Patent Publication Number: US-2021172605-A1

Title: Bluff-body piloted high-shear injector and method of using same

Description:
BACKGROUND 
     1. Technical Field 
     This disclosure relates generally to combustors for gas turbine engines, and more particularly to fuel injectors for use in a combustor. 
     2. Background Information 
     Combustors, such as those used in gas turbine engines, may generally include radially spaced inner and outer shells which define a combustion chamber therebetween. A bulkhead may be provided at the forward end of the combustion chamber to shield a forward section of the combustor from the relatively high temperatures in the combustion chamber. A series of fuel injectors may be used to inject fuel, air, and other fluids through the bulkhead and into the combustion chamber. Swirlers may be disposed downstream of the fuel injectors to provide mixing of the fluids injected by the fuel injectors. 
     However, conventional combustor and fuel injector configurations may allow the central recirculation zone of gases within the combustor to re-enter the swirler or portions of the combustor upstream of the combustion chamber. Fluctuation of this central recirculation zone may create a region susceptible to unsteady heat release inside the swirler which may then couple with the acoustic mode of the combustor. Accordingly, what is needed is an improved fuel injector which addresses one or more of the above-noted concerns. 
     SUMMARY 
     It should be understood that any of all of the features or embodiments described herein can be used or combined in any combination with each and every other feature or embodiment described herein unless expressly noted otherwise. 
     According to an embodiment of the present disclosure, a combustor for a gas turbine engine includes a combustion chamber defined between an inner shell and an outer shell. A hood chamber is separated from the combustion chamber by a bulkhead extending between the inner shell and the outer shell. The bulkhead includes at least one opening extending between the hood chamber and the combustion chamber. A fuel injector extends through the at least one opening. The fuel injector includes a primary fuel passage including a primary fuel outlet located within the combustion chamber. The fuel injector further includes a secondary fuel passage including a plurality of secondary fuel outlets located within the hood chamber. 
     In the alternative or additionally thereto, in the foregoing embodiment, the combustor further includes a swirler extending through the at least one opening and located radially outside of the fuel injector with respect to a fuel injector center axis. 
     In the alternative or additionally thereto, in the foregoing embodiment, the primary fuel outlet is located at or downstream of the swirler exit plane. 
     In the alternative or additionally thereto, in the foregoing embodiment, a downstream end of the fuel injector includes a tip surface and the primary fuel outlet is located in a center of the tip surface. 
     In the alternative or additionally thereto, in the foregoing embodiment, the tip surface is located at or downstream of the swirler exit plane. 
     In the alternative or additionally thereto, in the foregoing embodiment, the tip surface is substantially parallel to the swirler exit plane. 
     In the alternative or additionally thereto, in the foregoing embodiment, the fuel injector further includes a cooling air passage including a plurality of air outlets located in the tip surface radially outside of the primary fuel outlet with respect to the fuel injector center axis. 
     In the alternative or additionally thereto, in the foregoing embodiment, the fuel injector further includes an annular air gap disposed between the primary fuel passage and the cooling air passage. 
     In the alternative or additionally thereto, in the foregoing embodiment, the annular air gap is enclosed by a fuel injector body of the fuel injector and radially spaced from the primary fuel passage and the cooling air passage by the fuel injector body. 
     In the alternative or additionally thereto, in the foregoing embodiment, the fuel injector and the swirler define an annular swirler passage therebetween and the plurality of secondary fuel outlets is configured to direct secondary fuel through the annular swirler passage and into the combustion chamber. 
     In the alternative or additionally thereto, in the foregoing embodiment, the tip surface is disposed downstream of the bulkhead. 
     In the alternative or additionally thereto, in the foregoing embodiment, the plurality of secondary fuel outlets is disposed along a fuel injector plane located upstream of the swirler exit plane. 
     According to another embodiment of the present disclosure, a method for operating a fuel injector of a gas turbine engine is provided. The method includes injecting a primary fuel from a primary fuel passage of the fuel injector directly into a combustion chamber defined between an inner shell and an outer shell. The primary fuel passage includes a primary fuel outlet located within the combustion chamber. The method further includes injecting a second fuel from a secondary fuel passage of the fuel injector into a hood chamber separated from the combustion chamber by a bulkhead extending between the inner shell and the outer shell. The secondary fuel passage includes a plurality of secondary fuel outlets located within the hood chamber. 
