ES3026507T3 - Burner - Google Patents

Abstract

A microtube burner (1) consists of a plurality of conduits (41) extending through fluid chambers (31, 32, 33). Discharge means (51, 52) fluidly connect the chambers to the conduits. At least one of the conduits (41) has at least two discharge means (51, 52) for discharging fluid from a chamber (31, 32) into the conduit at at least two different longitudinal positions. (Automatic translation with Google Translate, no legal value)

Description

DESCRIPTION

Burner

Technical field

The present disclosure relates to the subject matter set forth in the claims. In particular, it relates to a burner. It further relates to a combustion chamber and a gas turbine engine incorporating the burner.

Background of the disclosure

Combustion systems and burners for the combustion of a fuel with low nitric oxide generation are known in the art. For this purpose, the fuel, particularly a gaseous fuel, is generally provided for combustion in a lean, intensively premixed fuel-oxidizer mixture. The oxidant is most commonly air. For better readability and ease of nomenclature, the term "air" will be used in this disclosure to generically indicate any oxidant. Those skilled in the art will readily understand, based on the foregoing, that the mention of air hereinafter constitutes a disclosure of a generic oxidant. "Air," in this sense, will be interpreted broadly to represent a generic oxidant.

Lean premixed flames raise the issue of combustion stability, as they generally occur with an equivalence ratio quite close to the lower extinction limit. Therefore, in certain operating modes, the premixed flames, or some of the premixed flames, are replaced or supplemented by so-called pilot flames. These are flames that burn less intensively premixed or even substantially non-premixed fuel-air mixtures, comprising zones of richer fuel-air mixtures and thus providing higher local combustion temperatures and producing combustion less sensitive to external influences. On the downside, however, nitric oxide formation increases disproportionately with combustion temperature, and it is therefore necessary to find a balance between nitric oxide formation and combustion stability. Diffusion flames, which burn a fuel-air stream with zones with equivalence ratios close to 1, i.e., near-stoichiometric zones, produce excellent combustion stability, but with high nitric oxide formation. Therefore, one of the goals in burner development and combustion engineering is to design burners and operating concepts that produce minimal combustion instabilities when burning lean premixes and/or enable combustion over a wide operating range with the least possible piloting.

Another aspect to consider in the design of burners and combustion systems is the growing demand for fuel flexibility. The combustion of so-called "blue" and "green" hydrogen, generated using renewable energy, can be seen as a suitable way to store and transport energy collected from, for example, solar and wind power plants. The operation of premix burners on fuels that produce higher reactivity than natural gas, such as, but not limited to, CO and hydrogen, or gas mixtures comprising high contents of C2+ species, i.e., hydrocarbon species containing two or more carbon atoms, CO, or hydrogen, as a non-limiting example, at 50% or more by volume, requires additional considerations. Hydrogen, for example, produces a short autoignition time, a significantly higher flame speed, and a wide flammability range. Thus, the operation of premix burners, for example, using hydrogen or hydrogen-rich mixtures as fuel increases the risk of flashback and burner overheating, which must be taken into account. The same applies to other fuels that, generally speaking, are more flammable than, for example, natural gas. Hydrogen combustion can produce locally higher flame temperatures compared to natural gas combustion, which could result in increased nitrogen oxide formation.

US 6,267,585 suggests hydrogen combustion by directly injecting hydrogen into air streams from perforated plates, whereby the hydrogen is combusted in microdiffusion flames. The document states that by reducing the size of the perforation die in the perforated plates, nitric oxide levels as low as 10 ppmv (parts per million, volumetric) can be achieved. A type of burner, sometimes referred to as a cluster burner or microtube burner, is known in the art and is suggested for hydrogen combustion. It generally comprises mixing tubes intended to be traversed by air and extending through a fuel plenum. The mixing tubes are in fluid communication with the fluid plenum, so that fuel can be mixed into the combustion air stream through the mixing tubes.

US 2013/0232979 discloses a burner comprising mixing tubes extending through a fuel plenum chamber. Nozzles extend into the mixing tubes for discharging fuel from the fuel plenum into the mixing tubes. WO 2015/182154 and US 2010/0218501 disclose further examples of burners of similar structure and function. US 2016/033133 suggests an arrangement of a multitude of individual multiple burner modules side by side, wherein each multiple burner module comprises an individual fuel plenum chamber and is equipped with an individual supply line. US 2015/076251 describes a multiple burner in which the mixing tubes are combined with a fuel cartridge. In addition, a cooling air plenum is provided downstream of the fuel plenum chamber. The cooling air plenum discharges the cooling air through the downstream end wall of the burner to effect effusion and film cooling and is not fluidically connected to the mixing tubes. US 4,100,733 suggests a microtube multiple burner in which radially inner and radially outer microtubes are arranged to be fed with fuel from separate fuel plenums. In embodiments, the fuel plenums are stacked along the flow direction through the microtubes. Another multiple burner is known from US 2013/074510, in which fuel is discharged from fuel plenums into tubes extending through the plenums.

Summary of the subject matter of this disclosure

It is an object of the present disclosure to provide a burner as initially mentioned. In aspects, a burner will be disclosed that avoids the drawbacks of the art outlined above. In more specific aspects, a burner will be proposed that enables the combustion of hydrogen or hydrogen-rich fuel or other highly reactive combustible gases or combustible gas mixtures over a wide load range and with minimized risk of flashback and nitric oxide formation. Such gases and gas mixtures are characterized, generally speaking, by at least one of a significantly shorter autoignition time, a significantly higher flame speed, and a significantly wider range of equivalence ratios over which they are flammable. In another aspect, a burner will be proposed that enables robust operation with lean premixes over a wide load range with minimized risk of flameout. In still other aspects, the burner will be suitable for operation on a wide range of fuels. In additional aspects, the burner will enable the use of inert fluids, in addition to fuel, for purposes such as, but not limited to, reducing nitric oxide formation, mitigating potential flashback problems, and other purposes.

In yet another aspect, the burner will be suitable for replacing existing burners in legacy combustors or combustion appliances, such as, but not limited to, gas turbine combustors. Such retrofitting of legacy combustors may enable those combustors to be operated with fuels for which the legacy burners being replaced were unsuitable or had limitations. Such retrofitting may also be suitable for improving fuel flexibility, emissions, operating range, and other characteristics of a legacy combustor. As a non-limiting example, a legacy combustor may be retrofitted for hydrogen combustion.

These objectives are achieved by the subject matter set forth in claim 1 and/or the details outlined in the dependent claims.

Other effects and advantages of the disclosed subject matter, whether explicitly mentioned or not, will become apparent in view of the disclosure provided below.

Accordingly, a burner is disclosed comprising a first upstream front wall and a second downstream front wall. A general airflow direction is defined from the first upstream front wall to the second downstream front wall. Therefore, the terms "upstream" and "downstream," as used in the context of the burner described herein, are to be understood as referring to the general airflow direction from the first upstream front wall to the second downstream front wall, unless otherwise defined in the specific context. It should be noted that, in general, one skilled in the art will be able to determine which of the front walls will act as the downstream front wall. The downstream front wall is generally intended, implicitly, to be provided so as to delimit a combustion space and, thus, can be defined in terms of materials used, cooling characteristics, coatings, and other characteristics characteristic of a burner's downstream front wall and by means of which one skilled in the art will readily distinguish the downstream front wall from the upstream front wall. At least one dividing wall extends across the general airflow direction and between the first and second end walls, whereby the at least one dividing wall divides the space between the upstream end wall and the downstream end wall into at least two independent fluid plenum chambers stacked along the general airflow direction. The end walls and the dividing walls will hereinafter be referred to as "cross walls." The burner further comprises at least one peripheral wall extending between at least one of the following: the two end walls, at least two dividing walls, and/or one end wall and one dividing wall. The peripheral wall may, in particular, be leak-tightly connected to the cross walls, to which it extends along the circumference of the respective cross wall, thereby forming an essentially closed plenum chamber between the respective cross walls. For the sake of clarity, it is noted that, within the scope of the present disclosure, each space between two of the cross walls within the burner will be understood to be a plenum or fluid plenum, regardless of whether or not the space is further confined by a peripheral wall. A plenum or fluid plenum may be referred to as a "closed chamber" if it is further confined by a peripheral wall, or an "open plenum" otherwise. In particular embodiments, the peripheral wall may extend from the upstream front wall to the downstream front wall and be leak-tightly connected to the upstream and downstream front walls along their respective circumferences, and additionally, in particular, to all dividing walls along their respective circumferences. In another example, the peripheral wall may extend from the upstream front wall to the downstream dividing wall and be leak-tightly connected to the upstream front wall and the downstream dividing wall along their respective circumferences, and additionally, in particular, to all intervening dividing walls along their respective circumferences. It is understood that the downstream plenum formed between the downstream dividing wall and the downstream front wall may, in particular, be intended to be used as a cooling air plenum and may therefore be open along the periphery to receive air from the outside. Plenums intended to be used with fuel or other agents other than air, or generally speaking, other than the oxidizing agent supplied to the burner, may, on the contrary, be closed by the peripheral wall and provided with fluid supply connectors. It will be understood that at least the closed plenum chambers comprise fluid supply connectors and are intended to be connected to supply lines fluidically connected to the plenum chambers. A plurality of passages are provided through the upstream and downstream front walls, and the at least one dividing wall. These passages are provided by openings in the cross walls, wherein openings in each cross wall are aligned to form a passage through which another element may be formed or extend. A plurality of conduits are provided and extend through at least some of the passages and thus through the fluid plenum chambers, wherein the walls of the conduits are leak-tightly connected to the first front wall, the second front wall, and the intervening dividing walls. In particular, the conduits may extend from the upstream front wall to the downstream front wall. In this way, the conduits provide a fluidic connection between an upstream side of the burner, adjacent to the first front wall, and a downstream side of the burner, adjacent to the second front wall. Each conduit has a first upstream end, adjacent to the first upstream front wall, and a second downstream end adjacent to the second downstream front wall. The first upstream end of each conduit opens onto the upstream side of the burner, and the second downstream end of each conduit opens onto the downstream side of the burner. A longitudinal direction is defined between said ends of each conduit. At their upstream ends, the conduits may be provided with a smooth flow inlet geometry, for example, a trumpet-shaped funnel geometry, or alternatively, they may comprise a rounded transition geometry towards the upstream front blade, to minimize total pressure losses of the fluid intended to flow through the conduits. The conduits are adapted to allow the flow of oxidizing agent, which is most commonly combustion air, to pass therethrough from the upstream side of the burner to the downstream side of the burner. The burner comprises discharge means for providing fluid communication between at least one of the fluid plenum chambers and the interior of at least one of the conduits, the discharge means being configured to discharge a fluid from a respective fluid plenum chamber into the conduit. At least one of the discharge means is provided in the form of at least one through-hole through a wall of the conduit and will also be referred to hereinafter as a "wall-opening type discharge means," and at least one of the discharge means is a discharge nozzle suspended in a conduit by one or more tubes, and may also be referred to hereinafter as a "nozzle type discharge means." The tube or tubes extend from a fluid plenum chamber to the discharge nozzle and provide fluid communication between said fluid plenum chamber and the discharge nozzle. The nozzle may be said to be suspended within the conduit. Multiple through-holes or a group of through-holes through the wall of a conduit may together form discharge means. The discharge nozzle may be, for example, shaped like a tube, drop, teardrop, cone, or pyramid, but not limited to such exemplary geometries, and be arranged with a longitudinal axis at least substantially parallel or coaxial to the longitudinal axis of the conduit. The nozzle comprises at least one discharge opening through which fluid originating from a fluid plenum chamber and conveyed to the nozzle may be discharged into the respective conduit. A discharge opening may be provided on an axial end face of the nozzle, in particular on an end face pointing towards the downstream end of the conduit in which the nozzle is arranged, or on a side wall of the nozzle, in particular in a downstream region of the nozzle or adjacent to the downstream end face of the nozzle. At least one of the conduits is provided with at least two discharge means, and each of the discharge means fluidically connects one of the at least two fluid plenum chambers with the interior of the conduit. The at least two discharge means are provided for discharging a fluid from the interior of the respective fluid plenum chamber at different positions along a longitudinal direction of the conduit. Said discharge positions may, in particular, be referenced to and measured from the downstream end of the respective conduit and to a downstream edge or opening formed by the discharge means. Said different longitudinal discharge positions for the same conduit may differ from one another, for example, by at least 2%, at least 5%, or at least 10%, or even at least 20% of the length of the respective conduit. As will be explained later, it may be the case that two discharge means out of the at least two discharge means are connected to the same plenum chamber or to different plenum chambers.

