Combustion system having combustion axial stage with burner bodies configured to inhibit flashback and formation of emissions

Abstract

A combustion system (100, fig 1) comprises a burner assembly (102) in an axial stage (103) downstream from a main combustion stage. The assembly includes a plurality of burner bodies 104 each arranged

Description

[0002] As will be appreciated by one skilled in the art, to further increase turbine firing temperatures and reduce emissions, such as NOx, CO, etc., axially staged combustion techniques have been implemented in modern turbines. Axially staged combustion is a combustion technique that distributes or otherwise splits the combustion process into separate stages. Although the level of emissions can be reduced by providing a portion of the fuel to be ignited downstream from a main combustion stage, there is a need for further improvements, particularly in the context of a fuel (or a fuel mixture) having a high energy density level, such as involving hydrogen fuel or hydrogen enriched fuel biends. The following are a few examples of patents that disclose axially staged combustion techniques used in a combustion turbine engine: US8752386, US8113000 and US7886539. BRIEF SUMMARY

[0003] In one aspect, a combustion system is provided. The system includes a burner assembly in a combustion axial stage disposed downstream from a main combustion stage of the combustion system. The burner assembly includes a plurality of burner bodies. Each respective burner body of the plurality of burner bodies is arranged to deliver to the combustion axial stage a respective mixture of reactants through an outlet port of the respective burner body. The respective burner body includes a fuel-interconnecting structure and an air guiding structure. The air guiding structure passes a flow of air, which constitutes one of the reactants. The fuel-interconnecting structure includes a plurality of fuel conduits each arranged to interconnect over a segment of the air guiding structure. Each of the plurality of fuel conduits extends along a respective longitudinal axis to convey a respective jet of fuel into the flow of air that passes along the segment of the air guiding structure, where the fuel constitutes another of the reactants. The respective longitudinal axis of a respective one of the plurality of fuel conduits is arranged to define a respective angle with respect to a normal line at a corresponding point of injection at the segment of the air guiding structure. The respective angle is configured so that the respective jet of fuel flow at least in part is opposed to the flow of air that passes along the segment of the air guiding structure. BRIEF DESCRIPTION OF DRAWINGS

[0004] FIG. 1 is a fragmentary sectional view of one embodiment of a disclosed combustion system where a burner assembly includes a plurality of burner bodies disposed in a combustion axial stage of a gas turbine engine.

[0005] FIG. 2 shows a zoomed-in view of a respective burner body of the plurality of burner bodies, where the respective burner body includes a fuelinterconnecting structure and an air guiding structure.

[0006] FIG. 3 illustrates a diagrammatic representation for conceptualizing a disclosed arrangement where a respective jet of fuel from a fuel conduit in the fuel-interconnecting structure at least in part is opposed to a flow of air that passes in the air guiding structure.

[0007] FIG. 4 is an isometric view of one example embodiment of the respective burner body.

[0008] FIG. 5 is a fragmentary, isometric view of a portion of the burner bodies.

[0009] FIG. 6 through FIG. 8 are respective fragmentary sectional views of respective alternative embodiments of disclosed combustion systems.

[0010] FIG. 9 is a fragmentary sectional view of one embodiment of a disclosed combustion system. DETAILED DESCRIPTION

[0011] During flashback, a flame can propagate in an upstream direction, and thus the flame can “flash back” onto combustor hardware. Sustained upstream propagation of flames can potentially result in substantial thermal damage to the combustor hardware and associated components. Hydrogen, and hydrogen enriched fuel blends, for example, tend to exhibit faster kinetics and higher flame speeds compared to traditional turbine fuels, thus making hydrogen, and hydrogen enriched fuel blends more susceptible to flashback.

[0012] Disclosed embodiments offer a reliable and cost-effective technical solution effective to, for example, inhibiting flame flashback in the context of an axially staged combustion system that, for example, utilizes a fuel (or a fuel mixture) having a high energy density level, such as involving hydrogen fuel, or hydrogen enriched fuel blends.

