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BURNER

20240060644 ยท 2024-02-22

    Inventors

    Cpc classification

    International classification

    Abstract

    A microtube cluster burner (1) comprises a multitude of ducts (41) extending through fluid plenums (31, 32, 33). Discharge means (51, 52) fluidly connect the plenums to the ducts. At least one of the ducts (41) is provided with at least two discharge means (51, 52) for discharging fluid from a plenum (31, 32) into the duct at at least two different longitudinal positions of the duct.

    Claims

    1. A burner (1) comprising a first, upstream front wall (11), second downstream front wall (12), a general airflow direction being from the first, upstream front wall to the second, downstream front wall, wherein at least one partition 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 partition wall divides a space between the first front wall and the second front wall into at least two separate fluid plenums (31, 32, 33, 35, 36, 37, 38) stacked along the general airflow direction, the burner further comprising at least one peripheral wall (28, 29) extending between at least one of: the front walls, at least two partition walls, and/or a front wall and at least one partition wall, wherein a multitude of passages (40, 40a, 40b, 40c) are provided through the first and second front walls and the at least one partition wall, wherein a multitude of ducts (41, 41a, 41b, 42, 43, 44a, 44b, 44c, 45, 46, 47, 48, 49, 141, 142) are provided, the ducts extending through at least some of the passages and the ducts extending through the fluid plenums wherein the duct walls are leak-proof connected to the first front wall, the second front wall and the at least one partition wall, so as 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 duct 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 plenums and the interior of at least one duct out of the multitude of ducts and each discharge means being configured for discharging a fluid from a fluid plenum into a duct out of the multitude of ducts, wherein at least one of the discharge means is a wall-opening type discharge means (51, 52, 52a, 52b, 53, 56, 57, 58, 152) which is provided as at least one through hole through a duct wall and wherein at least one of the discharge means is a nozzle type discharge means (61, 61a, 61b, 61c, 62, 65, 162) which is provided as a discharge nozzle which is suspended in a duct 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 duct (43, 44a, 44b, 44c, 45, 47, 48, 49, 141) out of the multitude of ducts is provided with at least two discharge means, wherein said at least two discharge means are provided to discharge a fluid from inside the respective fluid plenum at different positions along a longitudinal direction (451) of the duct.

    2. The burner according to claim 1, wherein at least one duct (43, 44a, 44b, 44c, 45, 47, 48, 49, 141) out of the multitude of ducts is fluidly connected to at least two fluid plenums (31, 32, 33) by a discharge means, wherein at least one first discharge means is provided for providing fluid communication with a first one of said at least two fluid plenums and at least one second discharge means is provided for providing fluid communication with a second one of said at least two fluid plenums.

    3. The burner according to claim 1, wherein at least one duct (43, 44a, 44b, 44c, 47, 49, 141) out of the multitude of ducts is configured with a first discharge means (51, 52, 53, 152) which is a wall-opening type discharge means and further with a second discharge means (61, 61a, 61b, 61c, 62, 65, 162) which is a nozzle type discharge means.

    4. The burner according to claim 1, 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 arranged downstream from the second fluid plenum (36) along the general airflow direction and a discharge position (s1) of the discharge nozzle of the second discharge means (162) providing fluid communication between the duct (141) and the second fluid plenum (36) is positioned downstream of the discharge position (s2) of the first discharge means (152).

    5. The burner according to claim 1, wherein a discharge position of any nozzle-type discharge means (61, 61a, 61b, 61c, 62, 65, 162) is positioned at a longitudinal position of the duct inside which the nozzle-type discharge means is arranged which corresponds to at maximum 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 claim 1, wherein at least a subset of the multitude of passages (40b, 40c) are arranged in at least one concentric hexagonal ring around a midpoint 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 at the downstream side of the burner form the passages in the concentric hexagonal ring has a velocity component which is tangential to a circle defined around the midpoint of the hexagonal ring.

    7. The burner according to claim 1, wherein at least one passage is provided with a cartridge (60) through the passage.

    8. The burner according to claim 1, 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 most 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 partition wall (23) delimiting the most downstream fluid plenum (33) from the second fluid plenum (35) when counted from the downstream side of the burner and further is in fluid communication with the downstream side (3) of the burner through the downstream front wall (12).

    9. The burner according to claim 1, wherein the most downstream fluid plenum (33) is in fluid communication with at least one duct through wall-opening type discharge means (53) provided as through holes in the duct walls.

    10. The burner according to claim 1, wherein at least one duct out of the multitude of ducts is configured as a piloting duct (49) and is in fluid communication with a fluid plenum (32) different from the most downstream fluid plenum through discharge means (65) configured to discharge into the piloting duct at a longitudinal distance, when measured from the downstream end of the duct and along a longitudinal extent of the duct, corresponding to at maximum five times the minimum hydraulic diameter of the duct.

    11. The burner according to claim 1, wherein a multitude of piloting ducts (49) are provided and each piloting duct is arranged in the centre of adjacent non-piloting ducts arranged on a concentric hexagon around the piloting duct.

    12. The burner according to claim 1, wherein at least a subset of the multitude of passages (40c; 40b, 40c) are arranged as outer passages on a concentric hexagonal ring around and adjacent at least one inner passage (40a; 40a, 40b), wherein at least one inner duct is provided in the at least one inner passage and at least one outer duct is provided in the outer passages, wherein the at least one inner duct has a most downstream discharge position at which a discharge means in fluid communication with a fluid plenum different from the most downstream fluid plenum is configured to discharge into the at least one inner duct which is positioned at a first longitudinal distance from the downstream end of the at least one inner duct, and wherein the at least one outer duct has a most downstream discharge position at which a discharge means in fluid communication with a fluid plenum different from the most downstream fluid plenum is configured to discharge into the at least one outer duct which is positioned at a second longitudinal distance from the downstream end of the at least one outer duct, wherein the second longitudinal distance is larger than the first longitudinal distance.