By virtue of the aforementioned subject matter, it is possible to discharge multiple combustible and non-combustible fluids into the combustion air flow through a microtube burner duct and to discharge fluids into the same duct at different longitudinal positions, thereby achieving specific and distinct mixing of the fluid and combustion air at the downstream end of the duct. This allows for greater versatility in burner operation.

The exterior geometry of the ducts corresponds to that of the passages. The interior cross-section of the ducts is rounded in some embodiments and, more particularly, circular. However, in other embodiments, the interior cross-section of a duct may be oval, elliptical, or polygonal in shape, where, in more particular examples, the interior cross-section of a duct may be in the shape of an equilateral polygon. It is understood that burner ducts of the type disclosed herein are referred to as "microtubes" in the art and, therefore, involve comparatively small cross-sectional dimensions. The cross-sectional area of a single duct may be 2000 mm2 or less, 1500 mm2 or less, 1000 mm2 or less, 500 mm2 or less, 300 mm2 or less, 100 mm2 or less, or 64 mm2 or less. In other respects, the hydraulic diameter, defined as four times the cross-sectional area divided by the length of the inner circumference of a conduit, may be 50 mm or less, 40 mm or less, 35 mm or less, 25 mm or less, 20 mm or less, 10 mm or less, or 8 mm or less.

One skilled in the art will appreciate that the further upstream a fluid is discharged into the duct within a conduit, i.e., the further from the respective downstream end of the conduit, the more intensely it premixes with the combustion air, or other oxidant, flowing through the duct, as it exits the duct at the downstream end thereof. Accordingly, a fuel discharged at a relatively downstream position of a conduit may combust with a relatively more pronounced diffusion combustion characteristic, whereas a fuel discharged at a relatively upstream position of a conduit may combust in a relatively more pronounced premixed combustion mode. In other words, the combustion of a fuel discharged at a relatively downstream position of a conduit will, generally speaking, be more robust, i.e., less susceptible to flame extinction, compared to the combustion of a fuel discharged at a relatively upstream position of a conduit, while the latter, generally speaking, produces fewer nitrogen oxides.

The term "longitudinal direction," as used herein, is not to be understood as vectorized, but rather generally refers to the orientation of a longitudinal extent in space, and may be equivalent to an axial direction, for example, of a duct. However, a duct may be curved, so that it has, strictly speaking, no axis, which could be implicitly interpreted as straight, but has a curved longitudinal direction. An axis of a duct or passage may, in particular, extend parallel to the longitudinal direction of the duct or passage. A "longitudinal position" indicates the position along that longitudinal direction as measured from a specific reference position, such as a downstream end of a duct or passage.

It is noted that, within the scope of this disclosure, the use of the indefinite article "a" or "an" in no way stipulates singularity or excludes the presence of a multitude of the named element or characteristic. Thus, it should be read as "at least one" or "one or a multitude of."

It is further noted that in the context of this disclosure the terms "neighbor" and "adjacent" are considered synonymous.

In some embodiments, a cartridge may be provided in or may extend through at least one of the passages. At least one cartridge may be provided, in more particular embodiments, to provide a liquid agent such as liquid fuel or water to a combustion space therethrough, and may more particularly comprise an atomizer, particularly at a distal end of the cartridge pointing toward the combustion space. The cartridge may also be adapted to provide steam, pilot fuel gas, or other gaseous agents therethrough. The cartridge may be a free-standing element and may be retractable relative to the burner. The cartridge may be provided directly through the passages, whereby an outer circumference of the cartridge seals with the cross walls of the burner. In other embodiments, the cartridge may be inserted into a conduit which in turn extends through a passage. It is appreciated that in such an embodiment, the conduit through which the cartridge extends may be provided without discharge means to provide fluidic communication with a fluid plenum chamber. However, in other embodiments, such discharge means may be provided such that fluid from a fluid plenum chamber may be discharged downstream of a tip of the cartridge or into an annular space provided between the outer wall of the cartridge and the inner wall of the conduit.

In particular, each of the passages may be provided with either a duct or a cartridge inside or through it.

The outer surfaces of the ducts or cartridges extending through the passages may be gastightly sealed to the cross walls through which they extend.

As will be appreciated and noted above, if a fluid is discharged into a conduit at a relatively upstream position, it has a longer path to mix with, for example, combustion air flowing through the duct before it is discharged into a combustion space at the downstream end of the duct compared to a fluid that is discharged into the duct at a relatively downstream position. Thus, if, for example, a gaseous fuel is discharged further upstream, it may be considered a premix fuel, while fuel discharged further downstream burns with a relatively diffusive flame characteristic, thereby providing additional robustness to the combustion of the premix fuel, particularly at low premix equivalence ratios. On the downside, burning less intensively premixed pilot fuel will result in comparatively higher nitrogen oxide formation. However, one of the advantages of a microtube burner of the type disclosed here is the relatively small size of the individual flame emanating from a single duct, and thus the relatively low residence time of the species at the elevated temperature level that promotes the formation of nitrogen oxide. Fuel discharge at a relatively upstream location and fuel discharge at a relatively downstream location can occur simultaneously, and in one or different ducts. Combustion of the less premixed fuel supports combustion of the more premixed fuel.

In non-limiting embodiments, at least one of the plurality of conduits is in fluid communication with at least two fluid plenum chambers, wherein at least first discharge means are provided for providing fluid communication with a first of said at least two fluid plenum chambers, and at least second discharge means are provided for providing fluid communication with a second of said at least two fluid plenum chambers. This allows fluids to be selectively discharged into the conduit from any of the plenum chambers connected thereto. It has therefore been found to be advantageous for the supply lines to the plenum chambers to be equipped with individual control valves that allow the supply of fluid to the plenum chambers to be controlled individually.

It may further be provided that at least one of the plurality of conduits is configured with first discharge means provided in the form of a wall-opening discharge means and further with second discharge means being a nozzle-type discharge means. This provides improved flexibility in the discharge of fluid in a conduit. In particular, it will be appreciated that a fluid discharged into a conduit through a nozzle-type discharge means may generally be discharged at or near the center of the conduit, while fluid discharged through a wall-opening discharge means is discharged into a boundary layer along the wall of the conduit and, depending on the momentum of the discharged fluid, may or may not penetrate the boundary layer. It will further be appreciated that if a fluid is discharged into a conduit through a nozzle-type discharge means, the actual discharge position may be displaced along the general airflow direction, or the longitudinal direction of the duct, respectively, whereas in the case of a wall-opening type discharge means, the discharge position is coupled to the position of the respective fluid plenum. To take advantage of this flexibility, it could thus be provided that the first discharge means are in fluid communication with a first fluid plenum and the second discharge means are in fluid communication with a second fluid plenum, wherein the first fluid plenum is disposed downstream of the second fluid plenum along the general airflow direction. A discharge position of the second nozzle-type discharge means, which provides fluid communication between the duct and the second fluid plenum, relatively upstream, may be located downstream of the discharge position of the first discharge means. Thus, fluid from a relatively upstream fluid plenum may be discharged into the downstream fluid conduit from a relatively downstream fluid plenum. In more specific embodiments, the discharge position of the second nozzle-type discharge means may be at most twice the minimum hydraulic diameter of the conduit downstream of the discharge position of the first discharge means. In other specific and non-limiting embodiments, the discharge position of the second nozzle-type discharge means may be provided upstream of the discharge position of the first discharge means by at most five times the minimum hydraulic diameter of the conduit and downstream of the discharge position of the first discharge means by at most two times the minimum hydraulic diameter of the conduit. The definition of the hydraulic diameter has been outlined above. It will be appreciated that the conduit may be provided with cross-sectional passages that narrow and widen along its longitudinal extension. Thus, the hydraulic diameter of the conduit may vary along its longitudinal extension. Reference is made to a minimum hydraulic diameter of the conduit.

In other embodiments, the discharge position of any discharge nozzle is located at a longitudinal position of the conduit within which the discharge nozzle is arranged that corresponds to a maximum of 20 minimum hydraulic diameters of the respective conduit when measured from a downstream end of the conduit and along the longitudinal direction of the conduit.

In non-limiting exemplary embodiments, at least two means for discharging a conduit may be fluidically connected to exactly the same fluid plenum and are provided for discharging fluid from the fluid plenum at two different positions along a longitudinal direction of the respective conduit. The aforementioned conduit may then discharge a relatively more intensely premixed fuel fraction together with a relatively less premixed fuel fraction into a combustion space, which may serve to support combustion of the relatively more intensely premixed fuel. It is noted that fluid may also be discharged from a particular plenum into conduits at more than two longitudinal positions within the respective conduit, which will produce more or less pronounced premixing of the diffusion flame characteristic of a resulting flame emanating from the respective conduit. In non-limiting embodiments, a first conduit may be provided with a first discharge means fluidically connecting the first conduit to a first plenum chamber, and a second conduit is provided with a second discharge means fluidically connecting the second conduit to the first fluid plenum chamber, wherein the first discharge means is arranged to discharge fluid from the first fluid plenum to the first conduit at a first longitudinal position of the first conduit as measured from the downstream end of the first conduit, and the second discharge means is arranged to discharge fluid from the first fluid plenum to the second conduit at a second longitudinal position of the second conduit as measured from the downstream end of the second conduit. Furthermore, the second conduit, in this non-limiting embodiment, is free of a discharge means fluidically connecting to the first fluid plenum chamber. Therefore, certain conduits may be operated as conduits with different premixing characteristics of the fuel discharged from the first fluid plenum at the downstream end of the conduits. Additionally, the first conduit may be free of discharge means fluidically connected to the first fluid plenum chamber and arranged to discharge fluid from the first fluid plenum chamber into the first conduit at the second longitudinal position of the first conduit as measured from the downstream end of the first conduit. The more intensively premixed fuel and the less intensively premixed fuel, in these embodiments, are provided from a single plenum chamber, and the mass flow ratio of the more intensively premixed fuel and the less intensively premixed fuel is thus fixed.