     In the alternative or additionally thereto, in the foregoing embodiment, the bulkhead includes an opening extending between the combustion chamber and the hood chamber. The method further includes providing a swirler extending through the at least one opening and located radially outside of the fuel injector with respect to a fuel injector center axis. The swirler includes a swirler exit plane defined by a downstream end of the swirler. 
     In the alternative or additionally thereto, in the foregoing embodiment, the primary fuel outlet is located at or downstream of the swirler exit plane. 
     In the alternative or additionally thereto, in the foregoing embodiment, a downstream end of the fuel injector includes a tip surface and the primary fuel outlet is located in a center of the tip surface. 
     In the alternative or additionally thereto, in the foregoing embodiment, the tip surface is located at or downstream of the swirler exit plane. 
     In the alternative or additionally thereto, in the foregoing embodiment, the method further includes injecting a cooling air from a cooling air passage into the combustion chamber. The cooling air passage includes a plurality of air outlets located in the tip surface radially outside of the primary fuel outlet with respect to the fuel injector center axis. 
     In the alternative or additionally thereto, in the foregoing embodiment, the plurality of secondary fuel outlets is disposed along a fuel injector plane located upstream of the swirler exit plane. 
     According to another embodiment of the present disclosure, a combustor for a gas turbine engine includes a combustion chamber defined between an inner shell and an outer shell. A hood chamber is separated from the combustion chamber by a bulkhead extending between the inner shell and the outer shell. The bulkhead includes at least one opening extending between the hood chamber and the combustion chamber. A swirler extends through the at least one opening. The swirler includes a swirler exit plane defined by a downstream end of the swirler. A fuel injector extends through the swirler. A downstream end of the fuel injector includes a tip surface located at or downstream of the swirler exit plane. The tip surface extends substantially parallel to the swirler exit plane. The fuel injector includes a primary fuel passage including a primary fuel outlet located within the combustion chamber. The primary fuel outlet is located in a radial center of the tip surface with respect to a fuel injector center axis. The primary fuel outlet further includes a secondary fuel passage including a plurality of secondary fuel outlets located within the hood chamber. The primary fuel outlet further includes a cooling air passage including a plurality of air outlets located in the tip surface radially outside of the primary fuel outlet with respect to the fuel injector center axis. 
     The present disclosure, and all its aspects, embodiments and advantages associated therewith will become more readily apparent in view of the detailed description provided below, including the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a side cross-sectional view of a gas turbine engine in accordance with one or more embodiments of the present disclosure. 
         FIG. 2  illustrates a cross-sectional view of an exemplary combustor of a gas turbine engine in accordance with one or more embodiments of the present disclosure. 
         FIG. 3  illustrates a side cross-sectional view a fuel injector of the combustor of  FIG. 2  in accordance with one or more embodiments of the present disclosure. 
         FIG. 4  illustrates a cross-sectional view of the fuel injector of  FIG. 3  taken along line  4 - 4  in accordance with one or more embodiments of the present disclosure. 
         FIG. 5  illustrates a cross-sectional view of the fuel injector of  FIG. 3  taken along line  5 - 5  in accordance with one or more embodiments of the present disclosure. 
         FIG. 6  illustrates a side cross-sectional view a fuel injector of the combustor of  FIG. 2  in accordance with one or more embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     It is noted that various connections are set forth between elements in the following description and in the drawings. It is noted that these connections are general and, unless specified otherwise, may be direct or indirect and that this specification is not intended to be limiting in this respect. A coupling between two or more entities may refer to a direct connection or an indirect connection. An indirect connection may incorporate one or more intervening entities. It is further noted that various method or process steps for embodiments of the present disclosure are described in the following description and drawings. The description may present the method and/or process steps as a particular sequence. However, to the extent that the method or process does not rely on the particular order of steps set forth herein, the method or process should not be limited to the particular sequence of steps described. As one of ordinary skill in the art would appreciate, other sequences of steps may be possible. Therefore, the particular order of the steps set forth in the description should not be construed as a limitation. 
