Venturi hybrid airblast-atomizing swirled mixing tube

Abstract

A fuel-air mixing tube extending along a centerline axis includes a fuel source, a venturi throat disposed axially downstream of the fuel source, a prefilming section, an outer axial swirler, and multiple air passages extending at least partially radially inward, upstream of the prefilming surface. The prefilming section broadens axially downstream from the venturi throat, and terminates at a prefilmer edge. The outer axial swirler is disposed circumferentially about the venturi throat, and is oriented to ingest air substantially axially. The outer axial swirler includes multiple swirler vanes configured to increase swirl of the ingested air at the prefilmer edge.

Description

[0001] VENTURI HYBRID AIRBLAST-ATOMIZING SWIRLED MIXING TUBE

[0002] CROSS-REFERENCE TO RELATED APPLICATION(S)

[0003] This application claims the benefit of U.S. Provisional Application No. 63 / 665,821 filed June 28, 2024 for “VENTURI HYBRID AIRBLAST-ATOMIZING SWIRLED MIXING TUBE” by G. Boardman, S. Kramer, B. Williams, and J. Ry on.

[0004] STATEMENT OF GOVERNMENT INTEREST

[0005] This invention was made with government support under Contract No. 80GRC022CA008 awarded by The National Aeronautics and Space Administration. The government has certain rights in the invention.

[0006] BACKGROUND

[0007] The present invention relates generally to gas turbine engines, and more particularly to injectors for staged combustion.

[0008] Brayton cycle engines generate thrust and extract power from combustion of mixtures of fuel and compressed air. Nozzles for injection of fuel into gas turbine engine combustors are designed to atomize and disperse fuel to promote uniform and consistent mixing, avoid coking, and improve combustor dynamics. Some injector nozzles are constructed to facilitate staged use, i.e., with injection of fuel in different patterns and rates during different engine states.

[0009] SUMMARY

[0010] In one aspect, this disclosure presents a fuel-air mixing tube extending along a centerline axis and including a fuel source, a venturi throat disposed axially downstream of the fuel source, a prefilming section, an outer axial swirler, and multiple air passages extending at least partially radially inward, upstream of the prefilming surface. The prefilming section broadens axially downstream from the venturi throat, and terminates at a prefilmer edge. The outer axial swirler is disposed circumferentially about the venturi throat, and is oriented to ingest air substantially axially. The outer axial swirler includes multiple swirler vanes configured to increase swirl of the ingested air at the prefilmer edge.

[0011] In another aspect, this disclosure presents a gas turbine engine combustor including a combustor liner, several fuel nozzles, and a cluster of fuel-air mixing tubes as described above, where the fuel source of each of the fuel-air mixing tubes is a respective one of the fuel nozzles.

[0012] The present summary is provided only by way of example, and not limitation. Other aspects of the present disclosure will be appreciated in view of the entirety of the present disclosure, including the entire text, claims, and accompanying figures.

[0013] BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1 is schematic cross-sectional view of a simplified gas turbine engine.

[0015] FIG. 2 is a schematic cross-sectional view of a gas turbine engine combustor region.

[0016] FIG. 3 is a perspective cross-sectional view of an example cluster of fuel / air mixing tubes.

[0017] FIG. 4 is a detailed cross-sectional view of one of the fuel / air mixing tubes of FIG. 3.

[0018] FIGs. 5a and 5b are perspective and cross-sectional illustrations, respectively, of an alternative embodiment fuel / air mixing tube cluster.

[0019] FIGs. 6a and 6b are perspective and cross-sectional views respectively, of another alternative embodiment fuel / air mixing tube cluster.

[0020] While the above-identified figures set forth one or more embodiments of the present disclosure, 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 and components not specifically shown in the drawings.

[0021] DETAILED DESCRIPTION

[0022] This disclosure presents fuel-air mixer tube for use along an outer circumference of a combustor liner, and several arrangements of clusters of such fuel -air mixer tubes. The mixer tubes presented herein receive fuel via fuel nozzle outlets with atomizer tips, and include a venturi throat immediately downstream of this atomizer tip, as well as a prefilming section downstream of the venturi throat, and an outer axial swirler coaxial and partially concentric with the prefilming section. In each mixer tube, fuel from the fuel nozzle outlet impinges upon the a prefilming surface of the prefilming section, forming a thin distributed film atomized at a terminal prefilmer edge of the prefilming surface. Most airflow through each mixer tube passes through the outer axial swirler, which imparts an axial swirl that promotes uniform dispersion and mixing of fuel at the prefilmer edge. Radially or partially radially extending (complex angled) passages into the mixing tube upstream of the prefilming section introduce swirl (which can be co-swirled or counter-swirled relative to the outer axial swirler) and direct flow across the atomizer tip.