In still other embodiments, a first conduit is provided with a first discharge means fluidically connecting the first conduit to a first fluid plenum and arranged and configured to discharge into the first conduit at a first position when measured from the downstream end of the first conduit, and a second conduit is provided with a second discharge means fluidically connecting the second conduit to a second fluid plenum and arranged and configured to discharge into the second conduit at a second position when measured from the downstream end of the second conduit. The first conduit may be fluidically isolated from the second fluid plenum, and the second conduit may be fluidically isolated from the first fluid plenum. In still other aspects, a first conduit is provided with first discharge means fluidically connecting the first conduit to a first fluid plenum chamber and arranged and configured to discharge into the first conduit at a first position when measured from the downstream end of the first conduit, and the first conduit is further provided with second discharge means fluidically connecting the first conduit to a second fluid plenum chamber and arranged and configured to discharge into the first conduit at a second position when measured from the downstream end of the first conduit. The second position is in both cases different from the first position, wherein the positions can be expressed in absolute dimensions or in multiples of a minimum hydraulic diameter of the respective conduit. The mass flow of fluid discharged from the plenum chambers at the first and second different positions can be controlled independently of each other by providing independent control valves in the supply lines to the plenum chambers. Therefore, the mass flow ratio of the more intensively premixed fuel and the less intensively premixed fuel can be controlled.

Although assumed to be self-evident, it is noted that in general a conduit may be provided with discharge means for discharging fluid into the conduit at more than two longitudinal positions of the conduit.

The concept of axial staging of fuel discharge into a duct has been outlined in some detail above - that is, the further upstream in a duct fuel is discharged into the duct, the more intensely mixed the fuel will be with combustion air upon exiting the duct, producing more premix-type combustion and related lower nitrogen oxide emissions, as compared to discharging fuel into the more downstream duct producing more diffusion-type combustion and related higher nitrogen oxide generation, which is otherwise less susceptible to interference. In embodiments, the burner proposed herein comprises a duct that is specifically configured as a pilot duct and is in fluid communication with a fluid plenum different from the more downstream fluid plenum via discharge means configured to discharge into the pilot duct a longitudinal distance, when measured from the downstream end of the duct and along a longitudinal extent of the duct, corresponding to at most five times the minimum hydraulic diameter of the duct. Thus, the fuel may remain virtually unmixed with the combustion air upon exiting the conduit and is burned in a diffusion flame. In more specific exemplary embodiments, a plurality of pilot conduits are provided, and each pilot conduit is disposed centrally of adjacent, i.e., immediately neighboring, non-pilot conduits. Non-pilot conduits, in this regard, are conduits that are in fluid communication with a fluid plenum different from the more downstream fluid plenum via discharge means configured to discharge into the non-pilot conduit at a longitudinal distance, when measured from the downstream end of the respective conduit and along a longitudinal axis of the respective conduit, corresponding to more than five times the minimum hydraulic diameter of the respective conduit, in particular six or more times, seven or more times, or ten or more times the minimum hydraulic diameter of the respective conduit. The non-pilot conduits may in particular be arranged in a concentric hexagon around the pilot conduit. In more particular embodiments, non-pilot ducts may be arranged adjacent to the pilot duct, where n is a natural number.

Every three neighboring passages may be arranged at the corners of an equilateral triangle. On a global scale, this arrangement results in the passages being provided in an equidistant pattern, where every two neighboring passages have the same distance from each other, and the mutual influence of the flows and flames emanating from them can be easily transposed from one pair of neighboring passages to another pair of neighboring passages. In more particular embodiments, this may result in an arrangement in which a burner comprises a central passage that is surrounded by several hexagonal rings in which further passages are arranged. Generally, in the nth hexagonal ring surrounding a central passage, when counting from the central passage, 6n passages are provided. Apart from the passages in the outer ring, each passage is surrounded by six neighboring passages in a hexagonal ring. For example, a duct provided as a dedicated pilot duct for a specific fuel may be surrounded by six neighboring ducts provided as dedicated premix ducts for that specific fuel. Likewise, a nozzle or cartridge may be disposed in or through a passageway that is surrounded by six other passageways. In this embodiment, the nozzle or cartridge may comprise an atomizer and may be adapted to supply liquid fuel therethrough, while, in operation with liquid fuel, the six neighboring passageways may be adapted to provide combustion air when the burner is operated with liquid fuel. One skilled in the art will readily conceive other arrangements not explicitly mentioned. The self-similar arrangement of passageways, or passageways and/or cartridges, respectively, facilitates the scalability of the burner. Furthermore, providing the burner in the shape of an overall hexagon facilitates the replacement of existing burners in a legacy combustion chamber with multiple burners of the type disclosed herein arranged side by side.

In some aspects, all of the burner passages are parallel to one another. More particularly, the passages may be parallel to a burner axis, wherein said burner axis is defined as a virtual axis perpendicular to the outer surface of the downstream front wall, or downstream face, of the burner, which is intended to face a combustion space arranged downstream of the burner. In other aspects, it may be provided that at least a subset of the multitude of passages is arranged in at least one concentric hexagonal ring around a center point. Said concentric hexagonal ring may be provided in the form of an equilateral hexagon, comprising in particular 6n passages, where n is a natural number. The passages arranged in the at least one concentric hexagonal ring are oriented such that the fluid discharged on the downstream side of the burner from the passages of the concentric hexagonal ring has a velocity component that is tangential to a circle defined around the center point of the hexagonal ring. For example, if a downstream face of the burner, which is the outer face of the downstream wall that does not face a plenum chamber, is a flat surface, the passages, and consequently any conduit or cartridge provided therethrough, are accordingly inclined with respect to a normal to the downstream face. In particular, all passages in a given hexagonal ring may be inclined at an identical angle. As will be readily appreciated by the skilled artisan, such a configuration is suitable for generating a macroscopic vortex downstream of the burner.

It is noted that the term "subset" of passages or ducts, as used within the scope of this document, may also mean, in a special case, all the passages or ducts of the burner, if, in a specific embodiment, the attributes conjugated with the subset apply to all the passages or ducts.

In a discharge means, to the extent that it comprises at least two discharge openings, the discharge openings may be provided such that the velocity vectors of all fluid streams emanating from the discharge openings lie at or substantially emanate from a common point in a cross-sectional view of a conduit. For example, if the interior cross-section of the conduit is circular or elliptical, or has the shape of an equilateral polygon, they may lie at or substantially emanate from a center of the cross-section of the conduit. Likewise, a single discharge opening of a discharge means may be provided such that the velocity vector of a fluid stream emanating from said opening is directed toward or substantially emanates from a center of the conduit. It will be appreciated that the geometric relationships with respect to the conduit in this context strictly relate to the open interior cross-section of the conduit. In other embodiments, however, at least one discharge opening of a discharge means may be provided such that the fluid is discharged with a velocity component tangential to the cross section of the conduit.

In addition, a discharge opening of a discharge means may be provided to discharge fluid in a direction perpendicular to the longitudinal direction of the conduit. It may also be inclined to discharge the fluid with a velocity component in the upstream or downstream direction of the conduit.

In embodiments, vortex generators and/or blades may be arranged within a duct. The vortices in the combustion air flow through a duct may serve to enhance mixing of fuel and other fluids discharged into the duct through the duct's discharge means with the combustion air flow. A plurality of blades may be arranged along the circumference of the duct to generate a swirl of the combustion air within the duct. In embodiments, the vortex generators and/or the blade row are arranged in an upstream section of a duct, for example, in the upstream 30%, 20%, or 10% of the longitudinal extent of the duct. The vortex generators and/or the blade row may be arranged upstream of any discharge means within the duct. However, they may also be arranged differently with respect to the discharge means, for example, between discharge means in the intended direction of combustion air flow or downstream thereof, as required. Furthermore, vortex generators and/or blade rows may be provided at more than one longitudinal position of a duct and/or longitudinal position with respect to the discharge means.

At least three fluid plenums may be stacked along the general direction of the airflow. Plenums may be provided for the supply of different fluids, for example, different fuels. For a specific fuel, two or more plenums may be provided to control the supply of said specific fuel to different ducts or the supply of said specific fuel at different longitudinal positions of the ducts for the purpose of controlling, for example, piloting. Additional plenums may be added to supply inert fluids such as steam or nitrogen, which could be useful for blowback control, or to supply, via internal atomizing nozzles within one or more ducts, water or liquid fuel or other liquid agent to the flow through said duct(s). The burner proposed herein thus provides superior versatility with regard to multi-fuel operation capability and the possibility of adding other fluids, since it is simply necessary to add another plenum to the stack of plenums.

The most downstream fluid plenum may be intended to be used as a coolant plenum. The most downstream fluid plenum may be provided with at least one of a fluidic connection to at least some of the conduits, for discharging fluid from the most downstream fluid plenum to said at least some of the conduits, and/or with front wall through-holes extending through the second downstream front wall, different from the passages through the downstream front wall, for discharging fluid from the most downstream fluid plenum to a downstream area of the burner and for cooling the downstream front plate by effusion cooling. The most downstream plenum may in particular be in fluidic communication with at least one or with a fraction of the conduits or with all of the conduits through wall-opening type discharge means. The discharge means providing fluid communication between the downstream plenum and a conduit may be configured to discharge fluid from the downstream plenum into the conduit with a downstream velocity component tangential to the inner surface of the conduit wall. The coolant then forms an inert boundary layer at the downstream end of the conduit that helps prevent backflow into the conduit. It is noted that, in embodiments, the downstream fluid plenum may be supplied with a coolant other than air, such as, for example, but not limited to, steam.

Furthermore, in non-limiting exemplary embodiments, the second fluid plenum, when measured from the downstream side of the burner, may be provided to be in fluid communication with the fluid surrounding the burner on its lateral sides. In this regard, in one aspect, no peripheral wall may be provided confining the second fluid plenum when measured from the downstream side of the burner, such that said plenum is an open plenum. In another aspect, said plenum may be confined by a perforated peripheral wall extending between the transverse walls adjacent to said plenum. Thus, when the burner is installed in a combustion apparatus, said second fluid plenum, when measured from the downstream side of the burner, is in fluid communication with a burner bell chamber within which combustion and cooling air is provided. The further downstream fluid plenum may then be in fluid communication with said second fluid plenum when counted from the downstream side of the burner through openings in the dividing wall delimiting the further downstream fluid plenum with respect to the second fluid plenum when counted from the downstream side of the burner. Thus, for example, impingement cooling of the downstream wall of the burner, which faces the combustion chamber, may be achieved. The further downstream fluid plenum, in this embodiment, may further be in fluid communication with the downstream side of the burner through the downstream front wall, in particular through openings provided therethrough, to provide additional cooling of the downstream wall of the burner. The spent cooling fluid is thus discharged into the combustion chamber. The most downstream fluid plenum may alternatively or additionally be configured to discharge the cooling air into the downstream portion of at least one conduit or at least some conduits.

