Mixer Assembly for a Gas Turbine Engine

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(12) United States Patent (1o)

Patent No.: US 8,973,368 B2

Dai et al. (45) Date of Patent:

Mar. 10, 2015

(54) MIXER ASSEMBLY FOR A GAS TURBINE 6,272,840 B1 8/2001 Crocker et al.

6,345,505 B1 * 2/2002 Green ............................. 60/748 ENGINE 6,354,072 B1 3/2002 Hura 6,363,726 B1 4/2002 Durbin et al.

(75) Inventors: Zhongtao Dai, Manchester, CT (US); 6,367,262 B1 4/2002 Mongia et al.

Jeffrey M. Cohen, Hebron, CT (US); 6,381,964 B1 5/2002 Pritchard, Jr. et al.

Catalin G. Fotache, West Hartford, CT 6,389,815 B1 5/2002 Hura et al.

(US); Lance L. Smith, West Hartford, 6,418,726 B1 7/2002 Foust et al.

CT (US); Donald J. Hautman, 6,484,489 B1 11/2002 Foust et al.

6,547,215 B2 4/2003 Matsusaka et al.

Marlborough, CT (US) 6,560,967 B1 5/2003 Cohen et al.

6,799,427 B2 * 10/2004 Calvez et al . ................... 60/737 (73) Assignee: United Technologies Corporation, 6,871,501 B2 * 3/2005 Bibler et al . .................... 60/772 Hartford, CT (US) 6,968,692 B2 11/2005 Chin et al.

7,010,923 B2 3/2006 Mancini et al.

(*) Notice: Subject to any disclaimer, the term of this 7,013,635 B2 3/2006 Cohen et al.

patent is extended or adjusted under 35 7,434,401 B2 * 10/2008 Hayashi .......................... 60/743 U.S.C. 154(b) by 62 days. 7,464,553 B2 12/2008 Hsieh et al.

7,537,646 B2 5/2009 Chen et al.

7,546,740 B2 6/2009 Chen et al.

(21) Appl. No.: 13/014,388 7,565,803 B2 7/2009 Li et al.

7,581,396 B2 9/2009 Hsieh et al.

(22) Filed: Jan. 26, 2011 7,621,131 B2 11/2009 Von Der Bank 7,669,421 B2 3/2010 Saitoh et al.

(65) Prior Publication Data 7,712,315 B2 5/2010 Hautman et al.

7,779,636 B2 8/2010 Buelow et al.

US 2012/0186256 Al Jul. 26, 2012 2004/0079085 Al 4/2004 Mancini et al.

(51) Int. Cl.

(Continued) F23R 3114 (2006.01) F23C 7/00 (2006.01) Primary Examiner Phutthiwat Wongwian F23R 3128 (2006.01) Assistant Examiner Steven Sutherland (52) U.S. Cl.

CPC . F23C 71004 (2013.01); F23R 3114 (2013.01); (74) Attorney, Agent, or Firm Miller, Matthias & Hull F23R 31286 (2013.01) LLP USPC ................... 60/748; 60/734; 60/737; 60/740; 60/776 (57) ABSTRACT (58) Field of Classification Search USPC ........... 60/734, 737, 740, 742, 746, 747, 748, A mixer assembly for a gas turbine engine is provided, includ- 60/776 ing a main mixer with fuel injection holes located between at See application file for complete search history.

least one radial swirler and at least one axial swirler, wherein (56) References Cited the fuel injected into the main mixer is atomized and dis- persed by the air flowing through the radial swirler and the U.S. PATENT DOCUMENTS axial swirler.

5,816,049 A * 10/1998 Joshi ............................... 60/737 6,082,111 A 7/2000 Stokes 18 Claims, 4 Drawing Sheets 6,161,387 A 12/2000 Green

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US 8,973,368 B2

Page 2 2008/0072605 Al 3/2008 Hagen et al.

(56) References Cited 2008/0078181 Al 4/2008 Mueller et al.

2009/0113893 Al 5/2009 Li et al.

U.S. PATENT DOCUMENTS 2009/0173076 Al 7/2009 Toon 2010/0050644 Al 3/2010 Pidcock et al.

2005/0028526 Al 2/2005 Von Der Bank 2010/0115956 Al 5/2010 Toon 2006/0248898 Al 11/2006 Buelow et al.

2010/0126177 Al 5/2010 Hautman et al.

