts the downstream end of the aerosol-forming substrate 12.

The hollow tubular cooling element 20 defines a hollow section of the aerosol-generating article 10. The hollow tubular cooling element 20 does not substantially contribute to the overall RTD of the aerosol-generating article 10. In more detail, an RTD of the hollow tubular cooling element 20 is about 0 millimetres of water gauge (mm H2O).

The hollow tubular cooling element 20 is provided in the form of a hollow cylindrical tube made of cardboard. The hollow tubular cooling element 20 defines an internal cavity that extends all the way from an upstream end of the hollow tubular cooling element 20 to a downstream end of the hollow tubular cooling element 20. The internal cavity is substantially empty, and so substantially unrestricted airflow is enabled along the internal cavity.

The hollow tubular cooling element 20 has a length of about 21 millimetres, an external diameter of about 7.2 millimetres, and an internal diameter of about 6.7 millimetres. A thickness of a peripheral wall of the hollow tubular cooling element 20 is about 0.5 millimetres.

The aerosol-generating article 10 comprises a ventilation zone 30 provided at a location along the hollow tubular cooling element 20. The ventilation zone 30 comprises a circumferential row of openings or perforations circumscribing the hollow tubular cooling element 20. The perforations of the ventilation zone 30 extend through the wall of the hollow tubular cooling element 20, in order to allow fluid ingress into the internal cavity from the exterior of the aerosol-generating article 10. A ventilation level of the aerosol-generating article 10 is about 40 percent.

The downstream filter segment 50 extends from the downstream end of the hollow tubular cooling element 20 to the downstream or mouth end 18 of the aerosol-generating article 10. The downstream filter segment 50 has a length of about 10 millimetres. An external diameter of the downstream filter segment 50 is about 7.2 millimetres. The downstream filter segment 50 comprises a low-density, cellulose acetate filter segment. The RTD of the downstream filter segment 50 is about 8 millilitres of water gauge (mm H₂O). The downstream filter segment 50 may be individually wrapped by a plug wrap (not shown).

The aerosol-generating article 10 further comprises an upstream wrapper 44 circumscribing the aerosol-forming substrate 12 and the hollow tubular cooling element 20. Accordingly, the upstream wrapper 44 overlies the perforations of the ventilation zone 30 provided on the hollow tubular cooling element 20. The upstream wrapper 44 may also comprise a circumferential row of perforations. The perforations of the upstream wrapper 44 overlap the perforations provided on the hollow tubular cooling element 20 in the ventilation zone 30.

The aerosol-generating article 10 also comprises a tipping wrapper 52 circumscribing the hollow tubular cooling element 20 and the mouthpiece element 50. The tipping wrapper 52 overlies the portion of the upstream wrapper 44 that overlies the hollow tubular cooling element 20. In this arrangement, the tipping wrapper 52 effectively joins the mouthpiece element 50 to the rest of the components of the aerosol-generating article 10. The width of the tipping wrapper is about 26 millimetres. The tipping wrapper 52 overlies the perforations of the ventilation zone 30 provided on the hollow tubular cooling element 20 and the upstream wrapper 44. Additionally, the ventilation zone 30 may comprise a circumferential row of perforations provided on the tipping wrapper 52. The perforations of the tipping wrapper 52 overlap the perforations provided on the hollow tubular cooling element 20 and the upstream wrapper 44.

Figure 2 illustrates an aerosol-generating system 100 according to the present disclosure. The aerosol-generating system 100 comprises the aerosol-generating article 10 of Figure 1 , and a downstream portion of an aerosol-generating device 1 . The aerosol-generating device 1 comprises a housing 4, extending between a downstream end 2 and an upstream end (not shown). The housing 4 comprises a peripheral wall 6. The peripheral wall 6 defines a device cavity for receiving a portion of the aerosol-generating article 10. The device cavity is defined by a substantially closed, upstream end and an open, downstream end. The downstream end of the device cavity is located at the downstream end 2 of the aerosol-generating device 1. The aerosol-generating article 10 is configured to be received through the open, downstream end of the device cavity and is configured to abut the closed, upstream end of the device cavity when the aerosol-generating article 10 is fully received in the device cavity.