     Referring to  FIG. 1 , an exemplary gas turbine engine  10  is schematically illustrated. The gas turbine engine  10  is disclosed herein as a two-spool turbofan engine that generally includes a fan section  12 , a compressor section  14 , a combustor section  16 , and a turbine section  18 . The fan section  12  drives air along a bypass flowpath  20  while the compressor section  14  drives air along a core flowpath  22  for compression and communication into the combustor section  16  and then expansion through the turbine section  18 . Although depicted as a turbofan gas turbine engine in the disclosed non-limiting embodiments, it should be understood that the concepts described herein are not limited to use with turbofans as the teachings may be applied to other types of turbine engines including those with three-spool architectures. 
     The gas turbine engine  10  generally includes a low-pressure spool  24  and a high-pressure spool  26  mounted for rotation about a longitudinal centerline  28  of the gas turbine engine  10  relative to an engine static structure  30  via one or more bearing systems  32 . It should be understood that various bearing systems  32  at various locations may alternatively or additionally be provided. 
     The low-pressure spool  24  generally includes a first shaft  34  that interconnects a fan  36 , a low-pressure compressor  38 , and a low-pressure turbine  40 . The first shaft  34  is connected to the fan  36  through a gear assembly of a fan drive gear system  42  to drive the fan  36  at a lower speed than the low-pressure spool  24 . The high-pressure spool  26  generally includes a second shaft  44  that interconnects a high-pressure compressor  46  and a high-pressure turbine  48 . It is to be understood that “low pressure” and “high pressure” or variations thereof as used herein are relative terms indicating that the high pressure is greater than the low pressure. An annular combustor  50  is disposed between the high-pressure compressor  46  and the high-pressure turbine  48  along the longitudinal centerline  28 . The first shaft  34  and the second shaft  44  are concentric and rotate via the one or more bearing systems  32  about the longitudinal centerline  28  which is collinear with respective longitudinal centerlines of the first and second shafts  34 ,  44 . 
     Airflow along the core flowpath  22  is compressed by the low-pressure compressor  38 , then the high-pressure compressor  46 , mixed and burned with fuel in the combustor  50 , and then expanded over the high-pressure turbine  48  and the low-pressure turbine  40 . The low-pressure turbine  40  and the high-pressure turbine  48  rotationally drive the low-pressure spool  24  and the high-pressure spool  26 , respectively, in response to the expansion. 
     Referring to  FIG. 2 , the combustor  50  includes an annular outer shell  52  and an annular inner shell  54  spaced radially inward of the outer shell  52 , thus defining an annular combustion chamber  56  therebetween. An annular hood  58  is positioned axially forward of the outer shell  52  and the inner shell  54  and spans between and sealably connects to respective forward ends of the outer shell  52  and the inner shell  54 . It should be understood that relative positional terms, such as “forward,” “aft,” “upper,” “lower,” “above,” “below,” and the like are relative to the normal operational attitude of the gas turbine engine  10  and should not be considered otherwise limiting. 
     A bulkhead  60  includes a first side  62  facing the combustion chamber  56  and a second side  64  opposite the first side  62 . The bulkhead  60  further includes an outer radial end  66  and an inner radial end  68  opposite the outer radial end  66 . The bulkhead  60  may be connected to and extend between the outer shell  52  and the inner shell  54 . For example, the bulkhead  60  may be connected to the outer shell  52  at the outer radial end  66  while the bulkhead  60  may be connected to the inner shell  54  at the inner radial end  68 . The bulkhead  60  divides the combustion chamber  56  and a hood chamber  70  (i.e., the combustion chamber  56  is disposed downstream of the bulkhead  60  while the hood chamber  70  is disposed upstream of the bulkhead  60 ). The bulkhead  60  may include an annular heat shield  110  mounted to the first side  62  of the bulkhead  60  and generally serving to thermally protect the bulkhead  60  and forward portions of the combustor  50 , such as the hood chamber  70 . 