2007/0017224 Al 1/2007 Li et al.

2010/0263382 Al 10/2010 Mancini et al.

2007/0028617 Al 2/2007 Hsieh et al.

2010/0269506 Al 10/2010 Nonaka et al.

2007/0028618 Al 2/2007 Hsiao et al.

2010/0287946 Al 11/2010 Buelow et al.

2007/0137207 Al 6/2007 Mancini et al.

2007/0163263 Al 7/2007 Thomson * cited by examiner

Patent Mar. 10, 2015 Sheet 1 of 4

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US 8,973,368 B2

MIXER ASSEMBLY FOR A GAS TURBINE carbon dioxide (CO 2) emissions, resulting in significant chal- ENGINE lenges to designing combustors that still produce low emis- sions despite increased combustor inlet pressure, tempera- STATEMENT OF FEDERALLY SPONSORED ture, and fuel/air ratio. Due to the limitation of emission 5 reduction potential for the rich burn-quick quench-lean burn RESEARCH OR DEVELOPMENT (RQL) combustor, lean burn combustors, and in particular the piloted lean premixed/partially premixed pre-vaporized com- This invention was made with Government support under bustor (PLPP), have become used more frequently for further Contract No. NNCOSCA92C awarded by the National Aero- reduction of emissions. However, one of the maj or challenges nautics and Space Administration (NASA). The U.S. Gov- for the development of PLPP is the requirement to sufficiently ernment has certain rights in the invention.

premix the injected fuel and combustion air in the main mixer CROSS REFERENCE TO RELATED of a mixer assembly within a given mixing time, which is APPLICATIONS required to be significantly shorter than the auto-ignition delay time.

This application is related to co-pending, commonly-as- 15 Mixer assemblies for existing PLPP combustors typically signed U.S. patent application (application Ser. No. 13/014, include a pilot mixer surrounded by a main mixer with a fuel 434), entitled "MIXERASSEMBLY FORA GAS TURBINE manifold provided between the two mixers to inject fuel ENGINE," filed on the date of filing of the present applica- radially into the cavity of the main mixer through fuel injec- tion, and is incorporated herein by reference in its entirety. tion holes. The main mixer typically employs air swirlers proximate and upstream of the fuel injection holes to impart BACKGROUND OF THE INVENTION a swirl to the air entering the main mixer and to provide rapid mixing of the air and the fuel, which is injected perpendicu- The subject matter disclosed herein relates generally to larly into the cross flow of the air atomizing the fuel for combustors for gas turbine engines and more particularly to mixing with the air. The level of atomization and mixing in mixer assemblies for gas turbine engines. 25 this main mixer configuration is largely dependent upon the Gas turbine engines, such as those used to power modern penetration of the fuel into the air, which in turn is dependent aircraft, to power sea vessels, to generate electrical power, upon the ratio of the momentum of the fuel to the momentum and in industrial applications, include a compressor for pres- of the air. As a result, the degree of atomization and mixing surizing a supply of air, a combustor for burning a hydrocar- may vary greatly for different gas turbine engine operating bon fuel in the presence of the pressurized air, and a turbine 30 conditions (e.g., low power conditions where there is poor for extracting energy from the resultant combustion gases.

atomization and mixing may result in higher emissions than Generally, the compressor, combustor, and turbine are dis- high power conditions where there is better atomization and posed about a central engine axis with the compressor dis- mixing). In addition, since the fuel injection holes are typi- posed axially upstream or forward of the combustor and the cally located downstream of the point where the air swirlers turbine disposed axially downstream of the combustor. In 35 produce the maximum turbulence, the degree of atomization operation of a gas turbine engine, fuel is injected into and and mixing is not maximized, increasing the amount of emis- combusted in the combustor with compressed air from the sions. Furthermore, since the fuel injection holes are typically compressor thereby generating high-temperature combustion located downstream of the air swirlers, the risk of flashback, exhaust gases, which pass through the turbine and produce flame holding and autoignition greatly increases due to the rotational shaft power. The shaft power is used to drive a 40 low velocity regions associated with fuel jets and walls. A compressor to provide air to the combustion process to gen- highly possible source for flashback, flame holding and autoi- erate the high energy gases. Additionally, the shaft power is gnition in the typical main mixer is caused by a wake region used to, for example, drive a generator for producing electric- that can form downstream of the fuel injection holes where ity, or drive a fan to produce high momentum gases for pro- injected fuel that has not sufficiently penetrated into the cross ducing thrust. 45 flow of the air (e.g., when air is flowing at low velocity) will An exemplary combustor features an annular combustion gather and potentially ignite. Another possible source is chamber defined between a radially inboard liner and a radi- related to boundary layers along the wall, which is thickened ally outboard liner extending aft from a forward bulkhead by fuel jets due to reduced velocity.

wall. The radially outboard liner extends circumferentially about and is radially spaced from the inboard liner, with the 50 BRIEF SUMMARY OF THE INVENTION combustion chamber extending fore to aft between the liners.

