Axial fuel stage injector having axially elongated mixing chambers, combustor including axial fuel stage injector, and gt system

Abstract

To provide an axial fuel stage injector having an axially elongated mixing chamber, a combustor including the injector, and a gas turbine system.SOLUTION: An axial fuel stage injector includes: axially elongated mixing chambers in fluid communication with a combustion liner of a combustor; and a mixing member including fuel injectors on opposing side walls of the mixing chambers. A high-pressure air injection member defines a set of HP air jets separated from an inlet of each mixing chamber. A fuel plenum of the mixing member delivers fuel from a fuel source to each set of the fuel injectors. Each set of HP air jets guides HP air from an HP air source, sucks LP air from a low pressure air source in some embodiments and guides the LP air together with the HP air to an inlet of each mixing chamber to which fuel is injected. The axially elongated mixing chamber guides an air fuel mixture to the combustion liner for combustion in a secondary combustion zone thereof.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates generally to turbomachine combustors, and more particularly to axial fuel stage (AFS) injectors having axially elongated mixing chambers, and combustor and gas turbine systems including AFS injectors. [Background technology]

[0002] A gas turbine system includes a combustion section that includes multiple combustors that combust fuel to generate a flow of combustion gases that are converted to kinetic energy in a downstream turbine section. Current combustors include head-end fuel nozzle assemblies for burning fuel in a primary combustion zone and axial fuel stage (AFS) injectors for burning fuel in a secondary combustion zone downstream of the primary combustion zone. For example, a portion of the air supply from a compressor discharge casing is delivered to the head-end fuel nozzle assemblies and AFS injectors in various flow paths. Current AFS injectors present challenges with respect to adequately mixing highly reactive fuels, such as hydrogen, with air and achieving desired low exhaust emissions and flame-holding capabilities. Summary of the Invention

[0003] All aspects, examples, and features described below can be combined in any technically possible manner.

[0004] A first aspect of the present disclosure is an axial fuel stage (AFS) injector for a combustor of a gas turbine (GT) system, the AFS injector including: a mixing element including a plurality of axially-elongated mixing chambers defined in the mixing element, each axially-elongated mixing chamber including an inlet and an outlet, each outlet configured to be in fluid communication with a combustion chamber of the combustor; and a set of fuel injectors defined in opposing sidewalls of each axially-elongated mixing chamber; an HP air injection element defining a set of high-pressure (HP) air jets spaced from the inlet of each axially-elongated mixing chamber; and a fuel plenum defined in the mixing element, the fuel plenum configured to deliver fuel from a fuel source to a respective set of fuel injectors, each set of HP air jets configured to direct HP air from the HP air source to an inlet of a respective mixing chamber where fuel is injected by the set of fuel injectors.

[0005] Another aspect of the present disclosure includes any of the aforementioned aspects, wherein the plurality of axially elongated mixing chambers includes a first axially elongated mixing chamber, a second axially elongated mixing chamber, and a third axially elongated mixing chamber between the first axially elongated mixing chamber and the second axially elongated mixing chamber.

[0006] Another aspect of the present disclosure includes any of the aforementioned aspects, wherein the third axially elongated mixing chamber extends radially at an angle perpendicular to the outer periphery of the combustion liner, and the first axially elongated mixing chamber and the second axially elongated mixing chamber are inclined in opposite circumferential directions relative to the third axially elongated mixing chamber.

[0007] Another aspect of the present disclosure includes any of the preceding aspects, wherein a set of HP air jets spaced from the inlet of each mixing element are configured to direct HP air into each axially-elongated mixing chamber at an angle identical to the angle of the respective axially-elongated mixing chamber.

[0008] Another aspect of the present disclosure includes any of the preceding aspects, wherein the set of HP air jets spaced from the inlet of the third axially elongated mixing chamber includes a pair of axially offset rows of HP air jets.

[0009] Another aspect of the present disclosure includes any of the aforementioned aspects, wherein the pair of HP air jets spaced from the inlets of the first and second axially elongated mixing chambers each include a radially inwardly extending collar having a first side thereof radially farther from the mixing element than a second, opposite side thereof.

[0010] Another aspect of the present disclosure includes any of the aforementioned aspects, wherein a first side of the collar of the pair of HP air jets spaced from the inlets of the first and second axially elongated mixing chambers each includes an opening defined therein.

[0011] Another aspect of the present disclosure includes any of the preceding aspects, wherein the sets of HP air jets spaced apart from the inlets of the first and second axially elongated mixing chambers each have a fewer number of HP air jets than the set of HP air jets spaced apart from the inlet of the third axially elongated mixing chamber.

[0012] Another aspect of the present disclosure includes any of the preceding aspects, wherein the set of HP air jets each include a flared inlet having an outer radius, and the flared inlets of the HP air jets for the first and second axially elongated mixing chambers have a first outer radius that is greater than a second outer radius of the flared inlet of the HP air jet of the third axially elongated mixing chamber.

[0013] Another aspect of the present disclosure includes any of the preceding aspects, wherein the placement of the sets of HP air jets spaced apart from the inlets of the first and second axially elongated mixing chambers is the same, and the placement of the set of HP air jets spaced apart from the inlets of the third axially elongated mixing chamber is different from the placement of the set of HP air jets spaced apart from the inlets of the first and second axially elongated mixing chambers.

[0014] Another aspect of the present disclosure includes any of the aforementioned aspects, wherein the fuel plenum extends into an upstream wall of each of the plurality of axially-elongated mixing chambers, and wherein each set of fuel injectors is closer to the inlet than to the outlet of each of the plurality of axially-elongated mixing chambers.

[0015] Another aspect of the present disclosure includes any of the aforementioned aspects, wherein the opposing sidewalls of the first and second axially-elongated mixing chambers include a first sidewall and an opposing second sidewall, and the set of fuel injectors defined in the first sidewall are arranged differently for each of the first and second axially-elongated mixing chambers than the set of fuel injectors defined in the second sidewall.

[0016] Another aspect of the present disclosure includes any of the aforementioned aspects, wherein the set of fuel injectors in the side walls of the first and second axially elongated mixing chambers are disposed in a different manner in the first side wall than in the opposing second side wall.

[0017] Another aspect of the present disclosure includes any of the preceding aspects, wherein each axially elongated mixing chamber has opposing ends that are semicircular.

[0018] Another aspect of the present disclosure includes any of the preceding aspects, wherein the mixing element includes a filter element upstream of the set of HP air jets.

[0019] Another aspect of the present disclosure includes any of the aforementioned aspects, wherein the mixing element and the HP air injection element each include at least one mounting element configured to receive a fastener to couple the mixing element and the HP air injection element to a flow sleeve that at least partially surrounds a combustion liner that defines the combustion chamber.

[0020] Another aspect of the present disclosure includes any of the aforementioned aspects, wherein each set of HP air jets is configured to draw low pressure (LP) air from a LP air source and direct the LP air along with the HP air to an inlet of each respective mixing chamber, the HP air source in direct fluid communication with a compressor discharge of the GT system, the LP air source in fluid communication with a cooling passage defined along at least a portion of the combustion liner, the cooling passage downstream of an impingement cooling member in direct fluid communication with the compressor discharge of the GT system.

[0021] Another aspect of the present disclosure is a combustor for a gas turbine system, the combustor body including a combustion liner; and a plurality of axially-elongated (AFS) injectors directed at the combustion liner, each AFS injector being a mixing element, the plurality of axially-elongated mixing chambers defined in the mixing element, each axially-elongated mixing chamber including an inlet and an outlet, each outlet configured to be in fluid communication with a combustion chamber of the combustor; and a set of fuel injectors defined in opposing sidewalls of each axially-elongated mixing chamber. a mixing element including a plurality of AFS injectors, a high-pressure (HP) air injection element defining a set of HP air jets spaced from an inlet of each axially elongated mixing chamber, and a fuel plenum defined in the mixing element, the fuel plenum configured to deliver fuel from a fuel source to each set of fuel injectors, each set of HP air jets configured to direct HP air from the HP air source to the inlet of a respective mixing chamber where fuel is injected by the set of fuel injectors.

[0022] Another aspect of the present disclosure includes any of the aforementioned aspects, wherein the plurality of axially elongated mixing chambers includes a first axially elongated mixing chamber, a second axially elongated mixing chamber, and a third axially elongated mixing chamber between the first axially elongated mixing chamber and the second axially elongated mixing chamber.

[0023] Another aspect of the present disclosure is a gas turbine (GT) system comprising: a compressor section; a combustion section operatively coupled to the compressor section; and a turbine section operatively coupled to the combustion section, the combustion section comprising: at least one combustor including a combustor body including a combustion liner; a head-end fuel nozzle assembly at a forward end of the combustor body; and a plurality of axially staged fuel (AFS) injectors directed into the combustor body downstream of the head-end fuel nozzle assembly, each AFS injector comprising a mixing element including a first axially elongated mixing chamber, a second axially elongated mixing chamber, and a third axially elongated mixing chamber between the first axially elongated mixing chamber and the second axially elongated mixing chamber, each AFS injector comprising: a mixing element including a first axially elongated mixing chamber, a second axially elongated mixing chamber, and a third axially elongated mixing chamber between the first axially elongated mixing chamber and the second axially elongated mixing chamber; The combustor includes at least one combustor including a mixing element including a plurality of axially-elongated mixing chambers including an inlet and an outlet, each outlet configured to be in fluid communication with a combustion chamber of the combustor, and a set of fuel injectors defined in opposing sidewalls of each axially-elongated mixing chamber, a high-pressure (HP) air injection element defining a set of HP air jets spaced from the inlet of each axially-elongated mixing chamber, and a plurality of AFS injectors including a fuel plenum defined in the mixing element, the fuel plenum configured to deliver fuel from a fuel source to each set of fuel injectors, each set of HP air jets configured to direct HP air from the HP air source to the inlet of a respective mixing chamber where fuel is injected by the set of fuel injectors.