An airflow path 5 is defined within the peripheral wall 6 of the aerosol-generating device 1 . The airflow path 5 extends between an inlet 7, located at the downstream end 2 of the aerosol-generating device 1 , and the closed end of the device cavity. Ambient air may be drawn into the aerosolgenerating device 1 through the inlet 7, along the airflow path 5 and into the device cavity through an aperture (not shown) provided at the closed end of the device cavity. Ambient air drawn into the device cavity through the airflow path 5 may enter the aerosol-generating article 10 at the upstream end 16 of the aerosol-forming substrate 12. In this way, the airflow path 5 of the aerosol-generating device 1 is in fluid communication with the aerosol-forming substrate 12 of the aerosol-generating article 10.

The aerosol-generating device 1 further comprises a heating element 15, in the form of a resistive heating element, a controller (not shown), and a power supply (not shown), in the form of a rechargeable battery. The controller is configured to control a supply of power from the power supply to the resistive heating element 15 for heating the heating element 15. The resistive heating element 15 is configured to controllably heat the aerosol-forming substrate 12 of the aerosol-generating article 10 during use, when the aerosol-generating article 10 is fully received in the device cavity.

The resistive heating element 15 extends from an upstream end to a downstream end defining a heating zone in the device cavity. The resistive heating element 15 has a length, LH, of about 12 millimetres. The length of the resistive heating element is about 2 millimetres shorter than the length of the aerosol-forming substrate 12 in the aerosol-generating article 10. When the aerosol-generating article 10 is fully received in the device cavity, as shown in Figure 2, the resistive heating element 15 is arranged such that the upstream end of the resistive heating element 15 aligns with the upstream end of the aerosol-forming substrate 12. Accordingly, an upstream portion of the aerosol-forming substrate 12 is circumscribed by the resistive heating element 15, and a downstream portion of the aerosol-forming substrate 12 is not circumscribed by the resistive heating element 15. The upstream portion of the aerosol-forming substrate 12 is arranged directly adjacent to the resistive heating element 15 and receives radiant heat directly from the resistive heating element 15 when the heating element is heated. The downstream portion of the aerosol-forming substrate 12, which has a length, LD, of about 2 millimetres, is exposed to less direct heat from the resistive heating element 15 when the heating element is heated.

In this embodiment, the ratio of the substrate length, Ls, to the heating element length, LH, is about 1.16.

When the aerosol-generating article 10 is fully received in the device cavity, an upstream portion of the hollow tubular cooling element 20 is also received in the device cavity. Such an upstream portion of the hollow tubular cooling element 20 is about 14 millimetres in length. Accordingly, about 28 millimetres of the aerosol-generating article 10 is received in the device cavity and about 17 millimetres of the aerosol-generating article 10 is located outside of the device cavity. In other words, a length, LP, of about 17 millimetres of the aerosol-generating article 10 protrudes from the aerosol-generating device 1 when the aerosol-generating article 10 is fully received in the device cavity. The ventilation zone 30 is arranged to be exposed when the aerosol-generating article 10 is fully received in the device cavity.

In use, the aerosol-generating article 10 is fully received in the device cavity of the aerosolgenerating device 1 when the aerosol-forming substrate 12 is inserted into the device cavity, and the upstream portion of the downstream section 14 protrudes from the aerosol-generating device 1 . The upstream portion of the downstream section 14 protruding from the aerosol-generating device 1 includes the mouthpiece element 50 and a portion of the tubular cooling element 20 comprising the ventilation zone 30, such that the perforations of the ventilation zone 30 are not covered by the peripheral wall 6 of the aerosol-generating device 1 .

When a user takes a puff on the aerosol-generating system 100, the pressure sensor 8 senses the air being drawn through the airflow path 5 from the inlet 7 through to the device cavity. In response to the pressure sensor 8 sensing a puff, the controller and power supply (not shown) supply power to the resistive heating element 15 to heat the heating element. The resistive heating element 15 generates heat, which is transferred directly to the upstream portion of the aerosol-forming substrate 12, which is directly adjacent to the heating element 15. This heating causes volatile compounds in the heated aerosol-forming substrate 12 to be released.

