US20250198620A1

US20250198620A1 - Fuel injection assembly having partial direct injectors

Info

Publication number: US20250198620A1
Application number: US18/543,135
Authority: US
Inventors: Homayoon FEIZ; Michael John Hughes; Jonathan Dwight Berry
Original assignee: GE Infrastructure Technology LLC
Current assignee: GE Vernova Infrastructure Technology LLC
Priority date: 2023-12-18
Filing date: 2023-12-18
Publication date: 2025-06-19
Also published as: DE102024137539A1; JP2025106072A

Abstract

A fuel injection assembly for a combustor of a gas turbine includes a fuel injector configured to couple to an outer sleeve of the combustor. A boss is configured to couple to a combustion liner of the combustor at a position axially and circumferentially aligned with the fuel injector. An insert is removably coupled to the boss. The insert includes a flange portion and an annular wall portion extending from the flange portion and defining a mixing channel. The insert defines a plurality of partial direct injectors spaced apart from one another and disposed about the mixing channel. A combustor including such a fuel injection assembly is also provided.

Description

FIELD

The present disclosure relates generally to fuel injectors for gas turbine combustors and, more particularly, to fuel injectors for use with an axial fuel staging (AFS) system associated with such combustors.

BACKGROUND

Turbomachines are utilized in a variety of industries and applications for energy transfer purposes. For example, a gas turbine engine generally includes a compressor section, a combustion section, a turbine section, and an exhaust section. The compressor section progressively increases the pressure of a working fluid entering the gas turbine engine and supplies this compressed working fluid to the combustion section. The compressed working fluid and a fuel (e.g., natural gas) mix within the combustion section and burn in a combustion chamber to generate high pressure and high temperature combustion gases. The combustion gases flow from the combustion section into the turbine section where they expand to produce work. For example, expansion of the combustion gases in the turbine section may rotate a rotor shaft connected, e.g., to a generator to produce electricity. The combustion gases then exit the gas turbine engine via the exhaust section.
In some combustors, the generation of combustion gases occurs at two axially spaced stages. Such combustors are referred to herein as including an “axial fuel staging” (AFS) system, which delivers fuel and an oxidant to one or more fuel injectors downstream of the head end of the combustor. In a combustor with an AFS system, a primary fuel nozzle at an upstream end of the combustor injects fuel and air (or a fuel/air mixture) in an axial direction into a primary combustion zone, and an AFS fuel injector located at a position downstream of the primary fuel nozzle injects fuel and air (or a second fuel/air mixture) as a cross-flow into a secondary combustion zone downstream of the primary combustion zone. The cross-flow is generally transverse to the flow of combustion products from the primary combustion zone.
Traditional gas turbine engines include one or more combustors that burn a mixture of natural gas and air within the combustion chamber to generate the high pressure and temperature combustion gases. As a byproduct, oxides of nitrogen (NOx) and other pollutants are created and expelled by the exhaust section. Regulatory requirements for low emissions from gas turbines are continually growing more stringent, and environmental agencies throughout the world are now requiring even lower rates of emissions of NOx and other pollutants from both new and existing gas turbines.
Burning a blend of natural gas and high amounts of hydrogen and/or burning pure hydrogen instead of natural gas within the combustor would significantly reduce or eliminate the emission of CO₂. However, because hydrogen burning characteristics are different than those of natural gas, traditional combustion systems, including traditional AFS fuel injectors, are not capable of burning high levels of hydrogen and/or pure hydrogen without issue. For example, burning high levels of hydrogen and/or pure hydrogen within a traditional combustion system could promote flashback or flame holding conditions in which the combustion flame migrates towards the fuel being supplied by the injector, possibly causing severe damage to the injector in a relatively short amount of time.
As such, a fuel injection assembly capable of delivering alternative fuels (such as hydrogen) and air to a secondary combustion zone, without causing flame holding or flashback issues, is desired in the art.

BRIEF DESCRIPTION

Aspects and advantages of the fuel injection assemblies and methods in accordance with the present disclosure will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the technology.
In accordance with one embodiment, a fuel injection assembly for a combustor of a gas turbine includes a fuel injector configured to couple to an outer sleeve of the combustor. A boss is configured to couple to a combustion liner of the combustor at a position axially and circumferentially aligned with the fuel injector. An insert is removably coupled to the boss. The insert includes a flange portion and an annular wall portion extending from the flange portion and defining a mixing channel. The insert defines a plurality of partial direct injectors spaced apart from one another and disposed about the mixing channel.
In accordance with another embodiment, a combustor for a gas turbine engine is provided. The combustor includes at least one fuel nozzle; a combustion liner extending downstream from the fuel nozzle; an outer sleeve spaced apart from and surrounding the combustion liner such that an annulus is defined therebetween; and a fuel injection assembly disposed downstream from the at least one fuel nozzle. The fuel injection assembly includes a fuel injector configured to couple to an outer sleeve of the combustor. A boss is configured to couple to a combustion liner of the combustor at a position axially and circumferentially aligned with the fuel injector. An insert is removably coupled to the boss. The insert includes a flange portion and an annular wall portion extending from the flange portion and defining a mixing channel. The insert defines a plurality of partial direct injectors spaced apart from one another and disposed about the mixing channel.
These and other features, aspects and advantages of the present fuel injection assemblies and methods will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the technology and, together with the description, serve to explain the principles of the technology.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present fuel injection assemblies and methods, including the best mode of making and using the present systems and methods, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:

FIG. 1 is a schematic illustration of a turbomachine, in accordance with embodiments of the present disclosure;

FIG. 2 illustrates a schematic view of a combustor as may be employed in the turbomachine of FIG. 1 , in accordance with embodiments of the present disclosure;

FIG. 3 illustrates a close-up perspective view of a portion of a combustor having a fuel injection assembly, in accordance with embodiments of the present disclosure;

FIG. 4 illustrates a cross-sectional view of a fuel injection assembly attached to the combustor from along the line 4-4 shown in FIG. 3 , in accordance with embodiments of the present disclosure;

FIG. 5 illustrates a cross-sectional view of a fuel injection assembly attached to a combustor, in accordance with embodiments of the present disclosure;

FIG. 6 illustrates a cross-sectional view of a boss of the fuel injection assembly from along the line 6-6 shown in FIG. 4 or FIG. 5 , in accordance with embodiments of the present disclosure; and

FIG. 7 illustrates a cross-sectional view of a portion of a boss having a partial direct injector defined therein, in accordance with embodiments of the present disclosure.