[0024] Two or more aspects described in this disclosure, including those described in this summary section, may be combined to form an embodiment not specifically described herein, i.e., all embodiments described herein can be combined with each other.

[0025] The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will become apparent from the description and drawings, and from the claims.

[0026] These and other features of the present disclosure will be more readily understood from the following detailed description of the various aspects of the disclosure, taken in conjunction with the accompanying drawings which illustrate various embodiments of the present disclosure. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is a functional block diagram of an exemplary gas turbine system that may be used with a combustor including an axial fuel stage (AFS) injector according to an embodiment of the present disclosure. [Figure 2] FIG. 1 is a cross-sectional side view of a combustor including an AFS injector according to an embodiment of the present disclosure. [Figure 3] FIG. 1 is a perspective, partially cross-sectional view of an AFS injector according to an embodiment of the present disclosure. [Figure 4] FIG. 4 is a cross-sectional view of the AFS injector taken along line 4-4 of FIG. 3 according to an embodiment of the present disclosure. [Figure 5] FIG. 5 is a cross-sectional view of an AFS injector taken along line 5-5 of FIG. 3 according to an embodiment of the present disclosure. [Figure 6A] 1A and 1B are top views of a mixing member of an AFS injector according to various embodiments of the present disclosure. [Figure 6B] 1A and 1B are top views of a mixing member of an AFS injector according to various embodiments of the present disclosure. [Figure 6C] 1A and 1B are top views of a mixing member of an AFS injector according to various embodiments of the present disclosure. [Figure 6D] 1A-1C are schematic diagrams of opposing sidewalls of an outer mixing chamber of a mixing element of an AFS injector according to an embodiment of the present disclosure. [Figure 6E] 1 is a schematic diagram of opposing side walls of a central mixing chamber of a mixing element of an AFS injector according to an embodiment of the present disclosure. FIG. [Figure 7] FIG. 1 is a top view of a high-pressure air injection member of an AFS injector according to an embodiment of the present disclosure. [Figure 8A] FIG. 2 is an enlarged perspective view of a set of high-pressure air jets in a high-pressure air injection member according to an embodiment of the present disclosure. [Figure 8B] FIG. 10 is an enlarged cross-sectional view of a set of high-pressure air jets in a high-pressure air injection member according to an embodiment of the present disclosure. [Figure 9] FIG. 1 is a cross-sectional view of multiple parallel sintered metal layers of a mixing element or high-pressure air injection element of an AFS injector according to an embodiment of the present disclosure. [Figure 10] FIG. 1 is a schematic block diagram of an exemplary additive manufacturing system for additively manufacturing mixing members and / or high-pressure air injection members of an AFS injector according to embodiments of the present disclosure.

[0028] It should be noted that the drawings of the present disclosure are not necessarily to scale. The drawings are intended to depict only typical aspects of the disclosure and therefore should not be considered limiting of the scope of the disclosure. In the drawings, like reference numerals represent like elements between the drawings. DETAILED DESCRIPTION OF THE INVENTION

[0029] As an initial issue, a clear description of the state of the art requires the selection of specific terminology when referring to and describing related machine components within an exemplary application of a turbomachine combustor and axial fuel stage (AFS) injector. In doing so, common industry terminology is used where possible and consistent with its accepted meaning. Unless otherwise noted, such terminology should be given a broad interpretation consistent with the context of this application and the appended claims. Those skilled in the art will understand that in many cases, a particular component may be referred to using several different or overlapping terms. What may be described herein as being a single component may include, and be referred to in other contexts as consisting of multiple components. Alternatively, what may be described herein as comprising multiple components may be referred to elsewhere as a single component.

[0030] Additionally, several descriptive terms may be used periodically herein, and it will prove useful to define these terms at the beginning of this section. These terms and their definitions are as follows, unless otherwise stated: As used herein, "downstream" and "upstream" are terms that indicate a direction relative to the flow of a fluid, such as a working fluid through a combustor of a turbomachine, or, for example, the flow of air through a combustor or AFS injector, or a coolant through one of the component systems of a turbomachine. The term "downstream" corresponds to the direction of fluid flow, and the term "upstream" refers to the direction opposite to the flow. The terms "forward" and "aft" refer to directions, unless otherwise specified, with "forward" referring to the front or compressor end of the turbomachine or combustor and "aft" referring to the aft or turbine end of the turbomachine or combustor.

[0031] The term “axial” refers to movement or position parallel to an axis, e.g., the axis of a combustor, the mixing chamber of an AFS injector, or a turbomachine. The term “radial” refers to movement or position perpendicular to an axis, e.g., the axis of a combustor or turbomachine. In such cases, if a first component is located closer to the axis than a second component, the first component may be referred to herein as being “radially inward” or “inward” of the second component. Conversely, if a first component is located farther from the axis than a second component, the first component may be referred to herein as being “radially outward” or “outward” of the second component. Finally, the term “circumferential” refers to movement or position around an axis, e.g., the circumferential inner surface of a combustor body or the circumferential interior of a casing extending around the combustor. As noted above, it will be understood that, depending on the context, such terms may be applied with respect to the axis of a combustor or the axis of a turbomachine.

[0032] Additionally, certain descriptive terms may be used periodically herein, as described below: The terms "first," "second," and "third" may be used interchangeably to distinguish one component from another, and are not intended to denote the location or importance of the individual components.

[0033] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the disclosure. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms unless the context clearly dictates otherwise. It will be further understood that the terms "comprise" and / or "comprising," as used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or sets thereof. "Optional" or "optionally" means that a subsequently stated event may or may not occur, or that a subsequently stated feature may or may not be present, and that the description includes instances in which the event occurs or the feature is present as well as instances in which the event does not occur or the feature is not present.

[0034] When an element or layer is referred to as "on," "engaged," "connected," "coupled," or "mounted" to another element or layer, it may be directly on, engaged, connected, coupled, or mounted to the other element or layer, or there may be intervening elements or layers. Conversely, when an element is referred to as "directly on," "directly engaged," "directly connected," or "directly coupled" to another element or layer, there are no intervening elements or layers. Other words used to describe relationships between elements should be interpreted similarly (e.g., "between" vs. "directly between," "adjacent" vs. "directly adjacent," etc.). As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. The verb forms of "couple" and "mount" may be used interchangeably herein.

[0035] An embodiment of the present disclosure provides an axial fuel stage (AFS) injector for a combustor, a combustor including the AFS injector, and a gas turbine (GT) system including the AFS injector. The AFS injector includes a mixing element including multiple axially elongated mixing chambers in fluid communication with a combustion liner of the combustor, and a set of fuel injectors defined in a sidewall of each axially elongated mixing chamber. A high-pressure (HP) air injection element defines a set of HP air jets spaced apart from the inlet of each axially elongated mixing chamber. A fuel plenum is defined in the mixing element to deliver fuel from a fuel source to each set of fuel injectors. Each set of HP air jets is configured to direct HP air from an HP air source and, optionally, draw LP air from a low-pressure (LP) air source and direct the LP air, along with the HP air, to the inlet of a respective axially elongated mixing chamber where fuel is injected by the set of fuel injectors. The axially elongated mixing chambers direct the air-fuel mixture into the combustion liner for combustion in a secondary combustion zone thereof. AFS injectors can be additively manufactured to include multiple parallel sintered metal layers.

[0036] In some embodiments, the AFS injector mixes two air sources, one high-pressure air from the compressor discharge, for example, and the other low-pressure air, for example, post-impingement cooling air, reducing pressure losses throughout the system and providing more efficient air use within the combustor. The AFS injector can rapidly premix the two air sources with a highly reactive fuel, for example, hydrogen, to achieve, for example, low nitrous oxide (NOx) emissions and acceptable flame-holding capabilities.

[0037] In each embodiment, the AFS injectors improve fuel-air mixing, minimize flow pressure loss, and prevent fuel from entering any low-velocity airflow zones. Additionally, the AFS injectors are packaged in a relatively small geometry, allowing them to be assembled onto the combustion liner of the combustor body, which is installed into the GT system through a relatively small opening in the compressor discharge casing.

[0038] 1 illustrates a functional block diagram of an exemplary gas turbine (GT) system 90 that may incorporate various embodiments of a combustor 100 and axial fuel stage (AFS) injector 150 (FIG. 2) of the present disclosure. As shown, the GT system 90 generally includes an inlet section 102 that may include a series of filters, cooling coils, water separators, and / or other devices for cleaning and otherwise conditioning a working fluid (e.g., air) 106 entering the GT system 90. The working fluid 106, i.e., air, flows to a compressor 108 in a compressor section 110 that gradually imparts kinetic energy to the working fluid 106 to generate compressed, high-pressure (HP) air 112 (hereinafter "HP air 112" or "compressed air 112"). The HP air 112 is typically mixed with fuel 114A and / or 114B from a fuel source 116 to form a combustible mixture in at least one combustor 100 in a combustion section 120 operatively coupled to the compressor section 110. The combustible mixture is combusted to generate high-temperature, high-pressure combustion gases 122.

