Abstract:
A method for assembling a turbine nozzle for a gas turbine engine. The method includes providing a turbine nozzle including a plurality of airfoil vanes extending between an inner band and an outer band, wherein the outer band includes a forward hook assembly having a rail and at least one hook, providing at least one scalloped recessed area within the forward hook assembly at least one hook to facilitate reducing stresses induced to the turbine nozzle, and coupling the turbine nozzle into the gas turbine engine using the forward hook assembly such that the turbine nozzle is at least partially supported by the forward hook assembly.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention relates generally to gas turbine engine nozzles and more particularly, to methods and apparatus for assembling gas turbine engine nozzles.  
         [0002]     Gas turbine engines include combustors which ignite fuel-air mixtures which are then channeled through a turbine nozzle assembly towards a turbine. At least some known turbine nozzle assemblies include a plurality of nozzles arranged circumferentially and configured as doublets. At least some known turbine nozzles include more than two circumferentially-spaced hollow airfoil vanes coupled by integrally-formed inner and outer band platforms. Specifically, the inner band forms a radially inner flowpath boundary and the outer band forms a radially outer flowpath boundary. Additionally, at least some known outer bands include a forward and an aft hook assembly that are used to couple the turbine nozzle within the engine. However, such hook assemblies may induce stresses in the turbine nozzle in areas adjacent the assembly, for example an intersection between the outer band and an airfoil vane, which may shorten a lifespan of the nozzle.  
       BRIEF SUMMARY OF THE INVENTION  
       [0003]     In one aspect, a method is provided for assembling a turbine nozzle for a gas turbine engine. The method includes providing a turbine nozzle including a plurality of airfoil vanes extending between an inner band and an outer band, wherein the outer band includes a forward hook assembly having a rail and at least one hook, providing at least one scalloped recessed area within the forward hook assembly at least one hook to facilitate reducing stresses induced to the turbine nozzle, and coupling the turbine nozzle into the gas turbine engine using the forward hook assembly such that the turbine nozzle is at least partially supported by the forward hook assembly.  
         [0004]     In another aspect of the invention, a turbine nozzle for a gas turbine engine includes an outer band comprising an inside face, an outside face, and a forward hook assembly extending outwardly from said inside face. The forward hook assembly includes a rail and at least one hook extending outwardly from the rail. The at least one hook includes at least one scalloped recessed area. The turbine nozzle also includes an inner band and at least one airfoil vane extending between the outer band and the inner band.  
         [0005]     In another aspect, a gas turbine engine includes at least one turbine nozzle assembly including an outer band, an inner band, and a plurality of airfoil vanes coupled together by the outer and inner bands. The outer band includes a forward hook assembly extending radially outwardly from the outer band. The forward hook assembly includes a rail and at least one hook extending outwardly from the rail. The at least one hook includes at least one scalloped recessed area. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]      FIG. 1  is a schematic illustration of an exemplary gas turbine engine.  
         [0007]      FIG. 2  is a perspective view of an exemplary embodiment of a turbine nozzle that may be used with the gas turbine engine shown in  FIG. 1 .  
         [0008]      FIG. 3  is a perspective view of a portion of the turbine nozzle shown in  FIG. 2 .  
         [0009]      FIG. 4  is another perspective view of a portion of the turbine nozzle shown in  FIG. 2 .  
         [0010]      FIG. 5  is another perspective view of a portion of the turbine nozzle shown in  FIG. 2 .  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0011]      FIG. 1  is a schematic illustration of a gas turbine engine  10  including, in serial flow arrangement, a fan assembly  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 . Engine  10  has an intake side  28  and an exhaust side  30 . In one embodiment, engine  10  is a CF-34 engine commercially available from General Electric Aircraft Engines, Cincinnati, Ohio.  
         [0012]     In operation, air flows through fan assembly  12  and compressed air is supplied to high-pressure compressor  14 . The highly compressed air is delivered to combustor  16 . Airflow from combustor  16  drives turbines  18  and  20 , and turbine  20  drives fan assembly  12 . Turbine  18  drives high-pressure compressor  14 .  
         [0013]      FIG. 2  is a perspective view of an exemplary embodiment of a turbine nozzle sector  50  that may be used with gas turbine engine  10  (shown in  FIG. 1 ).  FIG. 3  is a perspective view of a portion of turbine nozzle sector  50 .  FIG. 4  is another perspective view of a portion of turbine nozzle sector  50 .  FIG. 5  is another perspective view of a portion of turbine nozzle sector  50 . Nozzle sector  50  includes a plurality of circumferentially-spaced airfoil vanes  52  coupled together by an arcuate radially outer band or platform  54  and an arcuate radially inner band or platform  56 . More specifically, in the exemplary embodiment, each band  54  and  56  is integrally-formed with airfoil vanes  52 , and nozzle sector  50  includes two airfoil vanes  52 . In one embodiment, each arcuate nozzle sector  50  is known as a two vane segment.  