In embodiments, at least a subset of the multitude of passageways are arranged as outer passageways in a concentric hexagonal ring around and adjacent to the at least one inner passageway, wherein the at least one inner conduit is provided in the at least one inner passageway and the at least one outer conduit is provided in the outer passageways. In embodiments, the at least one inner passageway could be a single central passageway. In other embodiments, the at least one inner passageway is arranged in an inner hexagon that is surrounded by an outer hexagon in which the outer passageways are arranged. The at least one inner conduit has a downstream-most discharge position wherein a discharge means in fluid communication with a fluid plenum different from the downstream-most fluid plenum is configured to discharge into the at least one inner conduit that is located a first longitudinal distance from the downstream end of the at least one inner conduit. The at least one outer conduit has a downstream discharge position in which discharge means in fluid communication with a fluid plenum chamber different from the downstream fluid plenum chamber are configured to discharge into the at least one outer conduit that is located at a second longitudinal distance from the downstream end of the at least one outer conduit. The second longitudinal distance is greater than the first longitudinal distance. Therefore, a more intensely premixed fuel-air mixture exits the at least one outer conduit compared to the fuel-air mixture exiting the at least one inner conduit.

Each cross-section taken along the longitudinal extension of each duct, and more particularly perpendicular to the axis of the duct, among the multitude of ducts may have one of a circular or polygonal shape.

If a fluid plenum is provided in the form of a closed fluid plenum as defined above, supply connectors must be provided in fluidic connection with the closed fluid plenum. In embodiments of the burner, the burner thus comprises supply connectors configured for supplying fluid to at least some of the fluid plenums. In more specific embodiments, at least two of the fluid plenums are fluidically connected to a respective individual supply connector, wherein at least two supply connectors of different fluid plenums are arranged concentrically and coaxially.

The burner may be integrally formed by additive manufacturing. That is, the cross walls, peripheral walls, duct walls, discharge means, and, as appropriate, additional elements such as the aforementioned vortex generators and blades, are provided in the form of a seamless, one-piece monolithic element. The entire burner may be a seamless, one-piece monolithic element manufactured additively. In other embodiments, the burner may be assembled from layers, each layer comprising at least two cross walls and at least one plenum between the cross walls. The burner may be assembled from seamless, one-piece monolithic elements, each element comprising at least one plenum chamber bordered by two cross walls and, optionally, by a side wall, stacked one on top of the other.

At least one of the through-holes arranged in the wall of a duct among the multitude of ducts for providing fluidic communication with a fluid plenum chamber may have an elliptical cross-section, wherein in particular the long axis of the ellipse includes an angle of at most 30 degrees with one of a longitudinal axis of the duct, the general direction of air flow or a burner axis, and further wherein in particular the ratio of the length of the longer axis of the ellipse to the length of the short axis of the ellipse is 1.25 or more. In case a duct is curved, the angle specified above will be measured relative to a local axis at the location of the through-hole. A burner axis may be defined as an axis perpendicular to at least one of the upstream wall or a downstream wall. It may be advantageous for the long axis of the ellipse to be oriented at least approximately along a build direction of the burner during additive manufacturing of the burner. By applying this geometry, protruding structures at the boundary of the through-hole are reduced, which considerably facilitates the application of an additive manufacturing process. The build direction could be chosen along the duct axis or the general direction of the burner airflow.

At least one of the through-holes arranged in the wall of a duct among the multitude of ducts for providing fluidic communication with a fluid plenum chamber may have a polygonal-shaped cross-section having a polygonal-shaped boundary, the polygonal-shaped boundary comprising straight boundary segments, wherein said polygonal-shaped boundary comprises an upstream boundary section and a downstream boundary section, wherein at least one of the upstream boundary section and the downstream boundary section is shaped such that an included angle between each straight segment of the respective boundary section and one of a longitudinal axis of the duct, the general direction of air flow, or a burner axis is less than or equal to 45 degrees. The explanations given above about the longitudinal axis of the duct and the burner axis apply. Furthermore, this shape of the through-holes in the duct wall reduces protruding structures at the boundary of the through-hole, which considerably facilitates the application of an additive manufacturing process.

In some aspects of the present disclosure, the burner may comprise at least some conduits that differ from each other in terms of the minimum hydraulic diameter of the conduits.

In still further aspects, at least a subset of conduits among the multitude of conduits are provided with a nozzle-like discharge means within the respective conduit, whereby an outer boundary of a respective discharge nozzle provided within a conduit defines the closest residual flow cross-section between the discharge nozzle and the inner wall of the conduit. At least two conduits among the subset of conduits may be provided with different residual flow cross-sections. Generally speaking, a residual flow cross-section between a nozzle and an inner conduit wall will represent the narrowest flow cross-section within the conduit, i.e., a metering section. Thus, the mass flow rate or volumetric flow rate through individual conduits of said subset of conduits may be tuned by choosing this residual flow cross-section. Such intentionally chosen residual flow cross-sections may be achieved by a choice of interacting geometries of the nozzle and the inner wall of the conduit, i.e., by a choice of size and/or shape.

In embodiments, at least one of the plurality of ducts may be provided to comprise at least one longitudinal portion of tapered cross-section, wherein within a longitudinal portion of tapered cross-section the cross-sectional area of the at least one duct tapers progressively downstream of the general direction of airflow, or in a direction from an upstream end of the duct toward the downstream end of the duct, respectively, from a first cross-sectional area to a second cross-sectional area smaller than the first cross-sectional area. Within said at least one duct, a discharge nozzle is provided, and a downstream end of said discharge nozzle, with respect to the intended flow direction of the duct and/or the general direction of airflow, is located within a longitudinal portion of tapered cross-section. Provided that the discharge nozzle is configured to discharge at the downstream end, or adjacent to the downstream end, fluid from the discharge nozzle is discharged in an accelerated flow. Said longitudinal portion of tapered cross-section, in which the downstream end of said discharge nozzle is provided, may be configured such that the hydraulic diameter of the conduit at the position where the conduit has the first cross-sectional area is 1.12 times or more and 2.5 times or less the hydraulic diameter of the conduit at the position where the conduit has the second cross-sectional area.

As an even more specific example, the downstream end of the nozzles may be provided at different positions within the tapered cross-sectional longitudinal portions of different ducts, thereby producing different waste flow cross-sections and therefore different mass or volumetric flow rates through the different ducts.

In non-limiting embodiments, it may be provided that, of two fluid plenum chambers arranged upstream of the most downstream fluid plenum chamber, the one arranged most upstream is fluidically connected via discharge means to a greater number of conduits than the one arranged most downstream. This may be intended to supply both fluid plenum chambers with the same fuel.

It should be mentioned that, in principle, a plenum chamber, as defined between two adjacent transverse walls, can be subdivided into subplenums in a direction along the burner axis, or over the burner cross-section, respectively. In this way, the fluid supply to the ducts can be controlled not only along the general airflow direction or the burner axis, but also around the burner cross-section.

In other aspects, inserts may be provided within at least one of the plenum chambers to mitigate eventual non-uniformity of volumetric flow to the various discharge means with which the plenum chamber is in fluid communication.

Further disclosed is a combustion chamber comprising a combustion space and further comprising at least one embodiment of a burner as set forth above, wherein the second front, downstream wall of the burner faces the combustion space and the most downstream of the fluid plenums adjacent the second front, downstream wall is provided in the form of a coolant plenum. The coolant plenum may be connectable to, or connected to, a source of cooling air. In other aspects, the coolant plenum may be connectable to, or connected to, a source of an alternative coolant such as, but not limited to, steam. Connectable means in this context that there is a connecting line or feed line for the connection, but the same may be equipped with a shut-off and/or control device, such that fluid communication is not always necessarily present.

At least one fluid plenum may be fluidically connectable to a fuel gas source. At least one fluid plenum may be connectable to a fuel source containing at least 50% hydrogen by volume. At least one fuel plenum may be connectable to a source of an inert fluid. In particular, it may be appreciated that it is useful for a plenum to be connectable to a source of hydrogen-rich fuel or other highly reactive fuel, as compared to natural gas, if a downstream plenum is connectable to a source of an inert fluid to mitigate the risk of flashback.

At least one plenum chamber that is connectable to a source of fuel fluid may also advantageously be provided so as to be connectable to a source of purge fluid, such as air or inert fluid, to prevent backflow into the plenum chamber when it is not pressurized.

Furthermore, a gas turbine engine is disclosed comprising a combustion chamber of the type described above.

It is understood that the features and embodiments disclosed above may be combined with one another. It will further be appreciated that, within the scope of this disclosure and the claimed subject matter, additional embodiments are conceivable and are obvious and apparent to one skilled in the art by virtue of this disclosure.

Brief description of the drawings

The subject matter of the present disclosure will now be explained in more detail by means of selected exemplary embodiments shown in the accompanying drawings. The figures show

Fig. 1 shows an embodiment of the burner disclosed herein in a sectional view;

Fig. 2 illustrates a nozzle type discharge means;

Fig. 3 shows a second embodiment of the burner disclosed here in a sectional view;

Fig. 4 shows a third embodiment of the burner disclosed herein in a sectional view;

Fig. 5 shows an embodiment of the burner disclosed here with a cartridge inserted through a passage in a sectional view;

Fig. 6 shows an embodiment of the burner disclosed herein, wherein the ducts have different minimum cross-sectional areas, in a sectional view;

Fig. 7 shows an embodiment of the burner disclosed herein, wherein nozzle-type discharge means extend differently in depth into tapered sections of the ducts, in a sectional view;

Fig. 8 shows an embodiment of the burner disclosed herein, wherein two plenum chambers are connected to coaxial and concentric supply connectors, in a sectional view;

Fig. 9 illustrates the possible flow direction orientation of discharge media;

Fig. 10 illustrates a burner duct in a cross-sectional view, wherein the discharge means are arranged to discharge the fluid from a plenum chamber with a tangential velocity component;

Fig. 11 outlines the arrangement of blades at the inlet of a duct to induce a vortex flow of combustion air within the duct;

Fig. 12 illustrates the possible relative longitudinal discharge positions of a nozzle type discharge means and a wall opening type discharge means;

Fig. 13 outlines the hexagonal arrangement of passages and fuel ducts and/or nozzles of cartridges in embodiments of the burner disclosed herein;

Fig. 14 illustrates possible arrangements of pilot ducts, liquid fuel combustion nozzles or cartridges, steam or water injection nozzles or cartridges and the like with respect to a generally hexagonal passage arrangement;

Fig. 15 illustrates oblique steps to induce a macroscopic vortex downstream of the burner;

Fig. 16 shows an embodiment of the burner disclosed here with coolant discharge into the ducts in a sectional view;

Fig. 17 illustrates an exemplary elliptical wall opening in a duct wall;

Fig. 18 illustrates an exemplary polygonal wall opening in a duct wall; and

Fig. 19 outlines geometric details of the polygonal wall opening in Fig. 18.

It is understood that the drawings are highly schematic, and unnecessary details may have been omitted for educational purposes to facilitate understanding and representation. It is further understood that the drawings show only selected illustrative embodiments, and that embodiments not shown may nevertheless be clearly placed within the scope of the subject matter disclosed and/or claimed herein.