[0039] The combustion gases 122 flow through a turbine 128 of a turbine section 130 operably coupled to the combustion section 120 to generate work. For example, the turbine 128 may be connected to a shaft 132 such that rotation of the turbine 128 drives the compressor 108 to generate the HP air 112. Alternatively or additionally, the shaft 132 may connect the turbine 128 to another load, such as a generator 134 for generating electricity. Exhaust gases 136 from the turbine 128 flow through an exhaust section 138 that connects the turbine 128 to an exhaust stack 140 downstream of the turbine 128. The exhaust section 138 may include, for example, a heat recovery steam generator (not shown) for cleaning and extracting additional heat from the exhaust gases 136 before being released to the environment. If multiple combustors 100 are used, they may be spaced circumferentially around a turbine inlet 142 of the turbine 128.

[0040] In one embodiment, the GT system 90 may include an engine model commercially available from GE Vernova of Cambridge, Massachusetts. The present disclosure is not limited to operability with any one particular GT system and may be implemented in connection with other engines, including, for example, any of GE Vernova's HA, F, B, LM, GT, TM, and E-class engine models, as well as engine models from other companies. Furthermore, the present disclosure is not limited to implementation with a particular turbomachine and may be applicable, for example, to steam turbines, jet engines, compressors, turbofans, etc.

[0041] A description will now be given of a combustor 100 that can be used within the GT system 90. Figure 2 illustrates a cross-sectional side view of the combustor 100 positioned within the GT system 90. As described further herein, the combustor 100 may include one or more axially staged fuel (AFS) injectors 150 according to an embodiment of the present disclosure.

[0042] 2 , combustor 100 is at least partially surrounded by an outer casing 152, such as a compressor discharge casing and / or a turbine casing. The interior of outer casing 152 is in fluid communication with compressor discharge 109 of compressor 108 and forms HP air source 154. That is, HP air source 154 includes HP air 112 from the compressor discharge of compressor 108. HP source 154 is in direct fluid communication with compressor discharge 109 of GT system 90. However, HP air source 154 may be any source of HP air 112 that can enter any of the various openings or flow passages in combustor 100 for component cooling and / or combustion, i.e., within AFS injectors 150.

[0043] As shown in FIG. 2 , the combustor 100 for the GT system 90 includes a combustor body 160. The combustor body 160 can be fabricated using any now known or later developed technique. For example, the combustor body 160 can be additively manufactured. The combustor body 160 can include, for example, a combustion liner 164, which can include a cylindrical portion 166 and a tapered transition portion 168. The combustion liner 164 can have an axis A, the direction of which can vary slightly depending on the axial location within the curved combustion liner 164. The tapered transition portion 168 is at the aft end (to the right as shown in FIG. 2 ) of the cylindrical portion 166. As understood in the art, the tapered transition portion 168 transitions the hot gas path (HGP) from a circular cross-section of the liner's cylindrical portion 166 to a more arcuate cross-section for mating with the turbine inlet 142 of the turbine 128. The combustor 100 may also include an aft frame 170 at the aft end (to the right in FIG. 2) of the tapered transition section 168 .

[0044] The combustion liner 164 may contain and channel the combustion gases 122 to the turbine section 130 ( FIG. 1 ). More specifically, the combustion liner 164 defines a combustion chamber 172, i.e., a hot gas path (HGP), where combustion occurs. The combustion liner 164 may have a tapered transition portion 168 separate from the cylindrical portion 166, as in many conventional combustion systems. Alternatively, as shown in FIG. 2 , the combustion liner 164 may have a one-piece body (or “unibody”) construction in which the cylindrical portion 166 and the tapered transition portion 168 are integral with one another, i.e., as part of an additively manufactured, one-piece member. Thus, any description of the combustion liner 164 herein is intended to encompass both conventional combustion systems having separate cylindrical and tapered transition portions and combustion systems having a unibody liner.

[0045] The combustor body 160 also includes an airflow passage 174 defined at least in part by the cylindrical portion 166 of the combustion liner 164. As described herein, the airflow passage 174 is configured to deliver air (e.g., HP air 112A from the HP air source 154) at the forward end (left end in FIG. 2 ) of the combustion liner 164 to a head-end fuel nozzle assembly 176 (hereinafter “head-end assembly 176” for brevity) of the combustor 100. That is, it is sized, shaped, and / or arranged to deliver air, such as the HP air 112A from the HP air source 154, to the head-end assembly 176 of the combustor 100. The airflow passage 174 may be defined entirely within the cylindrical portion 166, or the airflow passage 174 may be provided between the cylindrical portion 166 and a flow sleeve 177 spaced along at least a portion of the outer surface of the cylindrical portion 166. Air flow passage 174 has an open end 178, or airflow opening, proximate head end assembly 176 through which HP air 112A from HP air source 154 enters, where HP air 112A from HP air source 154 may be drawn directly from the compressor discharge, i.e., without any other use of the air other than concurrent convective cooling of combustor body 160.

[0046] An annular partition 179, located between cylindrical portion 166 and flow sleeve 177, separates a forward portion of airflow passage 174 from an aft portion of airflow passage 174. The axial position of annular partition 179 is generally aligned with cap assembly 198, described below, so that the forward portion of airflow passage 174 is radially outward of head-end assembly 176 (rather than combustion chamber 172), thereby requiring less cooling. Aft of annular partition 179, flow sleeve 177 may include a plurality of impingement holes 192 (shown in outer sleeve 190) that allow HP air 112B to enter airflow passage 174. As a result of passing through impingement holes 192, HP air 112B experiences a pressure drop and becomes LP air 182, which flows through airflow passage 174 toward and / or into AFS injector 150, as described further herein.

[0047] Head end assembly 176 generally includes at least one axially-extending fuel nozzle 194 extending downstream from end cover 196 and a cap assembly 198 extending radially and axially within outer casing 152 downstream from end cover 196 and defining a forward boundary of combustion chamber 172. Head end assembly 176 may include any now known or later developed axially-extending fuel nozzle 194 for delivering first fuel 114A from axially-extending fuel nozzle 194 to primary combustion zone 202. In certain embodiments, axially-extending fuel nozzle 194 of head end assembly 176 extends at least partially through cap assembly 198 and provides a combustible mixture of fuel 114A and HP air 112A to primary combustion zone 202.

[0048] The combustor body 160 also includes axial fuel stage (AFS) injector openings or seats 180 directed toward the combustion liner 164 downstream of the head-end assembly 176. The openings or seats 180 extend through the wall of the combustion liner 164. One or more AFS injector openings or seats 180 (hereinafter, “openings 180”) may be provided and configured to receive the AFS injectors 150 and receive the HP air 112B from the HP air source 154, among other airflows described herein. Each AFS injector opening 180 may include any necessary structure, such as threaded fasteners, bolt holes, welded areas, etc., to allow the AFS injector 150 to be mounted thereto. As shown, the combustor 100 and combustor body 160 may include a plurality of circumferentially spaced AFS injector openings 180 and corresponding AFS injectors 150. Any number of AFS injectors 150 may be used.

[0049] As will be described, in some embodiments, the AFS injector 150 is also configured to receive (draw) low-pressure (LP) air 182 from a low-pressure (LP) air source 184, e.g., a cooling passage, and direct it along with fuel 114B to the combustion liner 164. The fuel 114B may be delivered from the fuel source 116 using any form of fuel line 188. The fuels 114A, 114B may be any now known or later developed fuel for the combustor 100, such as, but not limited to, fuel oil, natural gas, hydrogen, and / or blends thereof. The fuels 114A, 114B may be the same or different.

[0050] In several embodiments, LP air 182 can be delivered to AFS injectors 150 from LP air source 184 in various ways. In certain embodiments, LP air 182 originates from HP air source 154 but is used for cooling before use in AFS injectors 150. In one example, combustor body 160 further includes a cooling passage 186 defined at least in part by tapered transition portion 168 that provides LP air source 184. Cooling passage 186 may also be in fluid communication with other cooling passages (not shown) within combustor 100, for example, aft frame 170. In either case, LP air 182 from LP air source 184 can be used to cool one or more hot components of combustor 100. More specifically, LP air 182 from LP air source 184 passes through cooling passage 186, which may be defined at least in part by tapered transition portion 168, after being drawn from compressor discharge 109.

[0051] In one example, the cooling passage 186 may be formed by a flow sleeve 190 or within the tapered transition portion 168. If desired, impingement cooling holes 192 may be provided in the flow sleeve 190 surrounding the tapered transition portion 168 to allow HP air 112 to enter from the HP air source 154 and become the LP air 182. In this regard, the LP air source 184 includes the cooling passage 186 defined along at least a portion of the combustion liner 164, e.g., the tapered transition portion 168. Additionally, the cooling passage 186 may be downstream of the compressor discharge 109 of the GT system 90, i.e., an impingement cooling member (e.g., the portion 168 having the impingement cooling holes 192 in its outer sleeve or the sleeve 190 around the portion 168 having the holes 192 therein) that is in direct fluid communication with the HP air source 154. It should be noted that the hot components may include any portion of the combustor 100 requiring cooling, and the LP air 182 may be directed to enter the cooling passages in any manner desired. That is, the cooling passages 186 may be defined in or along (other) hot components of the combustor 100 other than the tapered transition portion 168, such as the aft frame 170. In either case, the cooling passages 186 are between the AFS injectors 150 and the HP air source 154, and in some embodiments, the cooling passages 186 are configured to deliver the LP air 182 from the LP air source 184 to the AFS injectors 150. Because the LP air 182 from the LP air source 184 is used to provide significant cooling of the components of the combustor 100, it may also be referred to herein as “post-cooling” or “post-impingement air.”