    13. The burner according to claim 1, wherein each cross-section taken along the longitudinal extent of each duct out of the multitude of ducts has one of a circular or polygonal shape.

    14. The burner according to claim 1, wherein the burner comprises at least one supply connector (311, 321, 331) for fluid supply of at least some of the fluid plenums, wherein at least two of the fluid plenums (31, 32, 33) are fluidly connected to a respective individual supply connector (311, 321, 331), wherein at least two supply connectors (311, 321) of different fluid plenums are arranged concentrically and coaxially.

    15. The burner according to claim 1, wherein at least one of the through holes (52a) arranged in the wall of a duct (142) out of the multitude of ducts for providing fluid communication with a fluid plenum (32) has an elliptically shaped cross-section, wherein in particular the long axis (528) of the ellipse includes an angle of at maximum 30 degrees with one of a longitudinal axis of the duct (451), the general airflow direction or a burner axis, and wherein further 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.

    16. The burner according to claim 1, wherein at least one of the through holes (52b) arranged in the wall of a duct (142) out of the multitude of ducts for providing fluid communication with a fluid plenum (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 (, ) included between each straight segment of the respective boundary section and one of a longitudinal axis (451) of the duct, the general airflow direction or a burner axis is smaller than or equal to 45 degrees.

    17. The burner according to claim 1, wherein at least a subset of ducts out of the multitude of ducts are provided with a nozzle type discharge means inside the respective duct, whereby an outer boundary of a respective discharge nozzle provided inside a duct defines a closest residual flow cross-section between the discharge nozzle and the inner wall of the duct, wherein at least two ducts (44a, 44b, 44c) out of the subset of ducts are provided with different residual flow cross-sections.

    18. The burner according to claim 1, wherein at least one duct (44a, 44b, 44c) out of the multitude of ducts comprises at least one tapering cross-section longitudinal portion, wherein within a tapering cross-section longitudinal portion the cross-sectional area of the at least one duct tapers downstream 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 a discharge nozzle (61a, 61b, 61c) is provided within said at least one duct with a downstream end of said discharge nozzle positioned within a tapering cross-section longitudinal portion, wherein in particular said tapering cross-section longitudinal portion 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 duct at the position where the duct has the second cross-sectional area.

    19. The burner according to claim 17, wherein at least some of the subset of ducts (44a, 44b, 44c) are provided with a discharge means (61a, 61b, 61c) provided as a discharge nozzle inside the respective duct and each of said discharge nozzles longitudinally extending, in relation to the general airflow direction, upstream of the tapering cross-section longitudinal portion, inside the tapering cross-section longitudinal portion, or both, wherein at least one first of the discharge nozzles extends further downstream into the respective tapering cross-section longitudinal portion than a second one of said discharge nozzles.

    20. A combustor 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 plenums (33) adjacent the second, downstream front wall is provided as a coolant plenum.

    21. A gas turbine engine comprising a combustor according to claim 20.

    Description

    BRIEF DESCRIPTION OF THE DRAWINGS

    [0057] The subject matter of the present disclosure is now to be explained in more detail by means of selected exemplary embodiments shown in the accompanying drawings. The figures show

    [0058] FIG. 1 shows an embodiment of the herein disclosed burner in a sectional view;

    [0059] FIG. 2 illustrates a nozzle-type discharge means;

    [0060] FIG. 3 shows a second embodiment of the herein disclosed burner in a sectional view;

    [0061] FIG. 4 shows a third embodiment of the herein disclosed burner in a sectional view;

    [0062] FIG. 5 shows an embodiment of the herein disclosed burner with a cartridge inserted through one passage in a sectional view;

    [0063] FIG. 6 shows an embodiment of the herein disclosed burner, wherein ducts have different minimum cross-sectional areas, in a sectional view;

    [0064] FIG. 7 shows an embodiment of the herein disclosed burner, wherein nozzle-type discharge means extend differently far into tapering sections of the ducts, in a sectional view;

    [0065] FIG. 8 shows an embodiment of the herein disclosed burner, wherein two plenums are connected to coaxial and concentric supply connectors, in a sectional view;

    [0066] FIG. 9 illustrates the possible streamwise orientation of discharge means;

    [0067] FIG. 10 illustrates a duct of a burner in a cross-sectional view, wherein discharge means are arranged to discharge the fluid from a plenum with a tangential velocity component;

    [0068] FIG. 11 outlines the arrangement of blades at the inlet of a duct to induce a vortex flow of combustion air inside the duct;

    [0069] FIG. 12 illustrates the possible relative longitudinal discharge positions of a nozzle-type discharge means and a wall-opening type discharge means;

    [0070] FIG. 13 outlines the hexagonal arrangement of passages and ducts and/or fuel nozzles of cartridges in embodiments of the herein disclosed burner;

    [0071] FIG. 14 illustrates possible arrangements of piloting 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;

    [0072] FIG. 15 illustrates tilted passages for inducing a macroscopic vortex downstream the burner;

    [0073] FIG. 16 shows an embodiment of the herein disclosed burner with coolant discharge into the ducts in a sectional view;

    [0074] FIG. 17 illustrates an exemplary elliptical wall opening in a duct wall;

    [0075] FIG. 18 illustrates an exemplary polygonal wall opening in a duct wall; and

    [0076] FIG. 19 outlines geometric details of the polygonal wall opening of FIG. 18.