[0023] FIG. l is a schematic cross-sectional view providing a simplified illustration of gas turbine engine 10. Gas turbine engine 10 is a Brayton-cycle gas turbine engine such as an aircraft engine with air inlet 12, compressor section 14, combustor 16, turbine section 18, and exhaust section 20, all oriented generally sequentially along from forward to aft along engine axis A. Gas turbine engine 10 receives environmental air via air inlet 12 and compresses this air through multiple stages of compressor rotors and stators in compressor section 14. Compressed air from compressor section 14 is mixed with fuel in combustor 16, and the resulting fuel / air mixture is ignited. Multiple stages of airfoils in turbine section 18 extract energy (via torque) from resulting high pressure combustion gasses before these gasses are expelled via exhaust section 20.

[0024] Gas turbine engine 10 provides one simplified example of a gas turbine engine to contextualize further discussion, below. The illustrated features of gas turbine engine 10 should not be understood as limiting. FIG. 1 illustrates gas turbine engine 10 with a single-spool architecture, for example, whereby a single turbine section drives a single compressor section. In other examples, however, gas turbine engine 10 can be a multi-spool (e.g., 2-spool or 3-spool) system with multiple mechanically separate stages of compressor and / or turbine. Gas turbine engine 10 can, for example, be an aircraft or industrial gas turbine engine.

[0025] FIG. 2 is a schematic cross-sectional view of a region of combustor 16 of gas turbine engine 10. More specifically, although combustor 16 can be an annular section extending about circumferentially fully about engine axis A, FIG. 2 illustrates only a representative module of combustor 16 with axial mixer 200, liner 202, axial fuel nozzle assembly 204, outer case 206, outer mixers 208 (shown as mixers 208a, 208b, and 208c), outer fuel nozzle assembly 210 (with individual fuel nozzles 210a, 210b, and 210c), and dome 212.

[0026] FIG. 2 presents a simplified cartoon of a gas turbine engine combustor region. It should be noted that elements and dimensions shown in FIG. 2 are not drawn to scale. The illustrated section of combustor 16 extends from engine axis A to outer case 210, which can for example be a structural case of combustor 16. FIG. 2 illustrates combustor 16 as capable of receiving fuel through outer case 206 for injection both at axial mixer 200 and outer mixers 208, with axial mixer 200 being disposed at a distal end of axial fuel nozzle assembly 204, and outer mixers 208a-c being disposed at a distal end of outer fuel nozzles 210a-c. Although FIG. 2 schematically illustrates outer mixers 208a-c and fuel nozzles 210a-c as arranged in an axial row, outer mixers 208a can more generally be arranged in any suitable location and arrangement downstream of dome 212. In some embodiments, separate outer mixers 208 can be distributed individually about a circumference of combustor 16. In other embodiments, as discussed in greater detail below with reference to the remaining figures, outer mixers 208 can be clustered into groups arranged and proportioned for staged fuel injection depending on engine state or power demand, i.e., with groups of outer mixers 208a, 208b, 208c being located and in some instances fabricated together.

[0027] Fuel nozzle assemblies 204 and 210 carry fuel from a fuel source to combustor 16. In many embodiments fuel nozzle assemblies 204 and 210 can include fuel lines, supports, and seals. In other embodiments, fuel nozzle assemblies 204 and 210 can be deemed to only encompass flow-defining fuel outlets coinciding with mixers 200, 208, with other fluid routing and metering elements being considered separate from fuel nozzle assemblies 204 and 210. In the most general case, fuel injected into combustor 16 from axial fuel nozzle assembly 204 passes through mixer 200 to form combustion flow F-Cl. Fuel nozzle assembly 204 can itself include fuel metering mechanisms, and / or can include multiple distinct fuel lines separately metered upstream of fuel nozzle assembly 204, such that fuel flow into combustor 16 can be controlled in both quantity and injection location relative to axial mixer 200. Fuel delivery to and / or through outer fuel nozzle assemblies 210 can be similarly metered, for example to separately control delivery of fuel to individual outer fuel nozzle assemblies 210a.

