Multi-fuel combustion system

Abstract

A multi-fuel combustion system for a turbine engine has a combustion chamber formed by a combustor liner. The combustion chamber defines a first combustion zone and a second combustion zone. A first fuel system is fluidly coupled with the first combustion zone, wherein the rotating fuel slinger provides a first fuel to the first combustion zone. A second fuel system is fluidly coupled with the second combustion zone, wherein the gaseous fuel injector provides a second fuel to the second combustion zone.

Description

Technical Field

[0001] The present subject matter generally relates to turbine engines having multi-fuel combustion systems. Background Art

[0002] The turbine engine is driven by the flow of combustion gases through the engine to rotate a plurality of turbine blades, which in turn rotate the compressor, thereby providing compressed air to the combustor for combustion. The combustor may be disposed within the turbine engine and fluidly coupled to the turbine into which the combustion gases flow.

[0003] Historically, fuel has been used in the combustors of turbine engines. Typically, air and fuel are fed into a combustion chamber, where they mix and then burn in the presence of air to produce hot gases. The hot gases are then fed to a turbine to generate power. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] In the attached figure:

[0005] Figure 1 is a schematic cross-sectional view of a turbine engine having a compressor section, a combustion section with a multi-fuel combustion system, and a turbine section according to various aspects described herein.

[0006] Figure 2 According to the various aspects described in this article Figure 1 Schematic cross-sectional view of a multi-fuel combustion system.

[0007] Figure 3 According to the various aspects described in this article Figure 2 FIG. 1 is a schematic cross-sectional view of a multi-fuel combustion system further illustrating fuel and air flows.

[0008] Figure 4 is an illustration of operations according to various aspects described herein having Figure 1 A flow chart of a method of implementing a multi-fuel combustion system for a turbine engine.

[0009] Figure 5 According to the various aspects described in this article Figure 2 A variation of the schematic cross-sectional view of FIG.

[0010] Figure 6 According to the various aspects described in this article Figure 2 and Figure 4 Another variation of the schematic cross-sectional view of FIG. DETAILED DESCRIPTION

[0011] Aspects of the disclosure described herein relate to a multi-fuel combustion system. The multi-fuel combustion system includes a combustion chamber partially defined by a combustor liner. The combustor liner may have a front liner and an aft liner. The front liner at least partially defines a first combustion zone within the combustion chamber, and the aft liner at least partially defines a second combustion zone within the combustion chamber.

[0012] The first fuel system includes a rotating fuel ejector that provides a first fuel to the first combustion zone. The rotating fuel ejector is rotationally driven and can atomize the received first fuel by rapidly rotating and ejecting the first fuel. In other words, the first fuel can be centrifuged radially outward within a portion of the rotating fuel ejector, while another portion of the rotating fuel ejector can receive and discharge the first fuel as a collection of droplets.

[0013] Exhaust gas from the first combustion zone enters the second combustion zone. That is, the second combustion zone is located fluidically downstream of the first combustion zone. The second combustion zone is supplied with a second fuel by a gaseous fuel injector of a second fuel system. Compared to the first fuel, the second fuel burns faster, hotter, cleaner, or any combination thereof. Combusting the exhaust gas from the first combustion zone in the second combustion zone reduces overall emissions from the combustor.

[0014] For purposes of illustration, the present disclosure will be described with respect to a turbine engine. However, it will be understood that the disclosed aspects described herein are not limited thereto, and that the combustors described herein may be implemented in engines including, but not limited to, turbojets, turboprops, turboshafts, and turbofans. The disclosed aspects discussed herein may have general applicability in non-aircraft engines having combustors, such as in other mobile applications and non-mobile industrial, commercial, and residential applications.

[0015] As used herein, the word "exemplary" means "serving as an example, instance, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. Furthermore, unless expressly stated otherwise, all embodiments described herein should be considered exemplary.

[0016] As used herein, the terms “first” and “second” may be used interchangeably to distinguish one component from another and are not intended to indicate the position or importance of each component.

[0017] The terms "front" and "rear" refer to relative positions within a turbine engine or vehicle and refer to the normal operating attitude of the turbine engine or vehicle. For example, for a turbine engine, front refers to the position closer to the engine inlet, while rear refers to the position closer to the engine exhaust.

[0018] As used herein, the term "upstream" refers to a direction opposite to the direction of fluid flow, while the term "downstream" refers to a direction in the same direction as the direction of fluid flow.

[0019] The term "fluid" may be a gas or a liquid, or a combination thereof. The term "fluidically coupled" refers to the ability of a fluid to establish a connection between designated areas. The term "fluid exposed" refers to one or more parts of an object being contacted by a fluid.

[0020] Furthermore, as used herein, the term "radial" or "radially" refers to directions away from a common center. For example, in the overall context of a turbine engine, radial refers to directions along a ray extending between the central longitudinal axis of the engine and the periphery of the engine.

[0021] All directional references (e.g., radial, axial, up, down, left, right, front, back, top, bottom, above, below, vertical, horizontal, upstream, downstream, forward, backward, etc.) are used for identification purposes only to help the reader understand the present disclosure and do not create limitations, especially limitations on the position, orientation, or use of the disclosed aspects described herein. Connection references (e.g., attach, couple, and connect) are to be interpreted broadly and may include intermediate structural elements between sets of elements and relative movement between elements, unless otherwise indicated. Therefore, a connection reference does not necessarily mean that two elements are directly connected and fixed relative to each other. The exemplary figures are for illustration purposes only. The dimensions, positions, order, and relative sizes reflected in the accompanying figures may vary.

[0022] The term "perpendicular" means substantially perpendicular, wherein the angle between the first line and the second line is within the range of 85° to 95°. The term "parallel" means substantially parallel, wherein the first line and the second line extend so that a third line can be drawn to intersect the first line and the second line, wherein the third line is within the range of 85° to 95° with both the first line and the second line.

[0023] The singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Also, as used herein, the term "set" or "a group of" elements may refer to any number of elements, including only one.

[0024] The use of "and" and "or" is to be interpreted broadly. For example, but not limitation, the use of "and" does not necessarily require all elements or features to be listed, and the use of "or" is inclusive unless such a construction is illogical.

