Combustion system having multistage burners arranged to mix air and fuel based on fuel property and engine load

Abstract

A combustion system for a gas turbine engine is provided. The combustion system includes a first burner stage (701-1), a second burner stage (701-2), and a third burner stage (701-3), where the first, second, and third burner stages (701) are radially and axially spaced apart from one another. The system offers superior engine operability (e.g., inhibiting NOx and CO emissions and thermoacoustic instabilities) by way of structural and / or operational relationships that permit distributing heat release axially and radially within the combustion system, while maintaining a compact system and involving relatively low mechanical complexity.

Description

Docket No. 2024PF00608COMBUSTION SYSTEM HAVING MULTISTAGE BURNERS ARRANGED TO MIX AIR AND FUEL BASED ON FUEL PROPERTY AND ENGINE LOADBACKGROUND

[0001] Disclosed embodiments relate to a combustion system for a gas turbine engine, and, more particularly, to a combustion system featuring multistage burners arranged to selectively mix air and fuel based on a property (e.g., a thermochemical property) of the fuel and engine load conditions.

[0002] Hydrogen has substantially different properties than fuels that have been commonly used in the context of a gas turbine engine, such as natural gas, etc. For example, the flame speed of hydrogen is substantially faster than that of natural gas, and therefore, fuel mixtures containing relatively high levels of hydrogen, up to pure hydrogen, are more susceptible to flashback and this can lead to undesirable issues in connection with combustor hardware subject to flashback. During flashback, flames can propagate upstream towards the incoming gas flow, specifically in boundary layers where the incoming gas flow velocity is lower, and this can lead to thermal damage of hardware subject to such flames.

[0003] Moreover, in the context of the presently ongoing global energy transition, yet to be fully realized, to greener forms of energy, it is not easy to predict with a high degree of certainty when hydrogen will be affordable and available in sufficiently large quantities to cost- effectively and consistently fuel gas turbines for power generation.

[0004] Internation Patent Application WO2015 / 182727, titled "Combustion Device for Gas Turbine Engine" involves a premix combustor that purportedly reduces NOx by uniformizing the flame temperature and promoting mixing of air and fuel. However, the combustion device disclosed in such application fails to disclose or suggest radial stages that are also distributed axially. Consequently, such a device lacks the capability to distribute heat release axially and radially.

[0005] At least in view of the foregoing considerations, there is a need of a flexible combustion system involving burner stages that are radially and axially spaced apart from one another, as featured in our disclosed embodiments. Our staging arrangement effectively inhibits occurrence of flashback without increasing undesirable emissions, and can utilize a fuel blend involving, for example, natural gas and hydrogen regardless of the content of hydrogen and natural gas in the fuel blend.Docket No. 2024PF00608BRIEF SUMMARY

[0006] In one aspect, a combustion system for a gas turbine engine is provided. The combustion system includes a first burner stage, a second burner stage, and a third burner stage, where the first, second, and third burner stages are radially and axially spaced apart from one another. A fuel delivery subsystem is fluidly coupled to the first, second and third burner stages to convey a fuel blend of a first fuel and a second fuel to one or more of the first, second and third burner stages based on a load condition of the gas turbine engine. Each respective one of the burner stages includes a respective hybrid mixer unit arranged in a combustor of the combustion system to mix compressed air and the fuel blend of the first fuel and the second fuel. Each respective hybrid mixer unit includes a respective first mixing stage configured to carry out premixed-based combustion and a respective second mixing stage configured to carry out diffusion-based combustion. A sensor is configured to sense a thermochemical property of the fuel blend to generate a signal indicative of the sensed thermochemical property of the fuel blend. A controller is responsive to the signal indicative of the sensed thermochemical property of the fuel blend to generate a control signal. A metering valve is responsive to the control signal from the controller to selectively control, based on the sensed thermochemical property of the fuel blend, a first portion of the fuel blend to be conveyed to the first mixing stage and a second portion of the fuel blend to be conveyed to the second mixing stage.BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0007] FIG. 1 is in part a fragmentary sectional view of a gas turbine in accordance with one embodiment.

[0008] FIG. 2 is a fragmentary, cutaway view of one example embodiment of a hybrid mixer unit.

[0009] FIG. 3 is a fragmentary, cutaway view of another example embodiment of a hybrid mixer unit.

[0010] FIG. 4 is a fragmentary isometric view of one example arrangement embodying several disclosed modular cartridges.

[0011] FIG. 5 is an isometric view illustrating further structural details in connection with a disclosed modular cartridge.Docket No. 2024PF00608

[0012] FIG. 6 is a flow sequence in connection with an additive manufacturing technique used to make disclosed modular cartridges.

[0013] FIG. 7 is a simplified schematic representation of aspects of a disclosed combustion system for a gas turbine engine involving first, second and third burner stages that are radially and axially spaced apart from one another.

[0014] FIG. 8 is a fragmentary sectional view of the burner stages in accordance with one example embodiment.

[0015] FIGs. 9 and 10 are respective fragmentary, isometric views of example arrangements of respective disclosed modular cartridges, as would be seen by an observer located downstream from and facing respective faces of the respective modular cartridges that include respective arrays of fluid ejection outlets.

[0016] FIG. 11 is a fragmentary sectional view of the burner stages in accordance with another example embodiment.