DETAILED DESCRIPTION

Reference now will be made in detail to embodiments of the present fuel injection assemblies and methods, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation, rather than limitation, of the technology. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present technology without departing from the scope or spirit of the claimed technology. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present disclosure covers such modifications and variations as come within the scope of the appended claims and their equivalents.
The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any implementation described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other implementations. Additionally, unless specifically identified otherwise, all embodiments described herein should be considered exemplary.
The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the subject technology. As used herein, the terms “first,” “second,” and “third” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components.
The term “fluid” may refer to a gas or a liquid. The term “fluid communication” means that a fluid is capable of flowing or being conveyed between the areas specified.
As used herein, the terms “upstream” (or “forward”) and “downstream” (or “aft”) refer to the relative direction with respect to fluid flow in a fluid pathway. For example, “upstream” refers to the direction from which the fluid flows, and “downstream” refers to the direction to which the fluid flows. The term “radially” refers to the relative direction that is substantially perpendicular to an axial centerline of a particular component; the term “axially” refers to the relative direction that is substantially parallel and/or coaxially aligned to an axial centerline of a particular component; and the term “circumferentially” refers to the relative direction that extends around the axial centerline of a particular component.
Terms of approximation, such as “about,” “approximately,” “generally,” and “substantially,” are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value, or the precision of the methods or machines for constructing or manufacturing the components and/or systems. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value or the precision of the methods or machines for constructing or manufacturing the components and/or systems. For example, the approximating language may refer to being within a 1, 2, 4, 5, 10, 15, or 20 percent margin in either individual values, range(s) of values, and/or endpoints defining range(s) of values. When used in the context of an angle or direction, such terms include within ten degrees greater or less than the stated angle or direction. For example, “generally vertical” includes directions within ten degrees of vertical in any direction, e.g., clockwise or counter-clockwise.
The terms “coupled,” “fixed,” “attached to,” and the like refer to both direct coupling, fixing, or attaching, as well as indirect coupling, fixing, or attaching through one or more intermediate components or features, unless otherwise specified herein. The terms “directly coupled,” “directly fixed,” “directly attached to,” and the like indicate that a first component is joined to a second component with no intervening structures. As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having” or any other variations thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of features is not necessarily limited only to those features but may include other features not expressly listed or inherent to such process, method, article, or apparatus.
Here and throughout the specification and claims, range limitations are identified and include all the sub-ranges contained therein unless context or language indicates otherwise. For example, all ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other.
As used herein, the term “premix” may be used to describe a component, passage, or cavity upstream of a respective combustion zone within which mixing occurs. For example, “premix” may be used to describe a component, passage, or cavity in which two fluids (such as fuel and air) are mixed together prior to being ejected from such component, passage, or cavity (e.g., into a combustion zone).
Referring now to the drawings, FIG. 1 illustrates a schematic diagram of one embodiment of a turbomachine, which in the illustrated embodiment is a gas turbine engine 10. Although an industrial or land-based gas turbine is shown and described herein, the present disclosure is not limited to an industrial or land-based gas turbine engine unless otherwise specified in the claims. For example, the technology as described herein may be used in any type of turbomachine including but not limited to a steam turbine, an aircraft gas turbine, or a marine gas turbine.
As shown, gas turbine engine 10 generally includes an inlet section 12, a compressor section 14 disposed downstream of the inlet section 12, a plurality of combustors 17 (shown in FIG. 2 ) within a combustion section 16 disposed downstream of the compressor section 14, a turbine section 18 disposed downstream of the combustion section 16, and an exhaust section 20 disposed downstream of the turbine section 18. Additionally, the gas turbine engine 10 may include one or more shafts 22 coupled between the compressor section 14 and the turbine section 18. The shaft 22 may be coupled to a generator, not shown, for producing electricity.
The compressor section 14 may generally include a plurality of rotor disks 24 (one of which is shown) and a plurality of rotor blades 26 extending radially outwardly from and connected to each rotor disk 24. Each rotor disk 24 in turn may be coupled to or form a portion of the shaft 22 that extends through the compressor section 14. The compressor section 14 further includes a plurality of stationary vanes (not shown), which are arranged in stages with the rotor blades 26 and which direct the flow against the rotor blades 26.
The turbine section 18 may generally include a plurality of rotor disks 28 (one of which is shown) and a plurality of rotor blades 30 extending radially outwardly from and being interconnected to each rotor disk 28. Each rotor disk 28 in turn may be coupled to or form a portion of the shaft 22 that extends through the turbine section 18. The turbine section 18 further includes an outer casing 31 that circumferentially surrounds the portion of the shaft 22 and the rotor blades 30, thereby at least partially defining a hot gas path 32 through the turbine section 18. The turbine section 18 further includes a plurality of stationary vanes (not shown), which are arranged in stages with the rotor blades 30 and which direct the flow against the rotor blades 30.
During operation, a working fluid such as air flows through the inlet section 12 and into the compressor section 14 where the air is progressively compressed by multiple compressor stages of rotating blades and stationary vanes, thus providing pressurized air 15 to the combustors 17 of the combustion section 16. The pressurized air 15 is mixed with fuel and burned within each combustor 17 to produce combustion gases 34. The combustion gases 34 flow through the hot gas path 32 from the combustion section 16 into the turbine section 18, in which energy (kinetic and/or thermal) is transferred from the combustion gases 34 to the rotor blades 30, causing the shaft 22 to rotate. The mechanical rotational energy may then be used to power the compressor section 14 and/or to generate electricity. The combustion gases 34 exiting the turbine section 18 may then be exhausted from the gas turbine engine 10 via the exhaust section 20.
FIG. 2 is a schematic representation of a combustor 17, as may be included in a can annular combustion system 16 for the gas turbine 10. In a can annular combustion system, a plurality of combustors 17 (e.g., 8, 10, 12, 14, 16, or more) are positioned in an annular array about the shaft 22 that connects the compressor section 14 to the turbine section 18.
