EP4675177A1

EP4675177A1 - Prefilm-airblast mini premixing tube for a staged main mixer in an axially staged, annular combustor

Info

Publication number: EP4675177A1
Application number: EP25172697.2A
Authority: EP
Inventors: Gregory Boardman; Brandon Williams; Jason Ryon
Original assignee: RTX Corp
Current assignee: RTX Corp
Priority date: 2024-07-01
Filing date: 2025-04-25
Publication date: 2026-01-07

Abstract

A fuel injector (110) in a combustor of a gas turbine engine includes a premixing duct (112) extending around a central axis (CA) from a first end (114) to a second end (116), and defining an inner chamber (120), a central body (124) with an inner face (126) and an outer face (128), and connected to the first end (114) of the premixing duct (112) with mixing walls (122). The central body (124) includes a diffuser channel (134) along the inner face (126) and a contoured center body (130) with a centerbody tip (132). The diffuser channel (134) is fluidly connected to the inner chamber (120) by the centerbody tip (132). The fuel injector (110) further includes a plurality of inner air swirlers (136) connected to the contoured center body (130), and an airblast weir ring prefilmer (138) between the plurality of inner air swirlers (136) and the premixing duct (112).

Description

BACKGROUND

The present disclosure relates to combustors, and in particular to premixing tubes used in a gas turbine engine.
Gas turbine engines mix fuel and air to increase combustion temperatures with the engine. For an axially staged, annular combustor, there is a need to premix fuel and air quickly in a compact, staged geometry. Main, staged mixers increase the degree that air and fuel are mixed. Mixers need to be functionally aerodynamic and void of internal separations and recirculation to avoid auto-ignition and internal flame holding. Further and earlier mixing would help operate an engine at increased temperatures without adverse effects.

SUMMARY

In one aspect, a fuel injector in a combustor of a gas turbine engine includes a premixing duct extending around a central axis from a first end to a second end, and defining an inner chamber, a central body with an inner face and an outer face, and connected to the first end of the premixing duct with mixing walls. The central body includes a diffuser channel along the inner face and a contoured center body with a centerbody tip. The diffuser channel is fluidly connected to the inner chamber by the centerbody tip. The fuel injector further includes a plurality of inner air swirlers connected to the contoured center body, and an airblast weir ring prefilmer between the plurality of inner air swirlers and the premixing duct.
In another aspect, a fuel injector system in a combustor of a gas turbine engine includes a shell defining a combustion chamber, a first fuel injector further which includes a first premixing duct around a central axis and having a first end and a second end, and defining a first inner chamber, a first central body with an inner face and an outer face, and connected to the first end of the first premixing duct with first mixing walls. The first central body can further include a first diffuser channel along the inner face, a first contoured center body with a first centerbody tip, wherein the first diffuser channel is fluidly connected to the first inner chamber by the first centerbody tip, a first plurality of inner air swirlers connected to the first contoured center body, and a first airblast weir ring prefilmer between the first plurality of inner air swirlers and the first premixing duct. The system further includes a second fuel injector which includes a second premixing duct around a central axis and having a first end and a second end, and defining a second inner chamber a second central body with an inner face and an outer face, and connected to the first end of the second premixing duct with second mixing walls. The second central body further includes a second diffuser channel along the inner face, and a second contoured center body with a second centerbody tip, wherein the second diffuser channel is fluidly connected to the second inner chamber by the second centerbody tip, a second plurality of inner air swirlers connected to the second contoured center body, and a second airblast weir ring prefilmer between the second plurality of inner air swirlers and the second premixing duct. The first fuel injector and second fuel injector are mounted through the shell and configured to deliver premixed fuel to the combustion chamber.
Features of embodiments are set forth in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a gas turbine engine fuel injector.
FIG 2A is a local cross-section view of a gas turbine engine fuel injector with internal helical fuel channels.
Fig 2B is a perspective cross-sectional view of a gas turbine engine fuel injector with contoured struts and vortex generators.
FIG 3. Is a cross-sectional view of a gas turbine engine fuel injector with a plurality of centerbody outlets.
FIG. 4 is a cross-sectional view of a gas turbine engine fuel injector with a feedback sensor or ignitor.
FIG. 5 is a cross-sectional view of a gas turbine engine fuel injector with a pilot fuel feed passage and a plurality of centerbody air feed conduits.
FIG. 6 is a cross-sectional view of fuel injector system for a gas turbine engine.