[0028] Axial mixer 200 is a fuel / air mixer with multiple radial swirlers and prefilming surfaces arranged to promote fuel atomization and dispersion, as discussed in greater detail below with respect to FIG. 3. Axial mixer 200 is distributed substantially symmetrically about a centerline (C, see FIG. 3) parallel or near parallel to engine axis A. By contrast, outer mixers 210 can be arranged about individual and / or cluster centerlines oriented generally radially towards engine axis A. Although FIG. 2 illustrates only one sectional region of combustor 16, combustor 16 can include multiple axial mixers 200 distributed circumferentially at locations on dome 212. Similarly, combustor 16 can include outer mixers 208 distributed circumferentially, or arranged in groupings distributed circumferentially, about an outer wall of liner 202.

[0029] As depicted in FIG. 2, combustor 16 receives compressed air from compressor section 14 as flow F-In. This flow F-In passes fuel nozzle assemblies 204 and is separated by liner 202 into outer flow F-O, inner flow F-I, and flow to axial mixer 200. Although liner 202 is schematically illustrated as a solid structure in FIG. 2, it should be understood that combustor liners such as liner 202 are perforated with holes allowing a degree of exchange between both inner flow F-I and outer flow F-0 and the combustor interior defined by liner 202. Airflow from flow F-In through axial mixer 200 is directed to atomize and disperse fuel for consistently uniform fuel / air mixing, generating mixed flow F-Ml . Outer mixers 208 are similarly arranged to receive outer flow F-0 and mix this airflow with fuel to produce mixed flow F-M2. Mixed flows F-Ml and F-M2 are ignited (igniter not shown), and combustion gasses exit combustor 16 as flow F-Out to turbine section 18.

[0030] FIG. 3 is a perspective cross-sectional view of cluster 300, a grouping of several fuel / air mixing tubes 308. Mixing tubes 308 can, for example, be fuel / air mixing structures as presented schematically in FIG. 2 and discussed generally with referent to outer mixers 208. More specifically, FIG. 3 depicts three mixing tubes 308a-c in a clustered arrangement, such that mixing tube 308a is shown in section. Mixing tubes 308b and 308c are shown in perspective views, with a view plane slightly indenting into mixing tube 308c. In the illustrated embodiment, all mixing tubes 308 in cluster 300 are collectively distributed about a common cluster centerline C-l, including additional mixing tubes forward of the view plane (now shown), such that cluster 300 includes a total of five distinct mixing tubes 308. Cluster centerline C-l can, for example, be orthogonal to engine axis A. FIG. 4 is a close-up cross-sectional view of mixing tube 308a, as a representative one mixing tubes 308a-c. FIGs. 3 and 4 are discussed together.

[0031] Each mixing tube 308 as illustrated in FIGs. 3 and 4 includes a respective fuel nozzle outlet 310, venturi throat 320, prefilming section 330, outer axial swirler 340, outlet duct 350, and outlet opening 360. In addition, cluster 300 includes cooling holes 370 to promote airflow around and past mixing tubes 308 to manage heat, and acceleration funnel 380 to accelerate airflow through cooling holes 370 disposed in a central region cluster 300 about cluster centerline C-l.

[0032] As shown in FIG. 4, mixing tube 308 extends generally along tube centerline C-2. Fuel nozzle outlet 310 receives fuel from fuel line 312 and is situated at atomizer tip 316, which defines a sharply angled distal surface of a fuel nozzle assembly 210 (see FIG. 2) to promote fuel atomization as fuel flow leaves fuel nozzle outlet 310. Several tip flow passages 314 provide tip flow F-T into mixing tube 308 and across (i.e. sweeping) atomizer tip 316. As depicted in FIGs, 3 and 4, tip flow passages 314 can be oriented generally radially inward and axially downstream relative to tube centerline C-2, and distributed circumferentially about mixing tube 308 at an axial location generally aligned with and directed towards fuel nozzle outlet 310. Although FIGs. 3 and 4 illustrate tip flow passages 314 angled strictly axially and radially with respect to tube centerline C-2, i.e., with each tip flow passage 314 oriented toward tube centerline C-2, variants of the illustrated tip flow passages can be skewed (e.g., clockwise or counterclockwise) to promote swirl at atomizer tip 316 to further promote fuel dispersion and guide fuel flow.