A plurality of circumferentially distributed fuel injectors are A mixer assembly for a gas turbine engine is provided, mounted in the forward bulkhead wall and project into the including a main mixer with fuel injection holes located forward end of the annular combustion chamber to supply the between at least one radial swirler and at least one axial fuel to be combusted. Air swirlers proximate to the fuel inj ec- 55 swirler, wherein the fuel injected into the main mixer is atom- tors impart a swirl to inlet air entering the forward end of the ized and dispersed by the air flowing through the radial combustion chamber at the bulkhead wall to provide rapid swirler and the axial swirler. This configuration reduces the mixing of the fuel and inlet air. dependence upon the ratio of the momentum of the fuel to the Combustion of the hydrocarbon fuel in air in gas turbine momentum of the air, increases the degree of atomization and engines inevitably produces emissions, such as oxides of 60 mixing by injecting the fuel at a point of high turbulence, and nitrogen (NOx), carbon dioxide (CO Z), carbon monoxide reduces the potential for flame holding by reducing the poten- (CO), unburned hydrocarbons (UHC), and smoke, which are tial for forming a wake region and lengthening the potential delivered into the atmosphere in the exhaust gases from the mixing distance.

gas turbine engine. Regulations limiting these emissions have According to one embodiment, a mixer assembly for a gas become more stringent. At the same time, the engine pressure 65 turbine engine is provided. The mixer assembly includes a ratio is getting higher and higher for increasing engine effi- main mixer comprising an annular inner radial wall, an annu- ciency, lowering specific fuel consumption, and lowering lar outer radial wall surrounding at least a portion of the

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annular inner radial wall, wherein the annular outer radial closed herein are not limited in application to the depicted wall incorporates a first outer radial wall swirler with a first embodiment of a gas turbine engine 10, but are applicable to other types of gas turbine engines, such as those used to power axis oriented substantially radially to a centerline axis of the modern aircraft, to power sea vessels, to generate electrical mixer assembly, a forward wall substantially perpendicular to 5 power, and in industrial applications.

and connecting the annular inner radial wall and the annular FIG. 2 is a partial perspective view of an exemplary outer radial wall forming an annular cavity, wherein the for- embodiment of a combustor 100 of a gas turbine engine 10.

ward wall incorporates a first forward wall swirler with a The combustor 100 is positioned between the compressor second axis oriented substantially axially to the centerline section 30 and the turbine section 50 of a gas turbine engine axis of the mixer assembly, and a plurality of fuel injection io 10. The exemplary combustor 100 includes an annular com- holes in the forward wall between the first outer radial wall bustion chamber 130 bounded by an inner (inboard) wall 132 swirler and the first forward wall swirler, wherein the first and an outer (outboard) wall 134 and a forward bulkhead wall outerradial wall swirler is on a first side of the plurality of fuel 136 spanning between the walls 132, 134 at the forward end injection holes and the first forward wall swirler is on a of the combustor 100. The bulkhead wall 136 of the combus- second side of the plurality of fuel injection holes.

15 for 100 carries a plurality of mixer assemblies 200, including In another embodiment, a mixer assembly for a gas turbine the fuel nozzle 152 of a fuel injector 150, a main mixer 220, engine is provided. The mixer assembly includes a main and a pilot mixer 210. It will be understood that, although mixer comprising an annular inner radial wall, an annular only a single mixer assembly 200 is shown in FIG. 2 for outer radial wall surrounding at least a portion of the annular illustrative purposes, the combustor 100 may include a plu- inner radial wall, wherein the annular outer radial wall incor- 2o rality of mixer assemblies 200 circumferentially distributed porates a plurality of outer radial wall swirlers with a first axis and mounted at the forward end of the combustor 100. A oriented substantially radially to a centerline axis of the mixer number of sparkplugs (not shown) are positioned with their assembly, a forward wall substantially perpendicular to and working ends along a forward portion of the combustion connecting the annular inner radial wall and the annular outer chamber 130 to initiate combustion of the fuel and air mix- radial wall forming an annular cavity, wherein the forward 25 ture. The combusting mixture is driven downstream within wall incorporates a first forward wall swirler with a second the combustor 100 along a principal flowpath 170 toward the axis oriented substantially axially to the centerline axis of the turbine section 50 of the engine 10. The fuel and air provided mixer assembly, and a plurality of fuel injection holes in the to the pilot mixer 210 produce a primary combustion zone forward wall between the plurality of outer radial wall swirl- 110 within a central portion of the combustion chamber 130.