Exemplary ways of carrying out the teaching of this disclosure

Figure 1 shows an exemplary embodiment of a burner 1. The burner may be particularly suitable for the combustion of hydrogen or hydrogen-rich fuels and other, highly reactive fuels compared to natural gas, although it is not limited to this application. The burner 1 comprises an upstream front wall 11 and a downstream front wall 12. A combustion air plenum may be located on an upstream side 2 of the burner 1. The combustion space is intended to be provided on the downstream side 3. The combustion air plenum may be provided, as a non-limiting example, such that compressed air is supplied to it from the compressor of a gas turbine engine, while the combustion space may be arranged to discharge into the expansion turbine of a gas turbine engine. Furthermore, as indicated above, "air" should be understood as representative of any oxidizing agent, or fluid comprising an oxidizing agent, that is suitable for the combustion of a fuel, and such oxidizing agent or fluid comprising an oxidizing agent is generally known to one of skill in the art, although for ease of description, air is used as a common example representative of generic oxidizing agents or suitable fluids containing oxidizing agents. A general direction of air flow is defined from the upstream wall 11 to the downstream wall 12. Partition walls 21, 22, and 23 are interposed between the upstream front wall 11 and the downstream front wall 12 and extend across the general direction of air flow. The front walls 11 and 12 and the partition walls 21, 22, and 23 may be generically referred to as cross walls since they extend transversely to or across the general direction of burner air flow. A space between the upstream front wall 11 and the downstream front wall 12 is divided into four plenums by the dividing walls, namely the upstream plenum 31 between the upstream front wall 11 and the dividing wall 21, the plenum 32 between the dividing walls 21 and 22, the plenum 35 between the dividing walls 22 and 23 and the downstream plenum 33 between the dividing wall 23 and the downstream front wall 12. The side wall 28 further confines the plenums 31 and 32, while the side wall 29 confines the downstream plenum 33. The plenum 35, on the other hand, is not confined by a side wall and is thus in direct fluid communication with fluid provided on the sides of the burner 1, which in most common, but not limited to, cases is identical to the fluid on the upstream side 2 of the burner 1. The plenums 31, 32 and 33 may thus be referred to as closed plenums, which require a supply line to be supplied with fluid, while the plenum 35 is referred to as an open plenum which may be supplied with fluid through open side walls. The plenum 35 may be in direct fluid communication with a combustion air plenum within which the burner is installed.

The most downstream plenum 33 is preferably used as a coolant plenum for cooling the downstream front wall 12, which is exposed to the heat of a combustion space on the downstream side 3 of the burner 1. The plenum 33 is fed from a coolant supply source via coolant feed connectors 331, whereby generally an air flow derived from the combustion air can be used for cooling purposes. Steam or any other suitable cooling fluid can also be applied. It may be provided that the coolant plenum 33 is not confined by a side wall and is therefore configured as an open plenum and can be placed within a larger air plenum of the combustion chamber, such that cooling air can flow into the cooling air plenum 33 from the entire circumference thereof. This may also be achieved to the extent that the side wall 29 of the plenum chamber 33 is perforated. The plenum chamber 31 may be supplied with fluid via a supply connector 311 which joins the plenum chamber 31 from the upstream side of the burner. The plenum chamber 32 may be supplied with fluid via a fluid supply connector 321 which extends from the upstream side of the burner and through the plenum chamber 31. As will be appreciated from Figure 1, the cross walls 11, 21, 22, 23 and 12 are provided with multiple sets of aligned openings such that passages 40 are formed, only some of which are designated by reference numerals, and which extend through the burner 1 from the upstream side 2 to the downstream side 3. Through passages 40, through cross walls 11, 21, 22, 23 and 12 and through plenum chambers 31, 32, 35 and 33 extend conduits 41, 42 and 45. The walls of the conduits are provided so as to be gas-tight with respect to the cross walls. It should be noted that, in certain embodiments, the conduits are seamlessly joined with the cross walls, insofar as the conduit walls and the cross walls are manufactured in a single monolithic piece. This may be achieved by additive manufacturing, although any suitable manufacturing method for manufacturing the burner 1 may be applied. Conduits 41, 42 and 45 provide fluid communication from the upstream side 2 to the downstream side 3 of the burner along their longitudinal directions. In operation, combustion air flows through conduits 41, 42, and 45 from the combustion air plenum of a combustion apparatus, or the upstream side 2 of the burner 1, to the combustion space, or the downstream side 3 of the burner 1. Through holes 51 are provided through the walls of the ducts, only some of which are designated by reference numerals, and they provide fluid communication between the plenum 31 and the conduits 41 and 45. The through holes 51 are discharge means for discharging a fluid from the plenum 31 into the conduits 41 and 45. The through holes 52 are provided through duct walls corresponding to the conduits 45 and provide fluid communication between the plenum 32 and the conduits 45. Additionally, the duct 42 is fluidically isolated from the plenum 31, and is fluidically connected to the plenum chamber 32 by a discharge means being a nozzle 62 suspended within the conduit 42. It is noted that the burner proposed here is not limited to only a single conduit of the conduit type 42, which is fluidically connected to only one plenum chamber through a nozzle type discharge means 62.

2 shows a nozzle-type discharge means comprising a nozzle 62 suspended within a conduit 42. The nozzle 62 is suspended within the conduit 42 by tubes 132, which provide a mechanical connection between the nozzle and the conduit wall. The tubes 132 provide fluid communication between the nozzle 62 and the plenum chamber 32. Although two suspension tubes 132 are shown, or are visible, respectively, in the exemplary embodiment, it is understood that more suspension tubes could be provided, while in other embodiments only a single suspension tube may be provided. The suspension tube(s) may also be supplemented by suspension struts, which provide mechanical fixation to the conduit wall, but otherwise do not serve to deliver fluid to the nozzle. The nozzle, in the embodiment shown, is arranged coaxial with the axis 451 of the conduit 42 and is provided centered within the conduit. The nozzle is provided with an opening in a front face of the nozzle that is downstream of the combustion air flow 4 through the conduit 42. Thus, fluid from the plenum chamber 32 may be injected into the combustion air flow 4 at the downstream end of the nozzle 62. The injection semi-angle α may be 30 degrees or less. In embodiments, however, discharge from the nozzle may be through differently arranged discharge openings. In still other embodiments, the nozzle 62 may be equipped with a liquid agent atomizer.

It will be appreciated that injection of a fluid into a conduit through a nozzle 62 produces different characteristics than discharge through openings in the duct wall. For example, nozzle 62 discharges a fluid in a core flow through conduit 42 rather than into a boundary layer in the duct wall, as occurs with discharge openings in the duct wall. In another aspect, the penetration of fluid discharged into a conduit through a wall opening may vary greatly depending on the differential pressure between the respective conduit and the fluid plenum, and thus, may depend on the mass flow rate or volumetric flow rate of discharged fluid. Fluid discharged from wall openings 51 and 52 in Figure 1 may penetrate to a different depth in axial flow through a conduit depending on the mass flow rate or volumetric flow rate of discharged fluid. As will be appreciated, this is not the case if a fluid is discharged from the plenum chamber 32 through the nozzle 62 in the embodiment of Figure 2. However, if the fluid is discharged from the nozzle 62 with a comparatively high momentum - i.e. a high volumetric flow rate - and at a low taper angle, it may be the case that a burst of relatively unmixed fluid travels downstream of the conduit, whereas if the fluid is discharged from the wall openings 51, 52 with a comparatively high momentum - i.e. a high volumetric flow rate - it will penetrate more deeply into the axial flow and in some cases may mix more intensely than at low volumetric flow rates. Furthermore, as will be appreciated, the discharge position from a wall opening is coupled to the position of the respective plenum chamber, whereas a nozzle 62 may extend further downstream, or also upstream, within the conduit and allow fluid from one plenum chamber to be discharged into the conduit away from the position of the plenum chamber from which the fluid originates. Furthermore, a nozzle within a conduit results in a constriction of the flow cross-section through the conduit, and may therefore produce downstream eddies, which may encourage mixing of the discharged fluid with the axial flow of, for example, combustion air through the conduit. Thus, providing discharge means from plenum chambers to conduits in a burner of the type outlined above can result in excellent results when both types of discharge means are suitably combined in different conduits, at a different distance from the downstream ends of the conduits. The absolute velocity or momentum of the fluid as it is discharged from the discharge means can, on the other hand, have a significant impact on the premixing behavior, as will be readily appreciated by one skilled in the art.

It is noted that more than one fluid plenum may be provided in fluidic communication with a conduit via nozzle-type discharge means, of the type such as discharge means 62 shown in Figure 1, and that more than one nozzle-type discharge means may be provided within a conduit. Likewise, more than one fluid plenum may be fluidically connected to one or more conduits via nozzle-type discharge means, and one or more conduits may be fluidically connected to one or more plenums via nozzle-type discharge means.

Referring again to Figure 1, it will be further appreciated that fluid discharged from fluid plenum 31 through wall openings 51 into conduits 41 and 45 travels a greater distance within the conduits before being discharged at the downstream side 3 of burner 1 as compared to fluid discharged through discharge means 52 and 62. If, for example, the same type of fuel, as a more specific example, gaseous fuel, is supplied to both plenums 31 and 32, fluid provided through plenum 32 and discharged into a conduit at a relatively downstream location may be less intensively premixed within a conduit than fuel discharged into a conduit at a relatively upstream location. As an example—depending on other burner and fuel parameters—the fuel discharged from the plenum 32 may support, by means of relatively diffusion-type combustion in the downstream space 3, the combustion of the more intensely premixed fuel in the plenum 31. This may be important in particular at low, sub-stoichiometric overall fuel/air ratios, which could result in the extinction of a completely premixed flame. Depending on the particular requirements, all or only some of the ducts may be equipped with discharge means for supplying fuel for the combustion of an intensely premixed fuel/air mixture, i.e., located relatively upstream in the duct. Likewise, all or only some of the ducts may be equipped with discharge means for supplying fuel for more diffusion-type combustion, i.e., located relatively downstream in the duct. As seen in Figure 1, some conduits may be intended only for a relatively distant upstream, or premix type, fuel supply, while others may be intended only for a relatively distant downstream, or diffusion type, fuel supply, while still other conduits may be equipped with discharge means for both supplies. It is noted that the mass flow of fuel through the plenum chambers 31 and 32 may be controlled through control means provided upstream of the fluid supply connectors 311 and 321. Although the control means are not shown, they are familiar to those skilled in the art. The mass flow of fuel into the plenum chambers 31 and 32 may thus be individually controlled, and thus the ratio between the mass flow or fuel discharged into the relatively upstream and relatively downstream conduits may be individually controlled. In other embodiments, however, discharge means may be provided in fluid communication with a single plenum chamber and configured to discharge fluid from the plenum chamber into the same or different conduits, or a combination thereof, at different distances from the downstream end of a conduit, resulting in a fixed mass flow ratio of differently mixed fluids at the downstream end of the conduits.

The coolant plenum chamber 33 arranged further downstream is fluidically isolated from the ducts and discharges the coolant through effusion cooling holes 121 in the downstream end wall and into the downstream space 3, i.e. into the combustion space, thereby effecting cooling of the downstream end wall 12.

In the embodiment of Figure 1, the ducts are shown to be slightly divergent at their downstream ends. Such a flared outlet of the ducts may be useful for reducing the exit velocity of the flow from a duct and thus reducing the risk of flame detachment from the microjet flames and thus ensuring stabilization of the microjet flames. However, the shape of the ducts at the downstream end could be chosen as needed to meet requirements, for example, regarding the velocity of the gas flow coming from a duct into the downstream space 3. The upstream end of the duct may in some cases be rounded or trumpet-shaped to reduce pressure losses.