As shown in FIG. 2 , the combustor 17 may define an axial direction A that extends along an axial centerline 170. The combustor may also define a circumferential direction C which extends around the axial direction A and the axial centerline 170. The combustor 17 may further define a radial direction R perpendicular to the axial direction A and the axial centerline 170.
As shown in FIG. 2 , the combustor 17 includes a combustion liner 46 that defines a combustion chamber 70. The combustion liner 46 may be positioned within (i.e., circumferentially surrounded by) an outer sleeve 48, such that an annulus 47 is formed therebetween. The combustion liner 46 may contain and convey combustion gases to the turbine section 18. The combustion liner 46 defines the combustion chamber 70 within which combustion occurs. As shown in FIG. 2 , the combustion liner 46 may extend between fuel nozzles 40 and an aft frame 118. The combustion liner 46 may have a generally cylindrical liner portion and a tapered transition portion that is separate from the generally cylindrical liner portion, as in many conventional combustion systems. Alternately, the combustion liner 46 may have a unified body (or “unibody”) construction, in which the generally cylindrical portion and the tapered portion are integrated with one another. Thus, any discussion of the combustion liner 46 herein is intended to encompass both conventional combustion systems having a separate liner and transition piece and those combustion systems having a unibody liner. Moreover, the present disclosure is equally applicable to those combustion systems in which the transition piece and the stage one nozzle of the turbine section 18 are integrated into a single unit, sometimes referred to as a “transition nozzle” or an “integrated exit piece.”
FIG. 2 illustrates a combustor 17 having both fuel nozzles 40 and one or more fuel injection assemblies 80 (also referred to as an axial fuel staging (AFS) system), as discussed further herein. The at least one fuel nozzle 40 may be positioned at the forward end of the combustor 17. Fuel may be directed through fuel supply conduits 38, which extend through an end cover 42, and into the fuel nozzles 40. The fuel nozzles 40 convey the fuel and compressed air 15 into a primary combustion zone 72, where combustion occurs. In some embodiments, the fuel and compressed air 15 are combined as a mixture prior to reaching the primary combustion zone 72.
The combustion liner 46 may be surrounded by an outer sleeve 48, which is spaced radially outward of the combustion liner 46 to define an annulus 47 through which compressed air 15 flows to a head end of the combustor 17. For example, compressed air 15 may enter the annulus 47 through the outer sleeve 48 (e.g., through impingement holes proximate the aft frame 118) and travel towards the end cover 42, such that the compressed air 15 within the annulus 47 flows opposite the direction of combustion gases 172 (34 in FIG. 1 ) within the combustion liner 46. Heat is transferred convectively from the combustion liner 46 to the compressed air 15, thus cooling the combustion liner 46 and warming the compressed air 15.
In some embodiments, the outer sleeve 48 may include a flow sleeve and an impingement sleeve coupled to one another. The flow sleeve may be disposed at the forward end, and the impingement sleeve may be disposed at the aft end. Alternately, the outer sleeve 48 may have a unified body (or “unisleeve”) construction, in which the flow sleeve and the impingement sleeve are integrated with one another in the axial direction. As before, any discussion of the outer sleeve 48 herein is intended to encompass both conventional combustion systems having a separate flow sleeve and impingement sleeve and combustion systems having a unisleeve outer sleeve.
The forward casing 50 and the end cover 42 of the combustor 17 define the head end air plenum 122, which includes the one or more fuel nozzles 40. The fuel nozzles 40 may be any type of fuel nozzle, such as bundled tube fuel nozzles or swirler nozzles (often referred to as “swozzles”). The fuel nozzles 40 may be positioned within the head end air plenum 122 defined at least partially by the forward casing 50. In many embodiments, the fuel nozzles 40 may extend from the end cover 42. For example, each fuel nozzle 40 may be coupled to an aft surface of the end cover 42 via a flange (not shown). As shown in FIG. 2 , the at least one fuel nozzle 40 may be partially surrounded by the combustion liner 46. The aft, or downstream ends, of the fuel nozzles 40 extend through or collectively define a cap plate 44 that defines the upstream end of the combustion chamber 70.
The fuel nozzles 40 may be in fluid communication with a first fuel supply 150 configured to supply a first fuel 158 to the fuel nozzles 40. In many embodiments, the first fuel 158 may be a fuel mixture containing natural gas (such as methane, ethane, propane, or other suitable natural gas) and/or hydrogen. In other embodiments, the first fuel 158 may be pure natural gas or pure hydrogen (e.g., 100% hydrogen, which may or may not contain some amount of contaminants), such that the first fuel is not a mixture of multiple fuels. In exemplary embodiments, the first fuel 158 and compressed air 15 may mix together within the fuel nozzles 40 to form a first mixture of compressed air 15 and the first fuel 158 before being ejected (or injected) by the fuel nozzles 40 into the primary combustion zone 72.
The forward casing 50 may be fluidly and mechanically connected to a compressor discharge casing 60, which defines a high-pressure plenum 66 around the combustion liner 46 and the outer sleeve 48. Compressed air 15 from the compressor section 14 travels through the high-pressure plenum 66 and enters the combustor 17 via apertures (not shown) in the downstream end of the outer sleeve 48 (as indicated by arrows near an aft frame 118). Compressed air travels upstream through the annulus 47 and is turned by the end cover 42 to enter the fuel nozzles 40 and to cool the head end. In particular, compressed air 15 flows from high-pressure plenum 66 into the annulus 47 at an aft end of the combustor 17, via openings defined in the outer sleeve 48. The compressed air 15 travels upstream from the aft end of the combustor 17 to the head end air plenum 122, where the compressed air 15 reverses direction and enters the fuel nozzles 40.
In the exemplary embodiment, the fuel injection assembly 80 is provided to deliver a second fuel/air mixture to a secondary combustion zone 74 downstream from the primary combustion zone 72. For example, a second flow of fuel and air may be introduced by one or more fuel injectors 200 to the secondary combustion zone 74.
The primary combustion zone 72 and the secondary combustion zone 74 may each be portions of the combustion chamber 70 and therefore may be defined by the combustion liner 46. For example, the primary combustion zone 72 may be defined from an outlet of the fuel nozzles 40 to the fuel injector 200, and the secondary combustion zone 74 may be defined from the fuel injector 200 to the aft frame 118. In this arrangement, the forwardmost boundary of the fuel injector 200 may define the end of the primary combustion zone 72 and the beginning of the secondary combustion zone 74 (e.g., at an axial location where a second flow of fuel and air are introduced).
Such a combustion system having axially separated combustion zones is described as an “axial fuel staging” (AFS) system. The fuel injection assemblies 80 may be circumferentially spaced apart from one another on the outer sleeve 48 (e.g., equally spaced apart in some embodiments). In many embodiments, the combustor 17 may include four fuel injection assemblies 80 circumferentially spaced apart from one another and configured to inject a second mixture of fuel and air into a secondary combustion zone 74 via the fuel injector 200. In other embodiments, the combustor 17 may include any number of fuel injection assemblies 80 (e.g., 1, 2, 3, or up to 10).