[0013] Before disclosed embodiments are explained in detail, it is to be understood that disclosed embodiments are not limited in their application to the details of construction and the arrangement of components set forth in this description or illustrated in the following drawings. Disclosed embodiments are capable of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

[0014] Various technologies that pertain to disclosed embodiments will now be described with reference to the drawings, where like reference numerals represent like elements throughout. The drawings discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged apparatus. It is to be understood that functionality that is described as being carried out by certain system elements may be performed by multiple elements. Similarly, for instance, an element may be configured to perform functionality that is described as being carried out by multiple elements. The numerous innovative teachings of the present application will be described with reference to exemplary non-limiting embodiments.

[0015] It should be understood that the words or phrases used herein should be construed broadly, unless expressly limited in some examples. For example, the terms “including,” “having,” and “comprising,” as well as derivatives thereof, mean inclusion without limitation. The singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Further, the term “and / or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. The term “or” is inclusive, meaning and / or, unless the context clearly indicates otherwise. The phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like. Furthermore, while multiple embodiments or constructions may be described herein, any features, methods, steps, components, etc. described with regard to one embodiment are equally applicable to other embodiments absent a specific statement to the contrary.

[0016] Also, although the terms “first”, “second”, “third” and so forth may be used herein to refer to various elements, information, functions, or acts, these elements, information, functions, or acts should not be limited by these terms. Rather these numeral adjectives are used to distinguish different elements, information, functions or acts from each other. For example, a first element, information, function, or act could be termed a second element, information, function, or act, and, similarly, a second element, information, function, or act could be termed a first element, information, function, or act, without departing from the scope of the present disclosure.

[0017] In addition, the term “adjacent to” may mean that an element is relatively near to but not in contact with a further element or that the element is in contact with the further portion, unless the context clearly indicates otherwise. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise. Terms “about” or “substantially” or like terms are intended to cover variations in a value that are within normal industry manufacturing tolerances for that dimension. If no industry standard is available, a variation of twenty percent would fall within the meaning of these terms unless otherwise stated.

[0018] Those of ordinary skill in the art will appreciate that hardware and software depicted in connection with disclosed embodiments may vary for particular implementations. The depicted examples are provided for the purpose of explanation only and are not meant to imply architectural limitations with respect to the present disclosure. Also, those skilled in the art will recognize that, for simplicity and clarity, the full structure and operation of all data processing systems suitable for use with the present disclosure is not being depicted or described herein. Instead, only so much of a data processing system as is unique to the present disclosure or necessary for an understanding of the present disclosure is depicted and described. The remainder of the construction and operation of the data processing system may conform to any of the various current implementations and practices known in the art.

[0019] FIG. 1 is a fragmentary sectional view of one embodiment of a disclosed combustion system 100 in a combustion turbine engine, such as a gas turbine engine. In one example embodiment, a burner assembly 102 is arranged in a combustion axial stage 103 of the engine. Combustion axial stage 103 is disposed downstream from a main combustion stage of the engine (not shown). In one example embodiment, burner assembly 102 includes a plurality of burner bodies 104 (nozzles) that are circumferentially distributed over a radially outward location of combustion axial stage 103. Each respective burner body 104 is arranged to deliver into combustion axial stage 103 a respective mixture of reactants through an outlet port 108 of the respective burner body 104.

[0020] The terms upstream and downstream refer to the flow direction of the airflow and / or working gas flow through the combustion system unless otherwise stated. When not differently specified, the terms axial, radial and circumferential are made with reference to a longitudinal axis 20 of combustion system 100.

[0021] Each respective burner body 104 includes a fuel-interconnecting structure 110 and an air guiding structure 112, which passes a flow of air (schematically represented by arrow 116 (FIG. 2)). In this example, air constitutes one of the reactants. Fuel-interconnecting structure 110 defines a plurality of fuel conduits 118, each arranged to interconnect with air guiding structure 112 thru a segment of air guiding structure 112. Each of the plurality of fuel conduits 118 extends along a respective longitudinal axis 120 to convey through a respective hole a respective jet of fuel into the flow of air that passes along the segment of air guiding structure 112, where the fuel constitutes another of the reactants.