The downstream portion of the aerosol-forming substrate 12, which is not arranged directly adjacent to the resistive heating element 15, is heated more slowly than the upstream portion, both by conduction through the aerosol-forming substrate, radiation from the heating element that was not absorbed by the upstream portion, and by the heated volatile compounds released from the upstream portion that are drawn from the upstream portion of the aerosol-forming substrate 12 through the downstream portion with the user’s puff. This heating of the downstream portion of the aerosolforming substrate also causes the downstream portion of the aerosol-forming substrate to release volatile compounds.

The released volatile compounds from both the upstream portion and the downstream portion of the aerosol-forming substrate are entrained in the airflow through the aerosol-generating article, and drawn through the downstream section 14. In the downstream section 14 the volatile compounds cool and condense to form an aerosol, which is delivered to a user at the upstream end 18 of the aerosol-generating article 10.

Figure 3 shows another aerosol-generating system 100 according to the present disclosure. The aerosol-generating system 100 of Figure 3 comprises an aerosol-generating device 1 which is substantially similar to the aerosol-generating device 1 described above in relation to the embodiment of Figure 2, and like reference numerals are used to denote like features. The aerosol-generating system 100 of Figure 3 also comprises the aerosol-generating article 10 of Figure 1 , which includes all of the same features as the aerosol-generating article 10 of Figure 2. The aerosol-generating device 1 of Figure 3 differs from the aerosol-generating device 1 of Figure 2 in that the resistive heating element 15 is an internal heating element, rather than an external heating element. The resistive heating element 15 of the aerosol-generating device 1 of Figure 3 has the form of a pin that extends into the device cavity from the substantially closed upstream end. The resistive heating element 15 of the aerosol-generating device 1 of Figure 3 is configured to penetrate the aerosol-forming substrate 12 of the aerosol-generating article 10 when the aerosolgenerating article 10 is fully received in the device cavity. The resistive heating element 15 has a length, LH, of about 12 millimetres, which is less than the length, Ls, of the aerosol-forming substrate 12, which is about 14 millimetres. When the aerosol-generating article 10 is fully received in the device cavity, the resistive heating element 15 extends into an upstream portion of the aerosolforming substrate 12 by a distance, LH, of 12 millimetres, and a downstream portion of the aerosolforming substrate 12, having a length, LD, of about 2 millimetres, is not penetrated by the resistive heating element 15.

Figure 4 shows another aerosol-generating system 100 according to the present disclosure. The aerosol-generating system 100 of Figure 4 comprises an aerosol-generating device 1 which is substantially similar to the aerosol-generating device 1 described above in relation to the embodiment of Figure 2, including all of the same features, and like reference numerals are used to denote like features. The aerosol-generating system 100 of Figure 3 also comprises an aerosol-generating article 10, which is substantially similar to the aerosol-generating article 10 of Figure 1 , and like reference numerals are used to denote like features.

The aerosol-generating article 10 of Figure 4 differs from the aerosol-generating article 10 of Figure 1 in that the aerosol-generating article 10 of Figure 4 comprises an upstream element 28 at the upstream end of the aerosol-generating article 10. The upstream element 28 abuts the upstream end of the aerosol-forming substrate 12 and defines the upstream end 16 of the aerosol-generating article. The upstream element 28 is a porous plug element with a low resistance to draw. The upstream element 28 helps to protect the aerosol-forming substrate 12, and ensure that debris from the aerosol-forming substrate 12 does not fall out of the aerosol-generating article 10 at the upstream end 16. In this embodiment, the upstream element 28 has a length of 5 millimetres, and the downstream filter element 50 has a reduced length of 5 millimetres, such that the overall length of the aerosol-generating article 10 is not changed by the introduction of the upstream element 28.

The aerosol-generating device 1 of Figure 4 is configured such that an upstream end of the resistive heating element 15 aligns with an upstream end of the aerosol-forming substrate 12 of the aerosol-generating article 10 when the aerosol-generating article 10 is fully received in the device cavity. The resistive heating element 15 has a length, LH, of about 12 millimetres, which is less than the length, Ls, of the aerosol-forming substrate 12, which is about 14 millimetres. As in Figure 2, when the aerosol-generating article 10 is fully received in the device cavity, an upstream portion of the aerosol-forming substrate 12 is circumscribed by the resistive heating element 15, and a downstream portion of the aerosol-forming substrate 12 is not circumscribed by the resistive heating element 15. The upstream portion of the aerosol-forming substrate 12 is arranged directly adjacent to the resistive heating element 15 and receives radiant heat directly from the resistive heating element 15 when the heating element is heated. The downstream portion of the aerosol-forming substrate 12, which has a length, LD, of about 2 millimetres, is exposed to less direct heat from the resistive heating element 15 when the heating element is heated. The ratio of the substrate length, Ls, to the heating element length, LH, is about 1.16.