[0033] Mixing tube 308 forms a venturi to accelerate airflow and better atomize fuel from fuel nozzle outlet 310. This venturi narrows from tip flow passages 314 to throat diameter Dt at venturi throat 320, then along prefilming surface 332 to maximum venturi diameter Dv at prefilmer edge 334. In at least some embodiments, additional compoundangled venturi air-swirl passages 322 and 324 are distributed circumferentially about venturi throat 320. Air-swirl flow F-A passes through air-swirl passages 322 / 324 to improve uniformity of atomization and spray of fuel across prefilming surface 332. In the illustrated embodiments, venturi air-swirl passages322 are distributed at a first axial location (relative to tube centerline C-2), while venturi air-swirl passages 324 are distributed at a second axial location downstream of venturi air-swirl passages 322. More generally, however, venturi throat 320 can have no air-swirl holes, a single stage of airswirl passages (e.g., 322), or two or more stages of air-swirl passages 322, 324, etc., with additional stages of air-swirl passages improving fuel distribution at the cost of additional part complexity. Furthermore, although air-swirl passages 322 are illustrated as co-swirled (i.e., oriented in the same compound angle swirl direction), alternative versions of air-swirl passages 322 can be counter-swirled relative to air-swirl passages 324, and / or relative to swirled variants of tip flow passages 314, to promote fuel dispersion. In at least some embodiments air-swirl passages 322 / 324 can be co-swirled with each and counter-swirled relative to outer axial swirler 340 (discussed below). More broadly, co-swirl can facilitate tighter recirculation by increasing swirl number in mixer tube 308, while counter-swirl between outer axial swirler 340 and co-swirl passages 322 can increase shear at prefilmer edge 334 (i.e., increasing differential velocity between air from outer axial swirler 340 and prefilming section 330). Lower swirl number can also help to avoid vortex breakdown.

[0034] Fuel expelled from fuel nozzle outlet 310 impinges upon prefilming surface 332 of prefilming section 330 as shown in FIG. 3, forming a relatively evenly distributed fuel spray film that atomizes efficiently as it leaves prefilmer edge 334. Prefilmer edge 334 can be sharply angled to facilitate atomization, and can in some embodiments include cutout slots 336 such as castellation or crenellation cutouts to increase a length of prefilmer edge 334 in contact with atomizing airflow from outer axial swirler 340, and can improve mixing by introducing additional turbulence.

[0035] Outer axial swirler 340 receives the majority of outer flow F-0 passing through mixing tube 308 as swirler flow F-S, for example approximately 90% of mixer air flow, or more than 85% of mixer air flow, with the remaining -10% passing through tip flow passages 314 and air-swirl passages 322, 324. Although mixer tube 308 is shown in FIG. 3 with outer axial swirler 340, other embodiments of mixer tube 308 can alternatively incorporate swirlers with radial or mixed inflow.

[0036] Outer axial swirler 340 is an annular passage extending axially from, in the illustrated embodiment, alongside venturi throat 320 to prefilmer edge 334 of prefilming section 330. Outer axial swirler 340 imparts circumferential swirl on swirler flow F-S via swirler vanes 342, which can for example be oriented at a 20-55° turning angle. Outer axial swirler 340 has an outer wall 344 that converges from a maximum swirler diameter DI to an outlet duct diameter D2, thereby constricting and accelerating airflow past prefilmer edge 334 to a reduced flow area 346 to more completely atomize and disperse filmed fuel into a consistently uniform fuel / air mixture. Atomized fuel and air mix through a premixing length L-P from prefilmer edge through outlet duct 350 to outlet opening 360. Outlet duct diameter D2 can be deliberately kept low to increase flow velocity exiting mixing tube 308, thereby reducing backflow and avoiding flame holding.