[0022] FIG. 3 is a diagrammatic representation for conceptualizing one disclosed arrangement where, as elaborated in greater detail below, a respective jet of fuel from a respective fuel conduit 118 (FIG. 2) in fuel-interconnecting structure 110 at least in part is opposed to the flow of air that passes in air guiding structure 112. In one example embodiment, the respective longitudinal axis 120 of a respective one of the plurality of fuel conduits 118 is arranged to define a respective angle 9 with respect to a normal line 124 at a corresponding point of injection at the segment of air guiding structure 112. Normal line 124 is perpendicular to a tangent line 126 at the point of injection. In one example embodiment, the respective angle 9 is configured so that the respective jet of fuel flow at least in part is opposed to the flow of air that passes along the segment of the air guiding structure. In one example embodiment, the respective angle 9 is in a range from -50 degrees to +110 degrees. For purposes of establishing an example reference frame, in case the value of angle 9 is equal to zero degrees, this would be indicative of a fully perpendicular relationship between the respective jet of fuel and tangent line 126, and when the angle 9 is turned in a counterclockwise direction from normal this would be considered a positive angle. Conversely, when the angle 9 is turned in a clockwise direction from normal this would be considered a negative angle.

[0023] It will be appreciated that in certain embodiments the fuel conduits 118 can be staggered relative to one another and need not be arranged to have any specific alignment relative to one another. For example, the fuel flow in fuel-interconnecting structure flowing along a substantially radial direction, as schematically indicated by arrow 156 in Fig 2, does not necessarily imply that the fuel conduits 118 need to be aligned relative to one another.

[0024] The foregoing feature (e.g., configuring the respective angle 9 so that the respective jet of fuel flow at least in part is opposed to the flow of air that passes along the segment of the air guiding structure) is conducive to rapid mixing of the fuel and air over a relatively short distance and in turn this is conducive to inhibiting emissions of NOx, for example. It will be appreciated that CO emissions are generally reduced due to the nature of axial stage fuel staging arrangements. For example, in certain embodiments just the main and pilot (or headend) stage may be operationally active up to a certain load level, and the axial stage may be turned on for load values above such load level. Until that load level is reached, airflow will be passing through the respective burner bodies 104 (e.g., the axial stage nozzles) making headend operation feasible with relatively less air and high fuel and in effect ensuring a substantially complete combustion at part load, which contributes to reducing CO emissions.

[0025] In one example embodiment, the respective burner body 104 houses air guiding structure 112 and fuel-interconnecting structure 110. In one example embodiment, as can be better appreciated in FIG. 4, the respective burner body 104 forms a streamlined body, such as a vane, a rectangular prism, a trapezoidal prism, etc. The streamlined body has a streamlined cross-sectional profile that extends along a longitudinal direction 130 perpendicular or inclined relative to a flow direction 132 of a portion of the air that flows externally between adjacent burner bodies of the plurality of burner bodies 104.

[0026] In one example embodiment, each of the plurality of burner bodies 104 is formed by a respective streamlined body. This feature is effective to, for example, inhibiting a pressure drop in the portion of the air that flows externally between adjacent burner bodies 104. Multiple streamlined burner bodies 104 or nozzles that are distributed in the circumferential direction make the air which is passing between these bodies relatively more streamlined and uniform. This air flow is conveyed into the headend of the combustion system with reduced pressure losses as well as more uniformity. This improved uniformity in the air flow into the main stage is effective for increasing margin against flashback, such as by substantially equally distributing air conveyed to each of the main nozzles, as opposed to, for example, situations in certain prior art implementation, where, for example, some of the main nozzles could otherwise be starved for air.