As shown in FIG. 2 , each fuel injection assembly 80 may include a fuel injector 200 and a boss 300 circumferentially and axially aligned with the fuel injector 200. The fuel injector 200 may be coupled to the outer sleeve 48, and the boss 300 may be coupled to the combustion liner 46 and disposed within the annulus 47. Particularly, the fuel injector 200 may couple to a radially outer surface of the outer sleeve 48, and the boss 300 may couple to a radially outer surface of the combustion liner 46. The boss 300 may be radially spaced apart from the fuel injector 200. As discussed in more detail below, the boss 300 may be fluidly coupled to the annulus 47, and the fuel injector 200 may be fluidly coupled to the high-pressure plenum 66.
A fuel supply conduit 102 may fluidly couple to the fuel injector 200. The fuel injector 200 may be in fluid communication with a second fuel supply 152 configured to supply a second fuel 160 to the fuel injector 200 via the fuel supply conduit 102. The second fuel supply 152 may be the same as or different from the first fuel supply 150, such that the fuel injector 200 may be supplied with the same fuel or a different fuel than the fuel nozzles 40. In many embodiments, the second fuel 160 may be a fuel mixture containing natural gas (such as methane, ethane, propane, or other suitable natural gas) and/or hydrogen. In other embodiments, the second fuel 160 may be pure natural gas or pure hydrogen (e.g., 100% hydrogen, which may or may not contain some amount of contaminants), such that the first fuel is not a mixture of multiple fuels. In exemplary embodiments, the second fuel 160 and compressed air 15 may mix together within the fuel injector 200 to form a mixture of compressed air 15 and the second fuel 160 before being injected into the boss 300, in which the mixture is further mixed (or diluted) with air from the annulus 47 prior to being injected into the secondary combustion zone 74.
Referring now to FIG. 3 , a close-up perspective view of a portion of the combustor 17 and the fuel injection assembly 80 is illustrated in accordance with embodiments of the present disclosure. As shown, the fuel injection assembly 80 may include the fuel injector 200 coupled to the outer sleeve 48. Particularly, the fuel injector 200 may couple to a radially outer or exterior surface of the outer sleeve 48. For example, the fuel injector 200 may include a main body 204 and an injector flange 206 extending outwardly from the main body 204. One or more fasteners 208 (such as threaded fasteners or other suitable fasteners) may extend through the injector flange 206 and into the outer sleeve 48 to couple the fuel injector 200 to the outer sleeve 48. One or more of the fasteners 208 may extend through the injector flange 206 and into the boss 300.
In many embodiments, the main body 204 of the fuel injector 200 may extend along an axial centerline 252 between a forward end wall 210 and an aft end wall 212. In many embodiments, the axial centerline 252 of the fuel injector 200 may generally align with the axial direction A of the combustor 17 (or may be sightly angled relative to the axial direction A of the combustor 17). Side walls 214 may extend generally axially between the forward end wall 210 and the aft end wall 212 with respect to the axial centerline 252 of the fuel injector 200. In many embodiments, the forward end wall 210 and the aft end wall 212 may each include a straight portion 216 and slanted portions 218. The straight portion 216 is oriented generally perpendicularly to the axial centerline 252 and slanted portions 218 each extend between the straight portion 216 and a respective side wall 214.
A conduit fitting 215 may extend outwardly from the forward end wall 210 of the main body 204 along the axial centerline 252. Particularly, the conduit fitting 215 may extend outwardly along the axial centerline 252 of the straight portion 216 of the forward end wall 210. The conduit fitting 215 may be fluidly coupled to the fuel supply conduit 102 such that it functions to receive a flow of fuel from the fuel supply conduit 102. The conduit fitting 215 may have any suitable size and shape and may be formed integrally with, or coupled to, any suitable portion(s) of the fuel injector 200 that enables the conduit fitting 215 to function as described herein.
In exemplary embodiments, the fuel injection assembly 80 may further include a debris filter 400 coupled to the fuel injector 200. The debris filter 400 may surround the fuel injector 200 such that all air entering the fuel injector 200 from high-pressure plenum 66 passes through the debris filter 400. For example, the debris filter 400 may extend between the forward end wall 210, the aft end wall 212, and the side walls 214. The debris filter 400 may include a plurality of holes 402 (FIGS. 4 and 5 ) defined therethrough that allow for fluid communication between the high-pressure plenum 66 and the fuel injector 200. The plurality of holes 402 may be sized to prevent debris from entering the fuel injector 200, which advantageously prevents the premix tubes 226 and their respective fuel ports 240 from being blocked. Additionally, the debris filter 400 may function as an inlet flow conditioner. That is, the debris filter 400 may function to reduce the non-uniformity of the compressed air from the high-pressure plenum 66 before it enters the fuel injector 200.
FIG. 4 illustrates a cross-sectional view of the combustor 17 from along the line 4-4 shown in FIG. 3 , in accordance with embodiments of the present disclosure. FIG. 5 illustrates a cross sectional view of another embodiment of the boss 300 attached to the combustor 17. As shown in FIGS. 4 and 5 , the combustor 17 may include a combustion liner 46 defining a combustion chamber 70, which includes the secondary combustion zone 74. An outer sleeve 48 may be radially spaced apart from the combustion liner 46, such that an annulus 47 is defined between the outer sleeve 48 and the combustion liner 46. The combustor 17, including the fuel injection assembly 80, may be disposed within the high-pressure plenum 66 (FIG. 2 ). The annulus 47 may be fluidly coupled to the high-pressure plenum 66 via one or more impingement apertures 90. The impingement apertures 90 may be oriented and sized to direct high-pressure air 92 from the high-pressure plenum 66 to impinge upon an outer surface of the combustion liner 46. During the impingement process, the high-pressure air 92 experiences a pressure drop by passing through impingement apertures 90 to become low-pressure air 94 and undergoes an energy transfer by removing heat from the combustion liner 46 (i.e., the low-pressure air 94 picks up heat). The low-pressure air 94 may be supplied to the fuel injector 200, as discussed below.
The fuel injection assembly 80 includes the fuel injector 200, the boss 300, and the debris filter 400. The fuel injection assembly 80 may also include an insert 600 removably coupled to the boss 300. The fuel injector 200 may be coupled (e.g., via one or more fasteners 208) to the outer sleeve 48, and the fuel injector 200 may extend radially outward from the outer sleeve 48 into the high-pressure plenum 66. The boss 300 may be fixedly coupled (e.g., via an annular weld joint 302) to the combustion liner 46 and disposed within the annulus 47. The insert 600 may removably couple to the boss 300 in any manner, such as via one or more fasteners, a friction fit, or other means. The insert 600 may be inserted into an opening defined by the boss 300. In some embodiments, the insert 600 and the boss 300 may be integrally formed as a single component (e.g., a monolithic component). However, forming the boss 300 and the insert 600 separately advantageously allows for the insert 600 to be easily removed, repaired, and/or replaced without causing damage to the combustor 17 or the fuel injection assembly 80.