[0017] FIG. 12 is a fragmentary sectional view of the burner stages illustrating respective example target flame temperatures by the first, second and third burner stages.DETAILED DESCRIPTION

[0018] The present inventor has recognized that there are mainly two basic approaches that have been explored while attempting to solve the challenges of burning hydrogen in a gas turbine. One known approach, for example, starts from a conventional Dry Low Emission (DLE)-based combustion system, where the robustness of the DLE-based combustion system to inhibit flashback is somewhat improved by having a flow field in a premixer without recirculation zones or with minimal recirculation zones and by introducing purge air in the boundary layers to avoid or inhibit boundary layer flashback. A second known approach involves a diffusion flame combustion system. In this second approach, opposite to the first approach, fuel is not premixed in air before entering the combustor, but the fuel is mixed with air directly in the combustion chamber and hence little or no fuel is present upstream of the combustor, thus reducing the possibility of flashback. Combustion systems based on this second approach traditionally produce relatively higher levels of nitrogen oxides (NOx) compared to the DLE-based combustion system approach. This second approach has evolved by way of micro-mixing techniques that can involve a substantial number of injection locations (e.g., in the tens or even hundreds of injection locations) each having relatively smaller flames,Docket No. 2024PF00608 thereby collectively reducing the time spent by the mixture in the hot regions of the flame and in turn reducing NOx production. This approach relies on a rapid and intense mixing of fuel jets in the cross-flowing air to minimize rich pockets in the flame (hot regions). However, known diffusion-based mixing (even when involving micro-mixing) still can produce relatively larger amounts of NOx than a comparable DLE-based combustion system, and therefore such known designs tend to be somewhat less competitive when the fuel is natural gas or with low levels of hydrogen blended with the natural gas.

[0019] Our disclosed embodiments feature a hybrid mixer unit that in a cost-effective and reliable manner preserves the respective advantages of the foregoing two approaches while inhibiting the individual challenges commonly associated with such approaches. That is, the hybrid mixer unit in our disclosed embodiments has a first mixing stage conducive to premixed-based combustion and further has a second mixing stage conducive to diffusionbased combustion. This provides an opportunity to selectively adjust or vary the amount of fuel conveyed to each mixing stage depending on a property of the fuel or fuel blend being utilized, where, for example, a larger portion of the fuel would be mixed by way of the first mixing stage for fuel blends having a relatively lower reactivity (e.g., lower hydrogen content) and where a larger portion of the fuel would be mixed by way of the second mixing stage for fuel blends having a relatively larger reactivity (e.g., higher hydrogen content).

[0020] The present inventor has further recognized that traditional manufacturing techniques may not be necessarily conducive to a cost-effective and / or realizable manufacturing of the hybrid mixer units featured in our disclosed combustion system. For example, traditional manufacturing techniques tend to fall somewhat short from consistently limiting manufacturing variability and may also fall short from cost-effectively and reliably producing the internal conduits (e.g., some of which involve miniaturized conduits) that are involved in the hybrid mixer units featured in the combustion system.

[0021] In view of this further recognition, in one non-limiting embodiment, the present inventor further proposes use of three-dimensional (3D) Printing / Additive Manufacturing (AM) technologies, such as laser sintering, selective laser melting (SLM), direct metal laser sintering (DMLS), electron beam sintering (EBS), electron beam melting (EBM), etc., that are conducive to cost-effectively making the disclosed hybrid mixer units. For readers desirous of general background information in connection with 3D Printing / Additive Manufacturing (AM) technologies, see, for example, textbook titled “Additive Manufacturing Technologies, 3DDocket No. 2024PF00608Printing, Rapid Prototyping, and Direct Digital Manufacturing”, by Gibson I., Stucker B., and Rosen D., 2010, published by Springer, and this textbook is herein incorporated by reference.

[0022] The disclosure below will initially focus on description of a hybrid mixer unit, which is a constituent unit of modular cartridges, where each modular cartridge individually houses an array of hybrid mixer units. The disclosure will then proceed to describe features and / or arrangements (e.g., multistage burner arrangement) of modular cartridges conducive to optimizing engine operability. These features and / or arrangements result in structural and / or operational relationships effective to distribute heat release axially and radially (often referred in the art as “fuel staging”) within the combustion system and in turn realize a compact combustion system involving a relatively straightforward mechanical design.

[0023] FIG. 1 is a fragmentary sectional view of a gas turbine 100 that in one non-limiting embodiment can provide, for example, a substantially inline air flow configuration, such as commonly used in aero-derivative and aero-engines. It will be understood that disclosed embodiments are not limited to the foregoing example categories of gas turbine engines. Gas turbine 100 includes a casing 104 that houses a compressor section 106 having a compressor outlet 108 that provides compressed air and further houses a combustion system 102, such as a combustor 110 that defines a combustion zone 112, where combustion occurs, such as schematically represented by flames 113. Compressed air (schematically represented by arrows 114) from compressor outlet 108 is conveyed to combustion system 102.

[0024] In one example embodiment, a cowl 116 may be arranged to route compressed air 114 into a modular cartridge 120 that houses an array of hybrid mixer units 200, 300 (FIG. 2 and FIG. 3 respectively) circumferentially distributed about a longitudinal axis 115 of the combustor. Hybrid mixer unit 200, 300 is a constituent unit of modular cartridge 120. It will be appreciated that cowl 116 is a structure that need not be utilized in every embodiment since, optionally, compressed air 114 could, by way of example, be directly conveyed from compressor outlet 108 to modular cartridge 120.

[0025] Hybrid mixer unit 200 is arranged in combustor 110 of combustion system 102 to mix compressed air 114 and a fuel blend 122 of a first fuel and a second fuel. In one example embodiment, the first fuel of fuel blend 122 has a first reactivity index value and the second fuel of the fuel blend 122 has a second reactivity index value, where the second reactivity index value is larger compared to the first reactivity index value.Docket No. 2024PF00608

[0026] In one example embodiment, the first fuel is natural gas or a similar fuel and the second fuel is hydrogen or a similar fuel. In one example embodiment, the respective content percentages of the first fuel and the second fuel in fuel blend 122 can range from 0% or so to 100% or so regarding the content of hydrogen or ranges from 0% or so to 100% or so regarding the content of natural gas, where in each case a sum of the respective content percentages of the first fuel and the second fuel is equal to a total of 100% . In a general case, the first fuel could be any fuel (like natural gas or similar) with relatively low or no hydrogen content and the second fuel could be just hydrogen or any fuel mixture with relatively high hydrogen content.