Figure 5 shows another aerosol-generating system 100 according to the present disclosure. The aerosol-generating system 100 of Figure 5 comprises an aerosol-generating device 1 , which is substantially similar to the aerosol-generating device 1 described above in relation to the embodiment of Figure 4, and like reference numerals are used to denote like features. The aerosol-generating system 100 of Figure 5 also comprises the aerosol-generating article 10 of Figure 4, which includes all of the same features as the aerosol-generating article 10 of Figure 4.

The aerosol-generating device 1 of Figure 5 differs from the aerosol-generating device 1 of Figure 2 in that the heating element 15 is a susceptor element rather than a resistive heating element. The susceptor element 15 of the aerosol-generating device of Figure 5 has the same size and form as the resistive heating element 15 of the aerosol-generating device 1 of Figure 4, and is arranged similarly to the resistive heating element 15. The susceptor element 15 circumscribes the device cavity to heat the outer surface of the aerosol-forming substrate 12 of the aerosol-generating article 10 when the aerosol-generating device 1 is fully received in the device cavity. The aerosolgenerating device 1 of Figure 5 further comprises an inductor coil 16, circumscribing the susceptor element 15. The inductor coil 16 has the same length as the susceptor element 15, and extends from the upstream end of the susceptor element 15 to the downstream end of the susceptor element 15.

The aerosol-generating device 1 of Figure 5 comprises a power supply and a controller (not shown), which are configured to supply an alternating current to the inductor coil 16. When an alternating current is supplied to the inductor coil 16, the inductor coil 16 generates an alternating magnetic field. In the arrangement of the aerosol-generating device 1 of Figure 5, the susceptor element 15 is located in the alternating magnetic field generated by the inductor coil 16 when an alternating current is supplied to the inductor coil 16. The susceptor element 15 is configured to heat up when penetrated by the alternating magnetic field, and in turn to transfer the heat to the aerosolforming substrate 12 in the aerosol-generating article 10 to generate an aerosol. Figure 6 shows an aerosol-generating article 10 that is substantially similar to the aerosolgenerating device 1 of Figure 4, and like reference numerals denote like features.

The aerosol-generating article 10 of Figure 6 comprises an upstream element 28, an aerosolforming substrate 12 at an upstream end 16 of the aerosol-generating article 10, and a downstream section 14 at a downstream end 18 of the aerosol-generating article 10. In this embodiment, the upstream end of the upstream element 28 defines the upstream end 16 of the aerosol-generating article 10. The aerosol-forming substrate 12 is located immediately downstream of the upstream element 28 and abuts the downstream end of the upstream element 28. The downstream section 14 is located immediately downstream of the aerosol-forming substrate 12 and abuts the downstream end of the aerosol-forming substrate 12. The downstream end of the downstream section 14 defines the downstream end 18 of the aerosol-generating article 10. The downstream section 14 comprises a hollow tubular cooling element 20 and a downstream filter segment 50, and comprises a ventilation zone 30 provided at a location along the hollow tubular cooling element 20.

In this embodiment, the aerosol-generating article 10 comprises a heating element 15, in the form of a susceptor element. The susceptor element 15 comprises a strip of aluminium embedded in the aerosol-forming substrate 12. The susceptor element 15 is arranged to extend along a central longitudinal axis of the aerosol-generating article, with an upstream end of the susceptor element 15 aligned with the upstream end of the aerosol-forming substrate 12. The length, LH, of the susceptor element 15 is less than the length, Ls, of the aerosol-forming substrate 12. In this embodiment, the susceptor length, LH, is about 12 millimetres and the substrate length, Ls, is about 14 millimetres.

Accordingly, an upstream portion of the aerosol-forming substrate 12 surrounds the susceptor element 15, and a downstream portion of the aerosol-forming substrate 12 does not surround the susceptor element 15.. The upstream portion of the aerosol-forming substrate 12 is arranged directly adjacent to the susceptor element 15, and receives radiant heat directly from the susceptor element 15, when the susceptor element is heated. The downstream portion of the aerosol-forming substrate, which has a length, LD, of about 2 millimetres, is exposed to less direct heat from the susceptor element 15 when the susceptor element is heated.