In many embodiments, the insert 600 may include a flange portion 304 and an annular wall portion 306. The annular wall portion 306 may define a mixing channel 312 that extends along a center axis 350. The center axis 350 may be disposed in the center of the mixing channel 312 and may be oriented generally radially (e.g., generally parallel to the radial direction R of the combustor 17). The flange portion 304 may extend generally axially and circumferentially, and the annular wall portion 306 may extend generally radially from the flange portion 304 (i.e., generally perpendicular from the flange portion 304) to a terminal end 313. The flange portion 304 may be fixedly coupled (e.g., via the annular weld joint 302) to the combustion liner 46.
The flange portion 304 may partially define the combustion chamber 70. For example, the flange portion 304 may include a radially outer surface 305 and a radially inner surface 309. The radially inner surface 309 may align with an interior surface 49 of the combustion liner 46, such that the flange portion 304 partially defines the combustion chamber 70 (e.g., the exhaust gases may contact the radially inner surface 309 of the flange portion 304). The flange portion 304 may extend outwardly from the annular wall portion 306 to an annular edge 310. The annular edge 310 may be the terminal end of the flange portion 304. In some embodiments, the annular edge 310 may be welded to the combustion liner 46 (e.g., via the annular weld joint 302). Alternately, the flange portion 304 may be removably coupled to the boss 300, e.g., by fasteners (such as bolts), a friction fit, interlocking features, or the like. A radial thickness of the flange portion 304 may be greater than a radial thickness of the combustion liner 46, such that the radially outer surface 305 of the flange portion 304 is radially spaced apart from a radially outer surface of the combustion liner 46.
The insert 600 may define the mixing channel 312, which may be generally rectangularly shaped (or stadium shaped as shown in FIG. 6 ). That is, side walls of the may be longer than the end walls, such that the mixing channel 312 is elongated in the axial direction A, which advantageously allows the fuel injection assembly 80 to introduce a larger amount of fuel/air without impeding a large portion of the annulus 47.
As shown in FIGS. 4 and 5 , the fuel injector 200 may further include a radially outer wall 220 and a radially inner wall 222 that at least partially define a fuel plenum 224. The radially outer wall 220 and the radially inner wall 222 may extend between the forward end wall 210 (FIG. 3 ), the aft end wall 212 (FIG. 3 ), and the side walls 214 of the fuel injector 200. In this way, the fuel plenum 224 may be defined collectively by the radially outer wall 220, the radially inner wall 222, the forward end wall 210, the aft end wall 212, and the side walls 214. The fuel plenum 224 may receive a flow of fuel via the conduit fitting 215 (FIG. 3 ).
In exemplary embodiments, the fuel injector 200 may further include a plurality of premix tubes 226 each extending along an injection axis 228 from an inlet end 230 on the radially outer wall 220, through the fuel plenum 224 and the radially inner wall 222, to an outlet end 232. The premix tubes 226 may extend radially inwardly beyond the radially inner wall 222 to the respective outlet ends 232, as shown, or the outlet ends 232 of some or all of the premix tubes 226 may be flush with the radially inner wall. Each of the premix tubes 226 may define a premix passage 234 extending between an inlet at the inlet end 230 to an outlet at the outlet end 232. In many embodiments, the injection axis 228 of each premix tube 226 may be the centerline of the premix tube 226. In many embodiments, each premix tube 226 of the plurality of premix tubes 226 may include one or more fuel ports 240 that fluidly couple the fuel plenum 224 to the premix passage 234. For example, as shown in FIG. 4 , each premix passage 234 may include two fuel ports 240 (e.g., a forward fuel port and an aft fuel port) diametrically opposed to one another, which advantageously provides for uniform fuel distribution within the premix passage 234.
In various embodiments, the plurality of premix tubes 226 may be fluidly coupled to a high-pressure air source (such as the high-pressure plenum 66 shown in FIG. 5 ). For example, the premix passages 234 may receive a flow of high-pressure air 92 (compressed air 15 in FIG. 2 ) from the high-pressure plenum 66 via an inlet at the inlet end 230. The mixing channel 312 may be fluidly coupled to a low pressure air source (e.g., the annulus 47). The mixing channel 312 may receive a mixture of high-pressure air 92 and fuel from each of the premix tubes 226, which are angled to direct flow into the mixing channel 312. Additionally, the mixing channel 312 may receive low pressure air 94 from the annulus 47.
The insert 600 may be radially spaced apart from the fuel injector 200, such that a radial gap is defined between the insert 600 and the fuel injector 200. A multi-fluid interaction region 600 may be defined between the outlets at the outlet ends 232 of the premix tubes 226 and the inlet of the mixing channel 312. For example, the multi-fluid interaction region 600 may receive a mixture of high-pressure air 92 and fuel from each of the premix tubes 226. Additionally, the multi-fluid interaction region 600 may receive low-pressure air 94 from the annulus 47, which advantageously further mixes the fuel/air within the mixing channel 312 and dilutes the fuel closer to a desired fuel/air ratio prior to delivering the fuel/air to the combustion chamber 70.
As shown in FIGS. 4 and 5 , the injection axis 228 of each premix tube 226 may be slanted towards the center axis 350 of the mixing channel 312. For example, each premix tube 226 may be oblique relative to the radial direction R, such that the injection axis 228 is angled relative to the generally radially oriented center axis 350 of the mixing channel 312. In this way, the outlet end 232 of each premix tube 226 may be closer to the center axis 350 of the mixing channel 312 than the inlet end 230. The outer premix tubes 226 (e.g., the premix tubes further away from the injection axis 350) may be slanted more than the inner premix tubes 226 (e.g., the premix tubes closer to the injection axis 350).
As shown in FIGS. 4 through 6 , the insert 600 may define a plurality of partial direct injectors 500 (or lean direct injectors) spaced apart from one another and disposed about (or collectively surrounding) the mixing channel 312. “Partial direct injector” may refer to an injector that injects air and fuel (e.g., partial air/fuel) directly into the combustion chamber 70 without complete mixing.
Each partial direct injector 500 may include a localized mixing chamber for fuel and air, which are injected into the combustion chamber 70 about the mixing channel 312. The plurality of partial direct injectors 500 may only inject a minority portion of the fuel/air provided to the fuel injection assembly 80. For example, between about 60% and about 95% of the fuel for the fuel injection assembly 80 may be provided to the fuel injector 200 (e.g., for the fuel plenum 224), and the remainder (e.g., between about 5% and about 40%) of the fuel to the fuel injection assembly 80 may be provided to the plurality of partial direct injectors 500. As such, the plurality of partial direct injectors 500 may collectively define a total volume that is between about 5% and about 30% of a volume of the mixing channel 312 (or such as between about 10% and about 20%).