[0027] The foregoing feature (each of the plurality of burner bodies 104 being formed by a respective streamlined body) is further effective to inhibit the circumferential footprint occupied by the plurality of burner bodies 104. In disclosed embodiments, the circumferential footprint occupied by the plurality of burner bodies is sufficiently inhibited or otherwise reduced to permit numerically increasing the plurality of burner bodies that can be circumferentially distributed over the radially outward location of the combustion axial stage compared to known arrangements involving burners with blunt bodies. By way of example, the number of streamlined burner bodies that can be circumferentially distributed over the radially outward location of combustion axial stage 103 may range from four burner bodies to one hundred burner bodies. In another example embodiment, the number of streamlined burner bodies that can be circumferentially distributed over the radially outward location of combustion axial stage 103 may range from ten burner bodies to forty burner bodies. That is, the number of streamlined burner bodies can be appropriately tailored based on the needs of a given application. Since in disclosed embodiments, the number of streamlined burners can be increased with ease compared to known arrangements involving burners with blunt bodies, this feature improves the distribution of fuel and air in any given axial stage and this in turn is conducive to inhibit formation of regions having uneven (e.g., higher, lower) volumetric heat generation. It will be appreciated that the rows in which burner bodies 104 are arranged can be staggered. For example, let us presume that in one example embodiment, a first row of axial stage nozzles involves ten nozzles and that a second downstream row also involves ten nozzles. In this example embodiment, the ten nozzles in the second downstream row can (but need not) be circumferentially staggered with respect to the nozzles in the first row.

[0028] As can be respectively appreciated in Figs 4 and 5, each respective burner body 104 has an air inlet port 134 to admit the air that forms the flow of air in the air guiding structure 112. In one example embodiment, each respective air guiding structure 112 includes a curving portion configured to turn the flow of air within the air guiding structure 112 from an axial direction to a radially inward direction so that the respective mixture of reactants exiting through outlet port 108 of respective burner body 104 forms a respective flame in combustion axial stage 103, as schematically represented by star-shaped lines 138 in FIG. 2.

[0029] In another embodiment, certain burner bodies 104 can be arranged in a reverse direction relative to the combustor axis, such that the air inlet port 134 is oriented to face the headend. For example, air inlet port 134 would be disposed at the trailing edge of the burner body 104 instead of the leading edge, as shown in the figures. This arrangement allows to convey air that has already experienced some streamlining to each of the receiving nozzles making feasible for even more uniformity in the air and thus improving on flashback margin, if so desired.

[0030] As can be respectively appreciated in FIG. 1 and FIG 2, the respective burner body 104 further defines a fuel plenum 140 fluidly coupled to convey fuel into air guiding structure 112 by way of fuel-interconnecting structure 110. In certain embodiments, as respectively shown, for example, in FIG. 1 and FIG. 6, a fuel manifold 150 is disposed externally relative to an engine casing 152. Fuel manifold 150 may be fluidly coupled to a cavity 154 in engine casing 152 and in turn to the fuel plenum 140 interiorly defined by the respective burner body 104. In the foregoing embodiments, fuel manifold 150 is radially aligned relative to fuel plenum 140, as schematically represented by arrows 156 in FIG. 2.

[0031] In certain alternative embodiments, as can be appreciated in FIG. 7 and FIG. 8, fuel manifold 150 may be axially offset relative to the respective burner body 104. FIG. 7 illustrates an embodiment having a fuel piping arrangement 160 which is routed within a combustor casing 153 and engine casing 152, whereas FIG. 8 illustrates an embodiment where fuel piping arrangement 160 is routed inwardly of casings 152, 153.

[0032] As can appreciated at least in FIG. 1 and FIG. 4, in certain example embodiments, the respective burner body 104 may be affixed to engine casing 152 by way of a threaded connection 162. This feature is conducive to user-friendly individualized replaceability, and serviceability of respective burner bodies.

[0033] In one example embodiment, as can be appreciated in FIG. 9, a combustor liner 164 and combustor casing 153 can be configured to define an air passageway 166 having a cross-sectional area (schematically represented by twin-headed arrow 168) arranged to pass the portion of the air (schematically represented by arrow 170) that flows externally between adjacent burner bodies of the plurality of burner bodies 104. As can be appreciated in FIG. 9, in one example embodiment, the cross-sectional area 168 has a progressively reduced cross-sectional area as one advances in an upstream direction away from combustion axial stage 103 toward the main combustion stage. This feature improves uniformity (e.g., inhibits wake vortices, or other turbulence) in the air flow 170 eventually conveyed to the main stage and this in turn is conducive to further inhibiting occurrence of flashback and higher levels of NOx and CO emissions. This arrangement also allows larger area at the expansion from main stage burner to liner helping flame stability especially at lower loads where fuel flow is lower and partial combustion would be problematic.