ers and the first forward wall swirler, wherein the plurality of so The fuel and air provided to the main mixer 220 produce a outer radial wall swirlers is on a first side of the plurality of secondary combustion zone 120 in the combustion chamber fuel injection holes and the first forward wall swirler is on a 130 that is radially outwardly spaced from and concentrically second side of the plurality of fuel injection holes.

surrounds the primary combustion zone 110.

FIG. 3 is an enlarged partial perspective view of an exem- BRIEF DESCRIPTION OF THE DRAWINGS 35 plary embodiment of the mixer assembly 200 for the exem- plary combustor 100 of FIG. 2. The exemplary mixer assem- For a further understanding of the disclosure, reference bly 200 includes a main mixer 220 and a pilot mixer 210. The will be made to the following detailed description which is to pilot mixer 210 and the main mixer 220 are concentrically be read in connection with the accompanying drawing, arranged with the pilot mixer 210 located in the center of the wherein: 40 main mixer 220, which surrounds a portion of the pilot mixer FIG. 1 is a schematic diagram of an exemplary embodi- 210. The mixer assembly 200 has a centerline axis 218. The ment of a gas turbine engine.

pilot mixer 210 includes an annular pilot mixer housing 212 FIG. 2 is a partial perspective view of an exemplary separating and sheltering the pilot mixer 210 from the main embodiment of a combustor of a gas turbine engine.

mixer 220. The main mixer 220 further includes an annular FIG. 3 is an enlarged partial perspective view of an exem- 45 main mixer outer radial wall 222 radially surrounding a por- plary embodiment of a mixer assembly for the exemplary tion of the annular pilot mixer housing 212, the outer surface combustor of FIG. 2.

of which forms an annular main mixer inner radial wall 219, FIG. 4 is an enlarged partial perspective view of another and a main mixer forward wall 224 substantially perpendicu- exemplary embodiment of a mixer assembly for the exem- lar to and connecting the annular main mixer outer radial wall plary combustor of FIG. 2.

5o 222 and the annular main mixer inner radial wall 219, forming DETAILED DESCRIPTION OF THE INVENTION a main mixer annular cavity 228. The annular main mixer outer radial wall 222 further incorporates a first outer radial FIG. 1 is a schematic diagram of an exemplary embodi- wall swirler 240, while the main mixer forward wall 224 ment of a gas turbine engine 10. The gas turbine engine 10 is further incorporates a first forward wall swirler 230 and a depicted as a turbofan that incorporates a fan section 20, a 55 plurality of fuel injection holes 226 circumferentially distrib- compressor section 30, a combustion section 40, and a turbine uted between the first outer radial wall swirler 240 and the section 50. The combustion section 40 incorporates a com- first forward wall swirler 230 around the main mixer forward bustor 100 that includes a plurality of fuel injectors 150 that wall 224. Although shown proximate to the first outer radial are positioned annularly about a centerline 2 of the engine 10 wall swirler 240 in the main mixer forward wall 224, the fuel upstream of the turbines 52, 54. Throughout the application, 60 injection holes 226 can be located proximate the first forward the terms "forward" or "upstream" are used to refer to direc- wall swirler 230 in the main mixer forward wall 224 as well.

tions and positions located axially closer toward a fuel/air The fuel injection holes 226 are in flow communication with intake side of a combustion system than directions and posi- a fuel manifold (not shown), which in turn is in flow commu- tions referenced as "aft" or "downstream." The fuel injectors nication with a fuel supply. Although described with respect 150 are inserted into and provide fuel to one or more com- 65 to liquid fuel, the exemplary embodiments of mixer assem- bustion chambers for mixing and/or ignition. It is to be under- blies 200 can also be used with gaseous fuel or partially stood that the combustor 100 and fuel injector 150 as dis- vaporized fuel. As can be seen in FIG. 3, the first outer radial