While the above-identified figures set forth embodiments of the present invention, other embodiments are also contemplated, as noted in the discussion. In all cases, this disclosure presents the invention by way of representation and not limitation. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art, which fall within the scope and spirit of the principles of the invention. The figures may not be drawn to scale, and applications and embodiments of the present invention may include features, steps and/or components not specifically shown in the drawings.

DETAILED DESCRIPTION

This disclosure presents a fuel injector and fuel injector system designed for use in a gas turbine engine. In particular, this disclosure involves fuel injectors that rapidly mix fuel and air en route to entering a combustion chamber.
FIG. 1 is a cross-sectional view of a gas turbine engine fuel injector. FIG 2A is a local cross-section view of a gas turbine engine fuel injector with internal helical fuel channels. FIG. 2B is an offset cross-sectional view of a gas turbine engine fuel injector with contoured struts and vortex generators. FIGs. 1-2B will be discussed together.
Fuel injector 110 includes premixing duct 112, with premixing duct 112 including first end 114, second end 116 and inner face 118. Premixing duct 112 defines inner chamber 120. Fuel injector 110 further includes mixing walls 122, and central body 124. Central body 124 includes inner face 126, outer face 128, contoured center body 130, center body tip 132, and diffuser channel 134. Fuel injector 110 further includes inner air swirlers 136, airblast weir ring prefilmer 138 (with outer face 140 and tip 160), contoured struts 142, vortex generators 144 (with sloping end 146 and flat end 148), heat shielded passageways 150, and internal helical fuel channels 152 (with cooling helical channels 154, weir injector helical channels 156, and near-tangential outlets 158). Fuel injector 110 is configured to be installed in a gas turbine engine combustor.
As discussed above, fuel injector 110 includes premixing duct 112 which includes first end 114, second end 116, and inner face 118. Premixing duct 112 defines inner chamber 120. Premixing duct 112 connect to mixing walls 122, which connect to central body 124. Central body 124 extends axially along central axis CA and includes inner face 126, outer face 128, contoured center body 130, center body tip 132, and defines diffuser channel 134. Fluid can flow axially along central axis CA from mixing walls 122, through diffuser channel 134 out center body tip 132 and into inner chamber 120. Multiple inner air swirlers 136 connect to outer face 128 of central body 124, and to mixing walls 122. Airblast weir ring prefilmer 138 is connected to mixing walls 122 and is located between inner face 118 of premixing duct 112 and inner air swirlers 136. Airblast weir ring prefilmer 138 includes outer face 140. Vortex generators 144 are distributed circumferentially around central axis CA, and are connected to inner face 118 of premixing duct 112. Each vortex generator 144 has an associated sloping end 146 and flat end 148. In the discussed embodiment, sloping ends 146 are oriented towards first end 114 of premixing duct 112, while flat ends 148 are oriented towards second end 116 of premixing duct. It will be understood by those skilled in the art that this orientation of the vortex generators 144 could flip depending on desired flow characteristics. Heat shielded passageways 150 can surround airblast weir ring prefilmer 138, between inner air swirlers 136 and inner face 118 of premixing duct 112. Heat shielded passageways 150 help prevent internal carbon growth in components of fuel injector 110. Internal helical fuel channels 152 are located within airblast weir ring prefilmer 138. Internal helical fuel channels 152 can consist of cooling helical channels 154 and/or weir injector helical channels 156 (shown in FIG. 2A). Weir injector helical channels 156 can deliver fuel into internal chamber 120 via near-tangential outlets 158 (shown in FIG. 1). FIG 2B shows inner air swirlers 136, contoured struts 142, and vortex generators 144 distributed circumferentially around the central axis CA of fuel injector 110.