     The bulkhead  60  includes at least one opening  72  extending through bulkhead  60  between the combustion chamber  56  and the hood chamber  70 . Each opening of the at least one opening  72  may accommodate a respective fuel injector  74  extending through the respective opening of the at least one opening  72  from the hood chamber  70  into the combustion chamber  56 . The fuel injector  74  may be configured to provide a mixture of fuel, air, and/or additional fluids for combustion in the combustion chamber  56 . 
     Referring to  FIGS. 2 and 3 , each opening of the at least one opening  72  may additionally include a swirler  76  mounted in the hood chamber  70  and extending through a respective opening of the at least one opening  72  from the hood chamber  70  into the combustion chamber  56 . The swirler  76  may be radially disposed about the fuel injector  74  with respect to a fuel injector center axis  78 . Accordingly, some or all of the fuel, air, and/or other fluids provided by the fuel injector  74  may pass through the swirler  76  which may provide additional mixing of the fuel, air, and/or other fluids. The swirler  76  may include a swirler exit plane  80  defined by a downstream end  82  of the swirler  76 . The swirler exit plane  80  may be disposed within the combustion chamber  56  downstream of the bulkhead  60 . 
     Referring to  FIGS. 3-5 , the fuel injector  74  includes a fuel injector body  84  having an upstream portion  86  and a bluff body portion  88  disposed downstream from the upstream portion  86 . The bluff body portion  88  includes an outer radial surface  90  and a tip surface  92  disposed at a downstream end of the fuel injector  74  and facing the combustion chamber  56 . An annular swirler passage  94  may be radially defined between the swirler  76  and the outer radial surface  90  with respect to the fuel injector center axis  78 . In various embodiments, the tip surface  92  may extend radially with respect to the fuel injector center axis. In various embodiments, the tip surface  92  may alternatively or additionally extend substantially parallel to the swirler exit plane  80  (i.e., the tip surface  92  may extend at an angle of five degrees or less relative to the swirler exit plane  80 ). In various embodiments, the tip surface  92  may be planar while in other embodiments the tip surface  92  may be convex or concave, may include one or more projections extending from the tip surface  92 , etc. In various embodiments, a diameter D 1  of the tip surface  92  may be greater than twenty percent of a diameter D 2  of an opening  122  of the swirler  76  at the downstream end  82  (e.g., along the swirler exit plane  80 ). In various other embodiments, the diameter D 1  of the tip surface  92  may be greater than forty percent of the diameter D 2  of the opening  122  of the swirler  76  at the downstream end  82 . 
     The fuel injector  74  includes a primary fuel passage  96  configured to direct fuel through the fuel injector body  76  and to inject the fuel directly into the combustion chamber  56  via a primary fuel outlet  98 . The primary fuel outlet  98  is located in the tip surface  92  of the bluff body portion  88 . In various embodiments, the primary fuel outlet  98  may be radially centered in the tip surface  92  with respect to the fuel injector center axis  78 . 
     The fuel injector  74  includes a secondary fuel passage  100  having a plurality of secondary fuel passage branches  102 . The secondary fuel passage  100  is configured to direct fuel through the fuel injector body  76  and into the combustion chamber  56  via a plurality of secondary fuel outlets  104  corresponding to the respective plurality of secondary fuel passage branches  102 . The plurality of secondary fuel outlets  104  may be located upstream of the primary fuel outlet  98  along a fuel injector plane  106  which may be located upstream or downstream of the bulkhead  60 . The plurality of secondary fuel outlets  104  may be circumferentially spaced about the exterior of the fuel injector  74  between the upstream portion  86  and the bluff body portion  88  of the fuel injector body  84 . The fuel injector plane  106  may be substantially parallel to the swirler exit plane  80  (i.e., the fuel injector plane  106  may be oriented at an angle of five degrees or less relative to the swirler exit plane  80 ). Fuel exiting the fuel injector  74  via the plurality of secondary fuel outlets  104  may be directed into the annular swirler passage  94  and subsequently into the combustion chamber  56 . 
     The fuel injector  74  includes a cooling air passage  106  configured to direct cooling air through the fuel injector body  76  and into the combustion chamber  56  via a plurality of air outlets  108 . The plurality of air outlets  108  is located in the tip surface  92  of the bluff body portion  88 . The plurality of air outlets  108  may be disposed radially outward from the primary fuel outlet  98  with respect to the fuel injector center axis  78 . The plurality of air outlets  108  may be circumferentially spaced about the fuel injector center axis  78  along the tip surface  92 . Cooling air exiting the plurality of air outlets  108  may mix with fuel exiting the primary fuel outlet  98  to create an anchored flame along the tip surface  92  within the combustion chamber  56 . 