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wall swirler 240 is positioned on a first side of the fuel injec- the swirlers may be altered to vary the swirl direction of air tion holes 226, while the first forward wall swirler 230 is flowing and are not limited to the exemplary swirl directions positioned on a second side of the fuel injection holes 226. In indicated. Furthermore, the number of radial and axial swirl- one embodiment, the first side is substantially opposite of the ers can be modified (e.g., the first outer radial wall swirler 240 second side. 5 can be replaced by a plurality of radial swirlers and the first The first outer radial wall swirler 240 is incorporated into forward wall swirler 230 can be replaced by a plurality of the annular main mixer outer radial wall 222 and has an axis axial swirlers).

248 oriented substantially radially to the centerline axis 218 FIG. 4 is an enlarged partial perspective view of another of the mixer assembly 200. The first forward wall swirler 230 exemplary embodiment of the mixer assembly 200 for the is incorporated into the main mixer forward wall 224 and is io exemplary combustor 100 of FIG. 2. As in FIG. 3, the exem- oriented substantially parallel or axially to the centerline axis plary mixer assembly 200 includes a main mixer 220 and a 218 of the mixer assembly 200. The swirlers 230, 240 each pilot mixer 210. The pilot mixer 210 includes an annular pilot have a plurality of vanes for swirling air traveling through the mixer housing 212 separating and sheltering the pilot mixer swirlers to mix the air and the fuel dispensed by the fuel 210 from the main mixer 220. The main mixer 220 further injection holes 226. The first outer radial wall swirler 240 15 includes an annular main mixer outer radial wall 222 radially includes a first plurality of vanes 242 forming a first plurality surrounding a portion of the annular pilot mixer housing 212, of air passages 244 between the vanes 242. The vanes 242 are the outer surface of which forms an annular main mixer inner oriented at an angle with respect to axis 248 to cause the air to radial wall 219, and a main mixer forward wall 224 substan- rotate in the main mixer annular cavity 228 in a first direction tially perpendicular to and connecting the annular main mixer (e.g., clockwise). The first forward wall swirler 230 includes 20 outer radial wall 222 and the annular main mixer inner radial a second plurality of vanes 232 forming a second plurality of wall 219, forming a main mixer annular cavity 228. The air passages 234 between the vanes 232. The vanes 232 are annular main mixer outer radial wall 222 further incorporates oriented at an angle with respect to the centerline axis 218 to a plurality of outer radial wall swirlers, including a first outer cause the air to rotate in the main mixer annular cavity 228 in radial wall swirler 270, a second outer radial wall swirler 280, a second direction (e.g., counterclockwise). 25 and a third outer radial wall swirler 290, while the main mixer In the exemplary embodiment of the main mixer 220 forward wall 224 further incorporates a plurality of forward shown in FIG. 3, the air flowing through the first outer radial wall swirlers, including a first forward wall swirler 250, a wall swirler 240 will be swirled in a first direction and the air second forward wall swirler 260, and a plurality of fuel inj ec- flowing through the first forward wall swirler 230 will be tion holes 226 circumferentially distributed between the sec- swirled in a direction substantially opposite of the first direc- 30 ond forward wall swirler 260 and the first outer radial wall tion. Also, in the exemplary embodiment of the main mixer swirler 270 around the main mixer forward wall 224.

220 shown in FIG. 3, the air flowing through the first outer Although shown proximate to the first outer radial wall radial wall swirler 240 has an axis 248 oriented substantially swirler 270 in the main mixer forward wall 224, the fuel radially to the centerline axis 218 of the mixer assembly 200, injection holes 226 can be located proximate the second for- while the air flowing through the first forward wall swirler 35 ward wall swirler 260 in the main mixer forward wall 224 as 230 has an axis oriented substantially axially to the centerline well. The fuel injection holes 226 are in flow communication axis 218 of the mixer assembly 200. In this configuration, the with a fuel manifold (not shown), which in turn is in flow fuel is injected through the fuel injection holes 226 between communication with a fuel supply. Although described with the radial first outer radial wall swirler 240 and the axial first respect to liquid fuel, the exemplary embodiments of mixer forward wall swirler 230. In one embodiment, the fuel is 40 assemblies 200 can also be used with gaseous fuel orpartially injected through the fuel injection holes 226 that are oriented vaporized fuel. As can be seen in FIG. 4, the first, second, and substantially perpendicularly to axis 248 and the flow of air third outer radial wall swirlers 270, 280, 290 are positioned on from the radial first outer radial wall swirler 240, which a first side of the fuel injection holes 226, while the first and atomizes and disperses the fuel. The fuel then is atomized and second forward wall swirlers 250, 260 are positioned on the dispersed again by the flow of air from the axial first forward 45 second side of the fuel injection holes 226. In one embodi- wall swirler 230, thus atomizing the fuel by airflow from two ment, the first side is substantially opposite of the second side.

