Abstract:
Aunitary swirler assembly that provides improved service life, having a ferrule body and a unitary swirler body. The unitary swirler body has oppositely-directed primary swirler passages and secondary swirler passages. A pair of rails formed on the unitary swirler body engage the ferrule body to limit relative movement, and prevent relative rotation, of the ferrule body and the unitary swirler body.

Description:
BACKGROUND OF INVENTION  
       [0001]     The invention relates to swirler assemblies for supplying compressed air to the combustor of gas turbine engines.  
         [0002]     A gas turbine engine includes a compressor that provides pressurized air to a combustor wherein the air is mixed with fuel and ignited for generating hot combustion gases. These gases flow downstream to one or more turbines that extract energy therefrom to power the compressor and provide useful work such as powering an aircraft in flight. In combustors used with aircraft engines, the fuel is typically supplied to the combustor through a plurality of fuel nozzles positioned at one end of the combustion zone. The air is supplied through surrounding assemblies, known as swirler assemblies, which impart a swirling motion to the air so as to cause the air and fuel to be thoroughly mixed. The swirler assemblies are mounted in a dome plate that is joined to the upstream ends of the combustor&#39;s inner and outer liners, and each fuel nozzle tip is received in a corresponding one of the swirler assemblies.  
         [0003]     One conventional swirler assembly is a three part assembly comprising a primary swirler, a secondary swirler and a retainer. The primary swirler has a plurality of circumferentially spaced swirl vanes or air passages. The vanes or passages are angled with respect to the axial centerline of the swirler assembly so as to impart a swirling motion to the air flow. The secondary swirler, also having a plurality of circumferentially spaced swirl vanes or air passages, is disposed immediately downstream of the primary swirler. The vanes or passages of the secondary swirler are angled so as to produce a swirl of air swirling in the opposite direction as the primary swirler to further promote fuel-air mixing. The retainer fits over the primary swirler and is welded to the secondary swirler to retain the two swirlers in engagement with one another.  
         [0004]     The air flow through the vanes or passages of the primary swirler creates a reaction force that tends to cause the primary swirler to rotate with respect to the secondary swirler and the fuel nozzle. However, if allowed to rotate, the primary swirler would fail to impart the necessary level of swirling to the air, and effective mixing of the air and fuel would not be achieved. Furthermore, rotation of the primary swirler would cause excessive wear to the fuel nozzle tip. Primary swirler rotation is thus prevented in conventional swirler assemblies by providing an outwardly extending tab on the primary swirler and a post on the secondary swirler, wherein the tab engages the post so as to limit relative rotation of the swirlers.  
         [0005]     However, the combustor structure is vibrationally active and there is substantial thermal expansion of components during operation of a gas turbine engine. As a result, there is relative movement between the tab and the post resulting in significant wear that eventually requires repair and increases maintenance costs. The repair process is relatively difficult because it requires removal of the permanently welded retainer. It is also possible that a worn tab and/or post could break off and cause damage to the turbine downstream. Furthermore, the retainer is susceptible to cracking during operation and often needs to be replaced.  
         [0006]     Accordingly, there is a need for an improved swirler assembly that can prevent and preferably prevent rotation of the primary swirler relative to the secondary swirler, to eliminate frequent repairs, and which is easy to field assemble and disassemble.  
       SUMMARY OF INVENTION  
       [0007]     The present invention provides a swirler assembly comprising: a ferrule body comprising 1) a substantially square base having an upper surface and a lower surface, having opposed first and second side edges, and having a centrally-positioned opening formed therein, 2) a ferrule extending from the upper surface and the central opening, and 3) a plurality of protrusions along the upper surface of each side edge; and a unitary swirler body comprising 1) a first swirl section having a plurality of angularly directed passages, 2) a second swirl section comprising a venturi and a plurality of oppositely-angled, directed passages disposed coaxially around the venturi, and 3) a pair of rails, each comprising an inwardly-extending flange, each formed on opposite sides of the venturi, wherein the rails engage the protrusions along the opposite sides edges of the ferrule body to limit separation of ferrule body and the unitary swirler body. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0008]     The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the concluding part of the specification. The invention, however, can be best understood by reference to the following description taken in conjunction with the accompanying drawing figures wherein identical reference numerals denote the same elements throughout the various views.  