[0025] As used herein, a "controller" (e.g., a "control module," "regulator module," "integrator module") may include a component configured or adapted to provide instructions, control, operation, or any form of communication to an operable component to affect its operation. Such a controller or module may include any known processor, microcontroller, or logic device, including, but not limited to, a field programmable gate array (FPGA), a complex programmable logic device (CPLD), an application specific integrated circuit (ASIC), a full authority digital engine control (FADEC), a proportional controller (P), a proportional integral controller (PI), a proportional differential controller (PD), a proportional integral differential controller (PID), a hardware accelerated logic controller (e.g., for encoding, decoding, transcoding, etc.), or a combination thereof. Although described herein as including separate elements, in non-limiting aspects, such controllers and modules may be combined on one or more devices including a common device (such as a single processor or microcontroller). Non-limiting examples of such controllers or modules may be configured or adapted to run, operate, or otherwise execute program code to affect operational or functional results, including performing various methods, functions, processing tasks, calculations, comparisons, sensing, or measurement values, etc., to enable or implement the technical operations or operations described herein. The operation or functional result can be based on one or more inputs, stored data values, sensed or measured values, true or false indications, etc. Although "program code" is described, non-limiting examples of operable or executable instruction sets can include routines, programs, objects, components, data structures, algorithms, etc. that have the technical effect of performing a specific task or implementing a specific abstract data type. In another non-limiting example, the controller, controller module, regulator module or integrator module can also include a data storage component accessible by the processor, including memory, whether transient, volatile memory, or non-transient or non-volatile memory. Additional non-limiting examples of memory can include random access memory (RAM), read-only memory (ROM), flash memory or one or more different types of portable electronic memory, such as disks, DVDs, CD-ROMs, flash drives, universal serial bus (USB) drives, etc., or any suitable combination of these types of memory. In one example, the program code can be stored in the memory in a machine-readable format accessible by the processor. In addition, the memory can store various data, data types, sensed or measured data values, inputs, generated or processed data, etc. that can be accessed by the processor when providing instructions, controls, or operations to achieve functions or operational results, as described herein. In another non-limiting example, the controller can compare a first value with a second value and operate or control the operation of an additional component based on the satisfaction of the comparison. For example, when a sensed, measured, or provided value is compared with another value (including a stored or predetermined value), the satisfaction of the comparison can result in an action, function, or operation that can be controlled by the controller.As used herein, the term "meets" of a comparison is used to indicate that a first value satisfies a second value, e.g., is equal to or less than the second value, or is within a range of values of the second value. It should be understood that such a determination can be readily modified to satisfy via a positive / negative comparison or a true / false comparison. Example comparisons may include comparing a sensed or measured value to a threshold value or a threshold range.

[0026] Furthermore, as used herein, although a sensor may be described as "sensing" or "measuring" a corresponding value, sensing or measuring may include determining a value indicative of or related to the corresponding value, rather than directly sensing or measuring the value itself. The sensed or measured value may be further provided to an additional component. For example, the value may be provided to a controller or processor, and the controller or processor may process the value to determine a representative value or an electrical characteristic representative of the value.

[0027] Figure 1 is a schematic diagram of a turbine engine 10. As a non-limiting example, the turbine engine 10 may be used with an aircraft. The turbine engine 10 may include at least a compressor section 12, a combustion section 14, and a turbine section 16 arranged in a serial flow arrangement. A drive shaft 18 rotationally couples the compressor section 12 and the turbine section 16 so that rotation of one affects rotation of the other and defines an engine centerline 20 of the turbine engine 10.

[0028] The compressor section 12 may include a low-pressure (LP) compressor 22 and a high-pressure (HP) compressor 24 fluidly coupled in series with each other. The turbine section 16 may include an HP turbine 26 and an LP turbine 28 fluidly coupled in series with each other. The drive shaft 18 may operably couple the LP compressor 22, the HP compressor 24, the HP turbine 26, and the LP turbine 28 together. Alternatively, the drive shaft 18 may include an LP drive shaft and an HP drive shaft. The LP drive shaft may couple the LP compressor 22 to the LP turbine 28, and the HP drive shaft may couple the HP compressor 24 to the HP turbine 26. The LP spool may be defined as the combination of the LP compressor 22, the LP turbine 28, and the LP drive shaft, such that rotation of the LP turbine 28 may apply driving force to the LP drive shaft, which in turn may rotate the LP compressor 22. The HP spool may be defined as the combination of the HP compressor 24, the HP turbine 26, and the HP drive shaft, such that rotation of the HP turbine 26 may apply driving force to the HP drive shaft, which in turn may rotate the HP compressor 24.

[0029] The compressor section 12 may include a plurality of axially spaced stages. Each stage includes a set of circumferentially spaced rotating blades and a set of circumferentially spaced stationary vanes. The compressor blades for a stage of the compressor section 12 may be mounted to a disk, which is mounted to the drive shaft 18. Each set of blades for a given stage may have its own disk. The vanes of the compressor section 12 may be mounted to a casing, which may extend circumferentially around the turbine engine 10. It should be understood that the representation of the compressor section 12 is merely schematic and that there may be any number of blades, vanes, and stages. Further, it is contemplated that there may be any number of other components within the compressor section 12.

[0030] Similar to the compressor section 12, the turbine section 16 may include a plurality of axially spaced stages, with each stage having a set of circumferentially spaced rotating blades and a set of circumferentially spaced stationary vanes. The turbine blades for a stage of the turbine section 16 may be mounted to disks, which are mounted to the drive shaft 18. Each set of blades for a given stage may have its own disk. The vanes of the turbine section may be mounted to the casing in a circumferential manner. It should be noted that there may be any number of blades, vanes, and turbine stages, as the illustrated turbine section is merely a schematic representation. Further, it is contemplated that there may be any number of other components within the turbine section 16.

[0031] The combustion section 14 may be disposed in series between the compressor section 12 and the turbine section 16. The combustion section 14 may be fluidly coupled to at least a portion of the compressor section 12 and the turbine section 16 such that the combustion section 14 at least partially fluidly couples the compressor section 12 to the turbine section 16. As a non-limiting example, the combustion section 14 may be fluidly coupled to the HP compressor 24 at an upstream end of the combustion section 14 and to the HP turbine 26 at a downstream end of the combustion section 14.

[0032] Included in the combustion section 14 is a kicker multi-fuel combustion system or multi-fuel combustion system 30. The multi-fuel combustion system 30 can receive a rotatable output from the drive shaft 18. That is, a portion of the multi-fuel combustion system 30 is rotatably coupled to the drive shaft 18, which is illustratively shown as an LP drive shaft, an HP drive shaft, or both. The multi-fuel combustion system 30 can be fluidly coupled to a portion of the drive shaft 18 to receive liquid fuel.

