WO2003012277A1

WO2003012277A1 - Vapourizer for liquefied gas

Info

Publication number: WO2003012277A1
Application number: PCT/GB2002/003396
Authority: WO
Inventors: Calvin Tan
Original assignee: NICHOL DONALD BONNAR
Current assignee: NICHOL DONALD BONNAR
Priority date: 2001-07-25
Filing date: 2002-07-24
Publication date: 2003-02-13
Anticipated expiration: 2004-01-25
Also published as: GB0118126D0

Abstract

A vapouriser (100) comprising a vapouriser body (102), an expansion chamber within and bounded by said vapouriser body, an inlet channel (104) leading from the exterior of said vapouriser body to said expansion chamber for admitting liquefied gas to said expansion chamber during use of the vapouriser, an outlet channel (106) leading from said expansion chamber to the exterior of said vapouriser body for discharging vapourised gas from said expansion chamber during use of the vapouriser, and heat transfer means (108) for transferring heat through said vapouriser body from ambient fluid around the exterior of the vapouriser body from ambient fluid around the exterior of the vapouriser to said expansion chamber during use of the vapouriser such as to vapourise liquefied gas entering said expansion chamber.

Description

VAPOURIZER FOR LIQUEFIED GAS

This invention relates to vapourisers, and relates more particularly but not exclusively to vapourisers of substances that are normally gaseous at ambient atmospheric pressure and temperature, but which are commonly stored as a pressurised liquid.

LPG (liquefied petroleum gases) are pressure-liquefied hydrocarbon gases such as propane, butane, and propane/butane mixtures that are commonly supplied in a container which is a portable pressure vessel (e.g. a self-standing steel cylinder fitted with a discharge control valve and a carrying handle) . Although such hydrocarbons are gases at typical ambient atmospheric pressures and temperatures, they can be liquefied by pressure alone at ambient temperatures, and thereupon occupy a much-reduced volume that facilitates transport and storage. Such containerised LPG is utilised as a fuel gas in circumstances where piped fuel gas distribution systems are not available. For some time there has been interest in utilising LPG as a fuel in vehicles that are self-propelled by internal combustion engines, particularly as an alternative fuel in vehicles whose internal combustion engines are normally fueled by liquid light hydrocarbons (i.e. by petrol, also known as "gasoline" which may be abbreviated to "gas" but which is not to be confused with truly gaseous fuels) . Such interest is partly based on the lower running costs of LPG compared to petrol, and partly on reduced atmospheric pollution by the exhaust gases of LPG-burning vehicles in comparison to petrol-burning vehicles. Kits are commercially available for converting vehicles that are manufactured and supplied as single-fuel vehicles for burning only petrol, to dual-fuel vehicles that can be switched, at will, between burning petrol and burning LPG as the engine fuel. Such kits may include an LPG storage tank, pipework, a flow control valve/regulator, and a vapouriser for converting the LPG that is stored as a liquid into a vapour suitable for use in the engine that otherwise burns vapourised petrol. However, the cost of supplying and fitting such a known conversion kit is typically such that an unfeasibly high distance has to be travelled before the lower running costs of LPG recoup the capital cost of conversion to dual-fuel operation.

Part of the cost of known conversion kits lies in the cost and complexity of the vapouriser that is essential for converting LPG from its stored liquid state to a vapour for combustion in the vehicle engine. Such cost and complexity are increased by the necessity of supplying a known vapouriser with waste heat from the vehicle engine in order to cause sustained vapourisation of the LPG, e.g. by pipework for circulating engine- cooling water to the vapouriser and then back to the engine, together with a water circuit inside the vapouriser body.

It is therefore an object of the invention to provide a vapouriser which obviates or mitigates such problems of known vapourisers.

According to a first aspect of the present invention there is provided a vapouriser comprising a vapouriser body, an expansion chamber within and bounded by said vapouriser body, an inlet channel leading from the exterior of said vapouriser body to said expansion chamber for admitting liquefied gas to said expansion chamber during use of the vapouriser, an outlet channel leading from said expansion chamber to the exterior of said vapouriser body for discharging vapourised gas from said expansion chamber during use of the vapouriser, and heat transfer means for transferring heat through said vapouriser body from ambient fluid around the exterior of the vapouriser to said expansion chamber during use of the vapouriser such as to vapourise liquefied gas entering said expansion chamber.

Said ambient fluid around said vapouriser may be ambient atmosphere, but alternatively, and in dependence on circumstances, the ambient fluid may be steam, water, or gaseous nitrogen.