Premixing duct 112 can include different diameters as defined by central axis CA at first end 114 of premixing duct 112 and at second end 116 of premixing duct 112. Having different radii at first end 114 and second end 116 improves the aerodynamics of premixing duct 112, and keeps flow velocities higher than flame speeds. This reduces the likelihood of flashback or burning withing central body 124 of injector 110, rather than in inner chamber 120.
Inner air swirlers 136 collectively create high swirl near airblast weir ring prefilmer 138 to increase circumferential fuel distribution and produce a thinner film of fuel on airblast weir ring prefilmer 138. Reducing swirl near central body 124 by placing components radially further from central axis CA can advantageously reduce the likelihood of separation around central body 124, reduce hot centerline recirculation into inner chamber 120, or both.
Airblast weir ring prefilmer 138 spreads fuel across a large surface as a thin film to be rapidly atomized. A larger radius of airblast weir ring prefilmer as measured from the central axis CA provides a thinner sheet of fuel for combustion. Inner air swirlers 136 and Contoured struts 142 together create a high shear zone at tip 160 of airblast weir ring prefilmer 138 for rapid mixing of fuel and air.
FIG. 3 is a cross-sectional view of a gas turbine engine fuel injector with centerbody outlets, with fuel and air flow paths. FIG. 4 represents an alternative to the fuel injector of FIG. 3, although elements of the structures and design features in each figure can be combined with one another. FIG 4 is a cross-sectional view of a gas turbine engine fuel injector with an ignitor or feedback sensor. FIG. 5 is a cross-sectional view of a gas turbine engine fuel injector with a pilot fuel feed passage and centerbody air feed conduits. FIGs. 3-5 will be discussed together.
Fuel injector 210 includes premixing duct 212, which extends from first end 214 to second end 216 and includes inner face 218. Premixing duct 212 defines inner chamber 220. Fuel injector 210 further includes mixing walls 222 and central body 224. Central body 224 includes inner face 226, outer face 228, contoured center body 230, center body tip 232, and diffuser channel 234. Fuel injector 210 further includes inner air swirlers 236, airblast weir ring prefilmer 238 with outer face 240 and tip 260, contoured struts 242, vortex generators 244 with sloping end 246 and flat end 248, heat shielded passageways 250, and internal helical fuel channels 252 with fuel passages 253 and near-tangential outlets 258. Fuel injector 210 further includes centerbody outlets 262, feedback sensor 264 with tip 266, centerbody air feed conduits 268, outer air flow passages 270, and radial inflow swirler passages 272. Fuel injector 210 can include pilot fuel feed tube 274 and effusion cooling holes 278 (shown in FIG. 5). Fuel injector 210 is configured to be installed in a gas turbine engine combustor.
As discussed above, fuel injector 210 includes premixing duct 212 which includes first end 214, second end 216, and inner face 218. Premixing duct 212 defines inner chamber 220. Premixing duct 212 connect to mixing walls 222, which connect to central body 224. Central body 224 extends axially along central axis CA and includes inner face 226, outer face 228, contoured center body 230, center body tip 232, and defines diffuser channel 234. Fluid can flow axially along central axis CA from mixing walls 222, through diffuser channel 234 out center body tip 232 via centerbody outlets 262 and into inner chamber 220. Centerbody outlets 262 are shown with openings perpendicular to central axis CA, but it is understood different angles of centerbody outlets 262 could be used to control the aerodynamics in inner chamber 220. Inner air swirlers 236 connect to outer face 228 of central body 224, and to mixing walls 222. Airblast weir ring prefilmer 238 is connected to mixing walls 222 and is between inner face 218 of premixing duct 212 and inner air swirlers 236. Airblast weir ring prefilmer 238 includes outer face 240. Vortex generators 244 are distributed radially around central axis CA, and are connected to inner face 218 of premixing duct 212. Vortex generators 244 have sloping end 246 and flat end 248. In the discussed embodiment, sloping end 246 is oriented