sides. Although shown proximate to the first outer radial wall The first, second, and third outer radial wall swirlers 270, swirler 240 in the main mixer forward wall 224, the fuel 280, 290 are incorporated into the annular main mixer outer injection holes 226 can be located proximate the first forward radial wall 222 and each have an axis 248 oriented substan- wall swirler 230 in the main mixer forward wall 224 and be 50 tially radially to the centerline axis 218 of the mixer assembly oriented substantially perpendicularly to the axis of the first 200. The first and second forward wall swirlers 250, 260 are forward wall swirler 230 and the flow of air from the radial incorporated into the main mixer forward wall 224 and are first forward wall swirler 230, which atomizes and disperses oriented substantially parallel or axially to the centerline axis the fuel. The fuel then is atomized and dispersed again by the 218 of the mixer assembly 200. Swirlers 250, 260, 270, 280, flow of air from the axial first outer radial wall swirler 240, 55 290 each have a plurality of vanes for swirling air traveling thus atomizing the fuel by airflow from two sides. In either through the swirlers to mix the air and the fuel dispensed by configuration, an intense mixing region 229 of fuel and air is the fuel injection holes 226.

created within annular main mixer cavity 228 axially adjacent The first outer radial wall swirler 270 includes a first plu- to the fuel injection holes 226, allowing the majority of fuel rality of vanes 272 forming a first plurality of air passages 274 and air to be mixed before entering the downstream end of the 60 between the vanes 272. The vanes 272 are oriented at an angle annular main mixer cavity 228. This configuration reduces with respect to axis 248 to cause the air to rotate in the main the dependence upon the ratio of the momentum of the fuel to mixer annular cavity 228 in a first direction (e.g., clockwise).

the momentum of the air, increases the degree of atomization The second outer radial wall swirler 280 includes a second and mixing by injecting the fuel at a point of high turbulence, plurality of vanes 282 forming a second plurality of air pas- and reduces the potential for flame holding by reducing the 65 sages 284 between the vanes 282. The vanes 282 are oriented potential for forming a wake region and lengthening the at an angle with respect to axis 248 to cause the air to rotate in potential mixing distance. The configuration of the vanes in the main mixer annular cavity 228 in a second direction (e.g.,

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counterclockwise). The third outer radial wall swirler 290 swirlers may be altered to vary the swirl direction of air includes a third plurality of vanes 292 forming a third plural- flowing and are not limited to the exemplary swirl directions indicated.

ity of air passages 294 between the vanes 292. The vanes 292 The terminology used herein is for the purpose of descrip- are oriented at an angle with respect to axis 248 to cause the 5 tion, not limitation. Specific structural and functional details air to rotate in the main mixer annular cavity 228 in a third disclosed herein are not to be interpreted as limiting, but direction. In one embodiment, the third direction can be sub- merely as basis for teaching one skilled in the art to employ stantially the same as the first direction which are substan- the present invention. While the present invention has been tially opposite of the second direction.

particularly shown and described with reference to the exem- The first forward wall swirler 250 includes a fourth plural- io plary embodiments as illustrated in the drawing, it will be ity of vanes 252 forming a fourth plurality of air passages 254 recognized by those skilled in the art that various modifica- between the vanes 252. The vanes 252 are oriented at an angle tions may be made without departing from the spirit and with respect to the centerline axis 218 to cause the air to rotate scope of the invention. Those skilled in the art will also in the main mixer annular cavity 228 in a fourth direction recognize the equivalents that may be substituted for ele- (e.g., counterclockwise). The second forward wall swirler 15 ments described with reference to the exemplary embodi- 260 includes a fifth plurality of vanes 262 forming a fifth ments disclosed herein without departing from the scope of plurality of air passages 264 between the vanes 262. The the present invention. Therefore, it is intended that the present vanes 262 are oriented at an angle with respect to the center- disclosure not be limited to the particular embodiment(s) line axis 218 to cause the air to rotate in the main mixer disclosed as, but that the disclosure will include all embodi- annular cavity 228 in a fifth direction (e.g., clockwise). In one 20 ments falling within the scope of the appended claims.