     As shown in  FIG. 3 , the tip surface  92  may be disposed within the combustion chamber  56  downstream of the bulkhead  60 . In other words, the tip surface  92  may be disposed within an entrance  122  of the combustion chamber  56  illustrated in  FIG. 3 , for example, as extending along a length L which may be parallel to the fuel injector center axis  78 . The length L includes a first length L 1  extending between the bulkhead  60  and the swirler exit plane  80 . The length L also includes a second length L 2  extending between the swirler exit plane  80  and a downstream position within the combustion chamber  56 . In various embodiments, the first length L 1  may be equal to the second length L 2 . 
     For example, the tip surface  92  may be disposed between the bulkhead  60  and the swirler exit plane  80 , between the heat shield  110  and the swirler exit plane  80 , along the swirler exit plane  80 , or downstream of the swirler exit plane  80  with respect to the fuel injector center axis  78 . Accordingly, the primary fuel outlet  98  and the plurality of air outlets  108 , disposed in the tip surface  92 , may also be disposed between the bulkhead  60  and the swirler exit plane  80 , between the heat shield  110  and the swirler exit plane  80 , along the swirler exit plane  80 , or downstream of the swirler exit plane  80  with respect to the fuel injector center axis  78 . 
     Airflow exiting the plurality of air outlets  108  may be used to cool the tip surface  92  while also mixing with the fuel exiting the primary fuel outlet  98  to create an anchored flame at the tip surface  92 . The location of the tip surface  92  within the combustion chamber  56 , for example, extending along the swirler exit plane  80 , may substantially prevent a central recirculation zone  114  of the combustion chamber  56  from entering and oscillating within the swirler  76  resulting in additional attenuation of acoustic oscillations within the combustor  50 . Disposition of the tip surface  92  too far upstream, for example, an upstream distance from the swirler exit plane  80  along the fuel injector center axis  80 , may result in reduced attenuation of the acoustic oscillations within the combustor  50 . Disposition of the tip surface  92  too far downstream, for example, a downstream distance from the swirler exit plane  80  along the fuel injector center axis  80 , may result in increased thermal stress on the fuel injector  74 . 
     Referring to  FIG. 6 , in various embodiments, the fuel injector  74  may include an annular air gap  112  disposed within the fuel injector body  84  between the primary fuel passage  96  and the cooling air passage  106 . The annular air gap  112  may be enclosed by the fuel injector body  84  and radially spaced from the primary fuel passage  96  and the cooling air passage  106  by the fuel injector body  84 . For example, the annular air gap  112  may be fluidly isolated from both the primary fuel passage  96  and the cooling air passage  106  by the fuel injector body  84 . The location of the annular air gap  112  between the primary fuel passage  96  and the cooling air passage  106  may thermally insulate the fuel passing through the primary fuel passage  96 , thereby preventing or reducing coking of the fuel. 
     Referring again to  FIG. 2 , in various embodiments, installation of the fuel injector  74  into the combustor  50  may require different structural features of the gas turbine engine  10  compared to gas turbine engines using conventional fuel injectors. For example, a diffuser case  116  or other case, through which the fuel injector  74  passes, may include a larger diffuser case boss hole  118  to accommodate an increased length of the fuel injector  74  along the fuel injector center axis  78 . Additionally, for example, the annular hood  58  may include a larger hood hole  120  for installation of the fuel injector  74  into the combustor  50 . 
     While various aspects of the present disclosure have been disclosed, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of the present disclosure. For example, the present disclosure as described herein includes several aspects and embodiments that include particular features. Although these particular features may be described individually, it is within the scope of the present disclosure that some or all of these features may be combined with any one of the aspects and remain within the scope of the present disclosure. References to “various embodiments,” “one embodiment,” “an embodiment,” “an example embodiment,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. Accordingly, the present disclosure is not to be restricted except in light of the attached claims and their equivalents.