[0052] As described above, the combustor 100 includes at least one axially staged fuel injector (AFS) 150 directed to the combustor body 160, i.e., the combustion liner 164. As described above, the AFS injector 150 may include a plurality of AFS injectors 150 spaced circumferentially around the combustor body 160. Each AFS injector 150 extends radially through the combustion liner 164 downstream of the head end assembly 176, i.e., downstream of the axially extending fuel nozzles 194. As will be further described, the AFS injector 150 is configured to receive HP air 112B from the HP air source 154 and, optionally, draw LP air 182 from the LP air source 184. In certain embodiments, the LP air 182 from the LP air source 184 may be routed to, for example, the AFS injector 150 in the cooling passage 186 to be combined with the HP air 112B and the second fuel 114B for combustion in a secondary combustion zone 204 downstream of the primary combustion zone 202.

[0053] Figures 3-5 show various views of an AFS injector 150 according to embodiments of the present disclosure. Figure 3 shows a perspective, partial cross-sectional view of the AFS injector 150. Figure 4 shows a cross-sectional view along line 4-4 in Figure 3. Figure 5 shows a cross-sectional view along line 5-5 in Figure 3. The AFS injector 150 includes a mixing element 210 and a high-pressure (HP) air injection element 212. Top views of the mixing element 210 according to various embodiments are shown in Figures 6A-6C, and top views of the HP air injection element 212 according to various embodiments are shown in Figure 7.

[0054] The mixing element 210 and the HP air injection element 212 are coupled together to form the AFS injector 150. More specifically, as shown in FIGS. 3-5 , the mixing element 210 and the HP air injection element 212 may each include a mounting element 213 configured to receive a fastener 215 (e.g., a bolt, weld, or other fastener) to couple the mixing element 210 and the HP air injection element 212 to an AFS injector mount 274 coupled to the combustor body 160, e.g., the outer sleeve 190. Alternatively, the mixing element 210 and the HP air injection element 212 may be formed as a single, integral piece, for example, by additive manufacturing. Each AFS injector 150 is aligned with and installed within a respective opening 180 in the combustion liner 164. Hereinafter, the HP air injection element 212 may also be referred to as the “injection element 212” for simplicity.

[0055] As shown in FIGS. 3-4 , the mixing element 210 includes a plurality of axially elongated mixing chambers 214 defined therein. The mixing element 210 may also be referred to as an injector body. In the illustrated example, the plurality of axially elongated mixing chambers 214 includes a first axially elongated mixing chamber 214A, a second axially elongated mixing chamber 214B, and a third axially elongated mixing chamber 214C between the first axially elongated mixing chamber 214A and the second axially elongated mixing chamber 214B. Although the mixing element 210 is shown with three axially elongated mixing chambers 214A-C, four or more axially elongated mixing chambers 214 may be provided. As shown in FIGS. 3-5 , each axially elongated mixing chamber 214A-C includes an inlet 216 and an outlet 218. Each inlet 216 is radially inward of the HP air injection member 212, and the outlets 218 are configured to be in fluid communication with the combustion liner 164 of the combustor 100 (FIG. 2). More specifically, the outlets 218 may be positioned and secured to the openings 180 in the combustion liner 164.

[0056] The axially elongated mixing chamber 214 can take a variety of forms. In the example shown in the drawings, each axially elongated mixing chamber 214A-C of the plurality of axially elongated mixing chambers 214 has a slot shape. More specifically, as shown in FIG. 4, each mixing chamber 214 has a generally elongated tubular chamber having opposing elongated sidewalls 220, 222 and opposing ends 224 (seen most clearly in FIGS. 6A-6C). The mixing chamber 214 is referred to as "axially elongated" because its longitudinal length, for example, of the slot, can be generally aligned with the axis A of the combustion liner 164. As shown in the top view of FIG. 6A, the opposing ends 224 can be substantially straight as they transition into the respective sidewalls 220, 222, or as shown in FIGS. 6B-6C, the opposing ends 224 can be rounded or semicircular as they transition into the respective sidewalls 220, 222. Although not shown, some curvature and / or narrowing from the inlet 216 to the outlet 118 may be provided in the axially extending mixing chamber 214, if desired.

[0057] 4, the third axially elongated mixing chamber 214C extends radially at an angle perpendicular to the outer periphery C of the combustion liner 164 (from right to left on the page of FIG. 4). Thus, the third axially elongated mixing chamber 214C extends radially from the axis A of the combustion liner 164, i.e., along the radial direction R. In contrast, the first axially elongated mixing chamber 214A and the second axially elongated mixing chamber 214B are inclined in opposite circumferential directions relative to the third axially elongated mixing chamber 214C. More specifically, the first axially elongated mixing chamber 214A is inclined at a first angle α1 relative to the third axially elongated mixing chamber 214C, and the second axially elongated mixing chamber 214B is inclined at a second angle α2 relative to the third axially elongated mixing chamber 214C. The first angle α1 and the second angle α2 may be equal.

[0058] Hereinafter, for brevity, the first and second axially elongated mixing chambers 214A-B will be referred to as the "mixing chambers" or "outer mixing chambers" 214A or 214B, as appropriate, and the third axially elongated mixing chamber 214C may be referred to herein as the "central mixing chamber 214C." Collectively, the mixing chambers may be referred to as "mixing chambers 214." The outer mixing chambers 214A-B may also be considered to be inclined relative to the axis A of the combustion liner 164 in a radial direction R, i.e., in a circumferential plane, i.e., the plane of the page in FIG. 4 . That is, the centerlines of the outer mixing chambers 214A-B are not parallel to or coextensive with the radius (R) relative to the axis A of the combustion liner 164. In this manner, the outer mixing chambers 214A-B (extending into and out of the page in FIG. 4 ) may be inclined to direct the air-fuel mixture 250 exiting therefrom toward the axis A of the combustion liner 164. It will be appreciated that the slope in the circumferential plane may vary depending on the number of mixing chambers 214 used.

[0059] The number and arrangement of the mixing chambers 214 may vary based on, for example, the fuel 114B used, the size of the combustor 100, among other factors. As shown in FIGS. 6A-6B, the mixing chambers 214 may be arranged with three mixing chambers 214A-C. FIG. 6C shows another example including five mixing chambers 214A-E. It is emphasized that the scope of this disclosure includes other arrangements not explicitly shown. The mixing chambers 214 of FIG. 6C may also include a slope relative to the radial direction R, as described with respect to FIG. 4.

[0060] The AFS injector 150 also includes a fuel plenum 230 defined in the mixing element 210. In an alternative embodiment, not shown, the fuel plenum 230 may be defined in the air injection element 212. The fuel plenum 230 may extend into an upstream portion of the sidewalls 220, 222 of each of the mixing chambers 214A-C, or at least an upstream portion of the sidewalls 220, 222 of any of the mixing chambers 214A-C necessary to supply the fuel 114B to the desired mixing chamber 214. More specifically, the fuel plenum 230 may extend around each mixing chamber 214 to any extent necessary to deliver the fuel 114B to locations where a set of fuel injectors 232 are located. The AFS injector 150 also includes an inlet port 234 in fluid communication with the fuel plenum 230 and configured to receive the fuel 114B from the fuel source 116 ( FIGS. 1-2 ). The inlet port 234 of each AFS injector 150 can be fluidly coupled to the fuel source 116, for example, by the fuel line 188 ( FIG. 2 ) and, optionally, a distribution plenum (not shown) around the combustion liner 164. In either case, the fuel plenum 230 is configured to deliver the fuel 114B from the fuel source 116 to each set of fuel injectors 232. As noted above, the fuel 114B may be any now known or later developed fuel for the combustor 100, such as, but not limited to, fuel oil, natural gas, etc. With the benefit of the AFS injectors 150, the fuel 114B may also include a highly reactive fuel, such as hydrogen. The fuel 114B may also include a blend of fuels, such as natural gas and hydrogen.

[0061] The mixing element 210 also includes a set of fuel injectors 232 defined in opposing sidewalls 220, 222 of each mixing chamber 114. Each fuel injector 232 is in fluid communication with the fuel plenum 230 so that the fuel 114B may be introduced into the respective mixing chamber 114, i.e., under pressure from the fuel source 116. The fuel injectors 232 may be arranged in any manner to achieve a desired air-fuel mixture 250. More specifically, each set of fuel injectors 232 is configured to entrain the fuel 114B from the injection element 212 into the HP airflow 244 to generate the desired air-fuel mixture 250 for combustion in the combustion liner 164. The type, number, spacing, and size of the fuel injectors 232 overall and within a given set may be selected depending, for example, on a variety of characteristics of the combustor 100, the HP air 112B, the LP air 182 (if used), and / or the fuel 114B. For example, with respect to fuel 114B, the properties may include, but are not limited to, gas type, level of reactivity, viscosity, desired flow rate or volume, pressure, temperature, etc. Similar properties of air 112B, 182 may also be considered.

[0062] 3 and 4 and the schematic diagram of FIG. 6D , each set 236 of fuel injectors 232 may include a single row of fuel injectors 232 on each of the opposing sidewalls 220, 222 of the respective mixing chamber 214. The fuel injectors 232 of opposing sets 236 for a particular mixing chamber 214 may have the same arrangement but will likely differ with respect to spacing, size, number, etc. of the fuel injectors 232 to better mix the fuel 114B ( FIG. 2 ) with the HP airflow 244. The fuel injectors 232 within a given set 236, and the fuel injectors 232 of different sets 236, need not be identical.