    [0077] It is understood that the drawings are highly schematic, and details not required for instruction purposes may have been omitted for the ease of understanding and depiction. It is further understood that the drawings show only selected, illustrative embodiments, and embodiments not shown may still be well within the scope of the herein disclosed and/or claimed subject matter.

    EXEMPLARY MODES OF CARRYING OUT THE TEACHING OF THE PRESENT DISCLOSURE

    [0078] FIG. 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, compared to natural gas, highly reactive fuels, while not being limited to this application. Burner 1 comprises upstream front wall 11 and downstream front wall 12. On an upstream side 2 of burner 1 a combustion air plenum may be located. On the downstream side 3 the combustion space is intended to be arranged. The combustion air plenum may for a non-limiting instance be provided to be supplied with compressed air 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. Further, as noted above, air is to be understood as being representative of any oxidation agent, or fluid comprising an oxidation agent, which is suitable for the combustion of a fuel, and said oxidation agent or fluid comprising an oxidation agent is generically disclosed to a skilled person, although for the ease of description air is used as a common example representative of generic oxidation agents or suitable fluids containing oxidation agents. A general airflow direction is defined from the upstream wall 11 to downstream wall 12. Partition walls 21, 22 and 23 are interposed between upstream front wall 11 and downstream front wall 12 and extend across the general airflow direction. Front walls 11 and 12 and partition walls 21, 22 and 23 may generically be referred to as transverse walls, as they extend transverse to or across the general airflow direction of the burner. A space between upstream front wall 11 and downstream front wall 12 is divided into four plenums by the partition walls, namely most upstream plenum 31 between upstream front wall 11 and partition wall 21, plenum 32 between partition walls 21 and 22, plenum 35 between partition walls 22 and 23 and most downstream plenum 33 between partition wall 23 and downstream front wall 12. Lateral wall 28 further encloses plenums 31 and 32, while lateral wall 29 encloses most downstream plenum 33. Plenum 35, in contrast, is not enclosed by a lateral wall and is thus in direct fluid communication with fluid provided on the sides of burner 1, which in most common, while not limiting, cases is identical with the fluid on the upstream side 2 of burner 1. Plenums 31, 32 and 33 may thus be referred to as closed plenums, which require a supply line to be supplied with a fluid, while plenum 35 is referred to as an open plenum which may be supplied with fluid through open lateral sides. Plenum 35 might be in direct fluid communication with a combustion air plenum inside which the burner is installed. Most downstream plenum 33 is preferably used as a coolant plenum in order to cool downstream front wall 12 which is exposed to heat from a combustion space at the downstream side 3 of burner 1. Plenum 33 is fed form a coolant supply through coolant feed connectors 331, whereby generally an air flow bled from the combustion air may be used for cooling purposes. Also steam or any other suitable cooling fluid may be applied. It may be provided that coolant plenum 33 is not enclosed by a lateral wall and is thus configured as an open plenum and may be placed inside a larger air plenum of the combustor, such that cooling air may flow into cooling air plenum 33 form the entire circumference thereof. This may also be achieved in that lateral wall 29 of plenum 33 is perforated. Plenum 31 may be supplied with a fluid through supply connector 311 which joins into plenum 31 from the upstream side of the burner. Plenum 32 may be supplied through a fluid supply connector 321 which extends form the upstream side of the burner and through plenum 31. As will be appreciated by virtue of FIG. 1, transverse walls 11, 21, 22, 23 and 12 are provided with multiple sets of aligned openings, such that passages 40, of which only some are designated by reference numbers, are formed and extend through burner 1 from the upstream side 2 to the downstream side 3. Ducts 41, 42 and 45 extend through passages 40, through transverse walls 11, 21, 22, 23 and 12 and through the plenums 31, 32, 35 and 33. The duct walls are provided gas-leak proof with the transverse walls. It should be noted that in embodiments the ducts are seamlessly joined with the transverse walls, in that the duct walls and the transverse walls are manufactured in one monolithic piece. This may be achieved by additive manufacturing, while any suitable manufacturing method may be applied to manufacture burner 1. Ducts 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 ducts 41, 42 and 45 from the combustion air plenum of a combustion appliance, or the upstream side 2 of burner 1, to the combustion space, or the downstream side 3 of burner 1. Through holes 51, only some of which are designated by reference numbers, are provided through the duct walls and provide fluid communication between plenum 31 and ducts 41 and 45. Through holes 51 are discharge means for discharging a fluid from plenum 31 into ducts 41 and 45. Through holes 52 are provided through duct walls of ducts 45 and provide fluid communication between plenum 32 and ducts 45. In addition, duct 42 if fluidly isolated from plenum 31, and is fluidly connected to plenum 32 by a discharge means which is a nozzle 62 suspended inside duct 42. It is noted that the herein proposed burner is not limited to just one single duct of the type of duct 42, which is fluidly connected to only one plenum through a nozzle-type discharge means 62.

    [0079] A nozzle type discharge means comprising a nozzle 62 suspended inside a duct 42 is shown in FIG. 2. Nozzle 62 suspended inside duct 42 by tubes 132, which provide a mechanical connection between the nozzle and the wall of the duct. Tubes 132 provide fluid communication between nozzle 62 and plenum 32. While two suspension tubes 132 are shown, or visible, respectively, in the exemplary embodiment, it is understood that more suspension tubes could be arranged, while in other embodiments only a single suspension tube may be provided. The suspension tube or suspension tubes may also be supplemented by suspension struts, which provide mechanical fixation to the duct wall, but otherwise do not serve to supply fluid to the nozzle. The nozzle, in the shown embodiment, is arranged coaxial with axis 451 of duct 42 and provided centrally within the duct. The nozzle is provided with an opening at a front face of the nozzle which is downstream with respect to the flow of combustion air 4 through duct 42. Fluid from plenum 32 may thus be injected into the flow of combustion air 4 at the downstream end of nozzle 62. A half angle of injection may be 30 degrees or less. In embodiments, however, discharge from the nozzle may be effected through differently arranged discharge openings. In still further embodiments nozzle 62 may be equipped with a liquid agent atomizer.