The device shown in Figure 3 differs from the embodiment of Figure 1 mainly in that it comprises conduits 43 which are equipped with wall-opening type discharge means 51 fluidically connecting conduits 43 to the upstream plenum chamber 31, while being further equipped with nozzle type discharge means 62 fluidically connecting conduits 43 with the plenum chamber 32 downstream of the position of the wall-opening type discharge means 51.

It should be noted that a duct may also be equipped with more than one nozzle-type discharge means, which may further be configured to discharge into the duct at different longitudinal positions of the duct. Two nozzle-type discharge means provided in the same duct may further be fluidically connected to the same fluid plenum or to different fluid plenums. It is further noted that for the purposes of this document, a longitudinal or upstream-downstream position within a duct, or any other reference to a longitudinal position within a duct, is generally referenced and measured from the downstream end of the respective duct, adjacent to the downstream plate 12. Such a dimension defines the distance for mixing fluids within a duct before discharging fluid into a combustion space and is thus a relevant parameter for a burner duct. Longitudinal dimensions within a conduit may further be expressed in multiples of the minimum hydraulic diameter of a conduit along its longitudinal extent, where the hydraulic diameter is determined as four times the local cross-sectional area divided by the circumference of a wall surrounding that cross-sectional area.

The burner 1 shown in the form of another exemplary embodiment in Figure 4 comprises conduits 48 and 49 which are configured as dedicated pilot conduits and which are characterized in that the position of a downstream discharge location in the conduits 48, 49 from a plenum different from the most downstream plenum 33, wherein said most downstream plenum is configured as a coolant plenum, is provided so as to be 5 times or less the minimum hydraulic diameter of the respective conduit upstream of the downstream end of the conduit. This is so close to the downstream end of the respective conduit that fuel discharged from either of the wall-opening type discharge means 54 provided in the conduits 48 or from the nozzle type discharge means 65 provided in the pilot conduit 49 will exit the conduit into the downstream combustion space or space 3 virtually unmixed with the combustion air flowing through the respective conduit and will thus produce a substantially diffusion type flame at the exit of the conduit. As outlined above, such flames produce greater nitrogen oxide formation, but on the other hand superior combustion robustness. Such substantial pilot flames can support the combustion of fuel discharged into the conduits 41, 48 and 49 relatively further upstream in the conduits via the discharge means 51, and thus become heavily premixed as they exit the conduits, particularly at low fuel/air ratios. In the exemplary embodiment shown, each of the pilot discharge means, located less than five minimum hydraulic diameters upstream of the downstream end of the respective conduit, is provided in a conduit which also comprises upstream discharge means 51. This is not necessarily the case. A pilot conduit may also be provided in the form of a self-contained pilot conduit having no other discharge means upstream of the pilot discharge means. However, distributing the more upstream discharge means into as many conduits as possible may produce advantages insofar as a given fuel mass flow through these upstream discharge means can be distributed into a maximum fraction of the combustion air, resulting in good conditions for reducing nitrogen oxide emissions when the burner is operated at high loads, i.e. with a comparatively high overall fuel/air ratio.

The skilled person will readily appreciate, in light of the present disclosure, that the burner disclosed herein is not limited to being provided with three plenum chambers, but more generally may usefully be provided with any number of plenum chambers such as two or more. For example, the burner shown in Figure 1 may be supplemented with two additional plenum chambers which are simply connected respectively to conduits via relatively upstream discharge means and relatively downstream discharge means such as conduits 41 and 42 in Figures 1 and 3. It may also be supplemented with a combined pilot/premix conduit as shown at 48 and 49 in Figure 4. By fluidically connecting to different plenum chambers, the same conduits may thereby be supplied with natural gas and/or a different fuel, such as hydrogen. Thus, a highly versatile burner is achieved that is suitable, for example, for the combustion of hydrogen or a hydrogen-rich fuel or other highly reactive fuel and for the combustion of natural gas in variable pilot/premix operation, through the same ducts. The order in which the different plenums are arranged along a general direction of burner airflow from the upstream side defined by the upstream front wall 11 to the downstream side defined by the downstream front wall 12, or the longitudinal position at which fluid from a specific plenum is discharged into the conduit, will be determined by one skilled in the art by applying his or her general knowledge and taking into account the effect of the mixing distance of a fluid within the duct from the fluid discharge position to the downstream end of the duct. One skilled in the art will readily appreciate that modules comprising fluid plenums adapted to discharge a specific fluid into at least some of the ducts can, in a virtually modular manner, be stacked one on top of another. This can be achieved by fabricating burners with a different number of "slices" comprising a fluid plenum, sections of conduits, appropriate discharge means for fluidically connecting the plenum to the interior of the conduits, and, optionally, a fluid supply connector for supplying fluid to the plenum. It could be considered to actually construct the burner from stacked modules. The number of plenums is, in principle, not limited. Limiting factors could be considered to include increased conduit lengths and, therefore, increased pressure losses, and other issues that might arise if fluids are discharged too far upstream of the downstream end of the conduit. The fluid plenums, with their specific discharge means through which they are fluidically connected to at least one conduit, can be stacked in any order that one skilled in the art might deem appropriate for a particular purpose. However, it might be advantageous for the most downstream plenum to be a coolant plenum. It will be appreciated that, due to the versatility of the burner disclosed herein, an exhaustive description of possible embodiments is not practical. However, with an understanding of the underlying principle behind the stacked microduct burner disclosed herein, and the function and merits of certain specific "module" embodiments, the skilled artisan will receive a comprehensive understanding.

Figure 5 outlines an embodiment of a burner 1 in which a cartridge 60 is provided through a passage 40. In certain embodiments, the cartridge 60 may be a free-standing, retractable element. The cartridge 60 may be provided instead of or within a duct. If the cartridge 60 is provided instead of a duct, it is understood that the cartridge 60 is preferably configured to achieve a gas-tight seal of the plenum chambers. In the embodiment shown, the cartridge 60 extends through a duct, whereby the sealing of the plenum chambers is achieved by the duct wall which may be manufactured seamlessly with front walls 11 and 12 and dividing walls 21, 22 and 23 in the primary forming process. Optionally, spiral or longitudinally extending flutes may be provided on an outer surface of the cartridge and/or the inner side of the duct wall through which the cartridge 60 extends. Combustion air may be provided through the flutes. The flutes may be spiral, at least at their downstream ends adjacent the downstream front wall 12 and where they open into the downstream space 3, to generate a turbulent flow of combustion air at or around the downstream end of the cartridge 60. A fluid 6 may be provided through the cartridge 60 to the downstream space 3. Such fluid may be vapor, or a gaseous fuel, or a mixture of gaseous fuel and another gaseous agent, which may be intended, for example, for diffusion-type combustion. The gaseous agent may be discharged with a vortex, which may rotate in conjunction with or counter-rotate with a combustion air vortex. In other embodiments, the cartridge 60 may comprise a liquid atomizing nozzle, thereby discharging the fluid 6 in the form of a spray cone 5. The liquid may be liquid fuel or water or a mixture thereof. It is understood that the cartridge 60 may be provided with, and may be discharged therethrough, additional agents, for example steam or atomizing air. A burner of the type disclosed herein may comprise more than one cartridge 60. The burner 1 of Figure 5 further comprises conduits 43 that are equipped with relatively upstream nozzle-type discharge means 61 in fluid communication with the plenum chamber 31 and relatively downstream wall-opening-type discharge means 52 in fluid communication with the plenum chamber 32.

Figure 6 shows an exemplary embodiment in which some of the conduits have different diameters. For example, conduits 41a and 41b, which are equipped with wall-opening type discharge means 51 relatively upstream and in fluid communication with plenum chamber 31 only, have different minimum hydraulic diameters. It will be appreciated that in a conduit without an insert, the longitudinal section having such a minimum hydraulic diameter defines a metering section. These different diameters, as will be readily appreciated, have an impact on the mass flow rate of combustion air through the respective conduits. If the discharge means 51 provided in conduits 41a and 41b have the same integral cross-section per conduit, it will be appreciated that the flow through conduit 41b exhibits a higher fuel-to-air ratio of the fuel discharged from plenum chamber 31 than the flow through conduits 41a. However, if the integral cross-section of the discharge means 51 of the conduits 41a is greater than the integral cross-section of the discharge means 51 in the conduits 41b, the equivalence ratios may or may not be equal, and due to the different minimum hydraulic diameters, the heat load on the downstream surface of the burner adjacent the downstream wall 12 may be caused to vary. In the conduits 42 and 43, however, a residual cross-section between an inner wall of the conduit and an outer wall of the nozzles 62 may define the metering section. The mass flow rate through the conduits 42 and 43 may thus be varied by providing different hydraulic diameters of the conduits 42 and 43 around the nozzles 62, different outer diameters of the nozzles 62, or both.

In the embodiment of Figure 7, the conduits 44a, 44b and 44c are fluidically connected to the plenum 32 through the wall-opening type discharge means 52, while the plenum 31 is fluidically connected to the conduits 44a, 44b and 44c through the nozzle type discharge means 61a, 61b and 61c, respectively. In the region of the nozzle type discharge means, each conduit has a longitudinal portion of tapered cross-section in which the conduit progressively narrows downstream of the general direction of air flow, that is, in a direction from the first front wall 11 to the second front wall 12, from a first cross-sectional area to a second cross-sectional area smaller than the first cross-sectional area. The nozzle-type discharge means 61c extends further into the tapered longitudinal cross-sectional portion of the conduits 44c than the nozzle-type discharge means 61b extends into the conduits 44b, and the nozzle-type discharge means 61b extends further into the tapered longitudinal cross-sectional portion of the conduits 44b than the nozzle-type discharge means 61a extends into the conduit 44a. Accordingly, the minimum flow cross-section, defined as a residual cross-section between an inner wall of a conduit and an outer wall of a nozzle, is smaller in the conduit 44c than in the conduit 44b, and the minimum flow cross-section is smaller in the conduit 44b than in the conduit 44a.

The device shown in Figure 8 outlines how two supply connectors 311 and 321 provided for feeding two plenum chambers may be arranged concentrically and coaxially.

As illustrated in Figure 9, the wall opening type discharge means may be arranged and configured to discharge the fluid from a plenum chamber to a conduit in one of the following options

• perpendicular to the longitudinal direction 451, such as the means 56 for discharging the plenum chamber 36;

• upstream of the direction of flow of the combustion air 4, or inclined in the upstream direction of the duct 46, respectively, such as the discharge means 57 of the plenum chamber 37; or

• downstream of the direction of flow of the combustion air 4, or inclined in the downstream direction of the duct 46, respectively, such as the discharge means 58 of the plenum chamber 38.

The direction along which the fluid is discharged into the conduit 46 from the respective discharge means 56, 57, 58 is indicated by the arrows emanating from the discharge means. It is noted that the application of this teaching is not limited to discharge means of the wall opening type.