[0037] The structure of mixing tubes 308 facilitates improved fuel / air mixing and is compatible use in closely grouped arrays such as cluster 300. Cluster 300 provides several (5, in the depicted embodiment) parallel mixing tubes 308. Fuel supplied through corresponding fuel nozzle assemblies 210 (e.g., 210a, 210b, 210c; see FIG. 2) to each mixing tube 308 can be metered separately. In some embodiments, fuel lines to a subset of mixing tubes in cluster 300 are metered together, but separately from at least one other of the mixing tubes in cluster 300. In this manner, fuel injection into combustor 16 can be staged according to engine state or desired engine power, for example to accommodate different flight stages (e.g., idle, cruise, climb) in an aircraft gas turbine engine. Fuel can be commonly supplied to cluster 300 and metered as it is distributed to individual mixing tubes 308, or can be supplied to each or a subset of mixing tubes 308 by fuel lines separated and separately metered remote from combustor 16. In the illustrated embodiment of FIG. 3, cluster 300 can include five distinct mixing tubes 308 as noted above. In some embodiments, fuel delivered to one mixing tube 308 (e.g., mixing tube 308a) can be metered separately from fuel delivered to all other mixing tubes 308, thereby allowing delivery of 0%, 20%, 80%, or 100% of the fuel capacity of cluster 300 as a whole, without separately modulating fuel flow rate within individual mixing tubes 308. This organization of mixing tubes 308 with cluster 300 can advantageously allow a single mixing tube 308 to be activated during, for example, an engine idle mode.

[0038] FIGs. 5a-b illustrate an alternative clustering arrangements to that depicted in FIG. 3, and FIGs. 6a-b illustrated a variation of the clustering arrangement of FIGs. 5a- b. FIGs. 5a-b are generally discussed together, and FIG. 6a-b are discussed by reference to FIGs. 5a-b. FIGs. 5a illustrates mirrored clusters 500a and 500b. Elements of FIGs. 5a, 5b, 6a, and 6b operate generally as described above with reference to FIGs. 3 and 4, and are not discussed separately herein except where different from cluster 300 and mixing tube 308. Reference numerals in FIGs. 5a, 5b, 6a, and 6b, where shown, are selected to match corresponding elements in FIGs. 3 and 4 having like numbers outside of hundreds-place digits.

[0039] Mirrored clusters 500a / b include common structure selected to facilitate mounting together (i.e., adjacently) at a common axial location (relative to engine axis A) on outer case 206. As shown in FIG. 5 a, each cluster 500a / b includes three separate mixing tubes 508a, 508b, and 508s substantially as described above with reference to FIGs. 3 and 4, with some mixing tubes 500a / b sharing a common outer wall 510. Unlike cluster 300, however, clusters 500a / b include mixing tubes of different diameters. As shown in FIG. 5a, mixing tube 500s is notably smaller than mixing tubes 500a / b, having a flow area of, e.g., half that of mixing tubes 500a / b. This arrangement, with two mixing tubes 500a / b each having twice the sectional area and throughput of a smaller mixing tube 500s, facilitates the same proportion (20% / 80%) noted above with respect to cluster 300, where one of five mixing tubes 308 receives is metered separately from other mixing tubes 308. In embodiments wherein mixing tubes 508a / b have the same scale and throughput as mixing tubes 308, The combination of mirrored clusters 500a and 500b can have the same overall throughput, and can be analogously staged, i.e., through metering of one mixing tube 308 or both small mixing tubes 508s separately from other mixing tubes in either arrangement.

[0040] FIGs 6a and 6b present broadly the same structure discussed above with respect to FIGs 5a and 5b, but with angled outlet ducts 650a and 650b. Rather than being oriented generally towards engine axis A as discussed above and illustrated in FIGs. 4-5b, mixing tubes 608a / b of clusters 600a and 600b are angled away from each other in angled outlet flows F-OA1 and F-OA2. Outlet ducts 650a and 650b can, for example, produce angled outlet flows F-OA1 and F-OA2 that are fluidly separated relative to corresponding outlet flows of mixing tubes 508a / b, diverging to improve staging by reducing interference between adjacent mixing tubes. Excessive turning angles can cause undesirable flow separation and consequently increase flame holding, necessitating a compromise in outlet duct turning angle to reduce flow interference without producing flow separation. Turning angle through outlet ducts 650a / b can, for example, fall between 10 to 30°.

[0041] Discussion of Possible Embodiments

[0042] The following are non-exclusive descriptions of possible embodiments of the present invention.

