Abstract:
A swirler for fuel injection in a gas turbine engine includes a frustoconical swirler body. A first and a second air flow path direct air in generally opposed circumferential directions into the swirler. These air paths intermix and create turbulence. As this turbulence encounters fuel droplets, the fuel is atomized, and uniformly distributed within the air flow. A shear layer is created adjacent an inner surface of the swirler body. In a separate feature, a third air flow path is directed into the air.

Description:
BACKGROUND 
       [0001]    This application relates to a swirler for a gas turbine engine fuel injector. 
         [0002]    Gas turbine engines are known and typically include a compressor which compresses air and delivers the air into a combustor. The air is mixed with fuel, and ignited. Products of this combustion pass downstream over turbine rotors, driving turbine rotors to rotate. 
         [0003]    The injection of the fuel and the mixing of the fuel with air are highly engineered processes in gas turbine engine design. Often, the fuel is injected within a conical body known as a swirler. Air may be injected through several paths, and in counter-rotating flow within the swirler. 
       SUMMARY 
       [0004]    In a first feature, a swirler for a gas turbine engine fuel injector includes a frustoconical swirler body extending from an upstream end to a downstream end. A fuel injector extends into the body, and has a downstream end for injecting fuel in a downstream direction. A first air flow path directs air in a first circumferential direction about a central axis of the swirler body. A second flow path extends delivers air to intermix with the air in the first flow path and in a circumferential direction generally opposed to the first circumferential direction. The first flow is provided in a greater volume than the volume provided in the second flow path, and the intermixed first and second flow paths create turbulence which atomizes and entrains fuel, and creates a shear boundary layer along an internal surface of the swirler. This provides good mixing and a generally uniform fuel/air mixture. 
         [0005]    In a second feature, first and second flow paths are positioned to inject air upstream of a downstream end of a he fuel injector where fuel is injected. A third flow path injects air into a swirler body at a location that is downstream of the downstream end of the fuel injector. The third flow path is generally in the same circumferential direction as the first flow path. Air is injected in the second flow path generally opposed to the direction of air flow from the first and third air flow paths. 
         [0006]    These and other features of the present invention can be best understood from the following specification and drawings, of which the following is a brief description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  schematically shows a gas turbine engine. 
           [0008]      FIG. 2  shows the flow of air, fuel, and the products of combustion in a gas turbine engine combustor. 
           [0009]      FIG. 3  shows an embodiment of a swirler. 
           [0010]      FIG. 4  shows a second embodiment swirler. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    A gas turbine engine  10 , such as a turbofan gas turbine engine, circumferentially disposed about an engine centerline, or axial centerline axis  12  is shown in  FIG. 1 . The engine  10  includes a fan  14 , compressor sections  15  and  16 , a combustion section  18  and a turbine section  20 . As is well known in the art, air compressed in the compressor  15 / 16  is mixed with fuel and burned in the combustion section  18  and expanded in turbine  20 . The turbine  20  includes rotors  22  and  24 , which rotate in response to the expansion. The turbine  20  comprises alternating rows of rotary airfoils or blades  26  and static airfoils or vanes  28 . In fact, this view is quite schematic, and blades  26  and vanes  28  are actually removable. It should be understood that this view is included simply to provide a basic understanding of the sections in a gas turbine engine, and not to limit the invention. This invention extends to all types of turbine engines for all types of applications. 
         [0012]      FIG. 2  shows a portion of the combustion section  18  including a combustor  62  which includes a swirler  50 . As known in the art, there are typically a plurality of swirlers spaced circumferentially about a central axis of the engine. Swirler  50  incorporates a fuel injector  58  injecting fuel from a forward, or downstream end  61 . In practice, the forward end  61  may be frusto-conical. The interior of body  51  of the swirler  50  is also frusto-conical heading in a downstream director from the fuel injector  58 . 
         [0013]    A first air path  52  extends through an upstream plate section  53  of the body  51 . A second flow path  54  extends just downstream of the flow path  53 . A third flow path  56  flows further downstream, and may be called an outer flow. 
         [0014]    Fuel is injected as shown schematically at  60 . As can be appreciated, flow paths  53  and  54  are upstream of the end  61  while the flow path  56  is downstream of the forward end  61  of the fuel injector. In fact, the flow path  56  leaves the body  51  downstream of an end  57 . 
         [0015]    As shown in  FIG. 3 , the flow path  53  is defined by a plurality of vanes  160 . The vanes  160  cause flow in one circumferential direction about a central axis of the swirler  50 . Further vanes  162  define the flow path  54 . These vanes direct the flow to be in a counter-direction relative to the flow from flow path  52 . These two flow paths intermix, and have a high counter-swirling flow which will improve entrainment of the fuel once the intermixed flows reach the injected fuel  60 . 
         [0016]    The flow through the flow path  56  is shown in  FIG. 3  to occur in a forward plate  70  through holes  72 . This flow is directed by angling the holes  72  such that the flow path  56  is generally in the same circumferential direction as the flow path  52 . It should be understood that the directions of the flow paths  52 ,  54 , and  56  need not be directly opposite, or identically in the same direction. Instead, it is generally true that flow path  52  and  56  are generally in the same circumferential direction, and opposed to the flow path  54 . In addition, as can be appreciated from the Figures, each of the three flow paths are defined by a plurality of flow directing members and a plurality of openings. The fact that the claims might refer to “the direction” of flow in any one of the three flow paths should not be interpreted as requiring that there be a single direction of flow across all of these pluralities of flow openings. Rather, there could be a number of varying angles to the flow. However, in general, the circumferential direction provided by the first and third flow path should be generally the same, and opposed to the flow direction of the second flow path. 
         [0017]    The first flow is provided in a greater volume than the volume provided in the second flow path, and the intermixed first and second flow paths create turbulence which atomizes and entrains fuel, and creates a shear boundary layer along an internal surface of the body  51 . This provides good mixing and a generally uniform fuel/air mixture. 
         [0018]    In embodiments, the first flow path will direct a greater volume of air than the second flow path. The ratio of the volume in the first flow path to the volume in the second flow path may be between 1.5-19. In one embodiment, the ratio was 9:1. The ratio of the sum of the first and second paths to the volume of the third path is between 3.0 and 19.0. The sizes of the flow passages that define the flow paths are designed to achieve these volumes. 
         [0019]    However, as the fuel and air leaves the ends  57  of the body  51 , the fuel can be caused to be thrown radially outwardly due to centrifugal forces. The third flow path  56  again counters this tendency, and ensures the uniform mixture continues downstream into the flame area. 
         [0020]    By injecting the third flow path downstream of the end  61 , the air in the flow path  56  tends to slow the counter-swirling air, and further ensure proper and more homogeneous mixing of the fuel and air. Thus, as shown at  58 , there is little or no vortex breakdown in the swirling air flow, and a more uniform air/fuel distribution. A flame  66  is shown at a shear layer, and the flame and vortex entrain hot products of the combustion as shown schematically at  64 . As can be appreciated, the flame  66 , the vortex  68 , and the products  64  are generally found within the combustor  62 . 
         [0021]      FIG. 4  shows an alternative embodiment  80 . As can be appreciated, the first flow path  52  is generally the same as in the  FIG. 3  embodiment. However, the second flow path  82  is formed further downstream. This location would still be upstream of the end  61  of the injector. 
         [0022]    In this embodiment, the third flow path  84  is defined by vanes  84 , rather than the holes  72  of the  FIG. 3  embodiment. The embodiment of  FIG. 4  will operate to provide very similar mixing and flow paths in the combustor as does the  FIG. 3  embodiment. 
         [0023]    Although embodiments of this invention have been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.