[0063] For example, as shown in the schematic diagram of FIG. 6D, the first and second axially elongated mixing chambers 214A, 214B can include a first side wall 220 and an opposing second side wall 222, and a set 236A of fuel injectors 232 defined in the first side wall 220 can be arranged in a different manner from a set 236B of fuel injectors 232 defined in the second side wall 222 for each of the outer mixing chambers 214A, 214B. For example, the number, size, and direction of the fuel injectors 232 can be different, particularly on different side walls 220, 222, among other physical characteristics. Regarding the number of injectors, in one non-limiting example, a set 236A of fuel injectors 232 on one side wall 220 can include X fuel injectors 232, and a set 236B of fuel injectors 232 on the other side wall 222 can include Y fuel injectors 232. The number X of the fuel injectors 232 in the set 236A on the side wall 220 is not equal to the number Y of the fuel injectors 232 in the set 236B on the side wall 222. In the illustrated example, X < Y. In one non-limiting example, the fuel injectors 232 for the outer mixing chambers 214A - B can be unevenly spaced on one or both of the side walls 220, 222.

[0064] In contrast, as shown in the schematic diagram of FIG. 6E, in the case of the central mixing chamber 214C, the opposing sets 236C and 236D of fuel injectors 232C and 232D can have different arrangements, but are likely to be the same with respect to the spacing, size, number, etc. of the fuel injectors 232. For example, as shown in the schematic diagram of FIG. 6E, the central mixing chamber 214C can include a first side wall 220 and an opposing second side wall 222, and a set 236C of fuel injectors 232C defined in the first side wall 220 can be arranged in the same or similar manner as a set 236D of fuel injectors 232D defined in the second side wall 222. In this example, the same number of fuel injectors 232 is defined on the opposing side walls 220, 222 of the central mixing chamber 214C. In another non-limiting example, the fuel injectors 232 for the central mixing chamber 214C can be evenly spaced on both side walls 220, 222.

[0065] 5 , each set of fuel injectors 232 may include a first set 236E of fuel injectors 232E axially spaced (relative to the axis of the respective mixing chamber 214) from a second set 236F of fuel injectors 232F in each mixing chamber 214 of the plurality of mixing chambers. More specifically, the first set 236E of fuel injectors 232E may be spaced a first distance D1 from the outlet 218 of the respective mixing chamber 214, and the second set 236F of fuel injectors 232F may be spaced a second distance D2 less than the distance D1 from the outlet 218 of each mixing chamber 214 of the plurality of mixing chambers. As shown, the first set 236E and the second set 236F form two rows. Rows of fuel injectors 232 such as those illustrated in FIG. 5 may be used in any mixing chamber 214. Although one or two axially spaced apart sets of fuel injectors 232A-B are shown on each sidewall 220, 222, in other embodiments, three or more sets of axially spaced apart fuel injectors are possible.

[0066] Regardless of the embodiment, each set of fuel injectors 232 may be closer to the inlet 216 than to the outlet 218 of each mixing chamber 214 (e.g., 214C) of the multiple mixing chambers. In any case, the placement of the fuel injectors 232 is configured to maximize mixing of the HP airflow 244, the LP airflow 182 (if used), and the fuel 114B ( FIG. 2 ). Other placements are possible, depending on, for example, the characteristics of the HP airflow 244, the LP airflow 182 (if used), the fuel 114B, and the combustor 100, among other factors.

[0067] The fuel injectors 232 can take any now known or later developed form of opening for delivering a particular type of fuel 114B to the respective mixing chambers 114. For example, the fuel injectors 232 can be cylindrical openings or can have a narrowed nozzle cross-section to distribute the fuel 114B. Additionally, the fuel injectors 232 can introduce the fuel 114B into the respective mixing chambers 214 in any desired direction. For example, the fuel injectors 232 can introduce the fuel 114B into the respective mixing chambers 214 at a perpendicular angle relative to the axis of the respective mixing chamber 214 and / or its upstream wall 222, at a non-perpendicular angle relative to the upstream wall 222 to impart rotation to the fuel 114B, and / or radially outward or inward relative to the axis of the respective mixing chamber 214, i.e., toward or away from the combustion liner 164.

[0068] The dimensions of the mixing chambers 214 can be user-defined based on, for example, the characteristics of the fuel 114B, the HP air 112B, the LP air 182 (if used), and / or the combustion liner 164, among many other factors. As shown in FIG. 4, the length L1 of each mixing chamber 214A-B from the inlet 216 to the outlet 218 (shown in FIG. 4 only for mixing chamber 214B for clarity) is approximately the same, while the length L2 of the central mixing chamber 214C may be longer. The dimensions of any portion of the mixing element 210 (and HP air injection element 212) of the AFS injector 150 can be customized to produce a desired air-fuel mixture 250 while maintaining a low profile to facilitate installation of the combustor 100 within the respective openings in the outer casing 152.

[0069] The HP air injection member 212 will be described with reference to Figures 3-5 and 7-8B. Note that the injection member 212 may also be referred to as a "top hat." The injection member 212 has a generally arcuate (e.g., C-shaped) cross-sectional profile configured to surround the radially outer portion of the mixing element 210. The periphery of the injection element 212 may include a flanged edge 217 (Figure 3) that contacts the outer sleeve 177, 190 when the AFS injector 150 is installed. The injection element 212 defines a set 240 HP air jets 242 for each mixing chamber 214. The outlets of the HP air jets 242 are spaced from the respective inlets 216 of each mixing chamber 214 when the AFS injector 150 is assembled. There are as many sets 240 HP air jets 242 within the injection element 212 as there are mixing chambers 214 present in a given mixing element 210. For example, as shown in Figure 7, three sets 240 of HP air jets 242, namely sets 240A, 240B, and 240C, are shown corresponding to the three mixing chambers 214A-C in Figure 6. The injection member 212 is in fluid communication with the HP air source 154 such that the HP air 112B enters the AFS injector 150 and is directed to the AFS injector 150 by the HP air jets 242 of set 240A.

[0070] As will be described, in some embodiments, each set 240 of HP air jets 242 is configured to channel HP air 112B from HP air source 154 and draw LP air 182 from LP air source 184, and channel the LP air 182 along with the HP air 112B into the inlet 216 of the respective mixing chamber 214. The collective flow is referred to herein as HP air flow 244 ( FIGS. 3-5 ), see the arrows pointing toward the inlet 216 of the respective mixing chamber 214. Thus, HP air flow 244 can include both HP air 112B and LP air 182. Note that HP air flow 244 maintains a relatively high pressure, though not as high as HP air 112B from HP air source 154, such as compressor discharge 109 ( FIG. 2 ), and is therefore referred to as a high-pressure flow despite its mixing with LP air 182.

[0071] 3-5, the injection member 212 may optionally include a filter element 246 upstream of the set of HP air jets 242. Note that the filter element 246 is not shown in FIG. 7 for clarity. The filter element 246 may include any now known or later developed filter structure capable of preventing undesirable contaminants from entering the AFS injector 150 from the HP air source 154.

[0072] 8A shows an enlarged perspective view of the HP air jets 242 of the sets 240A-C, and FIG. 8B shows a cross-sectional view of the HP air jets 242A-C of the injection member 212. As shown in FIGS. 3, 7, and 8A, the placement of the HP air jets 242 of the sets 240A-B spaced apart from the inlets 216 of the outer mixing chambers 214A-B is the same for sets 240A and 240B, but the placement of the HP air jets 242 of the set 240C spaced apart from the inlets 216 of the central mixing chamber 214C is different from the placement of the HP air jets 242 of the set 240A-B spaced apart from the inlets 216 of the mixing chambers 214A-B. The difference in placement can take any form, such as, but not limited to, the layout, size, shape, and / or number of the HP air jets 242 of each set 240. In terms of individual air jet size, the set 240A-B of HP air jets 242 for the outer mixing chambers 214A-B have a larger cross-sectional area than the set 240C for the central mixing chamber 214C.

[0073] In terms of numbers, each set 240 of HP air jets 242 can include any number of HP air jets 242. For example, the sets 240A-B of HP air jets 242 spaced from the inlets 216 of the outer mixing chambers 214A-B each have a fewer number of HP air jets 242 than the set 240C of HP air jets 242 spaced from the inlet 216 of the central mixing chamber 214C. A fewer number of HP air jets 242 can be advantageous in the outer mixing chambers 214A-B to reduce obstruction of the flow of LP air 182 (if used) to the central mixing chamber 214C as the LP air 182 enters the mixing element 210. In the example shown in FIGS. 3-5 and 7, each set 240A-B of HP air jets 242 for the outer mixing chambers 214A-B includes a single row of six HP air jets 242A-B. That is, each set 240A-B includes six HP air jets 242 in each row. In contrast, as shown in FIG. 7, the HP air jets 242 of set 240C for central mixing chamber 214C include a pair of axially offset rows 248A-B of HP air jets 242. For example, set 240C may include one row 248B of eleven HP air jets 242 and another row 248A of ten HP air jets 242. Although a specific number of HP air jets 242 is shown in each set 240, any number of HP air jets 242 may be used in each set 240A-C. In the illustrated example, each HP air jet 242 may have an airfoil cross-sectional shape to facilitate the passage of LP air 182 from the circumferentially outer side of injection member 212 (left and right sides in FIGS. 3-4 and 8A-8B) to mixing chamber 214, and particularly central mixing chamber 214C. However, the HP air jets 242 may alternatively have cross-sectional shapes such as, but not limited to, ovals, elongated openings or slots, or narrow longitudinal cross-sections (nozzle or venturi-like). While specific arrangements for each set are shown in the drawings, other arrangements are possible.

