Abstract:
A method facilitates manufacturing a combustor for a gas turbine engine. The combustor includes an inner and an outer liner, a dome, and flanges. The method comprises assembling the inner and outer liner such that each includes a series of liner panels, positioning a spatter shield against a downstream side of the inner and outer liners, wherein the spatter shield comprises molybdenum, positioning a mounting flange against the downstream side of the inner and outer liners, such that the spatter shield is positioned at least partially between the mounting flange and the inner and outer liners, and coupling the mounting flange to the inner and outer liners.

Description:
BACKGROUND OF THE INVENTION 
   This invention relates generally to gas turbine engines, and more particularly, to methods for fabricating combustors used with gas turbine engines. 
   A turbine engine includes a compressor for compressing air which is mixed with a fuel and channeled to a combustor wherein the mixture is ignited within a combustion chamber for generating hot combustion gases. At least some known combustors include a dome assembly, a cowling, and liners to channel the combustion gases to a turbine, which extracts energy from the combustion gases for powering the compressor, as well as producing useful work to propel an aircraft in flight or to power a load, such as an electrical generator. The liners are coupled to the dome assembly with the cowling, and extend downstream from the cowling to define the combustion chamber. At an aft end of the combustion chamber, the liners are coupled to a turbine nozzle by a mounting flange. 
   At least some known liners include a plurality of panels that are connected together with riveted, bolted, or welded connections. More specifically, within at least some known combustors, the liners are coupled together in series such that adjacent liners form an over hang portion of the liners. During assembly of the liners, it is known to use a spatter shield fabricated from copper to facilitate preventing secondary welding of the liner panels when the mounting flange is coupled to the liners. More specifically, at least some known spatter shields are fabricated from copper. 
   However, when electron beam welding is used to couple cobalt base alloys, the copper spatter shields may become inadvertently fused to the components being welded. Removing the fused shields from the panels may be a time-consuming process because acid may be required to dissolve the fused copper material from the liner panels. Alternatively, depending upon the amount of material that was fused to the panels, the panels, and/or shield, may be deemed non-salvageable. Furthermore, because of the susceptibility of the copper to fuse, weld cracks and/or weld heat affected zone (HAZ) cracking may occur during welding of the cobalt base alloys. 
   BRIEF SUMMARY OF THE INVENTION 
   In an exemplary embodiment, a method for manufacturing a combustor for a gas turbine engine is provided. The combustor includes an inner and an outer liner. The method comprises assembling the inner and outer liner such that each includes a series of liner panels, positioning a spatter shield against a downstream side of the inner and outer liners, wherein the spatter shield comprises molybdenum, positioning a mounting flange against the downstream side of the inner and outer liners, such that the spatter shield is positioned at least partially between the mounting flange and the inner and outer liners, and coupling the mounting flange to the inner and outer liners. 
   In another aspect of the invention, a spatter shield for use in manufacturing a gas turbine engine combustor is provided. The spatter shield comprises molybdenum. 
   In a further aspect, an apparatus for shielding a portion of a gas turbine engine combustor during assembly is provided. The apparatus comprises an arcuate body comprising molybdenum. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is schematic illustration of a gas turbine engine; 
       FIG. 2  is an enlarged cross-sectional view of an exemplary combustor that may be used with the gas turbine engine shown in  FIG. 1 ; 
       FIG. 3  is an enlarged cross-sectional view of a combustor liner that may be used with the combustor shown in  FIG. 2 ; 
       FIG. 4  is a perspective view of an assembled annular spatter shield that may be used in fabricating the combustor shown in  FIG. 3 ; and 
       FIG. 5  is a side view of the spatter shield shown in FIG.  4  and coupled in position during fabrication. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     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 . Compressor  12  and turbine  20  are coupled by a first shaft  22 , and compressor  14  and turbine  18  are coupled by a second shaft  21 . In one embodiment, gas turbine engine  10  is a GE90 engine commercially available from General Electric Aircraft Engines, Cincinnati, Ohio. In another embodiment, gas turbine engine  10  is a CF34 engine commercially available from General Electric Aircraft Engines, Cincinnati, Ohio. 
   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 from combustor  16  drives turbines  18  and  20  and exits gas turbine engine  10  through a nozzle  24 . 
     FIG. 2  is an enlarged cross-sectional view of a combustor  30 .  FIG. 3  is an enlarged view of a portion of combustor  30 . Combustor  30  may be used with gas turbine engine  10  shown in  FIG. 1 , and includes a dome assembly  32 . A fuel injector (not shown) extends into dome assembly  32  and injects atomized fuel through dome assembly  32  into a combustion zone  36  of combustor  30  to form an air-fuel mixture that is ignited downstream of the fuel injector 
   Combustion zone  36  is formed by annular, radially outer and radially inner supporting members (not shown) and combustor liners  40 . Combustor liners  40  shield the outer and inner supporting members from the heat generated within combustion zone  36  and include an inner liner  42  and an outer liner  44 . Outer liner  44  and inner liner  42  are annular and extend to define combustion zone  36 . Combustion zone  36  extends downstream from a combustor inlet  46  to a turbine nozzle (not shown). More specifically, each liner  42  and  44  is coupled to the turbine nozzle by a mounting flange  49  that extends downstream from each liner  42  and  44 . Outer and inner liners  44  and  42  each include a plurality of serially-coupled panels  50  which include a series of steps  52 , each of which forms a distinct portion of combustor liner  40 . 