[0027] As elaborated in greater detail below in the context of FIG. 2, hybrid mixer unit 200 includes a first mixing stage (schematically represented by twin-headed arrow 210) conducive to premixed-based combustion and a second mixing stage (schematically represented by the shorter twin-headed arrow 240) conducive to diffusion-based combustion. Unless otherwise stated, the description in connection with hybrid mixer unit 200 (other than the specific reference numerals) equally applies to hybrid mixer unit 300 in the context of FIG. 3.

[0028] One basic tenet embodied in disclosed embodiments is the ability to selectively distribute fuel blend 122 between the first and the second mixing stages 210, 240 as a function of a thermochemical property of fuel blend 122. In one example embodiment, the thermochemical property may be a reactivity index of fuel blend 122 or may be the fuel composition of fuel blend 122. The idea is to, for example, use mainly or exclusively the first mixing stage 210 (conducive to formation of premixed-based flames) for a low reactivity fuel blend and to use mainly or exclusively the second mixing stage 240 (conducive to formation of diffusion-based flames) for a high reactivity fuel blend. One goal behind hybrid mixer unit / s 200, 300 is to inhibit NOx emissions and flashback risks in an optimally balanced manner regardless of the respective contents of the first fuel and the second fuel in fuel blend 122.

[0029] In one example embodiment, combustion system 102 includes a fuel delivery subsystem 140 (FIG. 1) configured to convey fuel blend 122 to modular cartridge 120 and thus to the array of hybrid mixer units 200, 300 housed in modular cartridge 120. In one example embodiment, fuel delivery subsystem 140 includes a sensor 142 arranged to sense the thermochemical property of the fuel blend to generate a signal indicative of the sensed thermochemical property of the fuel blend. As noted above, in one example embodiment, theDocket No. 2024PF00608 sensed thermochemical property may be a reactivity index of fuel blend 122 or the fuel composition of fuel blend 122.

[0030] In one example embodiment, fuel delivery subsystem 140 further includes a controller 146 responsive to the signal indicative of the sensed thermochemical property of fuel blend 122 to generate a control signal, and a valve 144, such as three-way valve, responsive to the control signal from controller 146 to selectively control, based on the sensed thermochemical property of the fuel blend, a first portion of fuel blend 122 to convey to the first mixing stage and a second portion of fuel blend 122 to convey to the second mixing stage. That is, to selectively control the quantity of the first portion of fuel blend 122 to convey to first mixing stage 210 and the quantity of the second portion of fuel blend 122 to convey to second mixing stage 240. In one example embodiment, controller 146 includes a comparator module 148 configured to compare the thermochemical property of the fuel blend relative to a predefined threshold of the thermochemical property. For example, when the sensed thermochemical property of the fuel blend is below the predefined threshold, then the first portion of the fuel blend conveyed to the first mixing stage is larger relative to the second portion of the fuel blend conveyed to the second mixing stage. By way of comparison, when the sensed thermochemical property of the fuel blend is above or equal to the predefined threshold, then the second portion of the fuel blend conveyed to the second mixing stage is larger relative to the first portion of the fuel blend conveyed to the first mixing stage.

[0031] In one example embodiment, fuel delivery subsystem 140 further includes a controller 146 responsive to the signal indicative of the sensed thermochemical property of fuel blend 122 to generate a control signal, and a valve 144, such as three-way valve, responsive to the control signal from controller 146 to selectively control, based on the sensed thermochemical property of the fuel blend, a first portion of fuel blend 122 to convey to the first mixing stage and a second portion of fuel blend 122 to convey to the second mixing stage. That is, to selectively control the quantity of the first portion of fuel blend 122 to convey to first mixing stage 210 and the quantity of the second portion of fuel blend 122 to convey to second mixing stage 240. In one example embodiment, controller 146 includes a comparator module 148 configured to compare the thermochemical property of the fuel blend relative to a predefined threshold of the thermochemical property. For example, when the sensed thermochemical property of the fuel blend is below the predefined threshold, then the first portion of the fuel blend conveyed to the first mixing stage is larger relative to the second portion of the fuel blendDocket No. 2024PF00608 conveyed to the second mixing stage. By way of comparison, when the sensed thermochemical property of the fuel blend is above or equal to the predefined threshold, then the second portion of the fuel blend conveyed to the second mixing stage is larger relative to the first portion of the fuel blend conveyed to the first mixing stage.

[0032] FIG. 2 shows in part a fragmentary, cutaway view of one example embodiment of an array of disclosed hybrid mixer units 200 that may be housed in modular cartridge 120. As noted above, each hybrid mixer unit 200 includes first mixing stage 210 conducive to premixed-based combustion and second mixing stage 240 conducive to diffusion-based combustion. In one example embodiment, first mixing stage 210 comprises a premixing tube 212 having an inlet 214 to receive compressed air 114, a vane 216 (e.g., a swirler vane) disposed in premixing tube 212 proximate the inlet 214 of premixing tube 212, where vane 216 has at least one fuel hole 217 to eject the first portion of the fuel blend into the flow of compressed air passing by vane 216, so that a resulting mixture of the first portion of fuel blend 122 and compressed air 114 flows toward an outlet 218 of premixing tube 212. In one example embodiment, second mixing stage 240 comprises at least one fuel hole 242 proximate the outlet 218 of premixing tube 212 to eject by way of cross-flow injection the second portion of the fuel blend into the flow of the mixture that flows towards the outlet 218 of premixing tube 212. It will be appreciated that in alternative embodiments, vortex generators can be used in lieu of swirler vanes.