[0074] As shown in FIGURE 8B, each of the HP air jets 242 in set 240A-B includes a flared inlet 251 having a first outer radius R1, and each of the HP air jets 242 in set 240C includes a flared inlet 251 having a second outer radius R2. The first outer radius R1 is larger than the second outer radius R2. The different radii facilitate the flow of HP air 112B to the HP air jets 242 based on the desired volume and size of the HP air jets 242, and also reduce pressure loss.

[0075] Further, with regard to the configuration of the HP air jets 242, as shown in Figures 3, 4, and 8A-8B, each of the set 240A-B of HP air jets 242 spaced from the inlets 216 of the mixing chambers 214A, 214B includes a radially inwardly extending collar 252. The collar 252 has an airfoil cross-sectional shape (similar to the HP air jets 242 shown in Figure 7) with its first (leading) side 254 farther from the central mixing chamber 214C than its second, opposite (rear) side 256. That is, the first side 254 is circumferentially farther from the central mixing chamber 214C than the second side 256, which may be radially above (outside) the sidewalls 220, 222 of the central mixing chamber 214C. In some embodiments, the first side 254 presents a leading edge of the airfoil cross section of the collar 252 to the LP air 182 as it encounters the collar 252, and thus acts to facilitate the flow of the LP air 182 into at least the central mixing chamber 214C.

[0076] 3 and 8A, the first side 254 is radially farther from the mixing element 210 than the second side 256. More specifically, the first side 254 is radially farther from the radially outer surfaces of the side walls 220, 222 of the mixing chambers 214A, 214B, respectively, and the second side 256 is farther from the radially outer surfaces of the side walls 220, 222 of the central mixing element 214C. In this configuration, the collar 252 also directs the HP airflow 244 for the mixing chambers 214A-B more directly into the mixing chambers 214A-B, preventing blockage of the flow of LP air 182 toward the central mixing chamber 214C. In an optional embodiment, as shown in FIGS. 3 and 8A , the first side 254 of the collar 252 of each set 240A-B of HP air jets 242 can each include an opening 258 defined therein, i.e., on the side 254 facing the flow of LP air 182. The openings 258 can have any desired size and shape, such as circular, slotted (as shown), or other shapes. During operation, the openings 258 slightly change the path of the HP air 112B passing through the collar 252 toward the central mixing chamber 214C, thereby allowing the LP air 182 to more easily pass to the outer mixing chambers 214A, 214B without significant pressure loss. However, the HP air 112B within the collar 252 does not exit through the openings 258.

[0077] With respect to the intake of HP air 112B from the HP air source 154, a set 240 of HP air jets 242 are spaced apart from the inlet 216 of each mixing chamber 214 and are configured to direct an HP air stream 244 (see arrows) containing the HP air 112B therefrom into the respective mixing chamber 214. As described above, the injection member 212 is in fluid communication with the HP air source 154 such that the HP air 112B enters the HP air jets 242. The set 240 of HP air jets 242 are spaced apart from the inlet 216 of each mixing chamber 214 and are configured to direct the HP air 112B therefrom and, in some embodiments, draw LP air 182 therein to form the HP air stream 244. The HP jets 242 also direct the HP air stream 244 into the respective mixing chamber 214. More specifically, the HP jets 242 may direct the HP airflow 244 into each mixing chamber 214 at an angle α1, α2 that is the same as the angle of the respective mixing chamber 214 relative to the axis A of the combustion liner 164. While each HP jet 242 in a set does not necessarily have the angle of the respective mixing chamber 214, e.g., angle α1 or α2, the HP air jets 242 in a given set 240 are each angled such that the collective HP airflow 244, including the HP air 112B and LP air 182 (if used) from the given set, has an angle (not shown for clarity) that is the same as the angle of the respective mixing chamber 214 relative to the axis A of the combustion liner 164. 4, HP airflow 244 from HP air jets 242A of set 240A (FIG. 7) has an angle α1 with mixing chamber 214A, HP airflow 244 from HP air jets 242 of set 240B (FIG. 7) has an angle α2 with mixing chamber 214B, and HP airflow 244 from HP air jets 242 of set 240C (FIG. 7) has an angle with mixing chamber 214C (perpendicular to axis A of combustion liner 164). Collar 252 may also be angled at the same angle as mixing chambers 214A-B.

[0078] 3-5, the mixing chambers 214 mix the HP air flow 244 with the fuel 114B entering from the fuel injectors 232. As described above, each HP air jet 242 is configured to direct the HP air flow 244 toward the inlet 216 of the respective mixing chamber 214, which contains the HP air 112B from the HP air source 154. In some embodiments, the HP air jets 242 draw LP air 182 from the LP air source 184 internally into the space between the HP air jet 242 and the mixing element 210, i.e., form an ejector for the LP air 182. The HP air flow 244 impinges on the inlet 216 of the mixing chamber 214, or more precisely, on the leading edge of the mixing chamber 214, generating a vortex and promoting in-plane mixing (in the plane of the top surface of the mixing element 210) of the HP air 112B, the LP air 182, and the fuel 114B. In one non-limiting example, HP air 112B can comprise between 45-55% of the total air flow from HP air 112B and LP air 182, and LP air 182 can comprise between 45-55% of the total air flow from HP air 112B and LP air 182. In this manner, AFS injector 150 using two air sources reduces pressure losses throughout the system and more efficiently uses the air within combustor 100.

[0079] The AFS injector 150, i.e., the mixing element 210 and the injection element 212, can be made of any now known or later developed combustion- and oxidation-resistant material. The material can be a metal, either a pure metal or an alloy. The AFS injector 150 can include metals typically used in turbine components, such as turbine blades or nozzles, that have higher temperature and oxidation resistance than materials typically used in combustion hardware. In this case, the material may include, for example, but is not limited to, a non-reactive metal made from a non-explosive or non-conductive powder, such as a cobalt-chromium-molybdenum (CoCrMo) alloy, stainless steel, an austenitic nickel-chromium based alloy such as a nickel-chromium-molybdenum-niobium alloy (NiCrMoNb) (e.g., Inconel 625 or Inconel 718), a nickel-chromium-iron-molybdenum alloy (NiCrFeMo) (e.g., Hastelloy® X available from Haynes International, Inc.), a nickel-chromium-cobalt-molybdenum alloy (NiCrCoMo) (e.g., Haynes 233 or Haynes 282 available from Haynes International, Inc.), or a nickel-chromium-cobalt-titanium alloy (NiCrCoTi) (e.g., GTD 262 developed by General Electric Company). Other possibilities include, for example, Rene 108, CM 247, Mar M 247, and any precipitation hardenable (PH) nickel alloy.

[0080] In certain embodiments, the AFS injector 150, i.e., the mixing element 210 and / or the injection element 212, can be additively manufactured using any now-known or later-developed technique capable of forming a unitary body. Thus, as shown in FIG. 9 , the mixing element 210 and / or the injection element 212 includes multiple parallel sintered metal layers 270. FIG. 10 shows a schematic / block diagram of an exemplary computerized metal powder additive manufacturing system 310 (hereinafter, “AM system 310”) for producing the AFS injector 150, i.e., the mixing element 210 and / or the injection element 212, of which only a single layer is shown. While the teachings of the present disclosure are described with respect to constructing the mixing element 210 and / or the injection element 212 using multiple melt beam sources 312, 314, 316, 318, it is emphasized, and it will be readily appreciated, that the teachings of the present disclosure are equally applicable to constructing the mixing element 210 and / or the injection element 212 using any number of melt beam sources. In this example, the AM system 310 is configured for direct metal laser melting (DMLM). It is understood that the general teachings of the present disclosure are equally applicable to other forms of metal powder additive manufacturing, such as, but not limited to, selective laser melting (SLM), and possibly other forms of additive manufacturing (i.e., other than metal powder applications). While the layers of mixing elements 210 and / or injection elements 212 on the build platform 320 are shown as circular elements in FIG. 10 , it is understood that the additive manufacturing process can be readily adapted to produce any shape on the build platform 320.

[0081] The AM system 310 generally includes an additive manufacturing control system 330 (“control system”) and an AM printer 332. As illustrated, the control system 330 executes a set of computer-executable instructions or code 334 for generating the mixed member 210 and / or the jetting member 212 using multiple melt beam sources 312, 314, 316, 318. In the illustrated example, the four melt beam sources may include four lasers. However, the teachings of the present disclosure are applicable to any melt beam source, e.g., electron beam, laser, etc. The control system 330 is shown implemented in a computer 336 as computer program code. In this context, the computer 336 is shown as including a memory 338 and / or storage system 340, a processor unit (PU) 344, an input / output (I / O) interface 346, and a bus 348. Additionally, the computer 336 is shown as communicating with an external I / O device / resource 350.

[0082] Generally, processor unit (PU) 344 executes computer program code 334 stored in memory 338 and / or storage system 340. While executing computer program code 334, processor unit (PU) 344 can read and write data from memory 338, storage system 340, I / O devices 350, and / or AM printer 332. Bus 348 provides a communication link between each of the components in computer 336, and I / O devices 350 can comprise any device (e.g., keyboard, pointing device, display, etc.) that allows a user to interact with computer 336. Computer 336 is merely representative of various possible combinations of hardware and software. For example, processor unit (PU) 344 can comprise a single processing unit or can be distributed across one or more processing units at one or more locations, e.g., on a client and a server. Similarly, memory 338 and / or storage system 340 may reside in one or more physical locations. The memory 338 and / or storage system 340 may comprise any combination of various types of non-transitory computer-readable storage media including magnetic media, optical media, random access memory (RAM), read-only memory (ROM), etc. The computer 336 may comprise any type of computing device, such as an industrial controller, a network server, a desktop computer, a laptop, a handheld device, etc.