[0043] A fuel-air mixing tube for a gas turbine engine combustor and extending along a centerline axis comprising: a fuel source; a venturi throat disposed axially downstream of the fuel source; a prefilming section broadening axially downstream from the venturi throat and terminating at a prefilmer edge; an outer axial swirler disposed circumferentially about the venturi throat, oriented to ingest air substantially axially and comprising a plurality of swirler vanes configured to increase swirl of the ingested air at the prefilmer edge; and a plurality of air passages extending at least partially radially inward, upstream of the prefilming section.

[0044] The fuel-air mixing tube of the preceding paragraph can optionally include, additionally and / or alternatively, any one or more of the following features, configurations and / or additional components:

[0045] A further embodiment of the foregoing fuel-air mixing tube, wherein the plurality of air passages includes a plurality of circumferentially distributed compoundangle air-swirl passages disposed to ingest air at least partially radially to the venturi throat.

[0046] A further embodiment of the foregoing fuel-air mixing tube, wherein the plurality of circumferentially distributed compound-angle air-swirl passages includes multiple axial stages of circumferentially distributed compound-angle air-swirl passages.

[0047] A further embodiment of the foregoing fuel -air mixing tube, wherein a swirl orientation of the circumferentially distributed compound-angle air-swirl passages is opposite a swirl orientation of the outer axial swirler.

[0048] A further embodiment of the foregoing fuel-air mixing tube, wherein the prefilming section has a frustoconical cross-section defining a prefilming surface with diameter broadening from narrowest at the venturi throat to broadest at the prefilmer edge.

[0049] A further embodiment of the foregoing fuel-air mixing tube, wherein the fuel source is a fuel nozzle outlet having an atomizer tip disposed to spray fuel towards the prefilming surface. A further embodiment of the foregoing fuel-air mixing tube, wherein the plurality of air passages includes a plurality of circumferentially distributed tip flow passages directed across the atomizer tip.

[0050] A further embodiment of the foregoing fuel-air mixing tube, wherein the outer air swirler and the plurality of air passages are sized relatively such that at least 85% of airflow through the fuel-air mixing tube passes through the outer air swirler.

[0051] A further embodiment of the foregoing fuel-air mixing tube, wherein an outer wall of the outer axial swirler tapers towards the centerline beginning at an axial location upstream of the prefilmer edge.

[0052] A further embodiment of the foregoing fuel-air mixing tube, wherein the outer wall of the outer axial swirler tapers to a minimum diameter at an outlet duct downstream of the prefilmer edge.

[0053] A further embodiment of the foregoing fuel-air mixing tube, wherein the outlet duct is angled at a turning angle away from the centerline axis.

[0054] A further embodiment of the foregoing fuel-air mixing tube, wherein the turning angle is between 20° and 55°

[0055] A further embodiment of the foregoing fuel-air mixing tube, wherein the prefilmer edge includes a plurality of cutout slots configured to increase edge length and introduce turbulence into airflow across the prefilmer edge.

[0056] A further embodiment of the foregoing fuel-air mixing tube, wherein the cutout slots comprise crenellations or castellations.

[0057] A gas turbine engine combustor comprising: a combustor liner extending along an engine axis; and a plurality of fuel nozzles disposed radially outward of the combustor liner, relative to the engine axis; and a cluster of fuel-air mixing tubes according to claim 1, wherein the fuel source of each of the fuel-air mixing tubes is a respective one of the plurality of fuel nozzles.

[0058] The gas turbine engine combustor of the preceding paragraph can optionally include, additionally and / or alternatively, any one or more of the following features, configurations and / or additional components:

[0059] A further embodiment of the foregoing gas turbine engine combustor, wherein the cluster of fuel-air mixing tubes comprises multiple fuel-air mixing tubes distributed equidistantly from a cluster centerline of the cluster of fuel-air mixing tubes.

[0060] A further embodiment of the foregoing gas turbine engine combustor, wherein the cluster of fuel-air mixing tubes comprises a mirrored pair of groups of the fuel- air mixing tubes, with each group of the fuel-air mixing tubes comprising fuel-air mixing tubes of different sizes.

[0061] A further embodiment of the foregoing gas turbine engine combustor, wherein some of the plurality of fuel nozzles are meterable separately form others of the plurality of fuel nozzles, such that fuel flow through the cluster of fuel -air mixing tubes can be staged by delivering fuel to some but not others of the cluster of fuel-air mixing tubes.