[0033] In one example embodiment, modular cartridge 120 comprises a monolithic structure including a fuel gallery 220, where fuel gallery 220 includes a first fuel circuit 222 fluidly connected to convey to the at least one fuel hole 217 in vane 216 the first portion of the fuel blend. Fuel gallery 220 further includes a second fuel circuit 224 fluidly connected to convey to the at least one fuel hole 242 proximate the outlet 218 of premixing tube 212 the second portion of the fuel blend. To avoid pedantic and unnecessary repetition, the description below is given in the context of just one of the example hybrid mixer units shown in FIG. 2, although the FIG. 2 shows a non-limiting example of seven hybrid mixer units 200.

[0034] FIG. 3 shows in part a fragmentary, cutaway view of one example embodiment of a disclosed hybrid mixer unit 300. As noted above, hybrid mixer unit 300 includes a first mixing stage (schematically represented by twin-headed arrow 310) conducive to premixed-based combustion and a second mixing stage (schematically represented by shorter twin-headed arrow 340) conducive to diffusion-based combustion. In one example embodiment, firstDocket No. 2024PF00608 mixing stage 310 comprises a premixing tube 312 having an inlet 314 to receive a flow of compressed air 114, a vane 316 disposed in premixing tube 312 proximate the inlet 314 of premixing tube 312, where vane 316 has at least one fuel hole 317 to eject the first portion of the fuel blend into the flow of compressed air passing by vane 316 so that a resulting mixture of the first portion of fuel blend 122 and compressed air 114 flows toward an outlet 318 of premixing tube 312. In this example embodiment, second mixing stage 340 comprises a central lance 341 having at least one fuel hole 342 proximate an outlet 344 of central lance 341 to eject, such as by way of cross-flow injection, the resulting mixture of the first portion of fuel blend 122 and compressed air 114 into the flow of the second portion of the fuel blend that flows from an inlet 344 of central lance 341 towards an outlet 346 of central lance 341.

[0035] FIG. 4 shows in part a fragmentary isometric view of one example embodiment of disclosed modular cartridges 120 (to reduce the possibility of visual cluttering just three modular cartridges are shown in FIG. 4) that individually house an array of hybrid mixer units, such as hybrid mixer units 300. It will be appreciated that in alternative embodiments, modular cartridge / s 120 can be tailored to accommodate hybrid mixer units 200.

[0036] It will be appreciated that that disclosed embodiments can be used in different classes of gas turbine engines, where our presently disclosed combustion system is scalable to meet the combustion-related requirements of any given gas turbine engine from the different classes of gas turbine engines. The scalability of the design can be implemented based on the number of hybrid mixer units (200 or 300) operatively interconnected in each modular cartridge 120. The scalability can be realized without having to change a footprint of the modular cartridges 120. That is, the same modular cartridge can be tailored for use in different classes of gas turbine engines.

[0037] FIG. 5 shows in part an exploded, isometric view illustrating certain details in connection with a disclosed modular cartridge 120. In certain embodiments, a heat shield 402 (shown in exploded condition) may be used to thermally protect the mixing tubes 212 (or 312) of hybrid mixer units 200 (or 300). Additionally, cooling holes 404 may be provided to convey a cooling fluid, such as air, within modular cartridge 120. Respective inter-mixing tube volumes 406 defined between mixing tubes 212 (or 312) in the array of hybrid mixer units 200 (or 300) in modular cartridge 120 can be appropriately configured to provide a desired acoustic damping to the structures that define modular cartridge 120. That is, respective inter-mixingDocket No. 2024PF00608 tube volumes 406 can be designed to provide during operation a cooling functionality together with acoustic damping functionality.

[0038] FIG. 6 is a flow sequence in connection with a disclosed technique for manufacturing a 3D object, such as modular cartridge 120. A computer-readable three-dimensional (3D) model 602, such as a computer aided design (CAD) model of the 3D object (i.e., modular cartridge 120) may be processed in a processor 604, where a slicing module 606 converts model 602 into a plurality of slice files (e.g., 2D data files) that define respective cross- sectional layers of the 3D object. At least some of the plurality of slices define at least one void within at least some of the respective cross-sectional layers of the 3D object and collectively define the internal features, such as conduits, voids, structural arrangements, etc. to be constructed in the modular cartridge 120. Processor 604 may be configured to control an additive manufacturing system 608 to physically make the modular cartridge 120 with the structural and / or operational relationships, as described above in the context of Figs. 1 through 6.

[0039] The disclosure below will proceed to describe features and arrangements of disclosed embodiments configured to optimize engine operability. As noted above, these features and / or arrangements result in structural and / or operational relationships effective to distribute heat release axially and radially (often referred in the art as “fuel staging”) within the combustion system and realize a compact combustion system involving a relatively straightforward mechanical design.

[0040] Distributing heat release axially is believed to provide at least the following technical advantages:

[0041] Flame Stability: At ignition of the engine, e.g., from ignition to a synch-idle condition (e.g., full speed, no load), and in some cases at conditions involving relatively low engine power, for example, the compressor delivery temperature and the fuel flow required can be relatively low and this can lead to relatively low flame temperatures and hence poor flame stability, presuming all the air is mixed with the fuel. Consequently, by-passing some air (e.g., from the main flame) and re-introducing the bypassed air downstream of this main flame would lead to a relatively hotter and more stable primary flame.

[0042] NOx: An example goal is achieving increased combustor exit temperatures while maintaining low NOx emissions. It will be appreciated that as cooling air is introduced along the combustor liner, together with heat losses to the surroundings, the temperature of the fluidDocket No. 2024PF00608 decreases as it travels axially through the combustor liner. Adding a secondary combustion stage, for example, located closer to the combustor exit than the primary flame, will inhibit this temperature decrease or even “reheat” the fluid. Given that this secondary combustion stage is closer to the combustor exit, the post-flame residence time (for example, before reaching the nozzle guide vanes where cooling air is introduced) would be reduced thereby reducing thermal NOx production of this stage.

[0043] CO: Reheating the fluid with an axial combustion stage, e.g., after the primary flame, maintains a sufficient temperature downstream of the primary flame, and this would permit decreasing or avoiding quenching of the post-flame gases leading to lower CO emissions and improved combustion efficiency.