embodiment, the fourth direction is substantially opposite of the fifth direction. We claim: In the exemplary embodiment of the main mixer 220 1. A mixer assembly for a gas turbine engine comprising: shown in FIG. 4, the clockwise air passing through the first a main mixer comprising: outer radial wall swirler 270 and the third outer radial wall 25 an annular inner radial wall; swirler 290 counter-rates against the counterclockwise air an annular outer radial wall surrounding at least a portion passing through the second outer radial wall swirler 280, of the annular inner radial wall, wherein the annular increasing the turbulence, which improves mixing. Also, the outer radial wall incorporates a first outer radial wall counterclockwise air passing through the first forward wall swirler with a first axis oriented substantially radially to swirler 250 counter-rates against the clockwise air passing so a centerline axis of the mixer assembly; through the second forward wall swirler 260, increasing the a forward wall extending primarily radially outward with turbulence, which improves mixing. In addition, the air flow- respect to the first axis and connecting the annular inner ing through the first, second, and third outer radial wall swirl- radial wall and the annular outer radial wall, the inner ers 270, 280, 290 has an axis 248 oriented substantially radi- radial wall, forward wall, and outer radial wall forming ally to the centerline axis 218 of the mixer assembly 200, 35 a single annular cavity therebetween, wherein the for- while the air flowing through the first and second forward ward wall incorporates a first forward wall swirler with wall swirlers 250, 260 has an axis oriented substantially axi- a second axis oriented substantially axially to the cen- ally to the centerline axis 218 of the mixer assembly 200. In terline axis of the mixer assembly; and this configuration, the fuel is injected through the fuel injec- a plurality of fuel injection holes in the forward wall tion holes 226 between the radial first, second, and third outer 40 between the first outer radial wall swirler and the first radial wall swirlers 270, 280, 290 and the axial first and forward wall swirler, the fuel injection holes oriented to second forward wall swirlers 250, 260. inject a fuel into the main mixer, wherein the fuel is In one embodiment, the fuel is injected through the fuel atomized and dispersed by the airflow from the first injection holes 226 that are oriented substantially perpendicu- forward wall swirler and is subsequently atomized and larly to axis 248 and the flow of air from the plurality of outer 45 dispersed by the airflow from the first outer radial wall radial wall swirlers (first, second, and third outer radial wall swirler, wherein the first outer radial wall swirler is on a swirlers 270, 280, 290), which atomizes and disperses the first side of the plurality of fuel injection holes and the fuel. The fuel then is atomized and dispersed again by the flow first forward wall swirler is on a second side of the of air from the plurality of forward wall swirlers (first and plurality of fuel injection holes, the first side being oppo- second forward wall swirlers 240, 250), thus atomizing the 50 site the second side.

fuel by airflow from two sides. Although shown proximate to 2. The mixer assembly of claim 1, wherein the plurality of outer radial wall swirlers 270, 280, 290 in the the first outer radial wall swirler further comprises a first main mixer forward wall 224, the fuel injection holes 226 can plurality of vanes forming a first plurality of air pas- be located proximate the plurality of forward wall swirlers sages, wherein the first plurality of vanes are oriented at 250, 260 in the main mixer forward wall 224 and be oriented 55 an angle with respect to the first axis to cause the air substantially perpendicularly to the axis and the flow of air passing through the first outer radial wall swirler to from the plurality of forward wall swirlers 250, 260, which rotate in a first direction; and atomizes and disperses the fuel. The fuel then is atomized and the first forward wall swirler further comprises a second dispersed again by the flow of air from the plurality of outer plurality of vanes forming a second plurality of air pas- radial wall swirlers 270, 280, 290, thus atomizing the fuel by 60 sages, wherein the second plurality of vanes are oriented airflow from two sides. In either configuration, an intense at an angle with respect to the second axis to cause the air mixing region 229 of fuel and air is created within annular passing through the first forward wall swirler to rotate in main mixer cavity 228 axially adjacent to the fuel injection a second direction.