Said expansion chamber is preferably divergent from the intersection of said inlet channel with said expansion chamber to the intersection of said expansion chamber with said outlet channel, and said expansion chamber may be bell-shaped. Said expansion chamber is preferably shaped so as to minimise the formation of vortices in material flowing through said expansion chamber from said inlet channel to said outlet channel . Vortex minimisation may be achievable by any suitable means, for example by forming the internal surfaces of the expansion chamber either to be smooth (to take advantage of inherently low-friction characteristics of a polymer from which the expansion chamber is formed) , or to be formed with grooves or fins that are suitably dimensioned and suitably aligned. Said expansion chamber may be folded about a notional longitudinal axis extending from the intersection of said inlet channel with said expansion chamber to the intersection of said expansion chamber with said outlet channel whereby to reduce the external dimension of said vapouriser body in a direction generally along said axis, and the folding of said axis may be such that the axis is re-entrant to bring said inlet channel and said outlet channel mutually adjacent where said channels respectively intersect the exterior of said vapouriser body. Folding of said axis may be such as to cause material flowing through said expansion chamber from said inlet channel to said outlet channel to travel along a path locally having a low radius of curvature in the vicinity of the fold in said axis, whereby impurities of relatively high molecular weight tend to be diverted from said path for separation from the principal stream of material passing through said vapouriser. Such impurities can be trapped in a wick of absorbent material contained in a channel running along the length of the base of the expansion chamber; during servicing of the vapouriser, the wick can be removed, cleaned in a suitable solvent, dried, and replaced.

Said heat transfer means may comprise thermally conductive fins or other projections extending outwardly of the vapouriser body, said fins or other projections being arranged to absorb heat from ambient atmosphere around the vapouriser or from another ambient fluid around the vapouriser. The fins or other projections may be shrouded by a shroud means to duct the flow of ambient air or other ambient fluid across the fins or other projections. A fan or other fluid pump means may be provided to assist the flow of ambient air or other ambient fluid across the fins or other projections. The fan or other fluid pump means may be mounted on one end of the shroud means.

The vapouriser may be moulded or otherwise suitably formed of a polymer. Such polymers can optionally be selected from the group of polymers including polybutylene terephthalate and "TECHNYL A 218 MT15 V25" 0.25 glass-reinforced and 0.15 mineral-reinforced polyamide ("TECHNYL" is a Registered Trade Mark).

Alternatively, the vapouriser may be cast or otherwise fabricated from any suitable metal, e.g. from aluminium. At least the interior surface of said expansion chamber, and preferably also the interior surfaces of said inlet and outlet channels, are preferably coated or otherwise treated to be hydrophobic whereby to inhibit the deposition of ice during operation of the vapouriser.

According to a second aspect of the present invention, there is provided a method of vapourising a liquefied gas, the method comprising the step of providing a vapouriser according to the first aspect of the present invention, admitting liquefied gas to the inlet channel of said vapouriser and thence to the expansion chamber of said vapouriser, utilising the heat transfer means of said vapouriser to transfer heat from the ambient around said vapouriser to said expansion chamber whereby admitted liquefied gas is vapourised, and discharging vapourised gas from said outlet channel.

In said second aspect of the present invention, the liquefied gas may be LPG (liquefied petroleum gases) .

According to a third aspect of the present invention, there is provided a kit of parts for converting a vehicle powered by a petrol-burning internal combustion engine to become capable of substituting LPG for petrol, the kit of parts comprising a vapouriser according to the first aspect of the present invention.

According to a fourth aspect of the present invention there is provided a vehicle powered by an internal combustion engine burning vapourised LPG, wherein the vehicle carries LPG fuel that is initially in liquid form, the vehicle comprising a vapouriser according to the first aspect of the present invention, said vapouriser being connected to receive the LPG in liquid form and to discharge LPG in vapour form for combustion in the engine of the vehicle. The rate of supply of LPG to said vapouriser and the rate of heat transfer from ambient atmosphere around said vapouriser are preferably such that, in conjunction with volumetric intake of said engine, the vapourised LPG in the outlet channel of said vapouriser is substantially above the pressure of ambient atmosphere feeding said engine with combustion air whereby the fuel supply for said engine is self-pumping.