towards first end 114 of premixing duct 212, while flat end 248 is oriented towards second end 216 of premixing duct. It will be understood by those skilled in the art that this orientation of the vortex generators 244 could flip depending on desired flow characteristics. Heat shielded passageways 250 can surround airblast weir ring prefilmer 238, between inner air swirlers 236 and inner face 218 of premixing duct 212. Heat shielded passageways 250 help prevent internal carbon growth in components of fuel injector 210. Internal helical fuel channels 252 are located within airblast weir ring prefilmer 238 and fed with fuel via fuel passages 253. Weir injector helical channels 156 can deliver fuel into internal chamber 120 via near-tangential outlets 258. Fuel injector 210 can include feedback sensor 264 (shown in FIG. 4) inside of diffusion channel 234, with tip 266 of feedback sensor 264 extending into inner chamber 220 through centerbody tip 232. In an alternate embodiment, feedback sensor 264 and tip 266 can instead be an ignitor and an ignitor tip.
Fuel injector 210 can include pilot fuel feed tube 274 within diffuser channel 234 (shown in FIG. 5). Pilot fuel feed tube 274 can be heat shielded to prevent overheating of the pilot fuel. Pilot fuel feed tube 274 extends axially along central axis CA and delivers pilot fuel into inner chamber 220 with pressure swirl atomizer 276 through centerbody tip 232. Centerbody air feed conduits 268 can run parallel to pilot fuel tube 274 before exiting centerbody tip 232 via effusion cooling holes 278. Effusion cooling holes 278 can exit centerbody tip 232 at an acute angle as defined by the central axis CA.
Fluid can enter fuel injector 210 via several pathways. Fluid can flow via centerbody air feed conduits 268 into diffuser channel 234 axially along central axis CA, and enter inner chamber 220 via centerbody outlets 262 in centerbody tip 232. Fluid can flow into outer air flow passages 270, into contoured struts 242, and enter inner chamber 220 adjacent to outer face 240 of airblast weir ring prefilmer 238. Fluid can flow into radial inflow swirler passages 272, into inner air swirlers 236, and enter inner chamber 220 adjacent to airblast weir ring prefilmer 238. Fuel can flow into internal helical fuel channels 252, exit via near-tangential outlets 258, and form a thin film on the surface of airblast weir ring prefilmer 238, before mixing with fluid that entered inner chamber 220 via inner air swirlers 236 and/or contoured struts 242. Mixed fuel and fluid then interacts with vortex generators 244, and moves axially as defined by central axis CA from first end 214 of premixing duct 212 towards second end 216 of premixing duct. More fluid that has not mixed with fuel speeds up the mixture via centerbody outlets 262. In one exemplary embodiment, the amount of flowing air entering inner chamber 220 via outer air flow passages 270 is greater than the amount of flowing air entering inner chamber 220 via radial inflow swirler passages 272, which is greater than the amount of flowing air entering inner chamber 220 via centerbody air feed conduits 268. In another exemplary embodiment, fluid entering fuel injector 210 can consist of ten percent or less of flowing air entering the inner chamber 220 via centerbody air feed conduits 268, between forty and fifty percent of flowing air entering inner chamber 220 via radial inflow swirlers passages 272, and between fifty and sixty percent of flowing air entering inner chamber 220 via outer air flow passages 270.
FIG. 6 is a cross-sectional view of a fuel injector system for a gas turbine engine.
Fuel injector system 308 includes first fuel injector 310, second fuel injector 311, shell 312, and combustion chamber 314. First fuel injector 310 and second fuel injector 311 can be any fuel injector as described in the present application, or known to one skilled in the art. First and second fuel injectors 310, 311 are mounted within shell 312. Shell 312 defines combustion chamber 314. Fuel and fluid that enter fuel injectors 310, 311 enter combustion chamber 314 and provide fluid and fuel mixtures that are already well mixed before entering combustion chamber 314.
While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Discussion of Possible Embodiments