    [0080] It will be appreciated that the injection of a fluid into a duct through a nozzle 62 yields different characteristics than the discharge through openings in the duct wall. For instance, nozzle 62 discharges a fluid into a core flow through duct 42 rather than into a boundary layer at the duct wall, as is the case with discharge openings in the duct wall. In another aspect, the penetration of fluid discharged into a duct through a wall opening may strongly vary depending on the differential pressure between the respective duct and fluid plenum, and thus depend on the mass flow or volume flow of discharged fluid. The fluid discharged from wall openings 51 and 52 in FIG. 1 may penetrate differently deep into the axial flow through a duct dependent upon the mass flow or volume flow of discharged fluid. As will be appreciated, this is not the case if a fluid is discharged from plenum 32 through nozzle 62 in the embodiment of FIG. 2. However, if the fluid is discharged from nozzle 62 with a comparatively high momentumi.e., high volume flowand at a low cone angle, it might be the case that a streak of relatively unmixed fluid travels downstream the duct, while, if the fluid is discharged from wall openings 51, 52 at a comparatively high momentumi.e., high volume flowit will penetrate deeper into the axial flow and can in some cases mix more intensely than at low volume flows. Further, as will be appreciated, the position of discharge from a wall opening is coupled to the position of the respective plenum, while a nozzle 62 may extend further downstream, or also upstream, inside the duct and allow the fluid from a plenum to be discharged into the duct remote from the position of the plenum from which the fluid originates. Further, a nozzle inside a duct results in a constriction of the flow cross-section through the duct, and may hence yield downstream eddies, which may foster mixture of the discharged fluid with the axial flow of, e.g., combustion air through the duct. Thus, providing discharge means from plenums to ducts in a burner of the type outlined above may result in excellent results when appropriately combining both types of discharge means in different ducts, at different distance from the downstream ends of the ducts. The absolute velocity or momentum of the fluid upon being discharged from the discharge means may moreover have a significant impact on the premixing behaviour, as a person having skill in the art will readily appreciate.

    [0081] It is noted that more than one fluid plenum may be provided in fluid communication with a duct through nozzle-type discharge means, of the type like discharge means 62 shown in FIG. 1, and that more than one nozzle-type discharge means may be provided inside one duct. Also, more than one fluid plenum may be fluidly connected to one or more ducts through nozzle-type discharge means, and one or more ducts may be fluidly connected to one or more plenums through nozzle-type discharge means.

    [0082] Referring again to FIG. 1, it will further be appreciated that fluid discharged from fluid plenum 31 through wall openings 51 into ducts 41 and 45 travels a longer distance within the ducts before being discharged on the downstream side 3 of burner 1 that fluid discharged through discharge means 52 and 62. If for instance the same type of fuel, for a more specific instance gaseous fuel, is supplied to both plenums 31 and 32, the fluid provided through plenum 32 and discharged into a duct at a relatively downstream location may be less intensely premixed inside a duct than fuel discharged into a duct at a relatively upstream location. For one instancedependent upon other parameters of the burner and the fuelfuel discharged from plenum 32 may support, by a relatively diffusion type combustion in downstream space 3, combustion of more intensely premixed fuel from plenum 31. This can be important in particular at low, understochiometric, overall fuel/air ratios, which might result in the extinction of a completely premixed flame. Dependent upon the particular requirements, all or only some of the ducts may be equipped with discharge means intended to supply fuel for combustion of an intensely premixed fuel/air mixture, i.e. positioned relatively upstream in the duct. Likewise, all or only some of the ducts may be equipped with discharge means intended to supply fuel for more diffusion type combustion, i.e. positioned relatively downstream in the duct. As seen in FIG. 1, some ducts may be intended only for relatively far upstream, or premix type, fuel supply, while others may be intended only for relatively far downstream, or diffusion type, fuel supply, while yet other ducts may be equipped with discharge means for both. It is noted that the mass flow of fuel through plenums 31 and 32 may be controlled through control means provided upstream of the fluid supply connectors 311 and 321. While the control means are not shown, they are familiar to a skilled person. The fuel mass flow to plenums 31 and 32 may thus be controlled individually, and thus the ratio between the mass flow or fuel discharged into the ducts relatively upstream and relatively downstream may be individually controlled. In other embodiments, however, discharge means may be provided in fluid communication with one and the same plenum and configured to discharge fluid from the plenum into one and the same duct or into different ducts, or a combination thereof, at different distances from the downstream end of a duct, which results in a fixed mass flow ratio of differently mixed fluids at the downstream end of the ducts.

    [0083] Most downstream arranged coolant plenum 33 is fluidly isolated from the ducts and discharges the coolant though effusion cooling holes 121 in the downstream front wall and into downstream space 3, i.e., into the combustion space, thus effecting cooling of downstream front wall 12.

    [0084] In the embodiment of FIG. 1, the ducts are shown to be slightly divergent at their downstream ends. Such flared outlet of the ducts may be useful to reduce exit velocity of the flow from a duct and hence reduce the risk of flame lift-off of the microjet flames and hence to ensure stabilization of the microjet flames. However, the shape of the ducts at the downstream end might be chosen as needed to meet requirements, for instance, as to the velocity of the gas flow emanating from a duct into downstream space 3. The upstream end of the duct may in instances be rounded or trumpet-shaped to reduce pressure losses.