         [0014]     Inner band  56  includes an aft flange  60  that extends radially inwardly therefrom. More specifically, flange  60  extends radially inwardly from band  56  with respect to a radially inner surface  62  of band  56 . Inner band  56  also includes a forward flange  64  that extends radially inwardly therefrom. Forward flange  64  is positioned between an upstream edge  66  of inner band  56  and aft flange  60 , and extends radially inwardly from band  56 .  
         [0015]     Outer band  54  includes a cantilever mounting system  70  that includes a forward hook assembly  72  and an aft flange  74 . Cantilever mounting system  70  facilitates supporting turbine nozzle  50  within engine  10  from a surrounding annular engine casing (not shown). Forward hook assembly  72  extends radially outwardly from an outer surface  76  of outer band  54 . Forward hook assembly  72  includes a forward rail  78  and a hook  80 . Rail  78  extends radially outwardly from outer band outer surface  76  in a circumferential direction across outer band outer surface  76  and between a pair of oppositely disposed circumferential sector ends  82 .  
         [0016]     Engine  10  includes a rotor assembly (not shown), such as, but not limited to, a low pressure turbine (not shown), that includes at least one row of rotor blades (not shown) that is downstream from turbine nozzle sector  50 . The rotor assembly is surrounded by a rotor shroud (not shown) that extends circumferentially around the rotor assembly and turbine nozzle sector  50 . Cantilever mounting system  70  couples each turbine nozzle sector  50  to the rotor shroud through a hanger (not shown) that supports and is coupled to the shroud. More specifically, hook  80  is slidably coupled within a radially outer channel (not shown) defined within the hanger.  
         [0017]     Hook  80  does not extend continuously between circumferential ends  82 , but rather hook  80  includes one or more scalloped recessed areas  84 . Scalloped recessed area(s)  84  may facilitate reducing stresses, such as, but not limited to, mechanical and/or thermal stresses, induced to turbine nozzle sector  50 . For example, in some embodiments scalloped recessed area(s)  84  may facilitate reducing stresses induced into an intersection between an airfoil vane  52  and outer band  54 . Although one recessed area  84  is illustrated, hook  80  may include any number of scalloped recessed areas  84 . Moreover, scalloped recessed area(s)  84  may have any suitable size, shape, orientation, and/or location that facilitates reducing stresses induced into turbine nozzle sector  50 , whether such size, shape, orientation, and/or location is described and/or illustrated herein. Accordingly, scalloped recessed area(s)  84  may facilitate increasing an operational life of turbine nozzle sector  50  and/or reducing an amount of cooling air that may be necessary and/or desired to maintain to turbine nozzle sector  50  during operation. In addition, because forward hook assembly  72  is scalloped, an overall weight of turbine nozzle sector  50  is reduced in comparison to other known turbine nozzles that do not include recessed area(s)  84 .  
         [0018]     One or more seal assemblies  88  is positioned adjacent scalloped recessed area(s)  84 . Although one seal assembly  88  is illustrated, turbine nozzle sector  50  may include any number of seal assemblies  88 . Although seal assembly  88  may be positioned anywhere to facilitate reducing fluid leakage through a recessed area  84 , in the exemplary embodiment seal assembly  88  includes a seal member  90  that extends in sealing contact along a downstream side  90  of hook assembly rail  78  at least partially overlapping scalloped recessed area  84 . Moreover, in the exemplary embodiment seal member  90  extends in sealing contact along a radially outer surface  94  of hook  80 . Accordingly, seal assembly  88  may facilitate reducing fluid leakage through scalloped recessed area  84 . In some embodiments, fluid pressure facilitates maintaining seal member  90  in sealing contact with rail  78  and/or hook  80 . Moreover, in some embodiments, seal member  90  is slidably coupled to hook assembly  72  to facilitate sealing contact between member  90  hook assembly  72  during thermal expansion and/or contraction of hook assembly  72 . For example, in the exemplary embodiment seal member  90  is coupled to hook assembly  72  for movement within a slot  92  within hook radially outer surface  94 . Seal member  90  may be slidably coupled to hook assembly  72  in any suitable fashion, configuration, position, location, orientation, arrangement, and/or by any suitable structure and/or means.  
         [0019]     The above-described turbine nozzle includes a scalloped aft forward hook assembly that extends from the forward rail. The hook assembly includes one or more recessed areas that are circumferentially spaced across the outer band. The recessed areas not only reduce an overall weight of the turbine nozzle assembly, but also facilitate reducing mechanical and/or thermal stresses induced to the turbine nozzle. In addition, the turbine nozzle includes a seal assembly that at least partially overlaps a recessed area to facilitate reducing fluid leakage through the recessed area. As a result, the durability and useful life of the turbine nozzle are facilitated to be increased by the combination of the scalloped hook assembly and the seal assembly.  
         [0020]     Exemplary embodiments of turbine nozzles are described above in detail. The nozzles are not limited to the specific embodiments described herein, but rather, components of each turbine nozzle may be utilized independently and separately from other components described herein.  
         [0021]     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.