   Each combustor panel  50  includes a combustor liner surface  70 , an exterior surface  72 , and an overhang portion  74 . Combustor liner surface  70  and exterior surface  72  are connected together at overhang portion  74  and form a rear facing edge  76 . A plurality of air cooling slots  78  separate adjacent combustor panels  50 . 
     FIG. 4  is a perspective view of an assembled spatter shield  100  that may be used in fabricating combustor  30 .  FIG. 5  is a side view of assembled spatter shield  100  coupled in position during fabrication of combustor  30 . Spatter shield  100  is substantially planar and includes an annular body  102  that is toroidal. More specifically, body  102  is formed from a plurality of arcuate members  104  coupled together to form body  102 . Accordingly, body  102  has an inner diameter d i  defined by an inner perimeter  106 , and an outer diameter d o , defined by an outer perimeter  108 . Diameters d i , and d o , are variably selected based upon combustor  30  being manufactured. In the exemplary embodiment, spatter shield  100  is fabricated from molybdenum, which as described in more detail below, facilitates manufacture of combustor  30 . 
   During fabrication, initially combustor liners  40  are assembled. Specifically, as described in more detail above, panels  50  are serially connected in a series of steps  52 , such that panels  50  form a distinct portion of combustor liner  40 . More specifically, panels  50  are coupled together such that adjacent panels  50  are connected together at each overhang portion  74 , and such that each set of adjacent panels  50  are separated by at least one air cooling slot  78 . 
   Following the initial formation of liners  40 , each liner assembly  40  is coupled to a known weld fixture  110 . Weld fixture  110  facilitates aligning each liner  40  and maintaining each liner  40  in alignment while a mounting flange  49  is coupled to a downstream side  112  of each liner  40 . Once each liner  40  is positioned in alignment with respect to weld fixture  110 , mounting flange  49  is temporarily coupled to liner  40 . In one embodiment, flange  49  is coupled to liner  40  using known tack welding procedures. 
   Spatter shield  100  is then coupled in position relative to liner  40  and mounting flange  49 . More specifically, spatter shield  100  is aligned with respect to liner  40  and is then removably coupled to mounting flange  49  by a plurality of fasteners  120 . In the exemplary embodiment, fasteners  120  are binder clips that are spaced circumferentially around shield inner perimeter  106  to facilitate maintaining spatter shield  100  in alignment with respect to liner  40  and mounting flange  49 . 
   When secured in position by fasteners  120 , shield body  102  is substantially parallel to weld fixture  110  and is positioned to facilitate shielding at least a portion of liner  40  during fabrication of combustor  30 . More specifically, mounting flange  49  is coupled to liner  40  using an electron beam (EB) welding process, and shield  100  is positioned relative to fabrication of combustor  30  such that body  102  is slightly behind a weld joint  126  created between mounting flange  49  and liner  40 . Accordingly, as the electron beam traverses combustor  30  to form weld joint  126  between liners  40  and flange  49 , molybdenum shield  100  facilitates shielding liner  40  and thus, facilitates preventing weld and weld heat affected zone (HAZ) cracking of weld joint  126  that may occur with at least some other known spatter shields. 
   Additionally, because molybdenum shield  100  is not as susceptible to fusing as shields fabricated from copper, shield  100  also facilitates a more uniform weld joint  126  being formed between mounting bracket  49  and liner  40 , thus facilitating reduced weld cracking of joint  126 . As a result, shield  100  also facilitates reduced manufacturing times, as less time must be spent removing fused material from liner  40 , and reduced manufacturing costs, as less components are damaged and deemed unsalvageable. Furthermore, because shield  100  is fabricated from molybdenum, less welding material is inadvertently fused to shield  100 , such that shield  100  is reusable with other combustor fabrications. 
   The above-described spatter shield is cost-effective and highly reliable. The molybdenum shield facilitates shielding the liner as the mounting flange is coupled to the liner with electron beam welding. More specifically, the shield is positioned slightly behind the weld joint and facilitates preventing secondary welding on the combustor liner. In addition, because less welding material is inadvertently fused to the shield during EB welding, the shield is reusable. As a result, a spatter shield is provided which facilitates reducing manufacturing costs and combustor assembly times in a cost-effective and reliable manner. 
   Exemplary embodiments of spatter shields are described above in detail. The spatter shields are not limited to the specific embodiments described herein, but rather, components of each spatter shield and each method of fabrication may be utilized independently and separately from other components described herein. Each spatter shield can also be used in combination with other spatter shields. 
   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.