[0044] Thermoacoustic instabilities: Distributing the heat release axially with more uniformity through the combustor would reduce the Rayleigh Index. That is, this reduces the likelihood of unsteady heat release coupling with axial pressure waves, which in turn can lead to Intermediate Frequency Dynamics (IFD).

[0045] Distributing heat release radially is believed to provide at least the following technical advantages:

[0046] Flame Stability. Similar to axial staging, radial staging permits to by-pass some air to improve flame stability at relatively low engine power (e.g., mixing the total fuel with just a portion of air). However, presuming all radial stages are arranged in a common axial plane, then air will tend to cool and hence quench neighboring flames thereby producing relatively high CO emissions and in turn diminishing the gain in flame stability). Disclosed embodiments propose having radial stages that are also axially staged to inhibit the foregoing phenomenon while keeping a compact combustion system involving a relatively straightforward mechanical design.

[0047] NOx: Given that the radial stages in disclosed embodiments are also axially staged, it will be appreciated that disclosed embodiments further inhibit production of NOx emissions.

[0048] CO: As note above, the fact that the radial stages are also axially shifted, the cold air would not quench neighboring flames as much and therefore CO at low powers will be substantially improved over traditional radially staged system where all stages are located in common streamwise plane.

[0049] Thermoacoustic instabilities: Radial staging provides additional capability to counteract thermoacoustic instabilities, including axial and radial modes by changing the heat release / temperature distribution radially.Docket No. 2024PF00608

[0050] FIG. 7 is a simplified schematic representation of aspects of a disclosed combustion system 700 for a gas turbine engine. In one example embodiment, combustion system 700 includes a first burner stage 701i, a second burner stage 7012 and a third burner stage 70b, where the first burner stage 7011, the second burner stage 70b and the third burner stage 70b are radially and axially spaced apart from one another, as schematically shown in FIG. 8. To facilitate visualization of the spatial orientation involved, the longitudinal axis 115 of a combustor 802 and a radial axis 810 are shown in FIG. 8.

[0051] A fuel delivery subsystem 740 is fluidly coupled to the first, second and third burner stages 70h, 70b and 70b to convey the fuel blend 122 of the first fuel and the second fuel to one or more of the first, second and third burner stages 7011, 70b and 70b based on a load condition of the gas turbine engine and the thermochemical property of the fuel blend, as elaborated in greater detail below.

[0052] As schematically shown in FIG. 8, each respective one of the burner stages 701i, 70b and 70b includes a respective hybrid mixer unit 804i, 8042 and 804s arranged in combustor 802 of the combustion system to respectively mix compressed air and the fuel blend of the first fuel and the second fuel. Each respective hybrid mixer unit 804i, 8042 and 804s is as functionally described above, such as described in the context of FIGs. 2 through 4.

[0053] Each of hybrid mixer units 804i, 8042 and 804s includes a respective first mixing stage configured to carry out premixed-based combustion and further includes a respective second mixing stage configured to carry out diffusion-based combustion. That is, hybrid mixer unit 804i in first burner stage 7011 includes a respective first mixing stage 806i and a respective second mixing stage 808i, hybrid mixer unit 8042 in second burner stage 70b includes a respective first mixing stage 8O62 and a respective second mixing stage 8O82, and hybrid mixer unit 8043 in third burner stage 70b includes a respective first mixing stage 8O63 and a respective second mixing stage 8O83.

[0054] In one example embodiment, as shown in FIG. 7, each respective one of burner stages 701i, 70b and 70b further comprises a respective on-off valve 742i, 7422 and 7433 controllable to convey the fuel blend to one or more of the first, second and third burner stages 701i, 70b and 70b based on the load condition of the gas turbine engine. Each on-off valve 742i, 7422 and 7433 is responsive to a respective on-off control signal (such as may be supplied by controller 146 (FIG. 1)) to be set either in an open condition or in a closed condition based on the load condition of the gas turbine engine.Docket No. 2024PF00608

[0055] In one example embodiment, the load condition of the gas turbine engine comprises the following: a first load condition, when a value indicative of a load of the gas turbine engine is below a first threshold value, a third load condition when the value indicative of the load of the engine is above a second threshold value, and a second load condition when the value indicative of the load of the engine is between the first and second threshold values, and where the second threshold value is larger relative to the first threshold value.

[0056] In one example embodiment, the respective on-off valves 7422 and 743s of the second and third burner stages 7012 and 70b are closed and the respective on-off valve 742i of the first burner stage 7011 is open to convey the fuel blend just to the first burner stage 7011 upon occurrence of the first load condition (e.g., a relatively low engine load); the respective on-off valve 7423 of the third burner stage 7013 is closed and the respective on-off valves 742i and 7432 of the first and second burner stages 7011, 7012 are open to convey the fuel blend just to the first and second burner stages 701i, 7012 upon occurrence of the second load condition (e.g., a relatively mid-level engine load); and the respective on-off valves of the first, second and third burner stages 742i, 7422 and 7433 are open to convey the fuel blend to the first, second and third burner stages 742i, 7422 and 7433 upon occurrence of the third load condition (e.g., a relatively high engine load).

[0057] In one example embodiment, as further shown in FIG. 7, each respective one of burner stages 701i, 7012 and 70b further comprises a respective metering valve 744i, 7442 and 7443 responsive to a respective metering control signal (such as may be also supplied by controller 146 (FIG. 1)) to selectively control, based on the sensed thermochemical property of the fuel blend, a first portion of the fuel blend to be conveyed to the respective first mixing stage and a second portion of the fuel blend to be conveyed to the respective second mixing stage of burner stages 701i, 70b and 70b. For each respective one of burner stages 701i, 70b and 70b this functionality is as described above in paragraph

[0024] et seq. It will be appreciated that the respective first and second portions of the fuel blend to be conveyed to the respective first and second mixing stages of burner stages 7011, 70b and 70b need not be equal. For example, the respective first and second portions to be conveyed to the respective first and second mixing stages of burner stages 701i, 70b and 70b can be appropriately tailored to optimally reduce emissions based on different fuel reactivities, engine load, etc.Docket No. 2024PF00608

[0058] As described above in the context of FIG. 1, sensor 142 is configured to sense the thermochemical property of the fuel blend to generate a signal indicative of the sensed thermochemical property of the fuel blend.

