Abstract:
A method for assembling a gas turbine engine combustor facilitates reducing costs and time required for assembly. The combustor includes a spectacle plate, a plurality of swirlers, and a plurality of deflector plates. The method includes coupling an assembly fixture to at least one swirler, coupling the assembly fixture to the spectacle plate such that the swirler is maintained in alignment with respect to the spectacle plate during assembly of the combustor, and attaching the swirler to the spectacle plate.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates generally to gas turbine engine combustors and more particularly, to methods and apparatus for assembling gas turbine engine combustors.  
           [0002]    Gas turbine engines include combustors which ignite fuel-air mixtures. At least some known combustors include annular dome assemblies which support a plurality of other combustor components. For example, dome assembly spectacle plates enable premixers to mate with downstream swirlers. Aligning the swirlers with respect to the premixers may be a complex task since the design tolerances of the premixers typically require more radial tolerance than circumferential tolerance. In addition, variations in the machined surfaces of the combustor components may further complicate the alignment process.  
           [0003]    To facilitate aligning the swirlers with respect to the spectacle plate, at least some known swirlers include a locating pin that mates with a notch that is machined into the spectacle plate. More specifically, the locating pin and mating notch facilitate aligning or clocking the swirlers in such a manner to ensure radial movement of the premixers is permitted. In addition, the alignment of the swirlers directly influences the alignment of deflector plates that are coupled to the spectacle plate around the swirlers. More specifically, the locating pins facilitate the deflector plates being aligned with respect to the spectacle plate such that a pre-determined clearance is defined between adjacent deflector plates during the cold-assembled state.  
           [0004]    The alignment of the deflector plates during the cold-assembled state directly affects the clearances between the deflectors at operating temperatures, and thus, may affect the useful life of the combustor. However, despite the use of the locating pins, variations in the machined features of the deflector plates and in the mating hardware, may still cause undesirable clearance variations between adjacent deflector plates. In addition, manufacturing the swirlers to include the pins increases the costs in comparison to those swirlers which do not include the locating pins. Furthermore, over time continued operation of a combustor with undesirable clearances may damage combustor components.  
         BRIEF SUMMARY OF THE INVENTION  
         [0005]    In one aspect, a method for assembling a gas turbine engine combustor is provided. The combustor includes a spectacle plate, a plurality of swirlers, and a plurality of deflector plates. The method includes coupling an assembly fixture to at least one swirler, coupling the assembly fixture to the spectacle plate such that the swirler is maintained in alignment with respect to the spectacle plate during assembly of the combustor, and attaching the swirler to the spectacle plate.  
           [0006]    In another aspect, a combustor for a gas turbine engine is provided. The combustor includes a spectacle plate, and a plurality of swirlers attached to the spectacle plate. Assembling the combustor comprises coupling an assembly fixture to at least one said swirler, removably coupling each respective assembly fixture to the spectacle plate to maintain an alignment of each said respective swirler with respect to said spectacle plate, and uncoupling each respective assembly from said spectacle plate after each said swirler is attached to said spectacle plate.  
           [0007]    In a further aspect, an assembly fixture for a gas turbine engine combustor including a spectacle plate is provided. The assembly fixture is removably coupled to the spectacle plate during assembly of the combustor for aligning at least one of a plurality of swirlers and a plurality of deflector plates for attachment to the spectacle plate. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a schematic illustration of a gas turbine engine;  
         [0009]    [0009]FIG. 2 is side perspective view of an assembly fixture that may be used during assembly of the engine shown in FIG. 1;  
         [0010]    [0010]FIG. 3 is a side perspective view of the assembly fixture shown in FIG. 2 and coupled to a combustor spectacle plate;  
         [0011]    [0011]FIG. 4 is a perspective view of an alignment fixture that may be used during assembly of the engine shown in FIG. 1; and  
         [0012]    [0012]FIG. 5 is plan view of the alignment fixture shown in FIG. 4 and attached to combustor spectacle plate. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]    [0013]FIG. 1 is a schematic illustration of a gas turbine engine  10  including a low pressure compressor  12 , a high pressure compressor  14 , and a combustor  16 . Engine  10  also includes a high pressure turbine  18  and a low pressure turbine  20 . Combustor  16  includes an upstream side  22 , and at least one dome (not shown). In one embodiment, the gas turbine engine is a GE-90 engine commercially available from General Electric Company, Cincinnati, Ohio.  
         [0014]    In operation, air flows through low pressure compressor  12  and compressed air is supplied from low pressure compressor  12  to high pressure compressor  14 . The highly compressed air is delivered to combustor  16 . Airflow (not shown in FIG. 1) from combustor  16  drives turbines  18  and  20 .  
