Patent Publication Number: US-7581402-B2

Title: Turbine engine combustor with bolted swirlers

Description:
FIELD OF THE INVENTION 
     The invention relates in general to turbine engines and, more specifically, to fuel swirlers in the combustor section of a turbine engine. 
     BACKGROUND OF THE INVENTION 
     The use of fuel swirlers in the combustor section of a turbine engine is known.  FIG. 1  shows an exemplary prior art fuel swirler  10  for a main fuel nozzle  20 . The fuel swirler  10  includes a substantially cylindrical tapered body  11 . The fuel swirler  10  has a flared inlet end  12  and a tapered outlet end  14 . A plurality of swirler vanes  16  are disposed circumferentially around the inner peripheral surface  18  of fuel swirler  10  proximate the inlet end  12 . The swirler vanes  16  are attached to a hub  26 . The hub  26  surrounds the main fuel nozzle  20 . 
     The fuel swirler  10  surrounds a portion of a main fuel nozzle  20  proximate main fuel injection ports  22 . The fuel swirler  10  is positioned such that the swirler vanes  16  are upstream of the main fuel injection ports  22 . The inlet end  12  is adapted to receive compressed air  23  from the compressor section of the engine (not shown) and to channel it into the swirler vanes  16 . The swirler vanes  16  disrupt the flow of the compressed air  23  through the swirler  10  to promote mixing of the air  23  with fuel introduced through the ports  22 . The outlet end  14  of the swirler  10  is adapted to fit into a swirler extension sleeve  24 . 
     In prior art systems, the fuel swirler  10  is attached to a combustor support frame  30  by two support pins  28 . Each support pin  28  is welded at one end to the combustor support frame  30  and at the other end to the swirler body  11 . However, experience has revealed problems with such an attachment scheme. The support pins  28  are subjected to vibrational forces generated during combustion; consequently, the support pins  28  and/or the welds are susceptible to fatigue-induced cracking. The formation of cracks in the support pins  28  or welds has prompted unscheduled engine shut down and has lead to costly and protracted repair and replacement. 
     Further, attachment of the support pins  28  to the swirler  10  and combustor support frame  30  by welding can complicate the combustor assembly process. During post-welding cool down, the swirlers  10  have been known to move out of their design position. Combustor performance can be adversely affected if the swirlers  10  and the main fuel nozzle  20  are not properly aligned. Thus, the assembly process may require additional steps to realign these components. One realignment method includes physically bending the swirler  10  into the design position. However, such cold bending can cause residual stresses to develop in the pins  28 , and such stresses can further reduce the fatigue life of the swirler  10  and/or the pins  28 . Thus, there is a need for a swirler attachment system that minimizes the foregoing concerns. 
     SUMMARY OF THE INVENTION 
     Aspects of the invention are directed to a fuel swirler assembly for a turbine engine combustor. The fuel swirler assembly includes an elongated swirler body that has an inlet end and an outlet end. The swirler body defines a longitudinal axis. The swirler body has an outer peripheral surface and an inner peripheral surface. A plurality of swirler vanes extend radially inward from the inner peripheral surface of the swirler body. The vanes are arrayed about the inner peripheral surface of the swirler proximate the inlet end. 
     A bracket is secured to the outer peripheral surface of the swirler body. The bracket projects substantially radially outward from the swirler body to a radially distal end. The bracket includes a hole adapted for removably receiving a fastener. In one embodiment, the hole can be threaded. Thus, the hole can receive and can threadably engage a threaded fastener. 
     The hole extends radially inward from the radially distal end of the bracket. The bracket is located on the swirler body in a region defined between the inlet end and an axially central region of the swirler body. In one embodiment, the bracket and the swirler body can be unitary. Alternatively, the bracket and the swirler body can be separate. In such case, the bracket can be secured to the swirler body by welding. The bracket can further have a radially proximal end. The radially proximal end of the bracket can substantially matingly engage the outer peripheral surface of the swirler body. 
     In one embodiment, there can be a second bracket. The second bracket can be secured to the outer peripheral surface of the swirler body. In such case, the second bracket can be located in a region defined between the inlet end and an axially central region of the swirler body. Alternatively, the second bracket can be located on a swirler extension sleeve that is secured to the swirler body. The outlet end of the swirler body can be received within the swirler extension sleeve. 
     Aspects of the invention further relate to a swirler attachment system. The system includes a combustor support frame, a fuel swirler assembly including a bracket, and a fastener. The combustor support frame has an inner peripheral surface and an outer peripheral surface. A radial hole extends through the combustor support frame from the inner peripheral surface to the outer peripheral surface. 