Figure 7 illustrates an aerosol-generating system 100 according to the present disclosure. The aerosol-generating system 100 comprises the aerosol-generating article 10 of Figure 6, and a downstream portion of an aerosol-generating device 1 . The aerosol-generating device 1 of Figure 7 is substantially similar to the aerosol-generating device 1 of Figure 5, and like reference numerals denote like features.

The aerosol-generating device 1 of Figure 7 differs from the aerosol-generating device 1 of Figure 5 in that the aerosol-generating device 1 of Figure 7 does not comprise a susceptor element 15, as in this embodiment the susceptor element 15 is provided in the aerosol-generating article 1. In the aerosol-generating device 1 of Figure 7, the inductor coil 16 circumscribes the device cavity. The inductor coil 16 has the same length as the susceptor element 15 in the aerosolgenerating article 10, and is arranged such that an upstream end of the inductor coil 16 is aligned with the upstream end of the susceptor element 15 in the aerosol-generating article 10 when the aerosol-generating article 10 is fully received in the device cavity.

The aerosol-generating device 1 of Figure 7 comprises a power supply and a controller (not shown), which are configured to supply an alternating current to the inductor coil 16. When an alternating current is supplied to the inductor coil 16, the inductor coil 16 generates an alternating magnetic field in the device cavity. In the arrangement of the aerosol-generating system 100 of Figure 7, the susceptor element 15 of the aerosol-generating article 10 is located in the alternating magnetic field generated by the inductor coil 16 when the aerosol-generating article 10 is fully received in the device cavity and when an alternating current is supplied to the inductor coil 16. The susceptor element 15 is configured to heat up when penetrated by the alternating magnetic field, and in turn to transfer the heat to the aerosol-forming substrate 12 in the aerosol-generating article 10 to generate an aerosol.

When a user takes a puff on the aerosol-generating system 100 of Figure 7, the pressure sensor 8 senses the air being drawn through the airflow path 5 from the inlet 7 through to the device cavity. In response to the pressure sensor 8 sensing a puff, the controller and power supply (not shown) supply an alternating current to the inductor coil to generate an alternating magnetic field in the device cavity. The aerosol-generating article 1 is fully received in the device cavity, and the susceptor element 15 is heated when it is penetrated by the alternating magnetic field from the inductor coil 16. The susceptor element 15 generates heat, which is transferred directly to the upstream portion of the aerosol-forming substrate 12, which is directly adjacent to the susceptor element 15. This heating causes volatile compounds in the heated aerosol-forming substrate 12 to be released.

The downstream portion of the aerosol-forming substrate 12, which is not arranged directly adjacent to the susceptor element 15, is heated more slowly than the upstream portion, both by conduction through the aerosol-forming substrate, and by conduction from the heated volatile compounds released from the upstream portion that are drawn from the upstream portion of the aerosol-forming substrate 12 through the downstream portion with the user’s puff. This heating of the downstream portion of the aerosol-forming substrate 12 also causes the downstream portion of the aerosol-forming substrate 12 to release volatile compounds.

The released volatile compounds from both the upstream portion and the downstream portion of the aerosol-forming substrate 12 are entrained in the airflow through the aerosol-generating article 10, and drawn through the downstream section 14. In the downstream section 14 the volatile compounds cool and condense to form an aerosol, which is delivered to a user at the upstream end 18 of the aerosol-generating article 10.

Figure 8 shows an aerosol-generating article 10 comprising a first planar external layer 124 forming a first planar external surface 121 , a second planar external layer 125 forming a second planar external surface 122, and a frame 150 positioned between the first planar external layer 124 and the second planar external layer 125. The first planar external layer 124 and the second planar external layer 125 both comprise an aerosol-generating substrate comprising an aerosol-generating material, namely tobacco. However, it will be understood that in some embodiments only one of the first planar external layer 124 and the second planar external layer 125 may comprise an aerosolgenerating substrate. It will also be appreciated that in other embodiments the aerosol-generating substrate may be positioned in other locations in the aerosol-generating article 10.