BRIEF DESCRIPTION OF THE DRAWINGS:

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings wherein:

Fig. 1 is a first perspective view of a preferred embodiment of the invention, from above, to one side, and from the inlet/outlet end;

Fig. 2 is a second perspective view of the preferred embodiment, from above, to one side, and from the end opposite the inlet/outlet end;

Fig. 3 is a third perspective view of the preferred embodiment, from the same general direction as in Fig. 1 but from a greater height above the embodiment;

Fig. 4 is a fourth perspective view of the preferred embodiment, from the same general direction as in Fig. 2 but from a lower height and from a viewpoint more to the side;

Fig. 5 is a side elevation of the preferred embodiment;

Fig. 6 is a plan view of the preferred embodiment;

Fig. 7 is an end elevation of the preferred embodiment, viewed from the inlet/outlet end;

Fig. 8 is a horizontal section of the preferred embodiment, taken on the line VIII-VIII in Fig. 5;

Fig. 9 is a vertical section of the preferred embodiment, taken on the line IX-IX in Fig. 5 ;

Fig. 10 is a vertical section of the preferred embodiment, taken on the line X-X in Fig. 7; and

Fig. 11 is a perspective view of one half of an expansion chamber comprised in the preferred embodiment, viewed from above, to one side, and from the inlet/outlet end.

DETAILED DESCRIPTION OF THE EMBODIMENTS:

Referring first to Figs. 1-7, these are external views of a vapouriser 100 that is a preferred embodiment of the invention. A principal component of the vapouriser 100 is an expansion chamber whose body 102 is visible in Figs. 1, 3, & 7. The expansion chamber lies within and is bounded by the body 102 (details of the internal expansion chamber will be given subsequently) . The expansion chamber body 102 has an inlet 104 (Figs. 1 & 3- 7) for liquefied LPG, and an outlet 106 for vapourised LPG. The inlet 104 provides an inlet channel for feeding liquefied LPG into the expansion chamber, and the outlet

106 provides an outlet channel discharging vapourised LPG from the expansion chamber.

The exterior surface of the expansion chamber body 102 (other than the end provided with the inlet 104 and the outlet 106) is provided with a regular array of integrally formed fins 108 (Figs. 1, 3, & 5-7). The fins 108 serve to transfer heat from the ambient atmosphere surrounding the vapouriser 100, through the body 102, and into the internal expansion chamber so as to supply the heat necessary for sustained vapourisation of LPG. The fins 108 are shrouded by a shroud 110 (Figs. 1-7) of generally square cross-section that closely matches the overall square profile of the array of fins 108. The shroud 110 is open at the inlet/outlet end (see Figs. 1, 3, & 7), and the opposite end of the shroud is fitted with a fan assembly 112 (Figs. 4 & 5) having an axial fan rotated about the longitudinal axis of the shroud 110 by a hub motor (e.g. by a 12 volt DC motor, or by any other motor suited to the auxiliary power supply of the particular vehicle on which the vapouriser is employed) . The fan assembly 112 draws ambient air through the open end of the shroud 110 and over the fins 108, air being discharged from the opposite end of the shroud 110 through an exhaust duct 114 (Figs. 1-7) that is integrally formed with the shroud 110. The fan assembly can be seen in greater detail in Figs. 8 & 10.

Referring now to Figs. 8-10, Fig. 8 is a horizontal cross-section through the vapouriser 100, at the level of the inlet 104 to the internal expansion chamber 116 (which was not directly visible in the external views of Figs. 1-7), Fig. 9 is a transverse cross-section in a vertical plane through the expansion chamber 116, and Fig.10 is a longitudinal cross-section in a vertical plane through the expansion chamber 116. (Precise locations of these section planes are shown in Figs . 5 &

7) . Figs. 8 & 10 show the initial lateral and vertical width increases of the expansion chamber 116 along a notional axis 118 leading centrally through the chamber

116 from the inlet 104 to the outlet 106. Fig. 10 in particular shows that this notional axis 118 is folded or bent back on itself, such that the inlet 104 and the outlet 106 are mutually adjacent on the same end face of the body 102, and the overall length of the expansion chamber 116 is greatly reduced from the length that would be required by an unfolded straight axis. Thus folding of the expansion chamber 116 about its inlet-to-outlet axis 118 results in convenient side-by-side location of the inlet and outlet, and also results in a substantially less bulky vapouriser which is a significant advantage when the vapouriser 100 is to be fitted in a cramped and cluttered interior space of a vehicle. Folding of the axis 118 results in the expansion chamber 116 having two legs, namely a first leg from the inlet 104 to the axis fold at the opposite end of the expansion chamber 116, and a second leg from the axis fold to the outlet 106. These two legs are kept mutually separate (except at the axis fold) by means of an internal partition 120 that is curved as particularly shown in Fig. 10 in a manner that provides a continuous increase of the cross-sectional area of the flow path along the axis 118 from the inlet 104 to the outlet 106. Thus the expansion chamber 116 can be regarded as having a ^λbell' shape, i.e. the semi- conical shape of a church bell. This mode of shaping the expansion chamber 116 allows the LPG to flow through the expansion chamber 116 from the inlet 104 to the outlet 106 with minimal vortices and therefore minimal flow impediment, despite the substantial increase in the volume of the LPG as it transforms from a liquid at the inlet 104 to a vapour at the outlet 106. In suitable circumstances, the pressure of vapourised LPG discharged from the vapouriser 100 may be substantially higher than the internal pressure of the induction system of the engine being fed by the vapourised LPG, such that LPG fuel is self-pumping (in contrast to petrol-burning engines, wherein the petrol must either be pumped from a tank into the engine or gravity-fed into the engine from a tank well above engine height) .