[0033] Additionally or alternatively, the junction assembly 32 can selectively connect or disconnect the multi-fuel combustion system 30 to a fuel source. As non-limiting examples, the fuel source can be a liquid fuel, a hydrogen fuel, a gaseous fuel, or any combination thereof. In other words, the liquid fuel can be "turned off" or disconnected by the junction assembly 32, while the junction assembly 32 provides hydrogen fuel or another gaseous fuel, and vice versa.

[0034] During operation of the turbine engine 10, ambient or atmospheric air is drawn into the compressor section 12 via a fan upstream of the compressor section 12, where it is compressed, creating pressurized air. The pressurized air may then flow into the combustion section 14, where it is mixed with fuel and ignited, thereby generating combustion gases. The HP turbine 26 extracts some work from these combustion gases, which drives the HP compressor 24. The combustion gases are exhausted into the LP turbine 28, which extracts additional work to drive the LP compressor 22, and the exhaust gases are ultimately exhausted from the turbine engine 10 via an exhaust section downstream of the turbine section 16. Drive of the LP turbine 28 drives the LP spool, which rotates the fan and the LP compressor 22.

[0035] One or more components of turbine engine 10, such as, but not limited to, an engine starter or one or more portions of turbine section 16, provide rotational energy to drive shaft 18. Figure 2 As discussed further in , the drive shaft 18 may provide a rotatable output to a portion of a multi-fuel combustion system 30 .

[0036] Figure 2 is a schematic cross-sectional view of a multi-fuel combustion system 30. The multi-fuel combustion system 30 includes a combustor liner 34 having a forward liner 40 and an aft liner 42 axially spaced from the forward liner 40. A combustion chamber 44 may be formed by the combustor liner 34. The combustion chamber 44 may be an annular chamber. Alternatively, in another non-limiting example, the combustion chamber 44 may be a plurality of circumferentially spaced combustion chambers.

[0037] Combustion chamber 44 includes a radially extending portion 46 and an axially extending portion 48. Radially extending portion 46 may include a first combustion zone 50. Axially extending portion 48 may include a second combustion zone 52. In other words, combustion chamber 44 includes at least two combustion zones, a first combustion zone 50 and a second combustion zone 52, which are illustratively separated by a dashed line. It should be understood that the dashed line may be curved and may be located anywhere in combustion chamber 44 that divides combustion chamber 44 into two combustion zones. As used herein, a combustion zone includes a non-luminous area where air and fuel mix to produce combustion. A first flame may be located in a first region 54 within first combustion zone 50. A second flame may be located in a second region 56 within second combustion zone 52.

[0038] The first fuel system 60 is fluidly coupled to the first combustion zone 50. The first fuel system 60 includes a liquid fuel injector or nozzle having a kicker (shown as a rotating fuel kicker 62) for providing the first fuel 58 to the first combustion zone 50.

[0039] The rotating fuel kicker 62 is operably coupled to the drive shaft 18. That is, the rotor portion 64 of the rotating fuel kicker 62 can rotate when the drive shaft 18 rotates. Although shown as being permanently coupled to or formed with the drive shaft 18, it is contemplated that in different and non-limiting examples, the rotating fuel kicker 62 can be selectively operably coupled to the drive shaft 18.

[0040] The first fuel system 60 may include a fuel passage 66. As shown, for example, the fuel passage 66 may be defined by the drive shaft 18. Additionally or alternatively, a first conduit 68, shown in phantom, may provide the first fuel 58 to the rotating fuel kicker 62, wherein the first conduit 68 is positioned axially along the drive shaft 18 and radially outward of the drive shaft 18. The first conduit 68 may be connected to the fuel ejector 62 via the engagement assembly 32 ( Figure 1 ) is connected to the first fuel system 60.

[0041] The first fuel outlet (shown as outlet 70) of the rotating fuel kicker 62 discharges the first fuel 58 into the radially extending portion 46 of the combustion chamber 44 or the first combustion zone 50. A kicker injector centerline 72 can be defined by the outlet 70. The kicker injector centerline 72 can be perpendicular to the engine centerline 20. That is, the kicker injector centerline 72 can form an angle in the range of 85° to 95° with the engine centerline 20. Alternatively, the kicker injector centerline 72 can form an angle in the range of 20° to less than 85° with the engine centerline 20.

[0042] The first igniter 78 may be located in the first combustion zone 50. As an example, the first igniter 78 is shown as being located in the forward liner 40. Additionally or alternatively, the first igniter 78 for the first fuel in the first combustion zone 50 may be located at the aft liner 42. Although the first igniter 78 is shown as a single igniter, multiple igniters are contemplated.

[0043] A second fuel system 80 is fluidly coupled to the second combustion zone 52. The second fuel system 80 includes a fuel injector, shown as a gas fuel injector 82, and a fuel supply passage, shown as a gas fuel supply passage 84, which terminates in an outlet, shown as a gas fuel injector outlet 86. The gas fuel injector 82 provides the second fuel 74 to the second combustion zone 52. The second fuel can be provided to the gas fuel injector 82 via the gas fuel supply passage 84. That is, the gas fuel supply passage 84 is fluidly coupled to the gas fuel injector 82.

[0044] Although shown as a single gas fuel injector, the gas fuel injector 82 may be a group of circumferentially spaced gas fuel injectors. The group of circumferentially spaced gas fuel injectors may be circumferentially spaced about the engine centerline 20.

[0045] Optionally, a valve 88 may control the flow of the second fuel 74 from the gaseous fuel supply passage 84 into the gaseous fuel injector 82. The valve 88 may be located at the intersection of the gaseous fuel supply passage 84 and the gaseous fuel injector 82 or upstream.

[0046] The gas fuel injector centerline 92 may be defined by the gas fuel injector outlet 86. The gas fuel injector centerline 92 may be perpendicular to the engine centerline 20. Alternatively, the gas fuel injector centerline 92 may form an angle with the engine centerline 20 in the range of 20° to less than 85°, such as Figure 5-6 As further shown in .