[0059] In one example embodiment, each respective hybrid mixer unit in each respective one of burner stages 7011, 7012 and 7013 is a constituent unit (conceptually analogous to a building block) in a respective modular cartridge 900 (FIG. 9, FIG. 10) that houses respective pluralities of hybrid mixer units that in combination form the first, second and third burner stages 7011, 7012 and 70b. As can be further appreciated in FIGs. 9 and 10, first burner stage 7011 comprises a first array of fluid ejection outlets 902i located at a radially inward position relative to the second and third burner stages 7012 and 7013. That is, the first array of fluid ejection outlets 902i is located at a radially inward position relative to the respective arrays of fluid ejection outlets of the second and third burner stages 7012 and 7013.

[0060] The third burner stage 70b comprises a third array of fluid ejection outlets 9023 located at a radially outward position relative to the first and second burner stages 7011 and 7012. That is, the third array of fluid ejection outlets 9023 is located at a radially outward position relative to the respective arrays of fluid ejection outlets of the first and second burner stages 701i and 7012.

[0061] The second burner stage 7012 comprises a second array of fluid ejection outlets 9022 radially located between the first burner stage and the third burner stage 7011 and 70b. That is, the second array of fluid ejection outlets 9022 is located between the respective arrays of fluid ejection outlets of the first and third burner stages 7011 and 70b.

[0062] For the sake of simplicity of illustration, FIGs. 9 and 10 respectively just show a circumferential sector spanned by one example modular cartridge; it will be appreciated, however, that in a practical implementation further modular cartridges will be circumferentially disposed about longitudinal axis 115 of the combustor so that in turn the first, the second, and the third array of fluid ejection outlets 902i, 9022, 9023 are respectively circumferentially disposed about longitudinal axis 115 of the combustor.

[0063] As can be further appreciated in FIGs. 9 and 10, the first array of fluid ejection outlets 902i is located axially upstream relative to the second and third arrays of fluid ejection outlets 9022, 902s; the third array of fluid ejection outlets 9023 is located axially downstream relative to the first and second arrays of fluid ejection outlets 902i, 9022, and the second array of fluidDocket No. 2024PF00608 ejection outlets 9022 is axially located between the first and third arrays of fluid ejection outlets9021, 9023.

[0064] In one example embodiment, as can be appreciated in FIG. 9. the respective first, second, and third array of fluid ejection outlets 902i, 9022, 902s can each be configured to have a uniform cross-sectional area (e.g., same size) relative to one another. In another example embodiment, as can be appreciated in FIG. 10, the respective first, second, and third array of fluid ejection outlets 902i, 9022, 902s can each be configured to have a different cross-sectional area relative to one another, and / or the first, second, and third array of the fluid ejection outlets 902i, 9022, 9023 can be respectively configured to have a different number of fluid ejection outlets relative to one another depending on the needs of a given application.

[0065] In one example embodiment, as can be appreciated in FIG. 8, the respective first mixing stages 806i, 8O62, 8O63 of the first, second, and third burner stages 7011, 7012, 70b each includes a respective premixing tube 812i, 8122, 8123 configured to have different axial lengths relative to one another.

[0066] In one example embodiment, the respective premixing tube 812i of the first burner stage 701 i is configured with a shorter axial length relative to the respective axial lengths of the respective premixing tubes 8122, 8123 of the second and third burner stages 70b, 70b; the respective premixing tube of the third burner stage 70b is configured with a longer axial length relative to the respective axial lengths of the respective premixing tubes 812i, 8122 of the first and second burner stages 7011, 70 b; and the respective premixing tube of the second burner stage 70b has an axial length between the respective axial lengths of the respective premixing tubes 812i, 8123 of the first and third burner stages 7011, 70b. That is, the respective mixing lengths of first mixing stages 8O61, 8O62, 8O63 can be different. In one alternative embodiment, as can be seen in FIG. 11 , the respective mixing lengths of the respective first mixing stages 8O61, 8O62, 8O63 can be designed to have the same axial length.

[0067] In one example embodiment, the respective premixing tubes 812i, 8122, 8123 of the first, second and third burner stages 701i, 70b, 70b each includes a respective inlet 814i, 8142, 8143 to receive a respective flow of the compressed air; a respective vane 8161, 8I62, 8I63 disposed in the premixing tube proximate the respective inlets 814i, 8142, 8143. Each respective vane 8161, 8162, 8163 having at least one respective fuel hole 8181, 8182, 8183 to inject the first portion of the fuel blend into a flow of the compressed air passing by each respective vane soDocket No. 2024PF00608 that a resulting mixture of the first portion of the fuel blend and the compressed air flows towards a respective array of the arrays of fluid ejection outlets 902i, 9022, 902s.

[0068] In one example embodiment, the respective second mixing stages 808i, 8O82, 8O83 of the first, second, and third burner stages 7011, 7012, 7013 each includes at least one fuel hole proximate the respective fluid ejection outlet to inject, by way of cross-flow injection, the second portion of the fuel blend into the flow of the mixture that flows towards a respective array of the arrays of fluid ejection outlets 902i, 9022, 9023. The foregoing at least one fuel hole described in connection with the respective second mixing stages 8O81, 8O82, 8O83 of the first, second, and third burner stages 7011, 7012, 7013 is conceptually analogous to the at least one fuel hole 242 shown and described in the context of hybrid mixer unit 200 shown in FIG. 2. It will be appreciated that in alternative embodiments such at least one fuel hole described in connection with the respective second mixing stages 8O81, 8O82, 8O83 of the first, second, and third burner stages 7011, 7012, 70b can be conceptually analogous to the at least one fuel hole 342 shown and described in the context of hybrid mixer unit 300 shown in FIG. 3.