The above-described fold in the axis 118 results in a change in flow direction as the LPG passes through the expansion chamber 116, and this flow direction change tends to cause radially outward movement of impurities of molecular weight that is high relative to typical molecular weights in LPG. The expansion chamber body 102 can be modified from its illustrated form so as to collect such separated impurities, and to enable their discharge from time to time. Such impurities can be trapped in a wick (not shown) of absorbent material contained in a channel (not shown) running along the length of the base of the expansion chamber 116; during servicing of the vapouriser 100, the wick can be removed, cleaned in a suitable solvent, dried, and replaced.

The expansion chamber body 102 can be moulded from a suitable polymer, and because the body 102 is hollow, the body is conveniently formed in two complementary halves. One such body half is shown in Fig. 11. Suitable polymers include polybutylene terephthalate and "TECHNYL A 218 MT15 V25" 0.25 glass-reinforced and 0.15 mineral- reinforced polyamide ("TECHNYL" is a Registered Trade Mark) . As an alternative to being formed from a polymer, the body 102 could be cast and/or machined from any suitable suitable metal, e.g. aluminium. Other parts of the vapouriser 100, such as the shroud 110, can be formed of a suitable polymer, or from any other suitable material. Whatever material is selected for the body 102, at least the internal surfaces of the expansion chamber 116, and preferably also the internal surfaces of the inlet 104 and the outlet 106, are coated or otherwise treated to inhibit the deposition of ice during operation of the vapouriser 100, e.g. by making these surfaces hydrophobic by means of surface treatment with a molybdenum additive.

The vapouriser 100 is compact, and readily fabricated from economical materials. Thus the vapouriser of the invention is of lower cost than conventional vapourisers, and is easily installed both because of its compactness and because it requires no plumbing other than for the two connections for LPG. These factors make the invention especially attractive for retro-fitting in vehicles that are to be converted from petrol-only use to dual-fuel use; the vapouriser can be marketed as a standalone item, or as one item in a kit of parts for vehicle conversion (other parts including, for example, LPG storage tanks, pipework, and flow controls).

Mention has been made of alternative materials from which the vapouriser can be fabricated; other modifications and variations can be adopted without departing from the scope of the invention. For example, the fins 108 can be substituted by other shapes of heat-transferring projections. The expansion chamber 116 can have a shape other than the particular shape shown in the accompanying drawings. Ambient fluids other than atmospheric air around the vapouriser 100 can be utilised as a source of heat for sustained vapourisation of LPG; for example, if the vapouriser 100 were part of the fuel supply system for a marine vessel, the vapouriser could be plumbed into an open-circuit water cooling system as commonly employed for marine engines, or simply immersed in the water on which the vessel is floating. (In general terms, the ambient fluid requires only to be gaseous or liquid so as to be able to flow freely over the finned exterior of the vapouriser, and to be at an energy level that is higher than the energy level of the liquefied gas that is to be vapourised) . The vapouriser of the invention can also be used for vapourisation of liquefied gases other than LPG, for example for the vapourisation of liquefied breathing gases .

Claims

1. A vapouriser comprising a vapouriser body, an expansion chamber within and bounded by said vapouriser body, an inlet channel leading from the exterior of said vapouriser body to said expansion chamber for admitting liquefied gas to said expansion chamber during use of the vapouriser, an outlet channel leading from said expansion chamber to the exterior of said vapouriser body for discharging vapourised gas from said expansion chamber during use of the vapouriser, and heat transfer means for transferring heat through said vapouriser body from ambient fluid around the exterior of the vapouriser to said expansion chamber during use of the vapouriser such as to vapourise liquefied gas entering said expansion chamber .

2. A vapouriser according to claim 1, wherein said ambient fluid around said vapouriser is ambient atmosphere, steam, water, or gaseous nitrogen.

3. A vapouriser according to claim 1 or 2 , wherein said expansion chamber is divergent from the intersection of said inlet channel with said expansion chamber to the intersection of said expansion chamber with said outlet channel .