As shown in FIG. 4 , at least one partial direct injector 500 of the plurality of partial direct injectors 500 may be defined in the flange portion 304 of the insert 600. For example, the at least one partial direct injector 500 may be defined entirely in the flange portion 304 of the insert 600. In some embodiments, all of the partial direct injectors 500 may be defined in the flange portion 304 of the insert 600. The partial direct injectors 500 may be defined in the flange portion 304 between the radially outer surface 305 and the radially inner surface 309. Particularly, each partial direct injector 500 may extend within the flange portion 304 from an outlet 502 defined in the radially inner surface 309 to a fuel injection orifice 504 defined radially inward of the radially outer surface 305.
In other embodiments, as shown in FIG. 5 , at least one partial direct injector 500 of the plurality of partial direct injectors 500 may be defined in the annular wall portion 306 of the insert 600. For example, the at least one partial direct injector 500 may be defined entirely in the annular wall portion 306 of the insert 600. In some embodiments, all of the partial direct injectors 500 may be defined in the annular wall portion 306 of the insert 600. The partial direct injectors 500 may be defined in the annular wall portion 306 between the terminal end 313 of the annular wall portion 306 and the radially inner surface 309. Particularly, each partial direct injector 500 may extend within the annular wall portion 306 from an outlet 502 defined in the radially inner surface 309 to a fuel injection orifice 504 defined radially inward of the radially outer surface 305.
As shown in FIGS. 4 and 5 , each partial direct injector 500 may extend to an outlet 502 on a radially inner surface 309 of the insert 600. Additionally, each partial direct injector 500 may be defined in the insert 600 by a boundary surface 518. The boundary surface 518 may include a cylindrical portion 520 and a tapering portion 522. The cylindrical portion 520 may extend from the outlet 502 to the tapering portion 522, and the tapering portion 522 may extend from the cylindrical portion to the fuel injection orifice 504. The tapering portion 522 may be frustoconically shaped. That is, the tapering portion 522 may converge in diameter as the tapering portion 522 extends radially from the cylindrical portion 520 to the fuel injection orifice 504.
In exemplary embodiments, the insert 600 may further define an air supply circuit 506 and a fuel supply circuit 508 each fluidly coupled to the plurality of partial direct injectors 500. The air supply circuit 506 and the fuel supply circuit 508 may be separately fluidly coupled the plurality of direct injectors, such that the air supply circuit 506 and the fuel supply circuit 508 are fluidly separate but each provide fluid to the partial direct injectors 500 for mixing/injection into the combustion chamber 70. The air supply circuit 506 may be fluidly coupled to an air supply. In exemplary embodiments, as shown, the air supply may be the annulus 47. In other embodiments (not shown), the air supply may be the high-pressure plenum 66 or another air source. Similarly, the fuel supply circuit 508 may be fluidly coupled to a fuel supply 510. In some embodiments, the fuel supply circuit 508 may be fluidly coupled to the fuel injector 200 (e.g., the fuel plenum 224 and/or the conduit fitting 215 such that fuel is provided to both the fuel injector 200 and the partial direct injectors 500). In other embodiments, the fuel supply 510 may be a standalone fuel supply 510 independently fluidly coupled to the fuel supply circuit 508 in the insert 600.
As shown, the air supply circuit 506 includes an air inlet passage 512, an air plenum 514, and an air outlet passage 516. As shown, in some embodiments, the air inlet passage 512 may extend from an inlet on the annular edge 310 (FIG. 6 ) and/or an inlet on the radially outer surface 305 (FIGS. 4 and 5 ) to the air plenum 514. The air inlet passage 512 may be angled, slanted, and/or sloped relative to the radial direction R. The air plenum 514 may be annular in many embodiments (as shown in FIG. 6 ) and may be fluidly connected to the air inlet passage 512 (e.g., directly fluidly connected).
The fuel supply circuit 508 includes one or more fuel inlet passages 536. Each fuel inlet passage 536 of the one or more fuel inlet passages 536 may be fluidly coupled to a respective partial direct injector 500 of the plurality of partial direct injectors. Particularly, each fuel inlet passage 536 of the one or more fuel inlet passages may extend from the terminal end 313 of the annular wall portion 306 to the fuel injection orifice 504 of a respective partial direct injector 500. Each fuel inlet passage 536 may extend generally radially within the insert 600 immediately upstream of the fuel injection orifice 504 of the respective partial direct injector 500 to which the fuel inlet passage 536 is fluidly connected, such that the fuel inlet passage 536 introduces (or directs) fuel into the partial direct injector 500 along the radial direction R.
Particularly, as shown in FIG. 4 , the fuel inlet passage 536 may include a first portion 524, a second portion 526 (which may extend generally perpendicularly to the first portion), and a third portion 528. The first portion 524 of the fuel inlet passage 536 may extend generally radially from the terminal end 313 to the second portion 526 of the fuel inlet passage 536. The second portion 526 of the fuel inlet passage 536 may extend from the first portion 524 to the third portion 528. The second portion 526 may be generally perpendicular to one or both of the first portion 524 and the third portion 528, or the second portion 526 may be angled (i.e., at a non-perpendicular angle) relative to the first portion 524. The third portion 528 may extend generally radially from the second portion 526 to the fuel injection orifice 504 of the partial direct injector 500. In other embodiments, as shown in FIG. 5 , the fuel inlet passage 536 may extend entirely radially from the terminal end 313 to the fuel injection orifice 504 of the partial direct injector 500.
Referring now to FIG. 6 , a cross-sectional view of an insert 600, as taken from along the line 6-6 shown in FIG. 4 , is illustrated in accordance with embodiments of the present disclosure. As shown, the insert 600 may extend between a forward end 301 and an aft end 303. The insert 600 may define the mixing channel 312, which may be generally shaped as a geometric stadium (e.g., a rectangle having rounded ends or a rectangle having rounded corners). The plurality of partial direct injectors 500 may be defined in the insert 600 and positioned about the mixing channel 312, such that the plurality of partial direct injectors 500 collectively surrounds the mixing channel 312. The plurality of partial direct injectors 500 may be positioned closer to the mixing channel than the annular edge 310 of the boss.
As shown, the air supply circuit 506 includes one or more forward air inlet passages 512A, one or more aft air inlet passages 512B, an air plenum 514, and a plurality of air outlet passages 516 each fluidly coupled to a respective partial direct injector 500. As shown, in some embodiments, the air inlet passages 512A, 512B may each extend from an inlet on the annular edge 310 to the air plenum 514. The air plenum 514 may be annular and may surround the mixing channel 312. In exemplary embodiments, at least two air outlet passages 516 may fluidly couple to each partial direct injector 500 of the plurality of partial direct injectors 500. For embodiments having two air outlet passages 516 fluidly connected to a single partial direct injector 500, the two air outlet passages 516 may be diametrically opposed to one another (e.g., 180° apart) about the partial direct injector 500. In embodiments having more than two air outlet passages 516 connected to a single partial direct injector 500 (not shown), the air outlet passages 516 may be equally spaced apart about the partial direct injector 500. This advantageously distributes the air uniformly within the partial direct injector 500 for better mixing with fuel.