The following are non-exclusive descriptions of possible embodiments of the present invention.
A fuel injector in a combustor of a gas turbine engine includes a premixing duct extending around a central axis from a first end to a second end, and defining an inner chamber, a central body with an inner face and an outer face, and connected to the first end of the premixing duct with mixing walls. The central body includes a diffuser channel along the inner face and a contoured center body with a centerbody tip. The diffuser channel is fluidly connected to the inner chamber by the centerbody tip. The fuel injector further includes a plurality of inner air swirlers connected to the contoured center body, and an airblast weir ring prefilmer between the plurality of inner air swirlers and the premixing duct.
The fuel injector of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components:
The fuel injector can further include a plurality of vortex generators spaced along an inner face of the premixing duct.
The plurality of vortex generators can be triangular and oriented with a sloping end towards the first end of the premixing duct, and a flat end towards the second end of the premixing duct.
The plurality of vortex generators can be triangular and oriented with a flat end towards the first end of the premixing duct, and a sloping end towards the second end of the premixing duct.
The fuel injector can further include a plurality of heat shielded passageways surrounding the airblast weir ring prefilmer.
The airblast weir ring prefilmer can further include internal helical fuel channels.
The internal helical fuel channels can further include cooling helical channels configured to remove heat from the fuel injector, and weir injector helical channels configured to deliver fuel to the inner chamber via a plurality of near-tangential outlets.
The diffuser channel can enter the inner chamber via a plurality of centerbody outlets.
The plurality of centerbody outlets can exit the central body perpendicular to the central axis.
The fuel injector of the preceding paragraph can further include a plurality of effusion cooling holes exiting the central body at an acute angle as defined by the central axis.
The fuel injector can further include a feedback sensor within the diffuser channel.
The fuel injector can further include an ignitor within the diffuser channel.
The fuel injector can further include a plurality of contoured struts between an outer face of the airblast weir ring prefilmer and an inner face of the premixing duct.
The fuel injector can further include a pilot fuel feed tube within the diffuser channel, wherein the pilot fuel feed tube is heat shielded, a plurality of radially-extending inflow swirler passages directing air into the plurality of contoured struts, a plurality of outer air flow passages, and a plurality of centerbody air feed conduits within the central body.
The fuel injector of the preceding paragraph, wherein the amount of flowing air entering the inner chamber via the plurality of outer air flow passages is greater than the amount of flowing air entering the inner chamber via the plurality of radial inflow swirler passages, which is greater than the amount of flowing air entering the inner chamber via the plurality of centerbody air feed conduits.
The fuel injector can include a plurality of centerbody outlets that exit the central body perpendicular to the central axis.
The fuel injector can further include a plurality of effusion cooling holes exiting the central body at an acute angle as defined by the central axis.
A fuel injector system in a combustor of a gas turbine engine includes a shell defining a combustion chamber, a first fuel injector further which includes a first premixing duct around a central axis and having a first end and a second end, and defining a first inner chamber, a first central body with an inner face and an outer face, and connected to the first end of the first premixing duct with first mixing walls. The first central body can further include a first diffuser channel along the inner face, a first contoured center body with a first centerbody tip, wherein the first diffuser channel is fluidly connected to the first inner chamber by the first centerbody tip, a first plurality of inner air swirlers connected to the first contoured center body, and a first airblast weir ring prefilmer between the first plurality of inner air swirlers and the first premixing duct. The system further includes a second fuel injector which includes a second premixing duct around a central axis and having a first end and a second end, and defining a second inner chamber a second central body with an inner face and an outer face, and connected to the first end of the second premixing duct with second mixing walls. The second central body further includes a second diffuser channel along the inner face, and a second contoured center body with a second centerbody tip, wherein the second diffuser channel is fluidly connected to the second inner chamber by the second centerbody tip, a second plurality of inner air swirlers connected to the second contoured center body, and a second airblast weir ring prefilmer between the second plurality of inner air swirlers and the second premixing duct. The first fuel injector and second fuel injector are mounted through the shell and configured to deliver premixed fuel to the combustion chamber.
The arrangement of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components:
The system can further include a first plurality of contoured struts between an outer face of the first airblast weir ring prefilmer and an inner face of the first premixing duct, and a second plurality of contoured struts between an outer face of the second airblast weir ring prefilmer and an inner face of the second premixing duct.
The system can further include a first plurality of heat shielded passageways surrounding the first airblast weir ring prefilmer, and a second plurality of heat shielded passageways surrounding the second airblast weir ring prefilmer.
While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