         [0009]      FIG. 1  is an axial sectional view of the forward portion of combustor having a swirler assembly of the present invention.  
         [0010]      FIG. 2  is a perspective view of a ferrule body for the swirler assembly of the present invention.  
         [0011]      FIG. 3  is a perspective view of a unitary swirler body for the swirler assembly of the present invention.  
         [0012]      FIG. 4  is a perspective view of an assembled swirler assembly of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0013]     Referring to the drawings,  FIG. 1  shows the forward end of a combustor  10  of the type suitable for use in a gas turbine engine and including a hollow body  12  defining a combustion chamber  14  therein. The hollow body  12  is generally annular in form and is defined by an outer liner  16  and an inner liner  18 . The upstream end of the hollow body  12  is substantially closed off by a cowl  20  attached to the outer liner  16  by a first fastener  22  and to the inner liner  18  by a second fastener  24 . At least one opening  26  is formed in the cowl  20  for the introduction of fuel and compressed air. The compressed air is introduced into the combustor  10  from a compressor (not shown) in a direction generally indicated by arrow A of  FIG. 1 . The compressed air passes primarily through the opening  26  to support combustion and partially into the region surrounding the hollow body  12  where it is used to cool both the liners  16 ,  18  and turbomachinery further downstream.  
         [0014]     Disposed between and interconnecting the outer and inner liners  16 ,  18  near their upstream ends is an annular dome plate  28 . A plurality of circumferentially spaced swirler assemblies  30  (one shown in  FIG. 1 ) is mounted in the dome plate  28 . Each swirler assembly  30  includes a ferrule body  34  having a ferrule  48  with a central opening  42  that coaxially receives a fuel nozzle  44 , and a unitary swirler body  50 . The unitary swirler body is fixedly received in the dome plate  28 .  
         [0015]     The unitary swirler body  50  comprises a first swirler section  36  having a plurality of circumferentially spaced primary swirl vanes  40  defining a plurality of angularly directed primary passages  38 . The primary passages  38  are angled with respect to the axial centerline  32  of the swirler assembly  30  so as to impart a swirling motion to the air flow in a first direction tangential to the centerline  32 . The unitary swirler body  50  further comprises a second swirler section  56  having a venturi  54  and a plurality of circumferentially spaced swirl vanes  60  defining a plurality of oppositely-angled and directed secondary passages  58  disposed coaxially about the venturi  54 . The primary swirler section  36  and secondary swirler section  56  are rigidly connected, through the intermediate partition  64 , into a unitary body, to eliminate movement between the two sections. The venturi  54  and the central opening  42  of the ferrule  48  are both coaxially aligned with the axial centerline  32  of the swirler assembly  30 .  
         [0016]     A portion of air from the opening  26  passes into and through the primary passages  38 . The swirling air exiting the primary passages  38  interacts with fuel injected from the fuel nozzle  44 , and mixes with the fuel as they pass into and through the venturi  54 . The secondary passages  58  direct another portion of air from the opening  26  to swirl in an opposite tangential direction relative to the centerline  32 , which air interacts with the fuel/air mixture leaving the venturi  54 , to further atomize the fuel/air mixture and prepare the mixture for combustion in the combustion chamber  14 .  
         [0017]     It should be noted that although  FIG. 1  illustrates the swirler assembly of the present invention in a single annular combustor, the present invention is equally applicable to other types of combustors, including multi-annular combustors.  