[0083] As described above, the AM system 310, and particularly the control system 330, executes code 334 to generate the mixing element 210 and / or the jetting element 212. The code 334 may include, among other things, a set of computer-executable instructions 334S (also referred to herein as “code 334S”) for operating the AM printer 332, as well as a set of computer-executable instructions 334O (also referred to herein as “code 334O”) that define the mixing element 210 and / or the jetting element 212 that are physically generated by the AM printer 332. As described herein, the additive manufacturing process begins with a non-transitory computer-readable storage medium (e.g., memory 338, storage system 340, etc.) storing the code 334. The set of computer-executable instructions 334S for operating the AM printer 332 may include any now-known or later-developed software code capable of operating the AM printer 332.

[0084] The set of computer-executable instructions 334O defining the mixing element 210 and / or the injection element 212 may include a precisely defined 3D model of the mixing element 210 and / or the injection element 212 and may be generated from any of a wide variety of well-known computer-aided design (CAD) software systems, such as AutoCAD®, TurboCAD®, DesignCAD 3D Max, etc. In this regard, the code 334O may include any now known or later developed file format. Furthermore, the code 334O representing the mixing element 210 and / or the injection element 212 may be converted between different formats. For example, the code 334O may include a Standard Tessellation Language (STL) file generated for a 3D systems stereolithography CAD program, or an Additive Manufacturing File (AMF), an extensible markup language (XML)-based format standardized by the American Society of Mechanical Engineers (ASME) and designed to allow any CAD software to describe the shape and configuration of any three-dimensional object to be produced on any AM printer. The code 334O representing the mixing element 210 and / or the injection element 212 may also be converted into a set of data signals, transmitted, received as a set of data signals, converted into code, stored, etc., as needed. The code 334O may be configured according to embodiments of the present disclosure to enable the formation of boundaries and interior sections within overlapping field regions, as described. In either case, the code 334O may be input to the AM system 310 and may come from a part designer, intellectual property (IP) provider, design firm, operator or owner of the AM system 310, or other source. In either case, the control system 330 executes the code 334S and 334O to divide the mixing element 210 and / or the injection element 212 into a series of thin slices, which are assembled in successive layers of material using the AM printer 332.

[0085] The AM printer 332 can include a sealed processing chamber 360 to provide a controlled atmosphere for printing the mixed element 210 and / or the ejection element 212. A build platform 320, on which the mixed element 210 and / or the ejection element 212 are built, is positioned within the processing chamber 360. Several melt beam sources 312, 314, 316, 318 are configured to melt a layer of metal powder on the build platform 320 to produce the mixed element 210 and / or the ejection element 212. While four melt beam sources 312, 314, 316, 318 are shown, it is emphasized that the teachings of the present disclosure are applicable to systems using any number of sources, for example, one, two, three, or five or more sources. As understood in the art, each melt beam source 312, 314, 316, 318 can have fields that each include a non-overlapping field region capable of melting only metal powder, and two or more sources can include at least one overlapping field region capable of melting metal powder. In this regard, each melt beam source 312, 314, 316, 318 can generate a respective melt beam that melts particles for each slice, as defined by code 3340. For example, in FIG. 10, melt beam source 312 is shown using melt beam 362 to generate layers of mixing element 210 and / or injection element 212 in one region, and melt beam source 314 is shown using melt beam 362′ to generate layers of mixing element 210 and / or injection element 212 in another region.

[0086] Each melt beam source 312, 314, 316, 318 is calibrated in any now known or later developed manner, i.e., each melt beam source 312, 314, 316, 318 correlates the expected position of its laser or electron beam with its actual position relative to the build platform 320 to provide individual position corrections (not shown) to ensure its individual accuracy. In one embodiment, each of the multiple melt beam sources 312, 314, 316, 318 can generate melt beams, e.g., 362, 362′, having the same cross-sectional dimensions (e.g., shape and size during operation), power, and scan speed.

[0087] 10 , an applicator (or recoater blade) 370 produces a thin layer of raw material 372, which is laid out as a blank canvas from which each successive slice of the final mixed element 210 and / or jet element 212 will be produced. Various parts of the AM printer 332 may move to accommodate the addition of each new layer; for example, after each layer, the build platform 320 may lower and / or the chamber 360 and / or applicator 370 may raise. The process may use different raw materials in the form of fine metal powder, a stock of which may be held in a powder reservoir 368 accessible by the applicator 370.

[0088] The processing chamber 360 is filled with an inert gas, such as argon or nitrogen, and controlled to minimize or eliminate oxygen. The control system 330 is configured to control the flow of a gas mixture 374 within the processing chamber 360 from an inert gas source 376. In this case, the control system 330 can control a pump 380 and / or an inert gas flow valve system 382 to control the content of the gas mixture 374. The flow valve system 382 can include one or more computer-controllable valves, flow sensors, temperature sensors, pressure sensors, etc., capable of precisely controlling the flow of specific gases. The pump 380 may or may not include the valve system 382. If the pump 380 is omitted, the inert gas can enter a conduit or manifold before being introduced into the processing chamber 360. The inert gas source 376 can take the form of any conventional source for the materials contained therein, such as a tank, reservoir, or other source. Any sensors (not shown) necessary to measure the gas mixture 374 may be provided. The gas mixture 374 may be filtered using a filter 386 in a conventional manner.

[0089] During operation, a build platform 320 having metal powder thereon is provided within a processing chamber 360, and a control system 330 controls the flow of a gas mixture 374 within the processing chamber 360 from an inert gas source 376. The control system 330 also controls the AM printer 332, and in particular the applicator 370 and melt beam sources 312, 314, 316, 318, to sequentially melt layers of metal powder on the build platform 320 to produce the mixed element 210 and / or the jet element 212 according to embodiments of the present disclosure. While a particular AM system 310 is described herein, it is emphasized that the teachings of the present disclosure are not limited to any particular additive manufacturing system or method.

[0090] Once the mixing element 210 and the injection element 212 are formed, they may be assembled with other portions of the combustor 100 to form the AFS injector 150, as shown in FIG. 2. For example, as shown in FIGS. 3-5, the mixing element 210 and / or the injection element 212 may be fastened to an AFS injector mount 274 (FIGS. 3-5) on the combustion liner 164. More specifically, as described above, the mixing element 210 and the HP air injection element 212 may each include at least one mounting element 213 configured to receive a fastener 215, such as a bolt or a weld, to couple the mixing element 210 and the HP air injection element 212 to the combustion liner 164 that defines the combustion chamber 172, i.e., to the AFS injector mount 274 of the combustion liner 164.

[0091] 3-5 , the periphery of the HP injection member 212 rests on the outer surface of the forward flow sleeve 177 or the aft flow sleeve 190, and the mixing member 210 extends outward from the combustion liner 164 within openings in the flow sleeves 177, 190. A gap may be defined between the inner surface of the HP air injection member 212 and the mixing member 210, thereby permitting the flow of LP air 182 from the openings into the interior of the AFS injector 150. In such an embodiment, the LP air 182 is entrained in the HP air 112B flowing through the HP injection member 212.

[0092] In other embodiments (not shown), the use of LP air 182 can be omitted by blocking the flow from the LP air source 184 to the AFS injector 150 such that the AFS injector 150 is not in fluid communication with the LP air source 184. In such embodiments, the mixing element 210 and / or the injection element 212 can include an axially extending wall extending between the mixing element 210 and the inner surface of the HP injection element 212. This wall prevents LP air 282 from entering the mixing chamber 214. More specifically, this wall defines a sealed chamber between the mixing element 210 and the injection element 212 that prevents any additional (LP) air from entering the air-fuel mixture 250 exiting the HP air-fuel injector 232. An AFS injector 150 configured in this manner uses only HP air 112B to mix with fuel and does not receive post-impingement air as LP air 182.

[0093] Embodiments of the present disclosure may also include a combustor 100 for the GT system 90. The combustor 100 includes a combustor body 160 including a combustion liner 164. The combustor 100 may also include a plurality of AFS injectors 150 directed at the combustion liner 164, as described herein. Returning to FIG. 2 , the combustor 100 generally terminates at a point adjacent a first stage 260 of a static nozzle 262 of the turbine 128. The first stage 260 of the static nozzle 262 at least partially defines the turbine inlet 142 to the turbine 128. The combustor body 160, i.e., the combustion liner 164, at least partially defines a hot gas path (HGP) for channeling the combustion gases 122 from the primary combustion zone 202 and secondary combustion zone 204 to the turbine inlet 142 of the turbine 128 during operation of the GT system 90. Due to its small size, the AFS injector 150 can be assembled onto a combustion liner 164 of a combustor body 160 (FIG. 2), which can be installed generally axially into the GT system 90 through a relatively small opening (not shown) in the compressor discharge casing (within the casing 152).

[0094] 1 , the GT system 90 may include a compressor section 110, a combustion section 120 operably coupled to the compressor section 110, and a turbine section 130 operably coupled to the combustion section 120. As described herein, the combustion section 120 includes at least one combustor 100 including a combustor body 160 including a combustion liner 164 and a head-end fuel nozzle assembly 176 at a forward end of the combustor body 160. The combustor 100 may also include a plurality of AFS injectors 150 directed into the combustion body 160, i.e., the combustion liner 164, downstream of the head-end assembly 176, as described herein.