The aerosol-generating article 10 has a length extending in an x-direction, a width extending in a y-direction and a thickness extending in a z-direction. The aerosol-generating article 10 has a length of 30 millimetres, a width of 10 millimetres, and a thickness of 3.1 millimetres.

The aerosol-generating article 10 is a substantially flat aerosol-generating article or substantially planar aerosol-generating article. In particular, the thickness of the aerosol-generating article 10 is less than 50 percent of both the length and the width of the aerosol-generating article. The aerosol-generating article 10 has a generally rectangular cuboid shape and a laminated structure formed by the first planar external layer 124, the frame 150 and the second planar external layer 125. The first planar external layer 124, the frame 150 and the second planar external layer 125 are bonded together with an adhesive, in particular guar gum, as discussed in more detail below in relation to Figure 9.

Figure 9 shows an exploded view of the aerosol-generating article 10 of Figure 1 . The frame 150 has a length of 30 millimetres, a width of 10 millimetres, and a thickness of 2.7 millimetres. The frame 150 is made from cardboard and defines a frame aperture extending through the thickness of the frame 150. The frame aperture at least partially forms a cavity 130. The cavity 130 has length of 26 millimetres, a width of 6 millimetres, and a thickness of 2.7 millimetres. Therefore, the cavity 130 has a volume of about 421 .2 cubic millimetres. In this embodiment, the cavity 30 is substantially empty.

The frame 150 has a frame inner surface 152 extending in the z-direction or the transverse direction between the first planar external surface 121 and the second planar external surface 122. The frame inner surface 152 defines a cavity outer wall. The frame 150 has a frame outer surface 153 extending in the z-direction or the transverse direction between the first planar external surface 121 and the second planar external surface 122. The frame outer surface 153 at least partially defines one or more external surfaces of the aerosol-generating article, such as the front wall 113 and the back wall 114.

The frame 150 comprises a peripheral wall 151 that circumscribes the cavity 130. In more detail, the peripheral wall 151 is defined by the frame inner surface 152 and the frame outer surface 152. The peripheral wall 151 has a radial thickness, as measured between the frame inner surface 152 and the frame outer surface 153 in the x/y plane, of about 2 millimetres.

The first planar external layer 124 and the second planar external layer 125 have a thickness of 200 micrometres and are in physical contact with the frame 150. The first planar external layer 124 and the second planar external layer 125 are bonded to the frame with an adhesive 15. The first planar external layer 124 overlies an end of the cavity 130 and forms a first cavity end wall 131 . The second planar external layer 125 overlies an opposite end of the cavity 130 and forms a second cavity end wall 132. That is, the frame 150, the first planar external layer 124 and the second planar external layer 125 collectively define the cavity 130.

The air inlet 111 and the air outlet 112 are defined by, and extend through, the peripheral wall 151 of the frame 150. The air inlet 111 and the air outlet 112 each have a rectangular cross-section, a width of 2 millimetres, and a thickness of 0.9 millimetres. An airflow passage extends between the air inlet 111 and the air outlet 112 through the cavity 130.

Figure 10 is a schematic illustration of an aerosol-generating system 100 according to an embodiment of the disclosure. The aerosol-generating system 100 comprises the aerosol-generation article 10 of Figures 8 and 9. The aerosol-generating system 100 further comprises an aerosolgenerating device 1 for heating the aerosol-generating article 10. The aerosol-generating device 1 comprises a device cavity 9 that is configured to removably receive the aerosol-generating article 10. The aerosol-generating device 1 is configured to generate an alternating electric field in the device cavity 9 for dielectrically heating the aerosol-forming substrate of the aerosol-generating article 10, when the aerosol-generating article 10 is received in the device cavity 9.

The aerosol-generating device 1 comprises a load capacitor comprising a pair of electrodes 15, a first electrode and a second electrode, which are separated by the device cavity 9. The device cavity 9 and the aerosol-generating article 10 are configured such that the aerosol-forming substrate is in close proximity to both the first electrode 15 and the second electrode 15 when the aerosolgenerating article 10 is received in the device cavity 9. When the aerosol-generating article 10 is received in the device cavity 9, with the aerosol-forming substrate arranged between the first electrode 15 and the second electrode 15, the first electrode 15, the second electrode 15, and the aerosol-forming substrate form the load capacitor CL.