A fuel injector (110; 210) in a combustor of a gas turbine engine, the fuel injector comprising:
a premixing duct (112; 212) extending around a central axis (CA) from a first end (114; 214) to a second end (116; 216), and defining an inner chamber (120; 220);

a central body (124; 224) with an inner face (126; 226) and an outer face (128; 228), and connected to the first end (114; 214) of the premixing duct (112; 212) with mixing walls (122; 222), the central body (124; 224) comprising:
a diffuser channel (134; 234) along the inner face (126; 226); and

a contoured center body (130; 230) with a centerbody tip (132; 232), wherein the diffuser channel (134; 234) is fluidly connected to the inner chamber (120; 220) by the centerbody tip (132; 232); and

a plurality of inner air swirlers (136; 236) connected to the contoured center body (130; 230); and

an airblast weir ring prefilmer (138; 238) between the plurality of inner air swirlers (136; 236) and the premixing duct (112; 212).
The fuel injector of claim 1, further comprising a plurality of vortex generators (144; 244) spaced along an inner face (118; 218) of the premixing duct (112; 212).
The fuel injector of claim 2, wherein:
the plurality of vortex generators (144; 214) are triangular and oriented with a sloping end (146; 246) towards the first end (114; 214) of the premixing duct (112; 212), and a flat end (148; 248) towards the second end (116; 216) of the premixing duct (112; 212); or

wherein the plurality of vortex generators are triangular and oriented with a flat end towards the first end (114; 214) of the premixing duct (112; 212), and a sloping end towards the second end (116; 216) of the premixing duct (112; 212).
The fuel injector of any preceding claim, further comprising a plurality of heat shielded passageways (150; 250) surrounding the airblast weir ring prefilmer (138; 238).
The fuel injector of any preceding claim, wherein the airblast weir ring prefilmer (138; 238) further comprises internal helical fuel channels (152; 252), optionally wherein the internal helical fuel channels (152) further comprise cooling helical channels (154) configured to remove heat from the fuel injector, and weir injector helical channels (156) configured to deliver fuel to the inner chamber (120; 220) via a plurality of near-tangential outlets (158).
The fuel injector of any preceding claim, wherein the diffuser channel (234) enters the inner chamber (220) via a plurality of centerbody outlets (262), optionally wherein the plurality of centerbody outlets (262) exit the central body (224) perpendicular to the central axis (CA).
The fuel injector of claim 6, further comprising a plurality of effusion cooling holes (278) exiting the central body (224) at an acute angle as defined by the central axis (CA).
The fuel injector of any preceding claim, further comprising a feedback sensor (264) within the diffuser channel (234).
The fuel injector of any preceding claim, further comprising an ignitor within the diffuser channel (234).
The fuel injector of any preceding claim, further comprising a plurality of contoured struts (142; 242) between an outer face (140; 240) of the airblast weir ring prefilmer (138; 238) and an inner face (118; 218) of the premixing duct (112; 212).
The fuel injector of claim 10, further comprising:
a pilot fuel feed tube (274) within the diffuser channel (234), wherein the pilot fuel feed tube (274) is heat shielded;