Figure 10 shows a cross-section through a still more particular example of the embodiment shown in Figure 9 along the line X-X. The discharge means may be arranged and configured such that fluid is discharged from the plenum 36 to the conduit 46 with a tangential velocity component to form a vortex flow of discharged fluid as indicated by the circular arrows in Figure 10. It is noted that such a configuration of the discharge means is not limited to the embodiment of Figure 9 or any embodiment similar thereto. Such a configuration suitable for generating a vortex flow of discharged fluid from a plenum to a conduit may be applied, for example, but not limited to, discharge means discharging fluid in an upstream or downstream direction of the combustion air flow within a conduit, as for example shown at references 57 and 58 in Figure 9, or to a nozzle-type discharge means.

In further aspects, illustrated in Figure 11, at least one duct 46 may be provided with a row of vanes 452 arranged within the duct 46 and arranged around the circumference of the duct 46 and inclined at an angle to the longitudinal direction 451 of the duct 46, to induce a vortex flow as indicated at reference 401 over the combustion air flow 4. The vanes may in particular be provided at the upstream end of the duct 46 such that the vortex flow of combustion air is present essentially over the entire longitudinal extent of the duct 46. However, in other aspects, the vanes 452 may be arranged further downstream, to discharge fluids from certain plenum chambers in a purely axial flow of combustion air, while others may be discharged in a vortex flow of combustion air. The row of vanes 452 may be provided at the downstream end of the duct 46. Although it will be readily apparent to one skilled in the art, it should be mentioned that a vortex flow of combustion air may be combined with a tangential injection of at least one fluid from at least one plenum chamber, as outlined in connection with Figure 10. The vortices of combustion air and discharged fluid may rotate together or in opposite directions and may be affected by at least essentially the same tangential velocity components or different tangential velocity components and by an essentially identical or different number of eddies, as appropriate to one skilled in the art when applying his or her ordinary knowledge. The vanes 452 are in particular provided integrally and in one piece, i.e., seamlessly, with the burner, or the inner wall of a duct. It will be appreciated that, in particular, manufacturing the burner with additive manufacturing methods makes it possible to provide such rather small and complex geometries in an integral workpiece.

It is evident to one skilled in the art that the relative velocities of the combustion air and the fluid discharged into the combustion air flow within a duct can have a significant impact on the mixing of the fluids and can be applied to adjust the same and, therefore, the combustion behavior.

Figure 12 illustrates a detail of a possible further embodiment of the burner disclosed herein. Figure 12 shows a section of a burner with plenum chambers 36 and 37 and a duct 141 extending therethrough. Reference 4 indicates the flow of combustion air through duct 141. Plenum 36 is in fluid communication with duct 141 through nozzle-type discharge means 162, while plenum 37 is in fluid communication with duct 141 through wall-opening type discharge means 152. The nozzle-type discharge means 162 is configured to discharge fluid from the plenum 36 at a position s1 measured from the downstream end of the conduit 141, while the wall-opening type discharge means 152 is configured to discharge fluid from the plenum 37 at a position s2 measured from the downstream end of the conduit 141. Although the plenum 36 is located upstream of the plenum 37, fluid in the plenum 37 is discharged to the conduit 141 downstream of the discharge position s2 of the fluid from the downstream plenum 37. This illustrates the flexibility offered by a nozzle-type discharge means with respect to the discharge location of a fluid from a particular plenum to a conduit.

Figures 13a to 13d show plan views of the end faces of burners having a different number of passages. As can be easily seen, three adjacent passages are provided in each burner at the corners of an equilateral triangle. All embodiments shown, regardless of the number of passages, have in common that a central passage 40a is concentrically surrounded by concentric hexagonal rings of passages. The embodiment of Figure 13a has 7 passages, wherein a central passage 40a is surrounded by six passages 40b in a hexagonal arrangement. Every two adjacent passages 40b have the same distance from each other as from the central passage 40a. The embodiment of Figure 13b has 19 passages, wherein a central passage 40a is surrounded by six passages 40b in a first hexagonal ring and 12 passages 40c of a second hexagonal ring. As is evident when further considering Figures 13c and 13d, the burner can be easily scaled by adding additional concentric hexagonal rings of passages, each additional hexagonal ring comprising 6 more passages than the adjacent inner hexagonal ring. Each passage, excluding the passages in the outermost hexagonal ring, can in turn be considered to form the center of another hexagon of surrounding passages. In embodiments, the central passage 40a can be omitted. This self-similarity of the passage arrangement, together with the equidistant arrangement of all neighboring passages, facilitates scaling of the burner. On the one hand, a burner can be adapted to different burner sizes by adding additional hexagonal rings of passages of the same size and distance from each other. On the other hand, the cross-sections of the passages, or ducts, respectively, of a burner of a given size may have different dimensions. It should be noted that the ducts, or some of the ducts, may have a polygonal cross-sectional shape rather than circular or, generally speaking, rounded. In particular embodiments, at least some of the ducts may have the cross-sectional shape of an equilateral hexagon.

Figures 14a to 14c illustrate possible arrangements of pilot passages, liquid fuel nozzles, water or steam injection nozzles, etc., in a burner of the type described. It is clearly understood and goes without saying that said passages, nozzles, and the like extend through passages of the burner. As an example, as illustrated in Figure 11a, a pilot passage 49, represented by the solid dot, may be arranged in a central passage, while all other passages may be provided with any other type of passage. The burner of Figure 14b has six pilot passages arranged adjacent to one another in an equilateral hexagon. In the embodiment of Figure 14c, a pilot passage is provided in the center of each hexagonal arrangement of neighboring non-pilot passages. The person skilled in the art will appreciate that in the embodiments of Figure 14, for example, instead of the pilot lines 49, cartridges for the supply of water, steam, liquid fuel, pilot gas, etc. can be arranged.

Figure 15 illustrates how the passages 40b and 40c of the hexagonal rings, and consequently any means provided therethrough, may be inclined with respect to a burner axis 101, so as to discharge the flow coming from said passages, or ducts, respectively, with a macroscopic tangential component with respect to the burner axis. The burner axis 101 is defined so as to be at least essentially perpendicular to the downstream front face of the burner. The longitudinal direction of the central passage 40a, or duct respectively, is in particular aspects at least essentially parallel to the burner axis 101, while the longitudinal axis of the passages 40b and 40c is inclined approximately at an angle p with respect to the burner axis, so as to generate a vortex flow indicated by reference 102 downstream of the burner, or, more specifically, in the combustion space. In certain embodiments, a central passage may not be present. In this case, reference may be made, for example, to a center point of the hexagonal ring. It is understood that the inclination angle p of the passages may vary depending on the distance of a respective passage from the central passage 40a. As an example, the inclination angle p may increase with increasing distance from the central passage 40a or from the burner axis 101, or, in other aspects, with respect to a center point of the hexagonal ring. It is obviously not excluded that, in certain embodiments, the inclination angle p may decrease or may remain the same with increasing distance from the central passage 40a or from the burner axis 101, or, in other aspects, with respect to a center point of the hexagonal ring. Due to the self-similarity of the passage arrangement, a burner may be subdivided into smaller areas, where each area defines a local center and an enclosing hexagonal passage arrangement, where the passages surrounding a specific center may be inclined to provide a vortex around said local central passage. In other words, the passages of a concentric hexagonal ring are configured such that the fluid discharged to the burner's downstream side from the passages of the concentric hexagonal ring has a velocity component that is tangential to a circle defined around the center point of the hexagonal ring. It can be seen that an embodiment in which a macroscopic vortex is generated is useful, for example, when replacing vortex burners in a legacy combustion apparatus.

The example of Figure 16 relates to a specific embodiment of burner cooling. In the exemplary embodiments, the plenum chambers 31 and 32 are configured to discharge into conduits 47 through the wall-opening type discharge means 51 and the nozzle-type discharge means 62, respectively. The wall 23 is provided with through holes 122 fluidically connecting the open plenum chamber 35 and the more downstream plenum or cooling plenum 33. As outlined above, the open plenum 35 is in fluid communication with a space surrounding the burner 1, i.e., for example, with an air receiver. Air from the open plenum 35 flows through the opening 122 to the cooling plenum 33. By means of cooling air jets entering the plenum 33 through holes 122, impingement cooling of adjacent areas of the downstream wall 12 may be effected. Other areas of the downstream wall 12 are effusion cooled by cooling air being discharged into the downstream space 3 through through holes 121. A further fraction of the cooling fluid is discharged into the downstream portion of the conduits through coolant discharge means 53. For the sake of completeness, it is noted that coolant discharge means providing fluid communication between the more downstream plenum and the interior of a conduit may also be used in connection with embodiments wherein coolant is supplied to the plenum 33 through coolant feed connectors.

Although the exemplary embodiments shown above all have two fluid plenums in connection with the conduits, other than the most downstream plenum being configured as a cooling plenum to provide appropriate cooling for the downstream wall having a high thermal load, one skilled in the art will appreciate that more plenums may be provided in fluid communication with at least one conduit, and they may be adapted to provide different types of fuel, fuel intended for a different premixing prior to combustion, or steam or other inert fluids. In certain embodiments, a nozzle-type discharge means may be equipped with an atomizer, such that liquids, such as, for example, liquid fuel or water, may also be discharged into a conduit through said nozzle-type discharge means. In certain embodiments, the burner may be modular, each module comprising at least one fluid plenum between two transverse walls, a conduit segment or conduit segments extending through the transverse walls and the plenum or plenums, a discharge means for providing fluid from the plenum or plenums to the conduit segment or conduit segments, and, optionally, a fluid supply connector or fluid supply connectors in fluid communication with the fluid plenum or fluid plenums.

Figure 17 shows a detail of an exemplary embodiment of a burner of the type described herein. A through hole 52a through the wall of the conduit 142 to provide fluid communication with the plenum chamber 32 is elliptical in shape, with a long ellipse axis 528 and a short ellipse axis 529. The included angle between the long ellipse axis 528 and the longitudinal direction of the duct 451, the general direction of air flow, or an axis of the burner, is chosen in particular embodiments to be 30 degrees or less, and in more particular embodiments, as shown in Figure 17, the included angle between the long ellipse axis 528 and the longitudinal direction of the duct 451 is at least substantially zero. Furthermore, the ratio of the length a of the long ellipse axis to the length b of the short ellipse axis may be chosen to be 1.25 or more. This configuration offers advantages, particularly if the burner or a burner module is manufactured by additive manufacturing, where the construction direction can be chosen to be at least approximately parallel to the general direction of air flow, the duct axis, or the burner axis. The elliptical shape of the opening can facilitate such manufacturing in that protruding structures during manufacturing are significantly reduced. In other embodiments, the through-hole can, for the same reason, be lance-shaped or have the shape of a pointed arc with the apex pointing at least substantially in the construction direction of the additively manufactured structure.