[0069] FIG. 12 is a fragmentary sectional view of the burner stages the first, second, and third burner stages 7011, 7012, 70b illustrating target flame temperatures Tfiamei, Tfiame2 ,Tfiame3. FIG. 12 schematically shows different target flame temperatures for the first, second, and third burner stages 7011, 7012, 70b to optimize, for example, flame stability, combustion efficiency, thermoacoustic and emissions for the respective first, second, and third burner stages 7011, 7012, 7013. It will be appreciated that the target flame temperatures for the first, second, and third burner stages 7011, 7012, 70b need not be different since, depending on the needs of a given application, the target flame temperatures for the first, second, and third burner stages 701i, 7012, 70h can be substantially the same.

[0070] In operation, disclosed embodiments offer a cost-effective, safe, and reliable manner for burning any fuel blends, such as without limitation involving hydrogen and natural gas (e.g., from pure natural gas to pure hydrogen) while inhibiting NOx emissions and reducing flashback risks.

[0071] In operation, disclosed embodiments are believed to offer superior engine operability (e.g., inhibiting NOx and CO emissions and thermoacoustic instabilities) by way of structural and / or operational relationships that permit distributing heat release axially and radially within the combustion system, while keeping a compact and low mechanical complexity fuel delivery subsystem. For example, in disclosed embodiments a common fuel gallery permits delivery toDocket No. 2024PF00608 the first and second mixing stages in the hybrid mixer units. This substantially reduces the mechanical complexity and large footprint of multi-stage combustion systems involving separate fuel galleries.

[0072] In operation, disclosed embodiments offer a substantially compact injector (e.g., in the form of modular cartridges) adaptable for various classes of gas turbine engines, such as without limitation, aero-derivative and aero-engines in which the combustor is parallel to the engine axis.

[0073] Disclosed embodiments take advantage of additive manufacturing techniques that permit modular cartridges to have more injectors and further permit appropriately configuring the conduits in the modular cartridges, such as realizing length / diameter L / D ratio for such conduits within appropriate ranges.

[0074] In operation, disclosed embodiment offer user-friendly design scalability, such as based on the number of hybrid mixer units operatively interconnected in each modular cartridge. The scalability of the design can be realized without having to change a footprint of the modular cartridges. That is, the same modular cartridge can be tailored for use in different classes of gas turbine engines without changing the physical dimensions of the modular cartridges.

[0075] In operation, disclosed embodiments permit user-friendly servicing, such in-situ replacements and serviceability of individual modular cartridges, without involving engine removal.

[0076] In operation, disclosed embodiments offer acoustic damping, such as included in the cooling passages of the modular cartridge.

[0077] Although at least one exemplary embodiment has been described in detail, those skilled in the art will understand that various changes, substitutions, variations, and improvements disclosed herein may be made without departing from the scope of the disclosure in its broadest form.

[0078] None of the description in the present application should be read as implying that any particular element, step, act, or function is an essential element, which must be included in the claim scope. The scope of patented subject matter is defined only by the allowed claims. Moreover, none of these claims are intended to invoke a means plus function claim construction unless the exact words "means for" are followed by a participle.

Claims

Docket No. 2024PF00608CLAIMSWhat is claimed is:A combustion system for a gas turbine engine, comprising: a first burner stage; a second burner stage; a third burner stage, wherein the first, second, and third burner stages are radially and axially spaced apart from one another; a fuel delivery subsystem fluidly coupled to the first, second and third burner stages to convey a fuel blend of a first fuel and a second fuel to one or more of the first, second and third burner stages based on a load condition of the gas turbine engine; each respective one of the burner stages comprising: a respective hybrid mixer unit arranged in a combustor of the combustion system to mix compressed air and the fuel blend of the first fuel and the second fuel, each respective hybrid mixer unit including a respective first mixing stage configured to carry out premixed-based combustion and a respective second mixing stage configured to carry out diffusion-based combustion; a sensor configured to sense a thermochemical property of the fuel blend to generate a signal indicative of the sensed thermochemical property of the fuel blend; a controller responsive to the signal indicative of the sensed thermochemical property of the fuel blend to generate a control signal; and a metering valve responsive to the control signal from the controller to selectively control, based on the sensed thermochemical property of the fuel blend, a first portion of the fuel blend to be conveyed to the first mixing stage and a second portion of the fuel blend to be conveyed to the second mixing stage.

2. The combustion system of claim 1, wherein the first burner stage comprises a first array of fluid ejection outlets located at a radially inward position relative to the second and third burner stages, wherein the third burner stage comprises a third array of fluid ejection outlets located at a radially outward position relative to the first and second burner stages, andDocket No. 2024PF00608 wherein the second burner stage comprises a second array of fluid ejection outlets radially located between the first burner stage and the third burner stage.

3. The combustion system of claim 2, wherein the first, the second, and the third array of fluid ejection outlets are respectively circumferentially disposed about a longitudinal axis of the combustor.

4. The combustion system of claim 1 or 2, wherein each respective one of the burner stages further comprises a respective on-off valve controllable to convey the fuel blend to one or more of the first, second and third burner stages based on the load condition of the gas turbine engine.

5. The combustion system of any one of claims 2 to 4, wherein the first array of fluid ejection outlets is located axially upstream relative to the second and third arrays of fluid ejection outlets, wherein the third array of fluid ejection outlets is located axially downstream relative to the first and second arrays of fluid ejection outlets, and wherein the second array of fluid ejection outlets is axially located between the first and third arrays of fluid ejection outlets.