[0047] A second igniter 94 may be located in the second combustion zone 52. As an example, the second igniter 94 is located at the forward liner 40. Additionally or alternatively, the second igniter 94 for the second fuel in the second combustion zone 52 may be located at the aft liner 42. While the second igniter 94 is shown as a single igniter, multiple igniters are contemplated. It is further contemplated that the first igniter 78 and the second igniter 94 may be a single igniter. That is, the combustion chamber 44 includes at least one igniter, shown as the first igniter 78 and the second igniter 94 as an example.

[0048] A set of dilution holes 96 may be provided in the combustor liner 34. The set of dilution holes 96 is located in the second combustion zone 52 and is configured to direct air from an exterior 98 of the combustion chamber 44 into the second combustion zone 52. The set of dilution holes 96 may be adjacent to the gas fuel injector outlet 86 for temperature control, flame shaping, fuel-air mixing, etc. In other words, the set of dilution holes 96 may be spaced circumferentially around the gas fuel injector outlet 86. Any number of dilution holes may be provided in the set of dilution holes 96. The set of dilution holes 96 may have any suitable pattern or arrangement, including linear rows, irregular groups, variable apertures, etc., or combinations thereof.

[0049] As used herein, the term "adjacent" means within an axial distance of six times or less the diameter of the gas fuel injector outlet 86. That is, the axial distance from the gas fuel injector outlet 86 to at least one or more of the set of dilution holes 96 is equal to or less than 600% of the diameter of the gas fuel injector outlet 86. The set of dilution holes 96 is closer to the gas fuel injector outlet 86 than the dilution holes of a conventional fuel outlet that provides conventional liquid fuel to the combustion chamber. The set of dilution holes 96 is closer to the gas fuel injector outlet 86 because the reaction with the second fuel 74 will occur more quickly than with conventional fuel.

[0050] A dilution hole centerline 100 may be defined by each dilution hole in the set of dilution holes 96. An angle 102 defined as the intersection of the dilution hole centerline 100 and the gas fuel injector centerline 92 may be within a range greater than 0° and less than 90°.

[0051] The dilution hole centerline 100 may be parallel to the kicker injector centerline 72. Alternatively, the angle between the kicker injector centerline 72 and the dilution hole centerline 100 is non-zero. Alternatively, the gas fuel injector outlet 86 may be located axially rearward of the rotating fuel kicker 62 or the kicker injector centerline 72. Alternatively, in various and non-limiting examples, a portion of the gas fuel injector outlet 86 may be located axially forward of the rotating fuel kicker 62 or the kicker injector centerline 72, or axially aligned with at least a portion of the rotating fuel kicker 62 or the kicker injector centerline 72.

[0052] Figure 3 It is further shown that in the turbine engine 10 ( Figure 1 ) of the multi-fuel combustion system 30 during one or more portions of an operating cycle. The operating cycle may include, but is not limited to, starting, idling, takeoff, cruising, descent or landing, and shutdown. Figure 1 During startup, turbine engine 10 is provided with mechanical energy to begin rotating drive shaft 18 and one or more portions of compressor section 12 or turbine section 16. Once started, air is directed into LP compressor 22, which then supplies a pressurized air flow to HP compressor 24, which further pressurizes the air.

[0053] Reference again Figure 3 , from HP compressor 24( Figure 1 A portion of the pressurized air stream is mixed with the first fuel 58, the second fuel 74, or both in the multi-fuel combustion system 30 and ignited to generate combustion gases. Figure 1 ) can extract some work from these gases, and the HP turbine 26 drives the HP compressor 24 ( Figure 1 The combustion gases are discharged to the LP turbine 28 ( Figure 1 ), the LP turbine 28 can extract additional work to drive the LP compressor 22 ( Figure 1 ).

[0054] More specifically, the fuel passage 66, the first conduit 68, or a combination of the two provides the first fuel 58 to the rotor portion 64 of the rotating fuel ejector 62. The first fuel 58 can be a liquid fuel including, for example, kerosene or petroleum. The residence time of the first fuel 58 in the combustion chamber 44 is in the range of 3 milliseconds to 7 milliseconds. As a non-limiting example, the first fuel 58 can have a residence time in the range of 3 milliseconds to 5 milliseconds. The residence time of the first fuel 58 in the first combustion zone 50, or in at least a portion of the first combustion zone 50 and the second combustion zone 52, can be calculated. The residence time can be estimated by dividing the volume of the combustion chamber or combustion zone by the volume flow rate of the fuel flow. In other words, the residence time refers to the time required to evaporate the fuel (as needed), mix the fuel and air, and burn the fuel-air mixture or otherwise complete the chemical reaction of the fuel-air mixture in the combustion chamber or combustion zone. By including the swirl of the fuel-air mixture, this estimate can be further refined.

[0055] The outlet 70 of the rotating fuel ejector 62 discharges the first fuel 58 as atomized liquid fuel 118 into the radially extending portion 46 of the combustion chamber 44, or the first combustion zone 50. The first fuel 58 is atomized using the centrifugal force from the drive shaft 18. In other words, due to the rotating rotor portion 64, the first fuel 58 will move radially outward toward the outlet 70 due to the rotating drive shaft 18 and the inertia of the first fuel 58 within the rotor portion 64. The first fuel 58 exits the outlet 70 in the form of fine droplets. The first fuel 58 experiences pressure as it moves within the rotor portion 64 toward the outlet 70, resulting in pressure atomization of the first fuel 58. The pressure atomization of the first fuel 58 evenly distributes the first fuel 58 into the first combustion zone 50.

[0056] Optionally, the atomizing air flow 120 can be configured and oriented to shear the first fuel 58 as it passes through the outlet 70 and enters the first combustion zone 50. The atomizing air flow 120 can atomize the first fuel 58 in addition to the pressure atomization provided by the rotor section 64 to provide the atomized liquid fuel 118 to the first combustion zone 50.

[0057] Independently of or concurrently with the flow of the first fuel 58 to the rotating fuel ejector 62, the second fuel 74 may be provided to the gaseous fuel injector 82 via the gaseous fuel supply passage 84. The flow of the second fuel 74 may be controlled by a controller 122 in communication with, for example, the valve 88. It is also contemplated that the flow of the first fuel 58 may be controlled by the controller 122 or another controller or device.

[0058] The second fuel 74 may be a gaseous fuel, including a hydrocarbon fuel, a hydrogen fuel, or a mixture of different fuel types. The residence time of the second fuel 74 in the combustion chamber 44 is in the range of 0.2 milliseconds to 4 milliseconds. As a non-limiting example, the second fuel 74 in the second combustion zone 52 may have a residence time in the range of 1 millisecond to 3 milliseconds. The residence time of the second fuel 74 may be calculated for the second combustion zone 52, or for the second combustion zone 52 and at least a portion of the first combustion zone 50.