[0034] As can be appreciated in FIG. 5, in one example embodiment, the combustor liner includes a plurality of slots 170 each configured to receive radially inward edges of each respective burner body 104 so that each outlet port 108, for example, is practically flush with the combustor liner. A suitable gap may be provided between a respective slot 170 and the radially inward edges of a respective burner body 104 to permit appropriate thermal expansion / contraction. This feature permits a user-friendly fitting (e.g., press fit or interference fit) that facilitates integration of the burner bodies 104 with the combustor liner and effectively avoids a need for welding of the burner bodies 104 to the combustor liner.

[0035] In operation, disclosed embodiments offer a reliable and cost-effective technical solution effective to, for example, inhibiting flame flashback in the context of an axially staged combustion system that, for example, utilizes a fuel (or a fuel mixture) having a high energy density level, such as involving hydrogen fuel or hydrogen enriched fuel blends.

[0036] In operation, disclosed embodiments permit numerically increasing the burner bodies that can be circumferentially distributed over the radially outward location of the combustion axial stage compared to known arrangements involving burners with blunt bodies. This feature permits improving the distribution of fuel and air in any given axial stage and this in turn is conducive to inhibiting formation of regions having uneven (e.g., higher, lower) volumetric heat generation.

[0037] In operation, disclosed embodiments have features that result in reduced pressure losses while improving aerodynamic uniformity (e.g., inhibits wake vortices, or other turbulence) of air flow conveyed to the headend of the combustion system. Therefore, it should now be appreciated that disclosed embodiments are advantageously effective for achieving multiple objectives, such as burner bodies offering one or more of the following technical improvements: superior fuel / air mixing, better air flow uniformity to the main stage while inhibiting pressure loss reductions in such airflow.

[0038] In operation, disclosed embodiments have features conducive to rapid mixing of the fuel and air over a relatively short distance and in turn this is conducive to inhibiting emissions of NOx. Additionally, disclosed embodiments have features conducive to user-friendly replaceability, and serviceability of respective burner bodies.

Claims

1. A combustion system comprising:a burner assembly in a combustion axial stage disposed downstream from a main combustion stage of the combustion system,wherein said burner assembly comprises a plurality of burner bodies, each respective burner body of the plurality of burner bodies arranged to deliver to the combustion axial stage a respective mixture of reactants through an outlet port of the respective burner body,wherein the respective burner body comprises a fuel-interconnecting structure and an air guiding structure,wherein the air guiding structure passes a flow of air, which constitutes one of the reactants,wherein the fuel-interconnecting structure comprises a plurality of fuel conduits each arranged to interconnect over a segment of the air guiding structure, wherein each of the plurality of fuel conduits extends along a respective longitudinal axis to convey a respective jet of fuel into the flow of air that passes along the segment of the air guiding structure, wherein the fuel constitutes another of the reactants,wherein the respective longitudinal axis of a respective one of the plurality of fuel conduits is arranged to define a respective angle with respect to a normal line at a corresponding point of injection at the segment of the air guiding structure, wherein the respective angle is configured so that the respective jet of fuel flow at least in part is opposed to the flow of air that passes along the segment of the air guiding structure.

2. The combustion system of claim 1, wherein the respective angle is in a range from -50 degrees to +110 degrees.

3. The combustion system of claim 1 or claim 2, wherein the respective burner body houses the air guiding structure and the fuelinterconnecting structure.

4. The combustion system of any of the preceding claims, wherein the respective burner body comprises a streamlined body.

5. The combustion system of claim 4, wherein the streamlined body has a streamlined cross-sectional profile that extends along a longitudinal direction perpendicular or inclined relative to a flow direction of a portion of the air that flows externally between adjacent burner bodies of the plurality of burner bodies.