    [0085] The device shown in FIG. 3 differs from the embodiment of FIG. 1 mainly in comprising ducts 43 which are equipped with wall-opening type discharge means 51 fluidly connecting ducts 43 to upstream plenum 31, while they are further equipped with nozzle-type discharge means 62 fluidly connecting ducts 43 with plenum 32 downstream from the position of wall-opening type discharge means 51.

    [0086] It should be noted that a duct may as well 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 one and the same duct may further be fluidly connected to one and the same fluid plenum or to different fluid plenums. It is further noted that in the framework of the present document a longitudinal or upstream-downstream position within a duct, or any other reference to a longitudinal position within a duct, is generally referenced to and measured from the downstream end of the respective duct, adjacent downstream plate 12. Said dimension defines the distance for mixing of fluids within a duct before discharging fluid into a combustion space and thus is a relevant parameter for a duct of the burner. Longitudinal dimensions inside a duct may further be expressed in multiples of the minimum hydraulic diameter of a duct along its longitudinal extent, wherein the hydraulic diameter is determined as four timed the local cross-sectional area divided by the circumference of a wall encircling said cross-sectional area.

    [0087] The burner 1 shown as another exemplary embodiment in FIG. 4 comprises ducts 48 and 49 which are configured as dedicated piloting ducts and which are characterized in that the position of a downstream discharge location into ducts 48, 49 from a plenum different form most downstream plenum 33, wherein said most downstream plenum is configured as a coolant plenum, is provided 5 times or less the minimum hydraulic diameter of the respective duct upstream from the downstream end of the duct. This is so close to the downstream end of the respective duct that fuel discharged from any of wall-opening type discharge means 54 provided in ducts 48 or from nozzle-type discharge means 65 provided in piloting duct 49 will exit from the duct into combustion space or downstream space 3 virtually unmixed with the combustion air flowing through the respective duct and will thus yield in a markedly diffusion-type flame at the exit of the duct. As outlined above, such flames yield higher nitrogen oxide formation, but on the other hand superior robustness of combustion. Said marked pilot flames may support combustion of fuel discharged into ducts 41, 48 and 49 relatively far upstream in the ducts through discharge means 51, and thus intensely premixed when exiting the ducts, in particular at low fuel/air ratios. In the shown exemplary embodiment, each piloting discharge means, positioned less than five minimum hydraulic diameters upstream form the downstream end of the respective duct, is provided in a duct also comprising an upstream discharge means 51. This is not necessarily the case. A piloting duct may also be provided as a standalone piloting duct having no other discharge means upstream from the piloting discharge means. However, distributing the most upstream discharge means in as many ducts as possible may yield advantages in that a given fuel mass flow through these upstream discharge means may be distributed into a maximum fraction of the combustion air, which results in good conditions to reduce nitrogen oxides emissions when operating the burner at high loads, i.e. with an comparatively high overall fuel/air ratio.

    [0088] The skilled person will, in the light of the present description, readily appreciate that the herein disclosed burner is not limited to be provided with three plenums, but more generally may be usefully provided with any number of plenums of two and larger. For instance, the burner shown in FIG. 1 may be supplemented with two additional plenums which respectively are merely connected to ducts through relatively upstream discharge means and relatively downstream discharge means like ducts 41 and 42 in FIGS. 1 and 3. It may likewise be supplemented with a combined piloting/premix duct as shown at 48 and 49 in FIG. 4. In being fluidly connected to different plenums the same ducts may thus be supplied with either natural gas and/or a different combustible, like, for instance, hydrogen. Thus, achieved is a highly versatile burner which is suitable for instance for the combustion of hydrogen or a hydrogen rich or other highly reactive fuel and for the combustion of natural gas in a variable premix/piloting operation, through the same ducts. The order in which the different plenums are arranged along a general airflow direction of the burner from the upstream side defined by upstream front wall 11 to the downstream side defined by downstream from wall 12, or the longitudinal position at which fluid from a specific plenum is discharged into the duct, will be determined by the skilled person in applying his general knowledge and taking into account the effect of the mixing distance of a fluid inside the duct from the discharge position of the fluid to the downstream end of the duct. The skilled person will readily appreciate that modules comprising fluid plenums intended for discharging a specific fluid into at least some of the ducts may, in a virtually modular manner, be stacked upon each other. This can be achieved in manufacturing burners with a different number of slices comprising a fluid plenum, sections of the ducts, appropriate discharge means for fluidly connecting the plenum to the interior of the ducts, and, optionally, a fluid supply connector for supplying fluid to the plenum. It might be considered to actually build the burner from stacked modules. The number of plenums is in principle not limited. Limiting factors might be seen in the increasing length of the ducts and thus increasing pressure losses, and other issues which might arise if fluids are discharged too far upstream of the downstream end of the duct. The fluid plenums, with their specific discharge means through which they are fluidly connected to at least one duct, can be stacked in any order a skilled person may find suitable to fulfil a certain purpose. However, it might be found advantageous if the most downstream plenum is a coolant plenum. It will be appreciated that due to the versatility of the herein disclosed burner a comprehensive description of possible embodiments is not practical. However, in understanding the principle behind the stacked micro duct burner herein disclosed, and the function and merits of certain specific embodiments of modules, the skilled person receives a comprehensive teaching.