[0059] Alternatively, the gas fuel injector 82 may include one or more swirlers, air inlets, multiple fuel injectors, premixer vortex generators, or other fuel-air mixing devices arranged in discrete clusters or groups such that the fuel-air mixture has non-zero swirl at the gas fuel injector outlet 86 .

[0060] The second fuel 74 or a mixture of air and the second fuel 74 can exit the gas fuel injector 82 at the gas fuel injector outlet 86. The second fuel 74, including hydrogen, can burn faster or hotter than conventional fuels (e.g., the first fuel 58). The set of dilution holes 96 can provide an air flow 124 that provides temperature control, flame shaping, and fuel-air mixing, for example, in the second combustion zone 52. The set of dilution holes 96 can provide cooling for the combustor liner 34, however, the primary benefit of the air flow 124 adjacent to the gas fuel injector outlet 86 is to control temperature, provide flame shaping, and fuel-air mixing for the flame or combustion in the second zone 56.

[0061] The additional dilution holes may provide air flows 104, indicated by arrows, that direct air from the exterior 98 of the combustion chamber 44 to the first combustion zone 50, the second combustion zone 52, or both. The additional dilution holes may provide temperature control, flame shaping for one or both of the first zone 54 or the second zone 56, fuel-air mixing, etc.

[0062] Compressed air for the set of dilution holes 96, additional dilution holes, air stream 124, or other film holes extending through the combustor liner 34 may be from the compressor section 12 ( Figure 1 ). Compressor section 12 ( Figure 1) provides a compressed air flow 108 to an air channel compressor 110, as indicated by the arrows, which can further compress the air flow. That is, the compressed air flow 108 flows through the air channel compressor 110, where it becomes a further compressed air flow 112. An air channel diffuser 114 is fluidly coupled to and downstream of the air channel compressor 110. The further compressed air flow 112 is discharged into the air channel diffuser 114 and discharged to the exterior 98 of the multi-fuel combustion system 30 as a desired air flow 116. The air flow 116 from the exterior 98 of the multi-fuel combustion system 30 can enter the combustion chamber 44 as an atomizing air flow 120, an air flow 104 from the additional dilution holes indicated by the arrows, an air flow 124 from the set of dilution holes 96, or any combination thereof.

[0063] Additionally or alternatively, the air flow 116 provided to the exterior 98 of the multi-fuel combustion system 30 may be provided to the first fuel system 60 upstream of the outlet 70 , the second fuel system 80 upstream of the gaseous fuel injector outlet 86 , or a combination thereof.

[0064] Once the fuel and compressed air are provided to the multi-fuel combustion system 30, the turbine engine 10 ( Figure 1 ) can then move through different parts of the operating cycle by increasing, decreasing, or maintaining the amount of first fuel 58 provided to rotating fuel kickers 62 and the amount of second fuel 74 provided to gas fuel injectors 82. Additionally or alternatively, turbine engine 10 can then move through different parts of the operating cycle by increasing, decreasing, or maintaining the rotational speed of one or more components.

[0065] The rotating fuel kicker 62 may be designed for maximum fuel flow and may be optimized for cruise to improve combustion efficiency and reduce emissions from the first combustion zone 50, such as, but not limited to, nitrogen oxides (NOx), during the cruise portion of the operating cycle. x ) emissions. An operating cycle may include, but is not limited to, starting, idling, takeoff, cruising, descent or landing, and shutdown.

[0066] For example, during idle, when the rotating fuel ejector 62 rotates at a slower speed than during cruise, emissions from the first combustion zone 50 may increase compared to emissions during cruise. To reduce or eliminate emissions from the first combustion zone 50 during startup, idle, takeoff, cruise, descent or landing, shutdown, or any combination thereof, the second fuel 74 may be provided to the gaseous fuel injector 82. The emissions from the first combustion zone 50 are discharged to the second combustion zone 52, which, when ignited, combusts or otherwise eliminates at least a portion of the emissions from the first combustion zone 50.

[0067] The second fuel 74 is a hydrogen-based fuel that reduces environmentally undesirable byproducts. Hydrogen, or hydrogen mixed with another element, has a higher flame temperature than conventional fuels. In other words, hydrogen or hydrogen-blended fuels generally have a wider flammability range and a faster burning rate than conventional hydrocarbon-based fuels.

[0068] In various and non-limiting examples, the multi-fuel combustion system 30 can operate the turbine engine 10 using the first fuel 58, the second fuel 74, or both the first fuel 58 and the second fuel 74. This allows for the type of fuel available at different locations around the world to vary. For example, an airport may only have the first fuel 58 or the second fuel 74 available for refueling. The turbine engine 10 ( Figure 1 ) can complete an operating cycle using only the first fuel 58 or the second fuel 74.

[0069] Figure 4 The operation of a turbine engine 10 having a multi-fuel combustion system 30 is shown. Figure 1 ). The method 300 may include, at 302, providing mechanical energy to initiate rotation of at least a portion of the drive shaft 18 and the compressor section 12, thereby starting the turbine engine 10.

[0070] At 304, compressed air flows into the multi-fuel combustion system 30 ( Figure 3 )'s external 98( Figure 3 A compressed air flow 108 from the exterior 98 of the multi-fuel combustion system 30 may enter the combustion chamber 44 ( Figure 3 ).

[0071] During startup, idling, takeoff, cruise, descent or landing, shutdown, or any combination thereof, the rotating fuel ejector 62 ( Figure 3 ) of the first fuel 58( Figure 3 ) and the amount provided to the gas fuel injector 82 ( Figure 3 ) of the second fuel 74 ( Figure 3 That is, during the operating cycle, at 306, the amounts of the first fuel 58 and the second fuel 74 are changed or controlled during or between one or more phases of the operating cycle.

[0072] The first igniter 78 ( Figure 3 ), the second igniter 94 ( Figure 3 ) or a combination thereof may ignite or initiate combustion of the fuel-air in the combustion chamber 44. The ignition, amount, and type of fuel delivered to create the fuel-air mixture in the combustion chamber 44 may be controlled by a controller, such as controller 122 ( Figure 3 )) control. The controller can be connected with valve 88 ( Figure 3 ) communication.