6. The combustion system of any one of claims 1-2 or 4-5, wherein the load condition of the gas turbine engine comprises a first load condition when a value indicative of a load of the gas turbine engine is below a first threshold value, wherein the load condition of the gas turbine engine comprises a third load condition when the value indicative of the load of the engine is above a second threshold value, wherein the load condition of the gas turbine engine comprises a second load condition when the value indicative of the load of the engine is between the first and second threshold values, and wherein the second threshold value is larger relative to the first threshold value.

7. The combustion system of claim 6, wherein the respective on-off valves of the second and third burner stages are closed and the respective on-off valve of the first burner stage is open to convey the fuel blend just to the first burner upon occurrence of the first load condition.

8. The combustion system of claim 6 or 7, wherein the respective on-off valve of the third burner stage is closed and the respective on-off valves of the first and second burner stages areDocket No. 2024PF00608 open to convey the fuel blend just to the first and second burner stages upon occurrence of the second load condition.

9. The combustion system of any one of claims 6 to 8, wherein the respective on-off valves of the first, second and third burner stages are open to convey the fuel blend to the first, second and third burner stages upon occurrence of the third load condition.

10. The combustion system of claim 1 , wherein the respective first mixing stages of the first, second, and third burner stages each includes a respective premixing tube, the respective premixing tubes of the first, second, and third burner stages configured to have different axial lengths relative to one another.

11. The combustion system of claim 10, wherein the respective premixing tube of the first burner stage is configured with a shorter axial length relative to the respective axial lengths of the respective premixing tubes of the second and third burner stages.

12. The combustion system of claim 11, wherein the respective premixing tube of the third burner stage is configured with a longer axial length relative to the respective axial lengths of the respective premixing tubes of the first and second burner stages.

13. The combustion system of claim 12, wherein the respective premixing tube of the second burner stage has an axial length between the respective axial lengths of the respective premixing tubes of the first and third burner stages14. The combustion system of claim 1, wherein the respective first mixing stages of the first, second, and third burner stages each includes a respective premixing tube, the respective premixing tubes of the first, second, and third burner stages configured to have a uniform axial length relative to one another.

15. The combustion system of any one of claims 1, 10 or 14, wherein the respective fluid ejection outlets of the first, second, and third array of fluid ejection outlets have a uniform cross-sectional area relative to one another.

16. The combustion system of any one of claims 1, 10 or 14, wherein the respective fluid ejection outlets of the first, second, and third array of fluid ejection outlets have a different cross-sectional area relative to one another, or wherein the first, second, and third array of theDocket No. 2024PF00608 fluid ejection outlets are respectively configured to have a different number of fluid ejection outlets relative to one another.

17. The combustion system of claim 1, wherein the first fuel of the fuel blend has a first reactivity index value, and the second fuel of the fuel blend has a second reactivity index value, and wherein the second reactivity index value is larger compared to the first reactivity index value.

18. The combustion system of claim 1 or 17, wherein the first fuel is natural gas, and the second fuel is hydrogen.

19. The combustion system of claim 18, wherein respective content percentages of the first fuel and the second fuel in the fuel blend range from 0% to 100% content of hydrogen or ranges from 0% to 100% content of natural gas, and wherein in each case a sum of the respective content percentages of the first fuel and the second fuel is equal to a total of 100%.

20. The combustion system of claim 1 , wherein the controller includes a comparator module configured to compare the thermochemical property of the fuel blend relative to a predefined threshold of the thermochemical property.

21. The combustion system of claim 20, wherein, when the sensed thermochemical property of the fuel blend is below the predefined threshold of the thermochemical property, then the first portion of the fuel blend conveyed to the first mixing stage is larger relative to the second portion of the fuel blend conveyed to the second mixing stage.

22. The combustion system of claim 20, wherein, when the sensed thermochemical property of the fuel blend is above or equal to the predefined threshold of the thermochemical property, then the second portion of the fuel blend conveyed to the second mixing stage is larger relative to the first portion of the fuel blend conveyed to the first mixing stage.

23. The combustion system of claim 1, wherein the hybrid mixer unit in each respective one of the burner stages is a constituent unit in a respective modular cartridge that houses the respective hybrid mixer units in the first, second and third burner stages.

24. The combustion system of claim 23, wherein a plurality of the modular cartridges is circumferentially distributed about a longitudinal axis of the combustor.Docket No. 2024PF0060825. The combustion system of claim 10 or 14, wherein the respective premixing tubes of the first, second and third burner stages each includes a respective inlet to receive a respective flow of the compressed air, a respective vane or vortex generator disposed in the premixing tube proximate the inlet, the respective vane or vortex generator having at least one fuel hole to inject the first portion of the fuel blend into a flow of the compressed air passing by the vane or vortex generator, wherein a resulting mixture of the first portion of the fuel blend and the compressed air flows towards a respective fluid ejection outlet.

26. The combustion system of claim 25, wherein the respective second mixing stages of the first, second, and third burner stages each includes at least one fuel hole proximate the respective fluid ejection outlet to inject, by way of cross-flow injection, the second portion of the fuel blend into the flow of the mixture that flows towards the respective fluid ejection outlet.

27. The combustion system of claim 1 , wherein the thermochemical property of the fuel blend sensed by the sensor is selected from the group consisting of a reactivity index of the fuel blend, and a fuel composition of the fuel blend.

28. The combustion system of claim 23, wherein the respective modular cartridge comprises a monolithic structure including a respective fuel gallery for the first, second and third burner stages, the respective fuel gallery defined in the monolithic structure of the modular cartridge, wherein the respective fuel gallery includes a respective first fuel circuit for the first, second and third burner stages arranged to convey the first portion of the fuel blend to at least one fuel hole fluidly coupled to the respective first mixing stage of the first, second and third burner stages.

29. The combustion system of claim 28, wherein the respective fuel gallery further includes a a respective second fuel circuit fluidly arranged to convey the second portion of the fuel blend to at least one fuel hole fluidly coupled to the respective second mixing stage of the first, second and third burner stages.

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