    [0089] FIG. 5 outlines an embodiment of a burner 1 in which a cartridge 60 is provided through a passage 40. Cartridge 60 may in embodiments be a separate and retractable member. Cartridge 60 may be provided instead of or inside a duct. If cartridge 60 is provided instead of a duct, it is understood that cartridge 60 is preferably configured to achieve a gas-leak proof sealing of the plenums. In the embodiment shown, cartridge 60 extends through a duct, whereby sealing of the plenums is achieved by the duct wall which may be seamlessly manufactured with front walls 11 and 12 and partition walls 21, 22 and 23 in the primary forming process. Longitudinally extending or spiralling flutes may optionally be provided on an outer surface of the cartridge and/or the inner side of the wall of the duct through which cartridge 60 extends. Combustion air may be provided through the flutes. The flutes may be spiralling, at least at their downstream ends adjacent downstream front wall 12 and when opening out to the downstream space 3, so as to generate a swirling flow of combustion air at or around the downstream end of cartridge 60. A fluid 6 may be provided to downstream space 3 through cartridge 60. Said fluid may be steam, or a gaseous fuel, or mixture of gaseous fuel and other gaseous agent, which may for instance be intended for diffusion-type combustion. The gaseous agent may be discharged with a swirl, which may co- or counter-rotate with a swirl of combustion air. In other embodiments, cartridge 60 may comprise a liquid atomizing nozzle, thus discharging fluid 6 as a spray cone 5. The liquid may be liquid fuel or water or a mixture thereof. It is understood that further agents, for instance atomizing air or steam, may be provided to and discharged through cartridge 60. A burner of the herein disclosed type may comprise more than one cartridge 60. Burner 1 of FIG. 5 further comprises ducts 43 which are equipped with relatively upstream nozzle type discharge means 61 in fluid communication with plenum 31 and relatively downstream wall-opening type discharge means 52 in fluid communication with plenum 32.

    [0090] FIG. 6 shows an exemplary embodiment in which some of the ducts have different diameters. For instance, ducts 41a and 41b, which are equipped with relatively upstream wall-opening type discharge means 51 and in fluid communication with plenum 31 only, have different minimum hydraulic diameters. It will be appreciated that in a duct without an insert the longitudinal section having said minimum hydraulic diameter defines a metering section. These different diameters, as will be readily appreciated, have an impact on the mass flow of combustion air through the respective ducts. If discharge means 51 provided in ducts 41a and 41b have the same integral cross-section per duct, it will be appreciated that the flow through duct 41b exhibits a higher fuel/air ratio from fuel discharged from plenum 31 than the flow through ducts 41a. If, however, the integral cross-section of discharge means 51 of ducts 41a is larger than the integral cross-section of discharge means 51 in ducts 41b, the equivalence ratios mayor may notbe the same, and due to the different minimum hydraulic diameters the thermal load over the downstream surface of the burner adjacent downstream wall 12 may be varied. In ducts 42 and 43, however, a residual cross-section between an inner wall of the duct and an outer wall of nozzles 62 may define the metering section. The mass flow through ducts 42 and 43 may thus be varied in providing different hydraulic diameters of ducts 42 and 43 around nozzles 62, different outer diameters of nozzles 62, or both.

    [0091] In the embodiment of FIG. 7, ducts 44a, 44b and 44c are fluidly connected to plenum 32 through wall-opening type discharge means 52, while plenum 31 is fluidly connected to ducts 44a, 44b and 44c through nozzle-type discharge means 61a, 61b and 61c, respectively. In the region of the nozzle-type discharge means, each duct exhibits a tapering cross-section longitudinal portion in which the duct tapers downstream the general airflow direction, i.e., in a direction from first front wall 11 to second front wall 12, from a first cross-sectional area to a second cross-sectional area smaller than the first cross-sectional area. Nozzle-type discharge means 61c extend further into the tapering cross-section longitudinal portion of ducts 44c than nozzle-type discharge means 61b into ducts 44b, and nozzle-type discharge means 61b extend further into the tapering cross-section longitudinal portion of ducts 44b than nozzle-type discharge means 61a into duct 44a. Accordingly, the minimum flow cross-section, defined as a residual cross-section between the inner wall of a duct and the outer wall of a nozzle, is smaller in duct 44c than in duct 44b, and the minimum flow cross-section is smaller in duct 44b than in duct 44a.

    [0092] The device shown in FIG. 8 outlines how two supply connectors 311 and 321 provided for feeding two plenums may be arranged concentrically and coaxially.

    [0093] As illustrated in FIG. 9, wall-opening type discharge means may be arranged and configured to discharge the fluid form a plenum into a duct either [0094] perpendicular to the longitudinal direction 451, as for instance discharge means 56 of plenum 36; [0095] upstream the flow direction of combustion air 4, or inclined in the upstream direction of duct 46, respectively, as for instance discharge means 57 of plenum 37; or [0096] downstream the flow direction of combustion air 4, or inclined in the downstream direction of duct 46, respectively, as for instance discharge means 58 of plenum 38.

    [0097] The direction along which the fluid is discharged into duct 46 from the respective discharge means 56, 57, 58 is indicated by the arrows originating from the discharge means. It is noted that the application of said teaching is not limited to wall-opening type discharge means.

    [0098] FIG. 10 shows a cross-section through an even more particular example of the embodiment shown in FIG. 9 along line X-X. The discharge means may be arranged and configured such that the fluid is discharged from plenum 36 into duct 46 with a tangential velocity component so as to form a vortex flow of discharged fluid as indicated by the circular arrows in FIG. 10. It is noted that such a configuration of the discharge means is not limited to the embodiment of FIG. 9 or any embodiment similar thereto. Such configuration suited to generate a vortex flow of fluid discharged from a plenum into a duct may be applied, for instance, while not limited to, discharge means discharging the fluid in an upstream or downstream direction of the combustion air flow inside a duct, as for instance depicted at 57 and 58 in FIG. 9, or a nozzle-type discharge means.