a plurality of radially-extending inflow swirler passages (272) directing air into the plurality of contoured struts (242);

a plurality of outer air flow passages (270); and

a plurality of centerbody air feed conduits (268) within the central body (224).
The fuel injector of claim 11, wherein the amount of flowing air entering the inner chamber (220) via the plurality of outer air flow passages (270) is greater than the amount of flowing air entering the inner chamber (220) via the plurality of radially-extending inflow swirler passages (272), which is greater than the amount of flowing air entering the inner chamber (220) via the plurality of centerbody air feed conduits (268).
The fuel injector of claim 11 or 12, wherein a plurality of centerbody outlets (262) exit the central body (224) perpendicular to the central axis (CA), wherein the fuel injector (210) optionally further comprises a plurality of effusion cooling holes (278) exiting the central body (224) at an acute angle as defined by the central axis (CA).
A fuel injector system (308) in a combustor of a gas turbine engine comprising:
a shell (312) defining a combustion chamber (314);

a first fuel injector (310) further comprising:
a first premixing duct (112; 212) around a central axis (CA) and having a first end (114; 214) and a second end (116; 216), and defining a first inner chamber (120; 220);

a first central body (124; 224) with an inner face (126; 226) and an outer face (128; 228), and connected to the first end (114; 214) of the first premixing duct (112; 212) with first mixing walls (122; 222), the first central body (124; 224) comprising:
a first diffuser channel (134; 234) along the inner face (126; 226); and

a first contoured center body (130; 230) with a first centerbody tip (132; 232), wherein the first diffuser channel (134; 234) is fluidly connected to the first inner chamber (120; 220) by the first centerbody tip (132; 232);

a first plurality of inner air swirlers (136; 236) connected to the first contoured center body (130; 230); and

a first airblast weir ring prefilmer (138; 238) between the first plurality of inner air swirlers (136; 236) and the first premixing duct (112; 212); and

a second fuel injector (311) further comprising:
a second premixing duct (112; 212) around a central axis (CA) and having a first end (114; 214) and a second end (116; 216), and defining a second inner chamber (120; 220);

a second central body (124; 224) with an inner face (126; 226) and an outer face (128; 228), and connected to the first end (114; 214) of the second premixing duct (112; 212) with second mixing walls (122; 222), the second central body (124; 224) comprising:
a second diffuser channel (134; 234) along the inner face (126; 226); and

a second contoured center body (130; 230) with a second centerbody tip (132; 232), wherein the second diffuser channel (134; 234) is fluidly connected to the second inner chamber (120; 220) by the second centerbody tip (132; 232);

a second plurality of inner air swirlers (136; 236) connected to the second contoured center body (130; 230); and

a second airblast weir ring prefilmer (138; 238) between the second plurality of inner air swirlers (136; 236) and the second premixing duct (112; 212), wherein the first fuel injector (310) and second fuel injector (311) are mounted through the shell (312) and configured to deliver premixed fuel to the combustion chamber (314).
The system of claim 14, further comprising:
a first plurality of contoured struts (142; 242) between an outer face (140; 240) of the first airblast weir ring prefilmer (138; 238) and an inner face (118; 218) of the first premixing duct (112; 212), and a second plurality of contoured struts (142; 242) between an outer face (140; 240) of the second airblast weir ring prefilmer (138; 238) and an inner face (118; 218) of the second premixing duct (112; 212); and/or

a first plurality of heat shielded passageways (150; 250) surrounding the first airblast weir ring prefilmer (138; 238), and a second plurality of heat shielded passageways (150; 250) surrounding the second airblast weir ring prefilmer (138; 238).