         [0015]    [0015]FIG. 2 is side perspective view of an assembly fixture  40  that may be used during assembly of a gas turbine engine combustor, such as combustor  16  (shown in FIG. 1). FIG. 3 is a side perspective view of assembly fixture  40  coupled to a combustor spectacle plate  42 . In the exemplary embodiment, combustor  16  is a dual annular combustor. Combustor spectacle plate  42  is generally annular and includes a plurality of openings  46  positioned circumferentially through spectacle plate  42 . In one embodiment, spectacle plate  42  is a die formed sheet metal part. More specifically, in the exemplary embodiment, openings  46  are spaced circumferentially in two rows  50  and  52 . Rows  50  and  52  are known respectively, as an inner and outer annulus, and are separated by a raised flange portion  54  that includes a plurality of alternating slotted openings  56  and substantially circular openings  58 .  
         [0016]    Each spectacle plate opening  46  is substantially circular and is defined by a raised flange  70 . Each raised flange  70  has an inner diameter  72  that is sized to receive a portion of a swirler  74  therein, and a mating premixer (not shown). Swirlers  74  are known in the art are utilized to facilitate swirling incoming air to enhance flame stabilization and mixing downstream from swirlers  74 . Swirlers  74  include an inlet side  76 , an outlet side  78 , and an opening  80  extending therebetween. Swirlers  74  also include an outer flange  81  that is substantially circular and includes a pair of flats  82 . Flats  82  are substantially parallel, diametrically opposed, and a distance  84  apart.  
         [0017]    Assembly fixture  40  includes a bar clamp portion  90  and an attachment portion  92 . Bar clamp portion  90  is substantially H-shaped and includes a plurality of arms  96  extending radially outward from a center brace  97 . More specifically, arms  96  are arranged in pairs  98  and  99 . Within respective pairs  98  and  99 , arms  96  are substantially parallel and are separated by a distance  101  that is slightly larger than swirler flat distance  84 . Accordingly, arms  96  are sized to receive swirlers  74  therebetween such that swirler flats  82  remain in contact with clamp portion arms  96  while swirler  74  is held therebetween.  
         [0018]    Bar clamp portion center brace  97  extends between pairs of arms  98  and  99 , and includes an opening (not shown) that extends therethrough. More specifically, center brace  97  is substantially perpendicular to arms  96 . The center brace opening is substantially circular and is sized to receive a threaded portion  110  of attachment portion  92  therethrough. Attachment portion  92  also includes a bar clamp  112  that includes a threaded opening (not shown) that enables bar clamp  112  to threadingly couple to threaded portion  110 . Threaded portion  110  has a diameter  116  that is less than a width  118  of slotted opening  56 .  
         [0019]    During assembly of combustor  16 , a pair of swirlers  74  are coupled within respective bar clamp arm pairs  98  and  99 . More specifically, when swirlers  74  are coupled to assembly fixture  40 , each respective swirler flat  82  is in frictional contact with a respective arm  96 , such that swirler  74  is tightly held between parallel arms  96 . Assembly fixture  40  is then positioned adjacent to spectacle plate  42  such that each respective swirler  74  coupled to assembly fixture  40  is substantially aligned with respect to spectacle plate  42 . Specifically, assembly fixture  40  enables each swirler  74  to be aligned substantially concentrically with respect to a respective spectacle plate opening  46 .  
         [0020]    After each swirler  74  is aligned with respect to spectacle plate  42 , assembly fixture attachment portion  92  couples assembly fixture  40 , including swirlers  74 , to spectacle plate  42 , such that the alignment between swirlers  74  and respective openings  46  is maintained during assembly of combustor  16 . More specifically, after assembly fixture  40  is positioned adjacent spectacle plate  42 , attachment threaded portion  110  is inserted from an upstream side of spectacle plate  42  through a slotted opening  56  and through bar clamp portion center brace  97 . Bar clamp  112  is then threadingly coupled to portion  110  and tightened against clamp portion  90  to maintain assembly fixture  40  in alignment with respect to spectacle plate  42 . Swirlers  74  are then coupled to spectacle plate  42 . In the exemplary embodiment, swirlers  74  are tack-welded to spectacle plate  42 . Alternatively, swirlers  74  are brazed to spectacle plate  42 .  
         [0021]    After swirlers  74  are secured to spectacle plate  42 , assembly fixture attachment portion  92  is loosened to enable assembly fixture  40  to be removed from spectacle plate  42 . As a result, swirlers  74  are maintained in alignment with respect to spectacle plate  42  in a cost effective and highly reliable manner. Moreover, assembly fixture  40  enables swirlers  74  to have greater radial movement than circumferential movement to facilitate aligning the premixers with respect to swirlers  74 . Furthermore, assembly fixture  40  enables swirlers  74  to be fabricated without locating pins (not shown). As a result, overall assembly time and manufacturing costs of combustor  16  are facilitated to be reduced.  