[0062] Summation

[0063] Any relative terms or terms of degree used herein, such as “substantially”, “essentially”, “generally”, “approximately” and the like, should be interpreted in accordance with and subject to any applicable definitions or limits expressly stated herein. In all instances, any relative terms or terms of degree used herein should be interpreted to broadly encompass any relevant disclosed embodiments as well as such ranges or variations as would be understood by a person of ordinary skill in the art in view of the entirety of the present disclosure, such as to encompass ordinary manufacturing tolerance variations, incidental alignment variations, alignment or shape variations induced by thermal, rotational or vibrational operational conditions, and the like.

[0064] 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

CLAIMS:

1. A fuel -air mixing tube for a gas turbine engine combustor and extending along a centerline axis comprising: a fuel source; a venturi throat disposed axially downstream of the fuel source; a prefilming section broadening axially downstream from the venturi throat and terminating at a prefilmer edge; an outer axial swirler disposed circumferentially about the venturi throat, oriented to ingest air substantially axially and comprising a plurality of swirler vanes configured to increase swirl of the ingested air at the prefilmer edge; and a plurality of air passages extending at least partially radially inward, upstream of the prefilming section.

2. The fuel -air mixing tube of claim 1, wherein the plurality of air passages includes a plurality of circumferentially distributed compound-angle air-swirl passages disposed to ingest air at least partially radially to the venturi throat.

3. The fuel-air mixing tube of claim 2, wherein the plurality of circumferentially distributed compound-angle air-swirl passages includes multiple axial stages of circumferentially distributed compound-angle air-swirl passages.

4. The fuel-air mixing tube of claim 1, wherein a swirl orientation of the circumferentially distributed compound-angle air-swirl passages is opposite a swirl orientation of the outer axial swirler.

5. The fuel-air mixing tube of claim 1, wherein the prefilming section has a frustoconical cross-section defining a prefilming surface with diameter broadening from narrowest at the venturi throat to broadest at the prefilmer edge.

6. The fuel-air mixing tube of claim 5, wherein the fuel source is a fuel nozzle outlet having an atomizer tip disposed to spray fuel towards the prefilming surface.

7. The fuel-air mixing tube of claim 5, wherein the plurality of air passages includes a plurality of circumferentially distributed tip flow passages directed across the atomizer tip.

8. The fuel-air mixing tube of claim 1, wherein the outer air swirler and the plurality of air passages are sized relatively such that at least 85% of airflow through the fuel-air mixing tube passes through the outer air swirler.

9. The fuel-air mixing tube of claim 1, wherein an outer wall of the outer axial swirler tapers towards the centerline beginning at an axial location upstream of the prefilmer edge.

10. The fuel-air mixing tube of claim 9, wherein the outer wall of the outer axial swirler tapers to a minimum diameter at an outlet duct downstream of the prefilmer edge.

11. The fuel-air mixing tube of claim 10, wherein the outlet duct is angled at a turning angle away from the centerline axis.

12. The fuel-air mixing tube of claim 11, wherein the turning angle is between 20° and 55°13. The fuel-air mixing tube of claim 1, wherein the prefilmer edge includes a plurality of cutout slots configured to increase edge length and introduce turbulence into airflow across the prefilmer edge.

14. The fuel-air mixing tube of claim 13, wherein the cutout slots comprise crenellations or castellations.

15. A gas turbine engine combustor comprising: a combustor liner extending along an engine axis; and a plurality of fuel nozzles disposed radially outward of the combustor liner, relative to the engine axis; and a cluster of fuel-air mixing tubes according to claim 1, wherein the fuel source of each of the fuel-air mixing tubes is a respective one of the plurality of fuel nozzles.

16. The gas turbine engine combustor of claim 15, wherein the cluster of fuelair mixing tubes comprises multiple fuel-air mixing tubes distributed equidistantly from a cluster centerline of the cluster of fuel-air mixing tubes.

17. The gas turbine engine combustor of claim 15, wherein the cluster of fuelair mixing tubes comprises a mirrored pair of groups of the fuel-air mixing tubes, with each group of the fuel-air mixing tubes comprising fuel-air mixing tubes of different sizes.

18. The gas turbine engine combustor of claim 15, wherein some of the plurality of fuel nozzles are meterable separately form others of the plurality of fuel nozzles, such that fuel flow through the cluster of fuel-air mixing tubes can be staged by delivering fuel to some but not others of the cluster of fuel-air mixing tubes.

Images