         [0018]     In  FIG. 2 , the ferrule body  34  has a base  62 , shown as a flat member having an upper surface  63  and a lower surface  65 , defining a perimeter and outer side edges, including opposed side edges  46  and  47 . The ferrule body  34  also comprises a ferrule  48  formed on the upper surface  63  of the base  62  and having a central opening  42 . The base  62  is typically substantially square in shape, with the ferrule  48  centered. The ferrule body  34  is typically substantially symmetrical relative to a plane passing through a centerline  32  of the ferrule  48 , and through either a first axis X or a second axis Y. The first surface of the base  62 , from which the ferrule  48  extends, faces upstream when the swirler assembly  30  is properly positioned in the combustor  10 . A plurality of raised protrusions  70  occupy a portion of the outer side edges along the periphery of the base  62 , and typically are formed on the upper surface  63  of the base  62 , along the opposite side edges  46  and  47  of the ferrule  48 . More typically, the protrusions  70  are formed on a portion of each side edge  45 ,  46 ,  47  and  49 , in substantially the same pattern and arrangement. The embodiment in  FIG. 2  shows the protrusion  70  positioned at each corner  88  of the base  62 , and extending from each corner inwardly for a portion of the length of the each side edge.  
         [0019]     In  FIG. 3 , the first swirler section  36  comprises a base  74 , which is also a flat member defining a perimeter or outer edge around a central opening  52 . The base  74  has an upstream surface, which confronts the lower surface  65  of the ferrule body  34  (shown in  FIG. 2 ) when the swirler assembly  30  is assembled. A plurality of primary swirl vanes  40  define the plurality of primary passages  38  disposed circumferentially about the opening  52 . The swirler vanes  40  join together the down stream surface of the base  74  and an intermediate partition  64 . The intermediate partition  64  has a central opening defined by an inner edge that forms a venturi  54 . The venturi  54  extends axially (with respect to the axial centerline  32  of the swirler assembly  30 ) downstream from the inner edge of the intermediate partition  64 . A second swirler section  56  of the unitary swirler body  50  comprises secondary passages  58  defined by a plurality of circumferentially spaced secondary swirl vanes  60  disposed coaxially about the venturi  54 .  
         [0020]     A pair of retainer rails  76  extends axially outward from the upstream surface of the base  74 . Each retainer rail  76  is located along the outer edge of the base  74 , on opposite sides of the opening  52  so as to be arranged substantially parallel to one another. Each retainer rail  76  includes an inwardly-directed (that is, toward the axial centerline  32  of the swirler assembly  30 ) flange  78  thereon, for engaging the upper surface  72  of the protrusions  70  of the base  62  the ferrule body  34 . The spacing of the flange  78  from the upper surface of the base  74  is sufficient to provide clearance for the ferrule body  34  to slide into position. The symmetry of the ferrule body  34 , relative to a plane passing through a centerline  32  of the ferrule  48 , and through either a first axis X or a second axis Y, shown in  FIG. 4 , permits the ferrule body  34  to be inserted correctly into the unitary swirler body  50 , regardless of its orientation.  
         [0021]     The unitary swirler body  50  further includes a stop tab  82  formed on the outer edge of the base  74  and extending axially outward from the first surface thereof. The stop tab is configured to confine the ferrule body  34  in assembled position with the unitary swirler body  50 . The stop tab  82  is shown as a planar surface located on the outer edge of the base  74  that extends perpendicularly to the retainer rails  76 . A weld tab  84  is also formed on the outer edge of the base  74  but extends substantially radially outwardly therefrom. Typically the weld tab  84  is in the same plane as the base  74  of the unitary swirler body  50 , to permit the base  62  of the ferrule body  34  to slide under the rails  72  and into confronting position with the base  74 . The weld tab  84  is located on an opposite side of the venturi  54  from the stop tab  82 , and is configured to cooperate with a tack weld  86  (shown in  FIG. 4 ) to confine the ferrule body  34  in assembled position with the unitary swirler body  50 .  