[0073] More specifically, during startup or idle, the second fuel 74 may be provided to the gaseous fuel injector 82 and ignited by the second igniter 94. During takeoff, the first fuel 58 and the second fuel 74 may be provided to the rotating fuel ejector 62 and the gaseous fuel injector 82, respectively. Alternatively, the first igniter 78 may ignite the fuel-air mixture exiting the rotating fuel ejector 62 in the first combustion zone 50.

[0074] During cruise, the first fuel 58 may be provided to the rotating fuel kicker 62, and the amount of the second fuel 74 provided to the gaseous fuel injector 82 may be reduced or stopped. Alternatively, in a different and non-limiting example, when the liquid fuel is depleted or otherwise reduced, the amount of the second fuel 74 provided to the gaseous fuel injector 82 may be increased to maintain cruise.

[0075] During landing, the first fuel 58 and the second fuel 74 may be provided to the rotating fuel kicker 62 and the gas fuel injector 82, respectively. Optionally, the second igniter 94 may restart combustion in the second combustion zone 52.

[0076] During shutdown, the first fuel 58 may be reduced and stopped from being provided to the rotating fuel kicker 62 , and simultaneously or sequentially, the second fuel 74 may be reduced and stopped from being provided to the gaseous fuel injector 82 .

[0077] Furthermore, during any portion of the turbine engine's operation, the amount of liquid fuel and the amount of gaseous fuel may vary based on external conditions, desired thrust, or a combination thereof.

[0078] Figure 5 yes Figure 2 A variation of the schematic cross-sectional view of Figure 5 It is shown that the turbine engine 10 ( Figure 1 ) used in a multi-fuel combustion system 430.

[0079] Multi-fuel combustion system 430 is similar to multi-fuel combustion system 30 ( Figure 2 ), therefore, like parts will be identified by like numerals increased by four hundred (400), it being understood that the description of like parts of the multi-fuel combustion system 30 applies to the multi-fuel combustion system 430 unless otherwise noted.

[0080] Similar to the multi-fuel combustion system 30, the multi-fuel combustion system 430 is rotatably coupled to a drive shaft 418 that rotates about an engine centerline 420. Furthermore, the multi-fuel combustion system 430 includes a combustor liner 434 having a forward liner 440, an aft liner 442, a combustion chamber 444, a first combustion zone 450, a second combustion zone 452, a first fuel system 460 including a rotating fuel ejector 462 having an outlet 470 for providing a first fuel 458, an ejector injector centerline 472 defined by the outlet 470, a first igniter 478, a second fuel system 480, a gas fuel injector 482 having a gas fuel injector outlet 486 for providing a second fuel 474, a gas fuel injector centerline 492 defined by the gas fuel injector outlet 486, a second igniter 494, and a set of dilution holes 496.

[0081] The gas fuel injector centerline 492 may form an angle with the engine centerline 420 in the range of 20° to less than 85°. Angle 481 may be defined as the angle between the gas fuel injector centerline 492 and the kicker injector centerline 472. Angle 481 may be in the range of 0° to 90°. For example, angle 481 may be in the range of 5° to 40°. A non-zero angle 481 may extend fuel-air mixing and / or help direct exhaust gas from the second combustion zone 52.

[0082] A first radial distance 483 is measured radially outward from the engine centerline 420 to the outlet 470. A second radial distance 485 is measured radially outward from the engine centerline 420 to the gaseous fuel injector outlet 486. The second radial distance 485 is greater than the first radial distance 483.

[0083] The gaseous fuel injector outlet 486 may be located axially rearward of the outlet 470. An axial outlet distance 487 may be defined as the axial distance between the gaseous fuel injector outlet 486 and the outlet 470 measured parallel to the engine centerline 420.

[0084] While shown as being greater than the first radial distance 483 , it is contemplated that the axial outlet distance 487 may be less than the first radial distance 483 .

[0085] Positioning the gas fuel injector outlet 486 axially rearward of the outlet 470 and tilting the gas fuel injector centerline 492 forwardly will allow for increased residence time.

[0086] Figure 6 yes Figure 2 Another variation of the schematic cross-sectional view, wherein Figure 6 It is shown that the turbine engine 10 ( Figure 1 ) used in a multi-fuel combustion system 530.

[0087] Multi-fuel combustion system 530 is similar to multi-fuel combustion system 30 ( Figure 2 )、430( Figure 5 ), therefore, like parts will be identified with like numerals further increased by one hundred, and it should be understood that the description of like parts of the multi-fuel combustion systems 30, 430 applies to the multi-fuel combustion system 530 unless otherwise stated.

[0088] Similar to the multi-fuel combustion systems 30 and 430, the multi-fuel combustion system 530 is rotatably coupled to a drive shaft 518 that rotates about an engine centerline 520. Furthermore, the multi-fuel combustion system 530 includes: a combustor liner 534 having a forward liner 540 and an aft liner 542; a combustion chamber 544; a first combustion zone 550; a second combustion zone 552; a first fuel system 560 including a rotating fuel ejector 562 having an outlet 570 for providing a first fuel 558; a ejector injector centerline 572 defined by the outlet 570; a first igniter 578; a second fuel system 580; a gas fuel injector 582 having a gas fuel injector outlet 586 for providing a second fuel 574; a gas fuel injector centerline 592 defined by the gas fuel injector outlet 586; a second igniter 594; and a set of dilution holes 596.

[0089] A first radial distance 583 is measured radially outward from the engine centerline 520 to the outlet 570. A second radial distance 585 is measured radially outward from the engine centerline 520 to the gaseous fuel injector outlet 586. The second radial distance 585 is greater than the first radial distance 583.

[0090] The gaseous fuel injector outlet 586 may be located axially forward of the outlet 570. An axial outlet distance 587 may be defined as the axial distance between the gaseous fuel injector outlet 586 and the outlet 570 measured parallel to the engine centerline 520.

[0091] While axial exit distance 587 is shown as being less than first radial distance 583 , it is contemplated that axial exit distance 587 may be greater than first radial distance 583 .

[0092] Positioning the gas fuel injector outlet 586 axially forward of the outlet 570 and tilting the gas fuel injector centerline 592 forwardly will allow for increased residence time.

[0093] Benefits of aspects described herein provide multi-fuel combustion systems disclosing combustors that operate with liquid or conventional fuels, gaseous fuels (such as hydrogen), other sustainable aviation fuels, or any combination thereof.