4. A vapouriser according to any one of the preceding claims, wherein said expansion chamber is bell-shaped.

5. A vapouriser according to claim 4, wherein said expansion chamber is shaped so as to minimise the formation of vortices in material flowing through said expansion chamber from said inlet channel to said outlet channel.

6. A vapouriser according to claim 5, wherein vortex minimisation is achievable by forming the internal surfaces of the expansion chamber to be smooth.

7. A vapouriser according to claim 5, wherein vortex minimisation is achievable by forming the internal surfaces of the expansion chamber with grooves or fins that at suitably dimensioned and suitably aligned.

8. A vapouriser according to any preceding claim, wherein said expansion chamber is folded about a notional longitudinal axis extending from the intersection of said inlet channel with said expansion chamber to the intersection of said expansion chamber with said outlet channel whereby to reduce the external dimension of said vapouriser body in a direction generally along said axis.

9. A vapouriser according to claim 8, wherein the folding of said axis is such that the axis is re-entrant to bring said inlet channel and said outlet channel mutually adjacent where said channels respectively intersect the exterior of said vapouriser body.

10. A vapouriser according to claim 8 or 9 , wherein folding of said axis is such as to cause material flowing through said expansion chamber from said inlet channel to said outlet channel to travel along a path locally having a low radius of curvature in the vicinity of the fold in said axis, whereby impurities of relatively high molecular weight tend to be diverted from said path for separation from the principal stream of material passing through said vapouriser.

11. A vapouriser according to claim 10, wherein a wick of absorbent material is contained in a channel running along the length of the base of the expansion chamber to trap impurities.

12. A vapouriser according to any one of the preceding claims, wherein said heat transfer means comprise thermally conductive projections extending outwardly of the vapouriser body, said projections being arranged to absorb heat from ambient atmosphere around the vapouriser or from another ambient fluid around the vapouriser.

13. A vapouriser according to claim 12, wherein projections are shrouded by a shroud means to duct the flow of ambient air or other ambient fluid across the projections .

14. A vapouriser according to any one of claims 12 or 13, wherein a fan or other fluid pump means is provided to assist the flow of ambient air or other ambient fluid across the projections.

15. A vapouriser according to claim 14 when dependent upon claim 13, wherein the fan or other fluid pump means is mounted on one end of the shroud means.

16. A vapouriser according to any one of the preceding claims, wherein the vapouriser is moulded or otherwise suitably formed of a polymer.

17. A vapouriser according to claim 16, wherein such polymers are selected from the group of polymers including polybutylene terephthalate and "TECH YL A 218 MT15 V25" 0.25 glass-reinforced and 0.15 mineral- reinforced polyamide ("TECHNYL" is a Registered Trade

Mark) .

18. A vapouriser according to any one of claims 1 to 15, wherein the vapouriser is cast or otherwise fabricated from metal, such as aluminium.

19. A vapouriser according to any one of the preceding claims, wherein at least the interior surface of said expansion chamber is coated or otherwise treated to be hydrophobic whereby to inhibit the deposition of ice during operation of the vapouriser.

20. A method of vapourising a liquefied gas, the method comprising the step of providing a vapouriser according to the first aspect of the present invention, admitting liquefied gas to the inlet channel of said vapouriser and thence to the expansion chamber of said vapouriser, utilising the heat transfer means of said vapouriser to transfer heat from the ambient around said vapouriser to -said expansion chamber whereby admitted liquefied gas is _ vapourised, and discharging vapourised gas from said outlet channel .

21. A method according to claim 20, wherein the liquefied gas is LPG (liquefied petroleum gases) .

22. A kit of parts for converting a vehicle powered by a petrol-burning internal combustion engine to become capable of substituting LPG for petrol, the kit of parts comprising a vapouriser according to any one of claims 1 to 19.

23. A vehicle powered by an internal combustion engine burning vapourised LPG, wherein the vehicle carries LPG fuel that is initially in liquid form, the vehicle comprising a vapouriser according to any one of claims 1 to 19, said vapouriser being connected to receive the LPG in liquid form and to discharge LPG in vapour form for combustion in the engine of the vehicle .

24. A vehicle according to claim 23, wherein the rate of supply of LPG to said vapouriser and the rate of heat transfer from ambient atmosphere around said vapouriser are such that, in conjunction with volumetric intake of said engine, the vapourised LPG in the outlet channel of said vapouriser is substantially above the pressure of ambient atmosphere feeding said engine with combustion air whereby the fuel supply for said engine is self- pumping.

25 A vapouriser substantially as hereinbefore described with reference to and as shown in the accompanying drawings .

26. A method of vapourising- a liquefied gas substantially as hereinbefore described.