         [0022]    [0022]FIG. 4 is a perspective view of an alignment fixture  100  that may be used during assembly of a gas turbine engine combustor, such as combustor  16  (shown in FIG. 1). FIG. 5 is a plan view of alignment fixture  100  attached to combustor spectacle plate  42 . After swirlers  74  are secured to spectacle plate  42 , as described above, a plurality of deflector plates  102  are then secured to spectacle plate  42 . Each deflector plate  102  includes a center opening  104  that has a diameter  106 , a pair of opposing circumferential edges  108 , and a pair of opposing radial edges  111 . Center opening diameter  106  is sized to receive at least a portion of a respective swirler  74  therein. More specifically, center opening  104  enables each respective deflector plate  102  to be positioned adjacent spectacle plate  42  when swirlers  74  are attached such that a clearance  114  is defined between adjacent deflector plates  102 .  
         [0023]    Alignment fixtures  100  are utilized during assembly to facilitate maintaining a pre-determined clearance  114  between adjacent deflector plates  102 . Each alignment fixture  100  includes a first end  120 , a second end  122 , and a body portion  124  that extends therebetween. Ends  120  and  122  are identical, and each includes a pair of arms  126  that extend substantially perpendicularly from body portion  124 . A curved radius  130  extends through body portion  124  between parallel arms  126 . In one embodiment, alignment fixture  100  is fabricated from a material that has a lower coefficient of thermal expansion than that of a material used to fabricate deflector plates  102 .  
         [0024]    Alignment fixture  100  has a length  132  measured between arms  126  at opposite ends  120  and  122  that is larger than a height  134  of each respective deflector plate  102  measured with respect to radial edges  111 . Accordingly, fixture length  132  enables fixture  100  to be “clipped” over a respective deflector plate  102  such that deflector plate radial edges  111  are adjacent an inner surface  138  of each pair of arms  126 . To facilitate deflector plates  102  being received within arms  126 , an end  140  of each respective arm is chamfered.  
         [0025]    During assembly of combustor  16 , after swirlers  74  are secured to spectacle plate  42 , as described above, a plurality of deflector plates  102  are positioned adjacent spectacle plate  42 . More specifically, deflector plates  102  are positioned adjacent spectacle plate  42  such that each respective swirler is received within each deflector plate center opening  104 , and such that circumferential edges  108  between adjacent deflector plates  102  define clearance  114 .  
         [0026]    After at least a pair of deflector plates  102  have been positioned adjacent spectacle plate  42 , an alignment fixture  100  is coupled to a respective pair of deflector plates  102 . More specifically, alignment fixture  100  is coupled to adjacent deflector plates  102  and extends over clearance  114 . Alignment fixtures maintain alignment of deflector plates relative to spectacle plate  42  such that clearance  114  is maintained, and such that each respective deflector plate  102  is aligned substantially concentrically with each respective swirler  74 .  
         [0027]    After alignment fixtures  100  have been coupled between each respective pair of adjacent deflector plates  102 , deflector plates  102  are secured to spectacle plate  42 . More specifically, in the exemplary embodiment, spectacle plate  42  is heated in a braze furnace to secure deflector plates  102  to spectacle plate  42 . Because deflector plates  102  are fabricated from a material which has a larger coefficient of thermal expansion, deflector plates  102  thermally expand more than fixtures  100 . At braze temperature, deflector plates  102  are thermally locked into fixtures  100 , thus providing a self-alignment feature. As spectacle plate  42  is cooled, braze alloy solidifies, fixtures  100  are removed, and deflector plates  102  are maintained in alignment prior to any movement or handling of the assembly. As a result, deflector plates  102  are aligned in a cost-effective and highly reliable manner. Furthermore, fixtures  100  enable deflector plates  102  to be fabricated without locating grooves (not shown). As a result, overall assembly time and manufacturing costs of combustor  16  are facilitated to be reduced.  
         [0028]    The above-described assembly fixtures enable a combustor to be assembled in a cost-effective and reliable manner. During assembly, the assembly fixtures temporarily coupled to the combustor spectacle plate to initially maintain the alignment of swirlers with respect to the spectacle plate, and subsequently, maintain the alignment of deflector plates with respect to the spectacle plate. Moreover, such assembly fixtures are not limited to use during the initial assembly of combustors, but also facilitate repair and/or retrofit of combustors. Thus, assembly fixtures are provided, which facilitate the assembly of combustors in a cost-effective and reliable manner.  
         [0029]    While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.