In this aerosol-generating system 100, the first electrode 15 and the second electrode 15 form the heating element. The first electrode 15 and the second electrode 15 are substantially identical, and each electrode 15 extends from an upstream end of the device cavity 9 to a downstream end of the device cavity 9, defining a heating zone in the device cavity 9. Each electrode 15 has a length, LH, of about 26 millimetres. The length of the first electrode 15 and the second electrode 15 is about 4 millimetres shorter than the length of the aerosol-forming substrate in the aerosol-generating article 10, which is about 30 millimetres. When the aerosol-generating article 10 is fully received in the device cavity 9, the first electrode 15 and the second electrode 15 are arranged such that the upstream end of the electrodes 15 aligns with the upstream end of the aerosol-forming substrate. Accordingly, an upstream portion of the aerosol-forming substrate is arranged between the first electrode 15 and the second electrode 15, and a downstream portion of the aerosol-forming substrate is not arranged between the first electrode 15 and the second electrode 15.. The downstream portion of the aerosol-forming substrate, which has a length, LD, of about 2 millimetres, is exposed to less heat when the aerosol-generating system 100 is activated to dielectrically heat the aerosol-forming substrate.

In this embodiment, the ratio of the substrate length, Ls, to the heating element length, LH, is about 1.15.

The first electrode 15 and the second electrode 15 form part of a feedback loop of an oscillation circuit 60.

In some embodiments, the width of the aerosol-generating article 10 is slightly greater than the space between the first electrode 15 and the second electrode 15, such that the distal end of the aerosol-forming substrate is slightly compressed between the first electrode 15 and the second electrode 15. In some embodiments, the aerosol-generating article 10, in an initial, uncompressed form has a width between 5-30% larger than the distance between the first electrode 15 and the second electrode 15. This may reduce or prevent the build-up of air between the first electrode 15 and the second electrode 15 when the aerosol-generating article 10 is received in the device cavity 9, and may decrease the distance between first and second electrodes 15 for dielectric heating, thereby improving dielectric properties of the load capacitor CL formed by the first and second electrodes 15 and the aerosol-forming substrate.

In this embodiment, the aerosol-generating device 1 comprises the first electrode 15 and the second electrode 15. However, it will be appreciated that in other embodiments, the aerosolgenerating article 10 may comprise the first electrode 15 and the second electrode 15. In these embodiments, the aerosol-generating device 1 comprises a first electrical contact and a second electrical contact for contacting the first electrode 15 and the second electrode 15, respectively, when the aerosol-generating article 10 is received in the device cavity 9, such that an electrical connection is made between the first electrode 15 and the first electrical contact, and the second electrode 15 and the second electrical contact. The aerosol-generating device 1 further comprises a power supply 65, control electronics 70 electrically coupled to the oscillation circuit 60, and user interface (not shown), in the form of a touch screen display, electrically coupled to the control electronics 70. In this embodiment, the power supply 65 is a rechargeable lithium ion battery, for example with one or more lithium ion battery cells, and the aerosol-generating device 1 comprises a power connector that enables the aerosolgenerating device 1 to be connected to a mains power supply for recharging the power supply.

In use, power is supplied to the oscillation circuit 60 from the power supply 65 when a user activates the aerosol-generating device 1 . The control electronics 70 controls the supply of power from the power supply 65 to the oscillation circuit 60.

In this embodiment, the aerosol-generating device 1 is activated by a user pressing an activation button (not shown), which is provided on an external surface of the aerosol-generating device 1 . It will be appreciated that in other embodiments, the aerosol-generating device 1 may be activated in another manner, such as on detection of a user drawing on the aerosol-generating article 10 or on a mouthpiece (not shown) of the aerosol-generating device 1 by a puff sensor. When power is supplied to the oscillation circuit 60, the oscillation circuit 60 generates an alternating electric field in the device cavity 9, between the first and second electrodes 15 for dielectrically heating the aerosol-generating article 10, and in particular for dielectrically heating the aerosol-forming substrate, in the device cavity 9, to release volatile compounds from the aerosol-forming substrate, which condense to form an aerosol that is inhalable by a user of the aerosol-generating system 100.