     The fuel swirler assembly includes an elongated swirler body that has an inlet end and an outlet end. In addition, the swirler body has an outer peripheral surface and an inner peripheral surface. Further, the swirler body defines a longitudinal axis. The bracket is secured to the outer peripheral surface of the swirler body. The bracket projects substantially radially outward from the swirler body to a radially distal end. The bracket includes a hole adapted for removably receiving a fastener. The hole extends radially inward from the radially distal end of the bracket. The bracket is located on the swirler body in a region defined between the inlet end and an axially central region of the swirler body. 
     The fastener extends through the radial hole in the combustor support frame. The fastener is attached within with the hole in the bracket so as to secure the fuel swirler assembly to the combustor support frame. In one embodiment, the fastener can be a threaded bolt. Further, the radial hole in the bracket can be threaded. Thus, the hole can threadably engage the bolt. In one embodiment, the fastener and/or the hole in the bracket can include a special thread form to impede unwanted travel of the fastener. 
     The radial hole can be adapted to provide a substantially dowel fit with the bolt. In such case, movement of the bolt within the hole can be substantially minimized. Further, a lock washer can be provided and operatively positioned between the fastener and the outer peripheral surface of the combustor support frame. The lock washer can impede unwanted travel of the fastener. 
     The radially distal end of the bracket substantially engages the inner peripheral surface of the combustor support frame. The inner peripheral surface of the combustor support frame can have a seating surface. The seating surface can be adapted for substantially mating engagement with the radially distal end of the bracket. The seating surface can be defined by a recess in the inner peripheral surface of the combustor support frame. Alternatively, the seating surface can be defined by a protrusion extending radially inward from the inner peripheral surface of the combustor support frame. 
     The system can include a swirler base plate that can be secured to the combustor support frame. The swirler base plate can include an opening. The axial downstream end of the fuel swirler assembly can be positioned substantially adjacent to the opening. Thus, the fuel swirler assembly and the opening can be in fluid communication. Alternatively, the axial downstream end of the fuel swirler assembly can be received within the opening. 
     In one embodiment, the system can further include a swirler support plate and a swirler base plate. The swirler support plate can include an opening for receiving the axial downstream end of the fuel swirler assembly. In one embodiment, the swirler support plate can be made of four panels. The swirler base plate can include an opening. The opening in the swirler support plate can be disposed axially upstream of and in substantial alignment with the opening in the swirler base plate. A portion of the fuel swirler assembly can be received within the opening in the swirler support plate. The swirler base plate can be attached to the combustor support frame, and the swirler support plate can be attached to the swirler base plate. A portion of the fuel swirler assembly can extend through the opening in the swirler support plate such that the axial downstream end of the fuel swirler assembly can be positioned substantially proximate to the opening in the swirler base plate. A peripheral gap can be formed between the axial downstream end of the fuel swirler assembly and the swirler base plate. As a result, air can pass through the gap so as to minimize flashback potential. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of a prior main fuel swirler. 
         FIG. 2  is a cross-sectional view of a fuel swirler according to aspects of the invention. 
         FIG. 3  is a side elevational view of a fuel swirler according to aspects of the invention. 
         FIG. 4  is a cross-sectional view of a swirler attachment system according to aspects of the invention. 
         FIG. 5A  is a close up view of an interface between the swirler bracket and the combustor support frame according to aspects of the invention. 
         FIG. 5B  is a close up view of another interface between the swirler bracket and the combustor support frame according to aspects of the invention. 
         FIG. 6  is a cross-sectional view of the swirler attachment system according to aspects of the invention, showing a swirler support plate provided near the axial downstream end of the swirler. 
         FIG. 7  is a view of bolted swirlers and a support plate system according to aspects of the invention, viewed from line  7 - 7  in  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION 
     Embodiments of the present invention are directed to swirler attachment systems. Embodiments of the invention will be explained in the context of one possible system, but the detailed description is intended only as exemplary. Embodiments of the invention are shown in  FIGS. 2-7 , but the present invention is not limited to the illustrated structure or application. 
     A fuel swirler assembly  40  according to embodiments of the invention is shown in  FIGS. 2 and 3 . The fuel swirler assembly  40  can include a swirler body  41  having an inlet end  42  and an outlet end  44 . The fuel swirler assembly  40  can define a longitudinal axis  46 . The swirler body  41  can be generally cylindrical in conformation, but the swirler body  41  can have any shape including rectangular or polygonal, as dictated by design considerations and performance requirements. The swirler body  41  can have an outer peripheral surface  48  and an inner peripheral surface  50 . As shown, the swirler body  41  can taper from the inlet end  42  to the outlet end  44 , but, in some embodiments, the swirler body  41  may not be tapered. 