Referring now to FIG. 7 , a cross sectional view of the insert 600, from along the line 7-7 in FIG. 6 , is illustrated in accordance with embodiments of the present disclosure. As shown, the partial direct injector 500 may be defined in the insert 600 by a boundary surface 518. The partial direct injector 500 may extend radially between an outlet 502 on the radially inner surface 309 of the insert 600 and a fuel injection orifice 504 (or inlet). The boundary surface 518 may include a first cylindrical portion 520, a tapering portion 522, and, optionally, a second cylindrical portion 530. The first cylindrical portion 520 may define a first diameter, and the second cylindrical portion 530 may define a second diameter. The second diameter is smaller than the first diameter. The second cylindrical portion 530, where present, may extend radially from the fuel injection orifice 504 to the tapering portion 522 and may be used to facilitate additive manufacturing of the insert 600 (or the boss 300, in those instances where the boss 300 includes the partial direct injectors 500). The tapering portion 522 may increase in diameter as the tapering portion 522 extends radially from the second cylindrical portion 530 to the first cylindrical portion 520. The tapering portion 522 may be frustoconically shaped.
As shown, an air outlet passage 516 of the air supply circuit 506 may extend to the tapering portion 532 of the boundary surface 518. Particularly, two air outlet passages 516 may extend to the tapering portion 532 of the boundary surface 518. The two air outlet passages 516 may be diametrically opposed to one another (e.g., 180° apart) about the partial direct injector 500 to uniformly introduce air into the partial direct injector 500. The fuel inlet passage 536 of the fuel supply circuit 508 may extend to the partial direct injector 500 generally perpendicularly to the air outlet passage(s) 516. This may advantageously provide a cross flow between the air/fuel to increase mixing, thereby increasing the efficiency of the combustion process within the combustion chamber 70. Particularly, the fuel inlet passage 536 may extend to the fuel injection orifice 504 (and/or the second cylindrical portion 530) to fluidly couple to the partial direct injector 500.
The partial direct injectors 500 advantageously allow the combustor 17 to operate on high amounts of hydrogen without causing flameholding issues within the axial fuel staging injectors 80. For example, the fuel provided to the fuel injection assembly 80 may be partitioned between the fuel injector 200 and the partial direct injectors 500, which allows for more localized mixing and efficient combustion.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention 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 include 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.
Further aspects of the invention are provided by the subject matter of the following clauses:
According to a first aspect, a fuel injection assembly for a combustor of a gas turbine is provided, the fuel injection assembly comprising: a fuel injector configured to couple to an outer sleeve of the combustor; a boss configured to couple to a combustion liner of the combustor at a position axially and circumferentially aligned with the fuel injector; and an insert removably coupled to the boss, the insert comprising a flange portion, an annular wall portion extending from the flange portion, the annular wall portion defining a mixing channel, wherein the insert defines a plurality of partial direct injectors spaced apart from one another and disposed about the mixing channel.
The fuel injection assembly as in the previous clause, wherein at least one partial direct injector of the plurality of partial direct injectors is defined in the flange portion of the insert.
The fuel injection assembly as in any of the previous clauses, wherein at least one partial direct injector of the plurality of partial direct injectors is defined in the annular wall portion of the insert.
The fuel injection assembly as in any of the previous clauses, wherein the insert defines an air supply circuit and a fuel supply circuit each fluidly coupled to the plurality of partial direct injectors.
The fuel injection assembly as in any of the previous clauses, wherein the air supply circuit includes an air inlet passage, an air plenum, and a plurality of air outlet passages each extending from the air plenum to a respective partial direct injector of the plurality of partial direct injectors.
The fuel injection assembly as in any of the previous clauses, wherein the air plenum is annular.
The fuel injection assembly as in any of the previous clauses, wherein each partial direct injector extends to an outlet on a radially inner surface of the flange portion of the insert.
The fuel injection assembly as in any of the previous clauses, wherein each partial direct injector is defined in the insert by a boundary surface, and wherein the boundary surface includes a cylindrical portion and a tapering portion.
The fuel injection assembly as in any of the previous clauses, wherein an air outlet passage of an air supply circuit extends to the tapering portion of the boundary surface.
The fuel injection assembly as in any of the previous clauses, wherein a fuel inlet passage of a fuel supply circuit extends to the partial direct injector generally perpendicularly to the air outlet passage.
According to another aspect of the present disclosure, a combustor is provided, which comprises: at least one fuel nozzle; a combustion liner extending downstream from the fuel nozzle; an outer sleeve spaced apart from and surrounding the combustion liner such that an annulus is defined therebetween; and a fuel injection assembly disposed downstream from the at least one fuel nozzle, the fuel injection assembly comprising: a fuel injector coupled to the outer sleeve of the combustor; a boss coupled to the combustion liner of the combustor, the boss being axially and circumferentially aligned with the fuel injector; and an insert removably coupled to the boss, the insert comprising a flange portion, an annular wall portion extending from the flange portion, the annular wall portion defining a mixing channel, wherein the insert defines a plurality of partial direct injectors spaced apart from one another and disposed about the mixing channel.
The combustor as in the preceding clause, wherein at least one partial direct injector of the plurality of partial direct injectors is defined in the flange portion of the insert.
The combustor as in any of the preceding clauses, wherein at least one partial direct injector of the plurality of partial direct injectors is defined in the annular wall portion of the insert.
The combustor as in any of the preceding clauses, wherein the insert defines an air supply circuit and a fuel supply circuit each fluidly coupled to the plurality of partial direct injectors.
The combustor as in any of the preceding clauses, wherein the air supply circuit includes an air inlet passage, an air plenum, and a plurality of air outlet passages each extending from the air plenum to a respective partial direct injector of the plurality of partial direct injectors.
The combustor as in any of the preceding clauses, wherein the air plenum is annular.
The combustor as in any of the preceding clauses, wherein each partial direct injector extends to an outlet on a radially inner surface of the flange portion of the insert.
The combustor as in any of the preceding clauses, wherein each partial direct injector is defined in the insert by a boundary surface, and wherein the boundary surface includes a cylindrical portion and a tapering portion.
The combustor as in any of the preceding clauses, wherein an air outlet passage of an air supply circuit extends to the tapering portion of the boundary surface.
The combustor as in any of the preceding clauses, wherein a fuel inlet passage of a fuel supply circuit extends to the partial direct injector generally perpendicularly to the air outlet passage.