holes 226, allowing the majority of fuel and air to be mixed 3. The mixer assembly of claim 2, wherein the first direc- before entering the downstream end of the annular main 65 tion is substantially opposite of the second direction.

mixer cavity 228. The number of axial swirlers, the number of 4. The mixer assembly of claim 1, further comprising a radial swirlers, and the configuration of the vanes in the pilot mixer, at least a portion of which is surrounded by the

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main mixer, wherein the pilot mixer comprises an annular respect to the first axis to cause the air passing through housing having an outer surface that forms the annular inner the first outer radial wall swirler to rotate in a first direc- wall of the main mixer.

tion; and 5. The mixer assembly of claim 1, further comprising a fuel a second outer radial wall swirler comprising a second manifold in flow communication with the plurality of fuel 5 plurality of vanes forming a second plurality of air pas- injection holes.

sages, wherein the second plurality of vanes are oriented 6. The mixer assembly of claim 1, wherein the plurality of at an angle with respect to the first axis to cause the air fuel injection holes are oriented substantially perpendicularly passing through the second outer radial wall swirler to to the second axis.

rotate in a second direction.

7. The mixer assembly of claim 1, wherein the first side of 10 10. The mixer assembly of claim 9, wherein the first direc- the plurality of fuel injection holes is substantially opposite of tion is substantially opposite of the second direction.

the second side of the plurality of fuel injection holes.

11. The mixer assembly of claim 9, wherein the plurality of 8. A mixer assembly for a gas turbine engine comprising: outerradial wall swirlers further comprises a third outerradial a main mixer comprising: 15 wall swirler comprising a third plurality of vanes forming a an annular inner radial wall; third plurality of air passages, wherein the third plurality of an annular outer radial wall surrounding at least a portion vanes are oriented at an angle with respect to the first axis to of the annular inner radial wall, wherein the annular cause the air passing through the third outer radial wall outer radial wall incorporates a plurality of outer radial swirler to rotate in a third direction.

wall swirlers with a first axis oriented substantially radi- 12. The mixer assembly of claim 11, wherein the first ally to a centerline axis of the mixer assembly; ~~ direction is substantially the same as the third direction.

a forward wall extending primarily radially outward with 13. The mixer assembly of claim 8, wherein the first for- respect to the first axis and connecting the annular inner ward wall swirler further comprises a first plurality of vanes radial wall and the annular outer radial wall, the inner forming a first plurality of air passages, wherein the first radial wall, forward wall, and outer radial wall forming 25 plurality of vanes are oriented at an angle with respect to the a single annular cavity therebetween, wherein the for- second axis to cause the air passing through the first forward ward wall incorporates a first forward wall swirler with wall swirler to rotate in a fourth direction.

a second axis oriented substantially axially to the cen- 14. The mixer assembly of claim 8, further comprising a terline axis of the mixer assembly; and second forward wall swirler proximate the first forward wall a plurality of fuel injection holes in the forward wall 30 swirler.

between the plurality of outerradial wall swirlers and the 15. The mixer assembly of claim 14, wherein the second first forward wall swirler, the fuel injection holes ori- forward wall swirler further comprises a second plurality of ented to inject a fuel into the main mixer, wherein the vanes forming a second plurality of air passages, wherein the fuel is atomized and dispersed by the airflow from the second plurality of vanes are oriented at an angle with respect first forward wall swirler and is subsequently atomized 35 to the second axis to cause the air passing through the second and dispersed by the airflow from the first outer radial forward wall swirler to rotate in a fifth direction.

wall swirler, wherein the plurality of outer radial wall 16. The mixer assembly of claim 15, wherein the fourth swirlers is on a first side of the plurality of fuel injection direction is substantially opposite of the fifth direction.

holes and the first forward wall swirler is on a second 17. The mixer assembly of claim 8, wherein the plurality of side of the plurality of fuel injection holes, the first side fuel injection holes are oriented substantially perpendicularly being opposite the second side. 40 to the second axis.

9. The mixer assembly of claim 8, wherein the plurality of 18. The mixer assembly of claim 8, wherein the first side of outer radial wall swirlers further comprises: the plurality of fuel injection holes is substantially opposite of a first outer radial wall swirler comprising a first plurality the second side of the plurality of fuel injection holes.

of vanes forming a first plurality of airpassages, wherein the first plurality of vanes are oriented at an angle with