     The fuel swirler assembly  40  can include a swirler extension sleeve  52  having a proximal axial end  54  and a distal axial end  56 . As used in connection with the swirler extension sleeve  52 , the terms “proximal” and “distal” refer to the position of the ends  54 ,  56  of the swirler extension sleeve  52  relative to the swirler body  41 . The swirler extension sleeve  52  can be generally cylindrical in conformation. The outlet end of the swirler body  41  can be positioned so as to extend into the proximal end  54  of the swirler extension sleeve  52 . The swirler extension sleeve  52  and the swirler body  41  can be joined together, such as by welding. 
     It will be appreciated that the inlet end  42  of the swirler body  41  can define the axial upstream end  60  of the fuel swirler assembly  40 , and the distal axial end  56  of the swirler extension sleeve  52  can define the axial downstream end  62  of the fuel swirler assembly  40 . However, in some instances, the fuel swirler assembly  40  may not include a swirler extension sleeve  52 . In such case, the outlet end  44  of the swirler body  41  can define the axial downstream end  62  of the fuel swirler assembly  40 . Thus, when the axial downstream end  62  of the fuel swirler assembly  40  is referenced herein, it will be understood that such term can encompass either of the above possibilities. 
     According to embodiment of the invention, the fuel swirler assembly  40  can include a bracket  64  to facilitate attachment of the fuel swirler assembly  40  to a combustor support frame  66 . The bracket  64  can project substantially radially outward (relative to the longitudinal axis  46 ) from the outer peripheral surface  48  of the swirler body  41 . The bracket  64  can be a separate component that is secured to the outer peripheral surface  48  of the swirler body  41 . For example, the bracket  64  can be secured to the swirler body  41  by welding. Alternatively, the bracket  64  and the swirler body  41  can be a unitary structure, such as by casting. The bracket  64  can be made of any of a number of materials, but it is preferred if the bracket  64  is made of the same material as the swirler body  41  and/or the combustor support frame  66 . In one embodiment, the bracket  64  can be made of stainless steel, such as 304 stainless steel. 
     The bracket  64  can have any of a number shapes. In one embodiment, the bracket  64  can have a substantially cylindrical body  68  with a pair of attachment fins  70  on each side, as shown in  FIGS. 2 and 3 . The body  68  may or may not be tapered. Again, the bracket  64  shown in  FIGS. 2 and 3  is just one of many possible configurations, and a bracket  64  according to aspects of the invention is not limited to any particular shape. 
     The bracket  64  can have a radially proximal end  72  and a radially distal end  74  relative to the longitudinal axis  46  of the fuel swirler assembly  40 . When the bracket  64  is a separate component, it is preferred if the radially proximal end  72  of the bracket  64  is machined, for example, to be slightly curved, so as to substantially matingly engage a curved outer peripheral surface  48  of the swirler body  41 . 
     Each fuel swirler assembly  40  can have a single bracket  64  for attaching the fuel swirler assembly  40  to the combustor support frame  66 . The bracket  64  can be provided at various locations along the swirler body  41 . In one embodiment, the bracket  64  can be provided near the inlet end  42  of the swirler body  41 . Preferably, the bracket  64  is located within an axial upstream region  76  of the swirler body  41 . The axial upstream region  76  can be defined between the inlet end  42  of the swirler body  41  and a substantially axially central portion of the swirler body  41 . In some instances, there can be more than one bracket  64  associated with the fuel swirler assembly  40 . In one embodiment, there can be two brackets  64  associated with the fuel swirler assembly  40 . In such case, the additional bracket (not shown) can be provided on the swirler body  41 , preferably also located within the axial upstream region  76 . Alternatively, an additional bracket can be attached to the swirler extension sleeve  52  near the proximal axial end  54 . While being axially spaced apart, the brackets  64  can be substantially peripherally aligned, or the brackets  64  can be peripherally offset. 
     The bracket  64  can include a hole  78 , which can be threaded and provided by, for example, drilling and tapping. The hole  78  can extend substantially radially inward from the radially distal end  74  of bracket  64  toward the radially proximal end  72  of the bracket  64 . The radially distal end  74  of the bracket  64  can be machined so as to substantially matingly engage the combustor support frame  66 , and thereby facilitate proper alignment of the fuel swirler assembly  40 . In embodiments where the bracket  64  is a separate part that is welded to the swirler body  41 , the machining of the radially distal end  74  and the inclusion of the hole  78  can be completed after the welding operation and after the parts have cooled. Thus, any potential warpage caused by the welding can be compensated for without introducing residual stresses to the fuel swirler assembly  40 . 