Claims

What is claimed is:

1. A fuel injection assembly for a combustor of a gas turbine, the fuel injection assembly comprising:

a fuel injector configured to couple to an outer sleeve of the combustor;

a boss configured to couple to a combustion liner of the combustor at a position axially and circumferentially aligned with the fuel injector; and

an insert removably coupled to the boss, the insert comprising a flange portion, an annular wall portion extending from the flange portion, the annular wall portion defining a mixing channel, wherein the insert defines a plurality of partial direct injectors spaced apart from one another and disposed about the mixing channel.

2. The fuel injection assembly as in claim 1, wherein at least one partial direct injector of the plurality of partial direct injectors is defined in the flange portion of the insert.

3. The fuel injection assembly as in claim 1, wherein at least one partial direct injector of the plurality of partial direct injectors is defined in the annular wall portion of the insert.

4. The fuel injection assembly as in claim 1, wherein the insert defines an air supply circuit and a fuel supply circuit each fluidly coupled to the plurality of partial direct injectors.

5. The fuel injection assembly as in claim 4, wherein the air supply circuit includes an air inlet passage, an air plenum, and a plurality of air outlet passages each extending from the air plenum to a respective partial direct injector of the plurality of partial direct injectors.

6. The fuel injection assembly as in claim 5, wherein the air plenum is annular.

7. The fuel injection assembly as in claim 1, wherein each partial direct injector extends to an outlet on a radially inner surface of the flange portion of the insert.

8. The fuel injection assembly as in claim 1, wherein each partial direct injector is defined in the insert by a boundary surface, and wherein the boundary surface includes a cylindrical portion and a tapering portion.

9. The fuel injection assembly as in claim 8, wherein an air outlet passage of an air supply circuit extends to the tapering portion of the boundary surface.

10. The fuel injection assembly as in claim 9, wherein a fuel inlet passage of a fuel supply circuit extends to the partial direct injector generally perpendicularly to the air outlet passage.

11. A combustor comprising:

at least one fuel nozzle;

a combustion liner extending downstream from the fuel nozzle;

an outer sleeve spaced apart from and surrounding the combustion liner such that an annulus is defined therebetween; and

a fuel injection assembly disposed downstream from the at least one fuel nozzle, the fuel injection assembly comprising:

a fuel injector coupled to the outer sleeve of the combustor;

a boss coupled to the combustion liner of the combustor, the boss being axially and circumferentially aligned with the fuel injector; and

12. The combustor as in claim 11, wherein at least one partial direct injector of the plurality of partial direct injectors is defined in the flange portion of the insert.

13. The combustor as in claim 11, wherein at least one partial direct injector of the plurality of partial direct injectors is defined in the annular wall portion of the insert.

14. The combustor as in claim 11, wherein the insert defines an air supply circuit and a fuel supply circuit each fluidly coupled to the plurality of partial direct injectors.

15. The combustor as in claim 14, wherein the air supply circuit includes an air inlet passage, an air plenum, and a plurality of air outlet passages each extending from the air plenum to a respective partial direct injector of the plurality of partial direct injectors.

16. The combustor as in claim 15, wherein the air plenum is annular.

17. The combustor as in claim 11, wherein each partial direct injector extends to an outlet on a radially inner surface of the flange portion of the insert.

18. The combustor as in claim 11, wherein each partial direct injector is defined in the insert by a boundary surface, and wherein the boundary surface includes a cylindrical portion and a tapering portion.

19. The combustor as in claim 18, wherein an air outlet passage of an air supply circuit extends to the tapering portion of the boundary surface.

20. The combustor as in claim 19, wherein a fuel inlet passage of a fuel supply circuit extends to the partial direct injector generally perpendicularly to the air outlet passage.