6. The combustion system of claim 4 or claim 5, wherein the plurality of burner bodies each has a respective streamlined body, wherein the plurality of burner bodies is circumferentially distributed over a radially outward location of the combustion axial stage.

7. The combustion system of claim 6, wherein the respectivestreamlined body of each of the plurality of burner bodies is effective to inhibit a pressure drop in the portion of the air that flows externally between adjacent burner bodies of the plurality of burner bodies.

8. The combustion system of claim 7, wherein the respective streamlined body of each of the plurality of burner bodies is effective to inhibit a circumferential footprint occupied by the plurality of burner bodies.

9. The combustion system of claim 8, wherein the circumferential footprint occupied by the plurality of burner bodies is sufficiently inhibited to numerically increase the plurality of burner bodies circumferentially distributed over the radially outward location of the combustion axial stage.

10. The combustion system of claim 9, wherein a number of the burner bodies circumferentially distributed over the radially outward location of the combustion axial stage is in range from 4 to 100 burner bodies.

11. The combustion system of claim 4 or claim 5, wherein the streamlined body comprises a vane.

12. The combustion system of claim 4 or claim 5, wherein the streamlined body comprises a rectangular prism or a trapezoidal prism.

13. The combustion system of any of the preceding claims, wherein respective burner body has an air inlet port to admit air that forms the flow of air in the air guiding structure.

14. The combustion system of claim 1, wherein the air guiding structure has a curving portion configured to turn the flow of air from an axial direction to a radially inward direction.

15. The combustion system of claim 1, wherein the respective burner body further comprises a fuel plenum fluidly coupled to the fuel-interconnecting structure.

16. The combustion system of claim 1, further comprising a fuel manifold disposed externally relative to a casing, the fuel manifold fluidly coupled to the respective fuel plenum, wherein the fuel manifold is radially aligned relative to the respective burner body.

17. The combustion system of claim 1, further comprising a fuel manifold disposed externally relative to a casing, the fuel manifold fluidly coupled to the respective fuel plenum, wherein the fuel manifold is axially offset relative to the respective burner body.

18. The combustion system of claim 1, wherein the respective burner body is affixed to a casing by way of a threaded connection.

19. The combustion system of claim 1, further comprising a combustor liner and a casing that define a cross-sectional area arranged to pass a flow of the air that flows externally between adjacent burner bodies of the plurality of burner bodies, the cross-sectional area having a progressively reduced area as one advances in a direction from the combustion axial stage toward the main combustion axial stage.

20. The combustion system of claim 1, further comprising a combustor liner having a plurality of slots each configured to receive radially inward edges of the respective burner body.

21. The combustion system of claim 9, wherein a number of the burner bodies circumferentially distributed over the radially outward location of the combustion axial stage is in range from 10 to 40 burner bodies.

22. A combustion turbine engine comprising:a combustion system comprising:a burner assembly in a combustion axial stage disposed downstream from a main combustion stage of the combustion system, wherein said burner assembly comprises a plurality of burner bodies, each respective burner body of the plurality of burner bodies arranged to deliver to the combustion axial stage a respective mixture of reactants through an outlet port of the respective burner body,wherein the respective burner body comprises a fuelinterconnecting structure and an air guiding structure,wherein the air guiding structure passes a flow of air, which constitutes one of the reactants,wherein the fuel-interconnecting structure comprises a plurality of fuel conduits each arranged to interconnect over a segment of the air guiding structure, wherein each of the plurality of fuel conduits extends along a respective longitudinal axis to convey a respective jet of fuel into the flow of air that passes along the segment of the air guiding structure, wherein the fuel constitutes another of the reactants,wherein the respective longitudinal axis of a respective one of the plurality of fuel conduits is arranged to define a respective angle with respect to a normal line at a corresponding point of injection at the segment of the air guiding structure, wherein the respective angle is configured so that the respective jet of fuel flow at least in part is opposed to the flow of air that passes along the segment of the air guiding structure.

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