     Again, the fuel swirler assembly  40  can be attached to the combustor support frame  66 , which can be any suitable stationary structure in the combustor to which the fuel swirler assemblies  40  can be attached. Referring to  FIGS. 5A and 5B , the combustor support frame  66  can have an outer peripheral surface  80  and an inner peripheral surface  82 . For each fuel swirler assembly  40 , the combustor support frame  66  can provide a seating surface  84  for substantially mating engagement with the radially distal end  74  of the bracket  64 . 
     The seating surface  84  can be a localized precision machined area. The seating surface  84  can include any of a number of surface features, such as protrusions, to engage the radially distal end  74  of the bracket  64 . In one embodiment, the seating surface  84  can be defined by a recess  86  for receiving a portion of the bracket  64  including at least the radially distal end  74 , as shown in  FIG. 5A . The recess  86  can extend radially within the combustor support frame  66 , from the inner peripheral surface  82  toward the outward peripheral surface  80 . The recess  86  can be included in the combustor support frame  66  by machining. The recess  86  can have any of a number of shapes and, preferably, the recess  86  substantially corresponds to the shape of the radially distal end  74  of the bracket  64 . In one embodiment, the recess  86  can be substantially cylindrical. The recess  86  can include the seating surface  84  and at least one sidewall  88 . It is preferred if the seating surface  84  is machined for substantially mating engagement with the radially distal end  74  of the bracket  64 . Similarly, the sidewall  88  can be machined for additional substantially mating engagement with the bracket  64 . 
     In another embodiment, the seating surface  84  can be defined by a protrusion  85  provided on the inner peripheral surface  82  of the combustor support frame  66 , as shown in  FIG. 5B . The protrusion  85  can extend radially inward from the inner peripheral surface  82 . The protrusion  85  can be formed in the combustor support frame  66  by, for example, machining or casting. The protrusion  85  can have any of a number of shapes and, preferably, the protrusion  85  substantially corresponds to the shape of the radially distal end  74  of the bracket  64 . In one embodiment, the protrusion  85  can be substantially cylindrical. 
     A series of radial holes  90  can be machined in the combustor support frame  66  to provide the required circumferential location of each fuel swirler assembly  40  about the combustor support frame  66 . The radial holes  90  can extend from the outer peripheral surface  80  through the inner peripheral surface  82  of the combustor support frame  66 , opening to the seating surface  84 . Preferably, the radial hole  90  is substantially centered within the seating surface  84 . The radial holes  90  can have any of a number of shapes, but preferably they are substantially circular. Naturally, the number of seating surfaces  84  and/or radial holes  90  provided in the combustor support frame  66  will depend on the number of fuel swirler assemblies  40  used and the number of brackets  64  associated with each fuel swirler assembly  40 . In one embodiment, there can be eight radial holes  90  and seating surface  84  pairs arranged circumferentially about the combustor support frame  66 . 
     Thus, when the radially distal end  74  of the bracket  64  is positioned against the seating surface  84 , the hole  78  in the bracket  64  can be substantially aligned with a respective radial hole  90  in the combustor support frame  66 . A fastener can be used to attach the fuel swirler assembly  40  to the combustor support frame  66 . In one embodiment, the fastener can be a bolt  92 . In such case, the bolt  92  can be inserted from the outer peripheral surface  80  of the combustor support frame  66 , such that the head  94  of the bolt  92  operatively engages the outer peripheral surface  80  of the combustor support frame  66 . The shaft  96  of the bolt  92  can extend through the radial hole  90  and into threaded engagement with hole  78  in the bracket  64 . As the bolt  92  is tightened, the fuel swirler assembly  40  can be pulled into the design position. Preferably, the radial holes  90  in the combustor support frame  66  are sized so as to substantially form a dowel fit with the bolt  92 , thereby minimizing movement of the bolt  92  within the hole  78 . Dowel fit is intended to mean that a portion of the bolt  92  and the radial holes  90  are tightly toleranced. Movement of the bolt  92  can alter the position of the fuel swirler assembly  40  and affect combustor performance. 