Essentially, the same advantages can be achieved, for example, with a polygon-shaped wall opening 52b, as shown in Figures 18 and 19. The wall opening 52b, as shown, has a base and an apex pointing against the intended flow of combustion air 4. As outlined in more detail in Figure 19, the polygon-shaped wall opening 52b has a polygon-shaped boundary comprising straight boundary segments 521, 522, 523, 524 and 525. The boundary may also be considered to comprise an upstream boundary section 526 bordering the opening in a direction against the flow of combustion air 4 and a downstream boundary section 527 bordering the opening in the direction of the combustion air flow. The upstream boundary section 526 comprises straight boundary segments 522 and 523, while the downstream boundary section 527 comprises straight boundary segments 521, 524, and 525. The straight boundary segments 522 and 523 of the upstream boundary section 526 form an apex of the opening 52b that points upstream relative to the combustion air flow. The straight boundary segments 522 and 523 include interior angles 5 and £ with the longitudinal direction 451 of the duct 142 and that are 45 degrees or less. The exemplary opening is particularly suitable in connection with a component that is additively manufactured with a build direction against the intended combustion air flow 4. Generally, it can be seen that an opening defined within a boundary having a vertex pointing in the component's build direction, with the vertex confined between two straight boundary segments bordering the opening in the build direction, where those two boundary segments include an angle of 45 degrees or less with one parallel to the build direction, is beneficial in connection with an additively manufactured component. A two-vertex geometry, such as a rhombus-shaped geometry, could also be applied.

Although the subject matter of the disclosure has been explained by means of exemplary embodiments, it is understood that these are not intended to limit the scope of the claimed invention in any way. It will be appreciated that the claims may cover embodiments not explicitly shown or disclosed therein.

Claims (17)

1. A burner (1) comprising a first upstream front wall (11), a second downstream front wall (12), such that a general airflow direction runs from the first upstream front wall to the second downstream front wall, wherein at least one dividing wall (21, 22, 23, 25, 26) extends across the general airflow direction and between the first and second front walls, whereby the at least one dividing wall divides a space between the first front wall and the second front wall into at least two independent fluid plenum chambers (31, 32, 33, 35, 36, 37, 38) stacked along the general direction of air flow, the burner further comprising at least one peripheral wall (28, 29) extending between at least one option of: the front walls, at least two dividing walls, and/or a front wall and at least one dividing wall, wherein a plurality of passages (40, 40a, 40b, 40c) are provided through the first and second front walls and the at least one dividing wall, wherein a plurality of conduits (41, 41a, 41b, 42, 43, 44a, 44b, 44c, 45, 46, 47, 48, 49, 141, 142) are provided, the conduits extending through at least some of the passageways and the conduits extending through the fluid plenum chambers wherein the conduit walls are leak-tightly connected to the first front wall, the second front wall and the at least one dividing wall, to provide fluid communication between an upstream side of the burner adjacent the first front wall and a downstream side of the burner adjacent the second front wall, and wherein each conduit has a first upstream end adjacent the first upstream front wall (11) and a second downstream end adjacent the second downstream front wall (12), wherein the burner comprises discharge means (51, 52, 53, 56, 57, 58, 61, 61a, 61b, 61c, 62, 65, 152, 162) for providing fluid communication between at least one of the fluid plenum chambers and the interior of at least one conduit of the plurality of conduits and each of the discharge means being configured to discharge a fluid from a fluid plenum chamber into a conduit of the plurality of conduits, wherein at least one of the discharge means is a wall-opening type discharge means (51, 52, 52a, 52b, 53, 56, 57, 58, 152) that is provided in the form of at least one through hole through a conduit wall and wherein at least one of the discharge means is a wall-opening type discharge means (61, 61a, 61b, 61c, 62, 65, 162) of nozzle type discharge which are provided in the form of a discharge nozzle which is suspended in a conduit by a tube (132) extending from a fluid plenum to the discharge nozzle and providing fluid communication between said fluid plenum and the discharge nozzle, wherein at least one conduit (43, 44a, 44b, 44c, 45, 47, 48, 49, 141) of the multitude of conduits is provided with at least two discharge means, wherein said at least two discharge means are provided for discharging a fluid from within the respective fluid plenum at different positions along a longitudinal direction (451) of the conduit. 2. The burner according to claim 1, wherein at least one conduit (43, 44a, 44b, 44c, 45, 47, 48, 49, 141) of the plurality of conduits is fluidically connected to at least two fluid plenum chambers (31, 32, 33) by means of discharge means, wherein at least a first discharge means is provided to provide fluidic communication with a first of said at least two fluid plenum chambers and at least a second discharge means is provided to provide fluidic communication with a second of said at least two fluid plenum chambers. 3. The burner according to any of the preceding claims, wherein at least one duct (43, 44a, 44b, 44c, 47, 49, 141) among the multitude of ducts is configured with first discharge means (51, 52, 53, 152) which are wall-opening type discharge means and further with second discharge means (61, 61a, 61b, 61c, 62, 65, 162) which are nozzle type discharge means. 4. The burner according to the preceding claim, wherein the first discharge means (152) is in fluid communication with a first fluid plenum (37) and the second discharge means (162) is in fluid communication with a second fluid plenum (36), wherein the first fluid plenum (37) is disposed downstream of the second fluid plenum (36) along the general direction of air flow and a discharge position (s1) of the discharge nozzle of the second discharge means (162) providing fluid communication between the conduit (141) and the second fluid plenum (36) is located downstream of the discharge position (s2) of the first discharge means (152). 5. The burner according to any one of the preceding claims, wherein a discharge position of any nozzle-type discharge means (61,61a,61b,61c,62,65,162) is located at a longitudinal position of the duct within which the nozzle-type discharge means are arranged which corresponds to a maximum of 20 minimum hydraulic diameters of the respective duct when measured from a downstream end of the duct and along the longitudinal direction of the duct. 6. The burner according to any of the preceding claims, wherein at least a subset of the plurality of passages (40b, 40c) are arranged in at least one concentric hexagonal ring around a center point of the at least one concentric hexagonal ring, wherein the passages arranged in the at least one concentric hexagonal ring are oriented such that fluid discharged on the downstream side of the burner from the passages of the concentric hexagonal ring has a velocity component that is tangential to a circle defined around the center point of the hexagonal ring. 7. The burner according to any one of the preceding claims, wherein the second fluid plenum (35), when counted from the downstream side of the burner, is in fluid communication with the fluid surrounding the burner on its lateral sides, and wherein a more downstream fluid plenum (33) is in fluid communication with said second fluid plenum (35) when counted from the downstream side of the burner through the dividing wall (23) delimiting the more downstream fluid plenum (33) with respect to the second fluid plenum (35) when counted from the downstream side of the burner and is further in fluid communication with the downstream side (3) of the burner through the downstream front wall (12). 8. The burner according to any of the preceding claims, wherein the most downstream fluid plenum (33) is in fluid communication with at least one conduit through wall-opening type discharge means (53) provided in the form of through holes in the walls of the conduits. 9. The burner according to any one of the preceding claims, wherein at least one conduit among the multitude of conduits is configured in the form of a pilot conduit (49) and is in fluid communication with a fluid plenum (32) different from the most downstream fluid plenum via discharge means (65) configured to discharge into the pilot conduit at a longitudinal distance, when measured from the downstream end of the conduit and along a longitudinal extension of the conduit, corresponding to at most five times the minimum hydraulic diameter of the conduit, and preferably wherein a multitude of pilot conduits (49) are provided and each pilot conduit is arranged centrally of adjacent non-pilot conduits arranged in a concentric hexagon around the pilot conduit. 10. The burner according to any one of the preceding claims, wherein at least a subset of the plurality of passages (40c; 40b, 40c) are arranged as outer passages in a concentric hexagonal ring around and adjacent to the at least one inner passage (40a; 40a, 40b), wherein at least one inner conduit is provided in the at least one inner passage and at least one outer conduit is provided in the outer passages, wherein the at least one inner conduit has a downstream-most discharge position in which discharge means in fluid communication with a fluid plenum different from the downstream-most fluid plenum are configured to discharge into the at least one inner conduit that is located at a first longitudinal distance with respect to the downstream end of the at least one inner conduit, and wherein the at least one outer ... more downstream fluid impeller are configured to discharge into the at least one outer conduit that is located at a second longitudinal distance with respect to the downstream end of the at least one outer conduit, wherein the second longitudinal distance is greater than the first longitudinal distance. 11. The burner according to any one of the preceding claims, wherein at least one of the through holes (52a) arranged in the wall of a duct (142) among the multitude of ducts for providing fluid communication with a fluid plenum chamber (32) has an elliptical shaped cross section, wherein in particular the long axis (528) of the ellipse includes an angle of at most 30 degrees with one of a longitudinal axis of the duct (451), the general direction of air flow or an axis of the burner, and further wherein in particular the ratio of the length (a) of the long ellipse axis (528) to the length (b) of the short ellipse axis (529) is 1.25 or more. 12. The burner according to any one of the preceding claims, wherein at least one of the through holes (52b) arranged in the wall of a conduit (142) among the multitude of conduits for providing fluidic communication with a fluid plenum chamber (32) has a polygonal shaped cross section having a polygonal shaped boundary, the polygonal shaped boundary comprising straight boundary segments (521, 522, 523, 524, 525), wherein said polygonal shaped boundary comprises an upstream boundary section (526) and a downstream boundary section (527), wherein at least one of the upstream boundary section and the downstream boundary section is shaped such that an angle (5, e) included between each straight segment of the respective boundary section and one of a longitudinal axis (451) of the duct, the general direction of air flow or an axis of the burner is less than or equal to 45 degrees. 13. The burner according to any one of the preceding claims, wherein at least a subset of ducts among the multitude of ducts are provided with nozzle-type discharge means within the respective duct, whereby an outer boundary of a respective discharge nozzle provided within a duct defines the nearest residual flow cross section between the discharge nozzle and the inner wall of the duct, wherein at least two ducts (44a, 44b, 44c) among the subset of ducts are provided with different residual flow cross sections. 14. The burner according to any one of the preceding claims, wherein at least one duct (44a, 44b, 44c) out of the multitude of ducts comprises at least one longitudinal portion of tapered cross-section, wherein within a longitudinal portion of tapered cross-section the cross-sectional area of the at least one duct tapers progressively downstream of the general airflow direction from a first cross-sectional area to a second cross-sectional area smaller than the first cross-sectional area, and wherein within said at least one duct a discharge nozzle (61a, 61b, 61c) is provided with a downstream end of said discharge nozzle located within a longitudinal portion of tapered cross-section, wherein in particular said longitudinal portion of tapered cross-section in which the downstream end of said discharge nozzle is provided is configured such that the hydraulic diameter of the duct at the position where the duct has the first cross-sectional area is 1.12 times or more and 2.5 times or less the hydraulic diameter of the conduit at the position where the conduit has the second largest cross-sectional area. 15. The burner according to the preceding claim in dependence on claim 13, wherein at least some of the subset of ducts (44a, 44b, 44c) are provided with discharge means (61a, 61b, 61c) provided in the form of a discharge nozzle within the respective duct and each of said discharge nozzles extends longitudinally, relative to the general direction of air flow, upstream of the longitudinal portion of tapered cross-section, within the longitudinal portion of tapered cross-section, or both, wherein at least a first of the discharge nozzles extends further downstream in the respective longitudinal portion of tapered cross-section than a second of said discharge nozzles. 16. A combustion chamber comprising a combustion space (3) and further comprising at least one burner (1) according to any preceding claim, wherein the second downstream front wall (12) of the burner faces the combustion space and the most downstream of the fluid plenum chambers (33) adjacent to the second downstream front wall is provided in the form of a coolant plenum. 17. A gas turbine engine comprising a combustion chamber according to claim 16.