         [0022]     The bases  62  and  74  of the ferrule body  34  and unitary swirler body  50 , respectively, have substantially the same shape, although the base  74  of the unitary swirler body  50  is slightly larger. As shown in  FIG. 4 , the swirler assembly  30  is assembled by sliding the ferrule body  34  into engagement with the unitary swirler body  50  such that the bases  62  and  74  confront one another in a substantially coplanar manner. Furthermore, the retainer rails can be configured to confront sufficiently the opposing side edges  46 ,  47  of the base  62  the ferrule body  34  to prevent rotation of the ferrule body  34  relative to the unitary swirler body  50 . The upper surfaces  72  of the protrusions  70  along the side edges  46 ,  47  are also engaged by the retainer rail flanges  78  so as to axially hold the ferrule body  34  and unitary swirler body  50  together. The retainer rails  76  also limit lateral movement of the ferrule body  34  with respect to the unitary swirler body  50  along a first axis, denoted as axis X in  FIG. 4 , which lies in the plane defined by the bases  62  and  74 . That is, the two retainer rails  76  are spaced apart sufficiently in the X direction to allow limited lateral movement of the ferrule body  34  relative to the unitary swirler body  50 . Similarly, the stop tab  82  and a tack weld  86 , which is applied to the weld tab  84  after assembly of the ferrule body  34  and unitary swirler body  50 , operate to limit lateral movement of the ferrule body  34  along a second axis, denoted as axis Y in  FIG. 4 , which also lies in the plane defined by the bases  62  and  74 , perpendicular to axis X. In this case, the stop tab  82  and the tack weld  86  are spaced apart sufficiently in the Y direction to permit limited lateral movement of the ferrule body  34  relative to the unitary swirler body  50 . This arrangement allows the ferrule body  34  to float or move laterally so that the ferrule  48  can be coaxially aligned with, and receive, the fuel nozzle  44 , but otherwise prevents the ferrule body  34  and unitary swirler body  50  from becoming disengaged while the swirler assembly  30  is being installed in the combustor  10 .  
         [0023]     The flanges  78  are provided with scalloped ends, as described in U.S. Pat. No. 6,427,435, incorporated herein by reference. As shown in  FIG. 3 , the ends of the flange  78  are formed as a cutout  80 , which reduces the weld joint and bending stresses that occur from the forced vibration of the cantilevered flanges  78 . The curved cutouts  80  also reduce the stress concentration factor at the corners of the flanges, which is where most cracks initiate in conventional retainer segments.  
         [0024]     Once the swirler assembly  30  is installed in the combustor  10 , the fuel nozzle  44  centers and holds the ferrule body  34  in place between the two retainer rails  76 . Thus, the retainer rail flanges  78 , the stop tab  82  and the tack weld  86  typically provide no further function when the swirler assembly  30  is installed in the combustor  10 . Furthermore, air flow from the compressor during engine operation holds the ferrule body  34  against the unitary swirler body  50 .  
         [0025]     The two part assembly of the present invention reduces costs and facilitates manufacture since the fixturing and set-up for welding a separate retainer for the ferrule to the swirler is eliminated. Repair of the swirler assembly is easier because removing the ferrule body  34  during field repair simply requires removal of the small tack weld  86  rather than removing a permanently-welded retainer as before. The protrusions  70  provide significant less contact area with the flanges  78  of the retainer rails  76 , which limits the location where wear will occur to the protrusions  70  only, thus allowing better control of the location of the wear and of repair. The reduced contact area of the upper surfaces  72  of the protrusions  70  also significantly reduce frictional forces between the ferrule body  34  and the rails  76  and flanges  78  of the unitary swirler body  50 , and improves the ease of movement of the ferrule body  34  within the assembly during operation of the engine.  
         [0026]     While specific embodiments of the present invention have been described, it will be apparent to those skilled in the art that various modifications thereto can be made without departing from the spirit and scope of the invention as defined in the appended claims.