    [0099] In further aspects, illustrated in FIG. 11, at least one duct 46 may be provided with a row of vanes 452 disposed inside duct 46 and disposed around the circumference of duct 46 and inclined at an angle with respect to the longitudinal direction 451 of duct 46, so as to induce a vortex flow as indicated at 401 onto the flow of combustion air 4. The vanes may in particular be provided at the upstream end of duct 46 such that the vortex flow of combustion air is present essentially throughout the longitudinal extent of duct 46. However, in other aspects, vanes 452 may be arranged further downstream, so as to discharge fluids from certain plenums into a purely axial flow of combustion air, while others may be discharged into a vortex flow of combustion air. The row of vanes 452 may be provided at the downstream end of duct 46. While it should be readily apparent to a person having skill in the art, it shall 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, as outlined in connection with FIG. 10. The vortexes of combustion air and of discharged fluid may be co- or counterrotating and may be affected with at least essentially equal tangential velocity components or different tangential velocity components and with essentially identical or different swirl numbers, as found suitable by a person having skill in the art when applying her or his common knowledge. The vanes 452 are in particular provided integrally and in one piece, i.e., seamless, with the burner, or the inner wall of a duct. It will be appreciated that in particular manufacturing the burner with additive manufacturing methods enables providing such rather small and complex geometries in one integral workpiece.

    [0100] It is apparent to a person having skill in the art that the relative velocities of the combustion air and the fluid discharged into the flow of combustion air inside a duct may have a major impact on the mixing of the fluids and may be applied to tune mixing and hence combustion behaviour.

    [0101] FIG. 12 illustrates a detail of a further possible embodiment of the herein disclosed burner. FIG. 12 shows a section of a burner with plenums 36 and 37 and duct 141 extending therethrough. 4 denotes 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. Nozzle-type discharge means 162 is configured to discharge fluid from plenum 36 at a position s1 measured from the downstream end of duct 141, while wall-opening type discharge means 152 is configured to discharge fluid from plenum 37 at a position s2 measured from the downstream end of duct 141. Although plenum 36 is positioned upstream from plenum 37, fluid from plenum 37 is discharged into duct 141 downstream from the discharge position s2 of fluid from downstream plenum 37. This illustrates the flexibility a nozzle-type discharge means offers with respect to the discharge location of a fluid from, a specific plenum into a duct.

    [0102] FIGS. 13a through 13d show plan views on front faces of burners having different numbers of passages. As can easily be seen, in each burner each three neighbouring passages are provided on the corners of an equilateral triangle. All shown embodiments, irrespective of the number of passages, have in common that a centre passage 40a is concentrically encircled by concentric hexagonal rings of passages. The embodiment of FIG. 13a exhibits 7 passages, wherein a centre passage 40a is encircled by six passages 40b in a hexagonal arrangement. Each two neighbouring passages 40b have the same distance from each other than from central passage 40a. The embodiment of FIG. 13b exhibits 19 passages, wherein a central passage 40a is encircled by six passages 40b in a first hexagonal ring and 12 passages 40c of a second hexagonal ring. As is apparent when further considering FIGS. 13c and 13d, the burner can easily be scaled by adding further concentric hexagonal rings of passages, wherein each additional hexagonal ring comprises 6 passages more than the adjacent inner hexagonal ring. Each passage, apart from the passages on the outermost hexagonal ring, may in turn be considered to form the centre of another hexagon of surrounding passages. In embodiments, centre passage 40a may be omitted. This self-similarity of the arrangement of passages, along with the equidistant arrangement of all neighbouring passages, facilitates scaling of the burner. A burner may, on the one hand, be adapted to different burner sizes in adding additional hexagonal rings of passages of the same size and distance from each other. A burner of a given size may, on the other hand, be provided with different cross-sectional dimensions of the passages, or ducts, respectively. It shall be noted that the ducts, or some of the ducts, may have a polygonal rather than a circular or, more generally spoken, rounded cross-sectional shape. In particular embodiments, at least some of the ducts may exhibit the cross-sectional shape of an equilateral hexagon.

    [0103] FIGS. 14a through 14c illustrate possible arrangements of piloting ducts, liquid fuel nozzles, water or steam injection nozzles and so forth, in a burner of the described type. It is well understood and goes without saying that said ducts, nozzles and the like extend through passages of the burner. For one instance, as illustrated in FIG. 11a, a piloting duct 49, represented by the filled dot, may be arranged in a central passage, while all other passages may be provided with any other type of duct. The burner of FIG. 14b exhibits six piloting ducts arranged adjacent to each other on an equilateral hexagon. In the embodiment of FIG. 14c a piloting duct is provided in the centre of each hexagonal arrangement of neighbouring non-piloting ducts. The skilled person will appreciate that in the embodiments of FIG. 14 for instance cartridges for the supply of water, steam, liquid fuel, piloting gas and so forth may be arranged in the place of the piloting ducts 49.

    [0104] FIG. 15 illustrates how the passages 40b and 40c of the hexagonal rings, and, consequently, any means provided therethrough, may be inclined relative to a burner axis 101, so as to discharge the flow emanating from said passages, or ducts, respectively with a macroscopic tangential component relative to the burner axis. Burner axis 101 is defined at least essentially perpendicular to the downstream front face of the burner. The longitudinal direction of central passage 40a, or duct respectively, is in particular aspects at least essentially parallel to burner axis 101, while the longitudinal axis of passages 40b and 40c are inclined about an angle relative to the burner axis, so as to generate a vortex flow indicated at 102 downstream the burner, or, more specifically, in the combustion space. In certain embodiments, no central passage may be present. References may in this case be made, for instance, to a midpoint of the hexagonal ring. It is understood that the inclination angle of the passages may vary dependent on the distance of a respective passage from central passage 40a. For one instance, inclination angle may increase with increasing distance from central passage 40a or from burner axis 101, or, in other aspects, from a midpoint of the hexagonal ring. Of course, it is not excluded that, in embodiments, the inclination angle may decrease or may remain the same with increasing distance from central passage 40a or from burner axis 101, or, in other aspects, from a midpoint of the hexagonal ring. Due to the self-similarity of the arrangement of the passages, one burner may be subdivided into smaller areas, wherein each area defines a local centre and an encircling hexagonal passage arrangement, wherein the passages encircling a specific centre may be inclined to provide a vortex around said local central passage. In other words, the passages in a concentric hexagonal ring are configured such that fluid discharged at the downstream side of the burner form the passages in the concentric hexagonal ring has a velocity component which is tangential to a circle defined around the midpoint of the hexagonal ring. An embodiment in which a macroscopic vortex is generated may be found useful for instance when replacing vortex burners in a legacy combustion appliance.