[0095] The present disclosure provides various technical and commercial advantages, examples of which are described herein. As described herein, AFS injectors can accept high-pressure air and, optionally, low-pressure air, e.g., post-impingement cooling air, to reduce pressure losses throughout the system. The AFS injectors can rapidly premix an air source with a highly reactive fuel, e.g., hydrogen, to achieve, for example, low nitrous oxide (NOx) emissions and acceptable flame-holding capabilities. The AFS injectors enhance fuel-air mixing, minimize flow pressure losses, and prevent fuel from entering any low-velocity airflow zones. Additionally, the AFS injectors have a relatively small radial height from top to bottom, allowing them to be assembled onto the combustion liner of the combustor body, which is then axially installed in the GT system through a relatively small opening in the compressor discharge casing.

[0096] As used herein throughout this specification and claims, approximation language can be applied to modify any quantitative expression that can reasonably vary without resulting in a change in the relevant basic function. Thus, values ​​modified by terms such as "approximately," "about," and "substantially" are not limited to the exact value specified. In at least some instances, approximation language can correspond to the precision of the instrument used to measure the value. Here, and throughout this specification and claims, range limitations are combinable and / or interchangeable, and unless the context or language dictates otherwise, such ranges are identified and include all subranges encompassed therein. "About" or "approximately," as applied to a particular value in a range, applies to both endpoints and can indicate + / - 10% of the stated value, unless specifically dependent on the precision of the instrument used to measure the value.

[0097] The corresponding structure, material, acts, and equivalents of all means or step-plus-function elements in the following claims are intended to include any structure, material, or acts for performing the function in combination with other claimed elements that are specifically claimed. The description of the present disclosure has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the disclosure to the precise form disclosed. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the present disclosure. The embodiments were chosen and described to best explain the principles of the disclosure and its practical applications, and to enable those skilled in the art to understand the disclosure in order to envision embodiments with various modifications suitable for the particular use contemplated. [Explanation of symbols]

[0098] 90 Gas Turbine (GT) System 100 Combustor 102 Entrance Section 106 Working fluid (air) 108 Compressor 109 Compressor discharge port 110 Compressor Section 112 HP air 112A HP Air 112B HP Air 114A First Fuel 114B Secondary Fuel 116 Fuel source 118 Exit 120 Combustion Section 122 Combustion Gas 128 Turbine 130 Turbine Section 132 Shaft 134 Generator 136 Exhaust Gas 138 Exhaust Section 140 exhaust stack 142 Turbine inlet 150 Axial Fuel Stage (AFS) Injector 152 outer casing 154 HP Air Source 160 Combustor body 164 Combustion Liner 166 Cylindrical section 168 Tapered Transition 170 rear frame 172 Combustion Chamber 174 Air flow path 176 Head End Fuel Nozzle Assembly 177 Flow sleeve / outer sleeve / forward flow sleeve 178 Open end 179 Annular bulkhead 180 AFS injector opening or seat 182 Low Pressure (LP) Air 184 Low Pressure (LP) Air Source 186 Cooling passage 188 fuel line 190 Flow sleeve / outer sleeve / rear flow sleeve 192 Impingement cooling hole 194 Axially extending fuel nozzle 196 End cover 198 End Cap Assembly 202 Primary Combustion Zone 204 Secondary Combustion Zone 210 Mixed materials 212 High-pressure (HP) air injection element 213 Wearing Elements 214 Axially elongated mixing chamber 214A First axially elongated mixing chamber / outer mixing chamber 214B Second axially elongated mixing chamber / outer mixing chamber 214C Third axially elongated mixing chamber / central mixing chamber 215 Fasteners 216 Entrance 217 Flange edge 218 Exit 220 Opposing elongated side walls / first side wall 222 Opposing elongated side wall / second side wall / upstream side wall 224 Opposite ends of semicircle 230 Fuel Plenum 232 Fuel Injector 232A~F Fuel Injector 234 Inlet Port 236 A set of fuel injectors 240 HP air jet set 240A group 240B group 240C group 242 HP Air Jet 242A HP Air Jet 242B HP Air Jet 242C HP Air Jet 244 HP airflow 246 Filter material 248A Pair of axially offset rows 248B Pair of axially offset rows 250 air fuel mixture 251 Flared Entrance 252 colors 254 First Aspect 256 Second Aspect 258 Opening 260 First Section 262 Stationary Nozzle 270 Metal layer 274 AFS injector mount 310 Computerized Metal Powder Additive Manufacturing (AM) System 312 Melting Beam Source 314 Melting Beam Source 316 Melting Beam Source 318 Melting Beam Source 320 Building Platform 330 Additive Manufacturing (AM) Control System 332 AM Printer 334 Computer Program Code 334O Computer executable instructions or code 334S Computer executable instructions or code 336 Computer 338 memory 340 Memory System 344 Processor Unit (PU) 346 Input / Output (I / O) Interface 348 Bus 350 I / O devices / resources 360 Processing Chamber 362 Melting Beam 362' molten beam 368 Powder Reservoir 370 Applicator 372 raw materials 374 Gas Mixtures 376 Inert Gas Source 380 Pump 382 Flow Valve System 386 filters D1 First distance D2 Second distance L1 length L2 length R Radial direction R1 First outer radius R2 Second outer radius α1 First angle α2 Second angle

Claims

1. 1. An axial fuel stage (AFS) injector (150) for a combustor (100) of a gas turbine (GT) system (90), comprising: A mixing element (210), a plurality of axially elongated mixing chambers defined in the mixing element, each axially elongated mixing chamber including an inlet and an outlet, each outlet configured to be in fluid communication with a combustion chamber of the combustor; a pair of fuel injectors (236) defined in opposing sidewalls (220, 222) of each axially elongated mixing chamber (214); a high pressure (HP) air injection element (212) defining a pair of HP air jets (240) spaced from the inlet (216) of each axially elongated mixing chamber (214); a fuel plenum (230) defined in the mixing element (210), the fuel plenum (230) configured to deliver fuel (114A, 114B) from a fuel source (116) to a respective pair of fuel injectors (236); each set of HP air jets (240) configured to direct HP air (112) from an HP air source (154) to the inlets (216) of respective mixing chambers (214) into which fuel (114A, 114B) is injected by the set of fuel injectors (236); AFS injector (150).

2. 2. The AFS injector of claim 1, wherein the plurality of axially elongated mixing chambers includes a first axially elongated mixing chamber, a second axially elongated mixing chamber, and a third axially elongated mixing chamber between the first axially elongated mixing chamber and the second axially elongated mixing chamber.

3. 3. The AFS injector of claim 2, wherein the third axially elongated mixing chamber extends radially at an angle perpendicular to an outer periphery of the combustion liner, and the first axially elongated mixing chamber and the second axially elongated mixing chamber are inclined in opposite circumferential directions relative to the third axially elongated mixing chamber.

4. 4. The AFS injector of claim 3, wherein the set of HP air jets spaced from the inlet of each mixing element are configured to direct the HP air into each axially elongated mixing chamber at an angle identical to an angle of the respective axially elongated mixing chamber.

5. 4. The AFS injector of claim 3, wherein the set of HP air jets spaced from the inlet to the third axially elongated mixing chamber comprises a pair of axially offset rows of HP air jets.

6. 3. The AFS injector of claim 2, wherein the set of HP air jets spaced from the inlets of the first and second axially elongated mixing chambers each include a radially inwardly extending collar having a first side thereof radially farther from the mixing element than a second, opposite side thereof.

7. 7. The AFS injector of claim 6, wherein the first sides of the collars of the set of HP air jets spaced from the inlets of the first and second axially elongated mixing chambers each include an opening defined therein.

8. 3. The AFS injector of claim 2, wherein the set of HP air jets spaced apart from the inlets of the first and second axially elongated mixing chambers each has a fewer number of HP air jets than the set of HP air jets spaced apart from the inlet of the third axially elongated mixing chamber.

9. 3. The AFS injector of claim 2, wherein the set of HP air jets each includes a flared inlet having an outer radius, and the flared inlets of the HP air jets for the first and second axially elongated mixing chambers have a first outer radius that is greater than a second outer radius of the flared inlet of the HP air jet for the third axially elongated mixing chamber.

10. 3. The AFS injector of claim 2, wherein the arrangement of the set of HP air jets spaced apart from the inlets of the first and second axially elongated mixing chambers is the same, and the arrangement of the set of HP air jets spaced apart from the inlets of the third axially elongated mixing chamber is different from the arrangement of the set of HP air jets spaced apart from the inlets of the first and second axially elongated mixing chambers.

11. 2. The AFS injector of claim 1, wherein the fuel plenum extends into an upstream wall of each of the plurality of axially elongated mixing chambers, and wherein each set of fuel injectors is closer to the inlet than to the outlet of a respective axially elongated mixing chamber of the plurality of axially elongated mixing chambers.

12. 12. The AFS injector of claim 11, wherein the opposing sidewalls of the first and second axially-elongated mixing chambers include a first sidewall and an opposing second sidewall, and the set of fuel injectors defined in the first sidewall are arranged in a different manner than the set of fuel injectors defined in the second sidewall for each of the first and second axially-elongated mixing chambers.

13. 13. The AFS injector of claim 12, wherein the set of fuel injectors in the side walls of the first and second axially elongated mixing chambers are disposed in a different manner on a first side wall thereof than on an opposing second side wall thereof.

14. The AFS injector (150) of claim 1, wherein each axially elongated mixing chamber (214) has opposing semicircular ends (224).

15. The AFS injector (150) of claim 1, wherein the mixing element (210) includes a filter element (246) upstream of the set of HP air jets (240).

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