For the purpose of the present description and of the appended claims, except where otherwise indicated, all numbers expressing amounts, quantities, percentages, and so forth, are to be understood as being modified in all instances by the term "about". Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein. In this context, therefore, a number A is understood as A ± 10% of A. Within this context, a number A may be considered to include numerical values that are within general standard error for the measurement of the property that the number A modifies. The number A, in some instances as used in the appended claims, may deviate by the percentages enumerated above provided that the amount by which A deviates does not materially affect the basic and novel characteristic(s) of the claimed invention. Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein.

Claims

2. An aerosol-generating system according to claim 1 , wherein the ratio of the aerosol-forming substrate length to the heating element length is between about 1.1 and 1.16, and optionally is about 1.16.

3. An aerosol-generating system according to claim 1 or claim 2, wherein the aerosolgenerating system further comprises an aerosol-generating article comprising the aerosol-forming substrate.

4. An aerosol-generating system according to claim 3, wherein the aerosol-generating article comprises: a first planar external surface; a second planar external surface; a cavity; a frame positioned between the first planar external surface and the second planar external surface, the frame at least partially defining the cavity; and an air inlet and an air outlet, and an airflow passage extending between the air inlet and the air outlet through the cavity.

5. An aerosol-generating system according to any one of claims 1 to 4, wherein the aerosolgenerating system comprises an upstream end and a downstream end, and wherein a downstream portion of the aerosol-forming substrate extends beyond a downstream end of the heating element, and optionally wherein an upstream end of the heating element is aligned with an upstream end of the aerosol-forming substrate.

6. An aerosol-generating system according to claim 5, wherein the aerosol-forming substrate does not extend beyond the upstream end of the heating element.

7. An aerosol-generating system according to claim 5 or claim 6, wherein the aerosolgenerating system comprises an aerosol-generating article comprising the aerosol-forming substrate, wherein the aerosol-generating article comprises an airflow path between the upstream end and the downstream end, and wherein the aerosol-forming substrate is arranged in the airflow path.

8. An aerosol-generating system according to any one of claims 1 to 7, further comprising an aerosol-generating device comprising a device cavity configured to receive at least a portion of the aerosol-forming substrate.

9. An aerosol-generating system according to claim 8, wherein the aerosol-generating device comprises the heating element, and optionally wherein the heating element is arranged at or around the device cavity.

10. An aerosol-generating system according to claim 9, wherein the heating element extends into the device cavity and is configured to pierce the aerosol-forming substrate when the aerosolforming substrate is received in the device cavity.

11. An aerosol-generating system according to claim 9, wherein the heating element circumscribes the device cavity, and wherein the heating element is configured to circumscribe the aerosol-forming substrate when the aerosol-forming substrate is received in the device cavity.

12. An aerosol-generating system according to any one of claims 1 to 8, wherein the aerosolgenerating system comprises an aerosol-generating article comprising the aerosol-forming substrate, and wherein the aerosol-generating article comprises the heating element.

13. An aerosol-generating system according to claim 12, wherein the heating element is a susceptor element, and wherein the aerosol-generating device further comprises an inductor coil, wherein the inductor coil is configured to generate a varying magnetic field that penetrates the susceptor element when a portion of the aerosol-generating article is received in the device cavity of the aerosol-generating device.

14. An aerosol-generating article comprising: an aerosol-forming substrate; and a heating element, wherein: the heating element is arranged to heat the aerosol-forming substrate; the heating element has a heating element length; the aerosol-forming substrate has a substrate length, the aerosol-forming substrate length being greater than the heating element length; and the ratio of the aerosol-forming substrate length to the heating element length is between about 1.1 and 3.

15. An aerosol-generating article according to claim 14, wherein the ratio of the aerosol-forming substrate length to the heating element length is between about 1.1 and 1.16, and optionally is about 1.16.

16. An aerosol-generating article according to claim 14 or claim 15, wherein the aerosolgenerating article comprises: a first planar external surface; a second planar external surface; a cavity; a frame positioned between the first planar external surface and the second planar external surface, the frame at least partially defining the cavity; and an air inlet and an air outlet, and an airflow passage extending between the air inlet and the air outlet through the cavity.

17. An aerosol-generating article according to any one of claims 14 to 16, wherein the aerosolgenerating article comprises an upstream end and a downstream end, and wherein a downstream portion of the aerosol-forming substrate extends beyond the downstream end of the heating element, and wherein the upstream end of the heating element is aligned with the upstream end of the aerosol-forming substrate.