    [0105] The example of FIG. 16 relates to a specific embodiment of the cooling of the burner. In the exemplary embodiments, plenums 31 and 32 are configured to discharge into ducts 47 through wall-opening type discharge means 51 and nozzle-type discharge means 62, respectively. Wall 23 is provided with through holes 122 fluidly connecting open plenum 35 and most downstream plenum or cooling plenum 33. As outlined above, open plenum 35 is in fluid communication with a space surrounding burner 1, i.e., for instance with a reservoir of air. Air from open plenum 35 flows through opening 122 into cooling plenum 33. Through jets of cooling air entering plenum 33 through holes 122 impingement cooling of adjacent areas of downstream wall 12 may be effected. Other areas of downstream wall 12 are effusion cooled by cooling air which is discharged into downstream space 3 through through holes 121. A further fraction of the cooling fluid is discharged into the downstream part of the ducts through coolant discharge means 53. For the sake of completeness it is noted that coolant discharge means which provide fluid communication between the most downstream plenum and the interior of a duct may also be used in connection with embodiments in which coolant is supplied to plenum 33 through coolant feed connectors.

    [0106] While the above shown exemplary embodiments all exhibit two fluid plenums in connection with the ducts, apart from the most downstream plenum which is configured as a cooling plenum to provide appropriate cooling for the thermally highly loaded downstream wall, the skilled person will appreciate that more plenums may be provided in fluid communication with at least one duct, and be intended for providing different types of fuel, fuel intended for different premixing prior to combustion, or steam or other inert fluids. In embodiments, a nozzle-type discharge means may be equipped with an atomizer, such that also liquids, like, for instance, liquid fuel or water, may be discharged into a duct through said nozzle-type discharge means. In embodiments, the burner may be modular, each module comprising at least a fluid plenum between two transverse walls, a duct segment or duct segments extending through the transverse walls and the plenum or the plenums, a discharge means to provide fluid from the plenum or the plenums to the duct segment or the duct segments, and, optionally, a fluid supply connector or fluid supply connectors in fluid communication with the fluid plenum or fluid plenums.

    [0107] FIG. 17 depicts a detail from an exemplary embodiment of a burner of the herein described type. A through hole 52a through the wall of duct 142 for providing fluid communication with plenum 32 is elliptically shaped, with a long ellipse axis 528 and a short ellipse axis 529. An angle included between the long ellipse axis 528 and the longitudinal direction of the duct 451, the general airflow direction, or a burner axis, is in particular embodiments chosen to be 30 degrees or less, and in more particular embodiments, as shown in FIG. 17, an angle included between the long ellipse axis 528 and the longitudinal direction of the duct 451 is at least essentially zero. Moreover, the ratio between the length a of the long ellipse axis and the length b of the short ellipse axis may be chosen to be 1.25 or more. This configuration yields advantages in particular if the burner or a burner module is manufactured by additive manufacturing, wherein the building direction may be chosen at least approximately parallel to the general airflow direction, the duct axis or burner axis. The elliptic shape of the opening may facilitate said manufacturing in that overhanging structures during manufacturing are largely reduced. In other embodiments, the through hole may for the same reason be lancet-shaped or shaped as a pointed arch with the apex pointing at least essentially in the building direction of the additively manufactured structure.

    [0108] Essentially the same advantages may be achieved, for instance, with a polygon-shaped wall opening 52b as shown in FIGS. 18 and 19. 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 FIG. 19, polygon-shaped wall opening 52b has a polygon-shaped boundary which comprises straight boundary segments 521, 522, 523, 524 and 525. The boundary may also be considered as comprising an upstream boundary section 526 edging the opening in a direction against the flow of combustion air 4 and a downstream boundary section 527 edging the opening in the direction of the flow of combustion air. Upstream boundary section 526 comprises straight boundary segments 522 and 523, while downstream boundary section 527 comprises straight boundary segments 521, 524 and 525. Straight boundary segments 522 and 523 of upstream boundary section 526 form an apex of opening 52b pointing upstream relative to the flow of combustion air. Straight boundary segments 522 and 523 include inner angles and with the longitudinal direction 451 of duct 142 which are 45 degrees or less. The exemplarily shown opening is particularly suitable in connection with a component which is additively manufactured with a building direction against the intended flow of combustion air 4. Generally, an opening being defined within a boundary having an apex pointing into the building direction of the component and the apex being enclosed between two straight boundary segments edging the opening in the building direction, wherein those two boundary segments include an angle of 45 degrees or less with a parallel to the building direction, may be found beneficial in connection with an additively manufactured component. Also a geometry with two apexes, like e.g. a diamond-shaped geometry, might be applied.

    [0109] While the subject matter of the disclosure has been explained by means of exemplary embodiments, it is understood that these are in no way intended to limit the scope of the claimed invention. It will be appreciated that the claims cover embodiments not explicitly shown or disclosed herein, and embodiments deviating from those disclosed in the exemplary modes of carrying out the teaching of the present disclosure will still be covered by the claims.