[0094] Additional benefits of multi-fuel combustion systems include improved emissions. Multi-fuel combustion systems include ejector burners, in which liquid fuel, or a first fuel, is delivered to a first combustion zone using a rotating fuel ejector. The rotating fuel ejector can be designed for maximum fuel flow and optimized for cruise operation to improve combustion efficiency and reduce emissions from the first combustion zone.

[0095] The multi-fuel combustion system also includes a gas fuel injector that provides a gas fuel or a second fuel to the second combustion zone. The gas fuel or the second fuel burns cleaner than the liquid fuel or the second fuel.

[0096] When operating with two fuels, the second combustion zone receives the exhaust from the first combustion zone. The second combustion zone then burns the exhaust from the first combustion zone using the faster, hotter, and cleaner burning fuel. This results in a reduction in overall emissions from the multi-fuel combustion system.

[0097] The diffusion / dispersion rate of gaseous fuels (including hydrogen) is faster than that of atomized liquid fuels, which can result in shorter mixing times for the gaseous fuel and a greater likelihood that flames from the gaseous fuel will spread farther and faster, which can increase the risk of flashback and increase the impact of controlling the flame and limiting the spread of the flame by controlling the dispersion of the gaseous fuel.

[0098] Not every airport provides gaseous fuel. Similarly, not every airport provides traditional fuel or liquid fuel. As long as the aircraft can be provided with a predetermined amount of the first fuel (liquid fuel) or the second fuel (hydrogen-based fuel), the operating cycle can be completed.

[0099] Dilution holes adjacent to the gas fuel injectors help accommodate a gas fuel-air mixture having a lower density and higher velocity than the liquid fuel. For example, a flame-forming structure (such as the set of dilution holes) can contain the gas fuel-air mixture so that the flame velocity matches the flow velocity to provide a stable flame.

[0100] Further aspects are provided by the subject matter of the following clauses:

[0101] A multi-fuel combustion system for a turbine engine, the multi-fuel combustion system comprising: a combustion chamber formed by a combustor liner, the combustion chamber defining a first combustion zone and a second combustion zone; a first fuel system, the first fuel system being fluidly connected to the first combustion zone, wherein the first fuel system comprises a rotating fuel ejector for providing a first fuel to the first combustion zone; and a second fuel system, the second fuel system being fluidly connected to the second combustion zone, wherein the second fuel system comprises a gas fuel injector for providing a second fuel to the second combustion zone, wherein the second fuel is a gas fuel.

[0102] A multi-fuel combustion system for a turbine engine, the multi-fuel combustion system comprising: a combustion chamber formed by a combustor liner, the combustion chamber defining a first combustion zone and a second combustion zone; a first fuel system fluidly connected to the first combustion zone, wherein the first fuel system comprises a rotating fuel ejector for providing a first fuel to the first combustion zone; and a second fuel system fluidly connected to the second combustion zone, wherein the second fuel system comprises a fuel injector for providing a second fuel to the second combustion zone, wherein the second fuel is a hydrogen-based fuel.

[0103] A multi-fuel combustion system according to any preceding clause, wherein the rotating fuel kicker includes an outlet at a first radial distance from the engine centerline and the gas fuel injector includes an outlet located at a second radial distance from the engine centerline, wherein the first radial distance is less than the second radial distance.

[0104] A multi-fuel combustion system according to any preceding clause, wherein the residence time of the first fuel is in the range of 3 milliseconds to 5 milliseconds.

[0105] A multi-fuel combustion system according to any preceding clause, wherein the first fuel comprises kerosene or petroleum.

[0106] A multi-fuel combustion system according to any preceding clause, wherein the residence time of the second fuel is in the range of 1 millisecond to 3 milliseconds.

[0107] A multi-fuel combustion system according to any preceding clause, wherein the second fuel comprises hydrogen.

[0108] A multi-fuel combustion system as in any preceding clause, wherein the second combustion zone is located fluidly downstream of the first combustion zone, and wherein the gas fuel injector is located axially rearward of the rotating fuel kicker.

[0109] A multi-fuel combustion system as in any preceding clause, wherein the second fuel system is located fluidly downstream of the first fuel system, and wherein the gaseous fuel injector is located axially forward of the rotating fuel kicker.

[0110] A multi-fuel combustion system as in any preceding clause, wherein the second fuel system is located fluidly downstream of the first fuel system, and wherein a portion of the gaseous fuel injector is axially aligned with at least a portion of a kicker injector centerline.

[0111] A multi-fuel combustion system according to any preceding clause, wherein the gas fuel injectors are a group of circumferentially spaced gas fuel injectors.

[0112] A multi-fuel combustion system according to any preceding clause, wherein the rotating fuel kicker includes an outlet defining a kicker injector centerline, and the gas fuel injector includes an outlet defining a gas fuel injector centerline, wherein the angle measured between the kicker injector centerline and the gas fuel injector centerline is in the range of 5° to 40°.

[0113] A multi-fuel combustion system according to any preceding clause, wherein an angle measured between the kicker injector centreline and the engine centreline is in the range of 85° to 95°.

[0114] The multi-fuel combustion system of any preceding clause, further comprising a set of dilution holes positioned adjacent an outlet of the gas fuel injector.

[0115] A multi-fuel combustion system according to any preceding clause, wherein the combustion chamber is an annular chamber.

[0116] The multi-fuel combustion system of any preceding clause, further comprising a gas fuel supply passage fluidly coupled to the gas fuel injector.

[0117] The multi-fuel combustion system of any preceding clause, wherein a turbine engine comprises a compressor section, a combustion section, and a turbine section in a serial flow arrangement, wherein the multi-fuel combustion system is located in the combustion section of the turbine engine.

[0118] The multi-fuel combustion system of any preceding clause, wherein a turbine engine includes a drive shaft rotatably coupled to the compressor section and the turbine section, and wherein the drive shaft defines an engine centerline of the turbine engine.

[0119] The multi-fuel combustion system of any preceding clause, further comprising a fuel passage defined by a portion of the drive shaft, wherein the fuel passage is fluidly coupled to the rotating fuel kicker.

[0120] A multi-fuel combustion system according to any preceding clause, wherein an angle measured between the kicker injector centreline and the engine centreline is in the range of 20° to less than 85°.