     In some instances, it may be desirable to provide additional measures to prevent the bolt  92  from moving or otherwise coming loose during engine operation. To that end, a lock washer  98  can be positioned between the head  94  of the bolt  92  and the outer peripheral surface  80  of the combustor support frame  66 . Alternatively or in addition, the bolt  92  and/or the hole  78  in the bracket  64  can be provided with a special thread form so as to substantially lock the bolt  94  in place. Yet another possibility for bolt retention is to weld the bolt  92  to the combustor support frame  66 . It will be appreciated that the above are merely a few examples of the various manners in which the fastener can be substantially locked in place. 
     The bracket  64  can be used to support at least the axial upstream end  60  of the fuel swirler assembly  40 . Additional support for the axial downstream end  62  of the fuel swirler assembly  40  can be provided as well. Support of the axial downstream end  62  of the fuel swirler assembly  40  can be achieved in numerous ways. For instance, as noted above, an additional bracket  64  can be provided on the fuel swirler assembly  40 . In such case, no further support may be needed for the axial downstream end  62  of the fuel swirler assembly  40 . In such case, the axial downstream end  62  of the fuel swirler assembly  40  can be positioned substantially adjacent to a swirler base plate  100 , as shown in  FIG. 4 . “Substantially adjacent” is intended to mean direct contact between the axial downstream end  62  of the fuel swirler assembly  40  and the swirler base plate  100  as well as these components being spaced apart. 
     The swirler base plate  100  can be anchored to the combustor support frame  66  and/or a pilot cone  102  by, for example, welding. A plurality of openings  104  can be provided in the swirler base plate  100  for interfacing with the axial downstream end  62  of the fuel swirler assembly  40 . The openings  104  can be a through hole or they can be the product of bends in the swirler base plate  100 . While the term “plate” may connote a flat plate, embodiments of the invention are not limited to flat plates as the swirler base plate  100  can include any of a number of curves and bends, among other non-flat features. Typically, the swirler base plate  100  can be shaped from a metal sheet and the openings  104  can be formed in a drawing process. 
     Especially in cases where only one bracket  64  is provided on the fuel swirler assembly  40 , there are various options for supporting the axial downstream end  62  of the fuel swirler assembly  40 . In one embodiment, the axial downstream end  62  of the fuel swirler assembly  40  can be positioned within the opening  104  in the swirler base plate  100 . The details and benefits of such an arrangement are described in detail in U.S. Pat. No. 6,705,087, which is incorporated herein by reference. 
     Alternatively, a swirler support plate  106  can be provided to support the axial downstream end  62  of the fuel swirler assembly  40 , as shown in  FIG. 6 . The swirler support plate  106  can be secured to the swirler base plate  100  by, for example, welding. In one embodiment, the swirler support plate  106  can have a generally S-shaped profile. The swirler support plate  106  can be a single plate or it can be multiple plates. For instance, the swirler support plate  106  can include four individual panels, only two of such panels  106   a ,  106   b  being shown in  FIG. 7 . The swirler support plate  106  can provide a plurality of openings  108  for receiving the axial downstream end  62  of each fuel swirler assembly  40 , such as the distal axial end  56  of the swirler extension sleeve  52 . 
     The swirler support plate  106  can provide advantages in reducing the potential for flashback, which occurs when the combustion flame travels upstream and attaches to the swirler base plate  100  or the axial downstream end  62  of the fuel swirler assembly  40 . Flashback can damage these components and interfere with efficient combustor operation. One way to reduce flashback potential is to provide a film of air on the outside of the fuel swirler assembly  40 . Because the axial downstream end  62  of the fuel swirler assembly  40  can be supported by the swirler support plate  106 , a gap  110  can be provided between the swirler base plate  100  and the axial downstream end  62  of the fuel swirler assembly  40 . Compressed air can be supplied from the compressor to the gap  110  by one or more cutouts  112  provided in the swirler support plate  106 . The gap  110  allows a film of air to develop over the axial downstream end  62  of the fuel swirler assembly  40  and the swirler base plate  100 , thereby discouraging flashback. 
     It will be appreciated that, in comparison to the prior welded pin approach, embodiments of the invention described above can reduce the time and cost associated with installing fuel swirlers in the combustor section. The system can avoid the issues associated with the welding process including, for example, distortion and material defects. The attachment system according to aspects of the invention can provide advantages during repair service as the system permits easy replacement of individual swirlers and does not require special tools or fixtures. Further, the design can improve reliability in manufacturing and reduce service cost and time in replacing a swirler. There is also potential for improved swirler alignment because there is no weld distortion introduced at a final assembly. 
     The foregoing description is provided in the context of one possible system for attaching fuel swirlers to a combustor support frame. It will of course be understood that the invention is not limited to the specific details described herein, which are given by way of example only, and that various modifications and alterations are possible within the scope of the invention as defined in the following claims.