[0121] A kicker multi-fuel combustion system for a turbine engine, the turbine engine including a compressor section, a combustion section, and a turbine section in a serial flow arrangement, and a drive shaft coupled to one or more portions of the compressor section or the turbine section, the drive shaft defining an engine centerline, the kicker multi-fuel combustion system comprising: a combustion chamber having a radially extending portion and an axially extending portion; a liquid fuel injector having a kicker operably coupled to the drive shaft and having an outlet, the outlet using centrifugal force from the rotation of the drive shaft to discharge atomized liquid fuel into the radially extending portion of the combustion chamber; and a gas fuel injector having a gas fuel injector outlet for discharging gas fuel into the combustion chamber downstream of the outlet.

[0122] The kicker multi-fuel combustion system of any preceding clause, further comprising a fuel passage defined by a portion of the drive shaft, wherein the fuel passage is fluidly coupled to the liquid fuel injector.

[0123] The kicker multi-fuel combustion system of any preceding clause, further comprising a gas fuel supply passage fluidly coupled to the gas fuel injector, wherein a valve controls the flow of the gas fuel into the gas fuel injector.

[0124] The kicker multi-fuel combustion system of any preceding clause, further comprising a set of dilution holes positioned adjacent to an outlet of the gas fuel injector, wherein a dilution hole centerline is defined by dilution holes in the set of dilution holes, and wherein the dilution hole centerline forms a non-zero angle with a gas fuel injector centerline defined by the gas fuel injector outlet.

[0125] A kicker multi-fuel combustion system according to any preceding clause, wherein the liquid fuel injector includes an outlet defining a kicker injector centerline, and the gas fuel injector includes an outlet defining a gas fuel injector centerline, wherein the angle measured between the kicker injector centerline and the gas fuel injector centerline is in the range of 5° to 40°, and wherein the angle measured between the kicker injector centerline and the engine centerline is in the range of 85° to 95°.

[0126] A method for operating a turbine engine, the turbine engine comprising a compressor section in a serial flow arrangement, a combustion section having a multi-fuel combustion system, and a turbine section, and a drive shaft coupled to one or more portions of the compressor section or the turbine section, the drive shaft defining an engine centerline, the method comprising: rotating at least a portion of the drive shaft and the combustion section to start the turbine engine; causing compressed air to flow from the compressor section to the outside of the multi-fuel combustion system; causing a portion of the compressed air to flow from the outside of the multi-fuel combustion system to a combustion chamber defined by a combustor liner of the multi-fuel combustion system; changing the amount of liquid fuel provided to a first combustion zone of the combustion chamber, wherein the liquid fuel is provided by a rotating fuel ejector; and changing the amount of gas fuel provided to a second combustion zone of the combustion chamber, wherein the gas fuel is provided by a gas fuel injector downstream of the rotating fuel ejector.

[0127] The method of any preceding clause, further comprising igniting the fuel-air mixture in the combustion chamber with a first igniter or a second igniter.

[0128] The method of any preceding clause, wherein varying the amount of the liquid fuel and varying the amount of the gaseous fuel comprises providing the liquid fuel and the gaseous fuel at takeoff.

[0129] A method as in any preceding clause, wherein varying the amount of the gaseous fuel comprises reducing or stopping the gaseous fuel during cruising.

[0130] A method as in any preceding clause, wherein varying the amount of the liquid fuel and varying the amount of the gaseous fuel comprises providing the liquid fuel and the gaseous fuel upon landing.

[0131] A method as in any preceding clause, further comprising restarting combustion via the second combustion zone during landing.

[0132] Although described with respect to a turbine engine, it should be understood that the combustor described herein can be used in any engine having a combustor. It should be understood that the application of the disclosed aspects discussed herein can also be applied to engines having a propeller section or a fan and supercharger section, as well as turbojets, turbochargers, and turboshafts in aviation, marine, and stationary applications.

[0133] To the extent not already described, the various features and structures of the various embodiments may be combined or substituted for one another as desired. The fact that a feature is not shown in all embodiments does not mean it cannot be shown; rather, it is done for the sake of brevity. Thus, various features of different embodiments may be mixed and matched as desired to form new embodiments, regardless of whether the new embodiments are explicitly described.

[0134] This written description uses examples to describe the aspects of the disclosure described herein, including the best mode, and also to enable any person skilled in the art to practice aspects of the disclosure, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the various aspects of the disclosure is defined by the claims and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.

Claims

1. A multi-fuel combustion system for a turbine engine, characterized in that: The multi-fuel combustion system comprises: a combustion chamber formed by the combustor liner, the combustion chamber defining a first combustion zone and a second combustion zone; a first fuel system fluidly coupled to the first combustion zone, wherein the first fuel system includes a rotating fuel kicker for providing a first fuel to the first combustion zone; and A second fuel system is fluidly coupled to the second combustion zone, wherein the second fuel system includes a gaseous fuel injector for providing a second fuel to the second combustion zone, wherein the second fuel is a gaseous fuel.

2. The multi-fuel combustion system according to claim 1, characterized in that: in, The rotating fuel kicker includes an outlet located at a first radial distance from an engine centerline, and the gaseous fuel injector includes an outlet located at a second radial distance from the engine centerline, wherein the first radial distance is less than the second radial distance.

3. The multi-fuel combustion system according to claim 1, characterized in that: in, The residence time of the first fuel is in the range of 3 milliseconds to 5 milliseconds.

4. The multi-fuel combustion system according to claim 3, characterized in that: in, The first fuel comprises kerosene or petroleum.

5. The multi-fuel combustion system according to claim 3, characterized in that: in, The residence time of the second fuel is in the range of 1 millisecond to 3 milliseconds.

6. The multi-fuel combustion system according to claim 3, characterized in that: in, The second fuel includes hydrogen.

7. The multi-fuel combustion system according to claim 1, characterized in that: in, The second combustion zone is located fluidly downstream of the first combustion zone, and wherein the gas fuel injector is located axially rearward of the rotating fuel kicker.

8. The multi-fuel combustion system according to claim 1, characterized in that: in, The second fuel system is located fluidly downstream of the first fuel system, and wherein the gaseous fuel injector is located axially forward of the rotating fuel kicker.

9. The multi-fuel combustion system according to claim 1, characterized in that: in, The second fuel system is located fluidly downstream of the first fuel system, and wherein a portion of the gaseous fuel injector is axially aligned with at least a portion of a kicker injector centerline.

10. The multi-fuel combustion system according to claim 1, characterized in that: in, The gas fuel injectors are a group of circumferentially spaced gas fuel injectors.

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