Abstract:
A method and system of supporting removable static components in a turbine engine stator assembly is described. The method comprises the steps of engaging a stator hanger located at a first location on a first static component with a post located on a first static structure whereby the post supports at least a part of the weight of the first static component, engaging a stator stopper located at a second location on the first static component that is located circumferentially apart from the first location with the stator hanger that is located on a second static component, and engaging a hook located at a third location on the first static component with a second static structure whereby the second static structure supports at least a part of the weight of the first static component.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to gas turbine engine components, and more specifically to mounting of stators in turbine engines. 
     Gas turbine engines typically include a core engine having a compressor for compressing air entering the core engine, a combustor where fuel is mixed with the compressed air and then burned to create a high energy gas stream, and a first or high pressure turbine which extracts energy from the gas stream to drive the compressor. In aircraft turbofan engines, a second turbine or low pressure turbine located downstream from the core engine extracts more energy from the gas stream for driving a fan. The fan provides the main propulsive thrust generated by the engine. 
     An annular turbine nozzle is located between the combustor and high pressure turbine and between stages of the turbine. The turbine nozzle includes a pair of radially spaced inner and outer bands disposed concentrically about a longitudinal axis of the core engine and airfoils supported between the inner and outer annular bands. In the annular turbine nozzle assembly, the airfoils are arranged in circumferentially spaced relation from one another and extend in radial relation to the core engine axis. The annular turbine nozzle assembly is formed by a plurality of arcuate segments (alternatively referred to herein as “stator vane” or “stator vanes”) which fit end-to-end together to form the 360 degree circumferentially extending nozzle assembly. Each turbine nozzle segment includes arcuate segments of the inner and outer bands and one or more airfoils mounted between the inner and outer band segments. 
     The turbine nozzle provides the function of directing and/or re-directing hot gas flow from the combustor into a more efficient direction for impinging on and effecting rotation of the rotor stages of the turbine. The directing process performed by the nozzle also accelerates gas flow resulting in a static pressure reduction between inlet and outlet planes and creates high pressure loads and moments on the nozzle and its support system. Additionally, the turbine nozzle and its support systems also experience loads and moments due to the high thermal gradients from the hot combustion gases and the coolant air at the radial support surfaces. 
     In conventional nozzle support systems, the nozzle segments are attached by bolted joints or a combination of bolts and some form of clamping arrangement to an engine support structure. Such arrangements, however, create significant bending stresses in the nozzle and support due to mechanical loads and moments experienced by the nozzle airfoils and due to differential thermal expansion and contraction. Furthermore, holes required for receiving the bolts inherently create stress concentrations and may provide potential leakage paths. And, the nuts and bolts required for the assembly add undesirable weight to the engine and increase assembly and disassembly time. 
     In some designs of smaller turbine engines, turbine nozzles are supported only at their radially outer band in essentially a cantilever type arrangement since their radially inner band extends adjacent a rotating engine structure to which the turbine rotor stages are attached. In some stages, such as the first stage nozzle, the nozzle is attached to the engine stationary structure via a radially inner mount or flange structure coupled to the inner band. The radially outer band is not mechanically retained but is supported against axial forces by a circumferential engine flange. In other stages, such as stage  2  turbine of an engine, the turbine nozzle may be attached at its radially outer band but be free at its radially inner band. In either design, the use of bolts and clamps at circumferential locations about a turbine nozzle band act as a restriction to the band, which band is hotter than the structure to which it is attached, causing radial bowing of the outer band of the nozzle, causing out-of-roundness and stressing of the airfoils attached to the band. Such stressing of the airfoils may lead to formation of cracks in the airfoil. 
     A need exists for the development of alternative designs methods which will provide improvements in mounting and supporting stator components such as turbine nozzle segments to the engine support structure. Accordingly, it would be desirable to have a method and system for mounting static components in a turbine engine, such as a stator vane, to the engine support structure that react the loads and moments without using bolts and nuts. It is desirable to have a reaction mount system for a turbine stator component such that the stator can be easily replaced in an assembly. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The above-mentioned need or needs may be met by exemplary embodiments described herein which provide a method and system for supporting removable static components in a turbine engine. The method comprises the steps of engaging a stator hanger located at a first location on a first static component with a post located on a first static structure whereby the post supports at least a part of the weight of the first static component, engaging a stator stopper located at a second location on the first static component that is located circumferentially apart from the first location with the stator hanger that is located on a second static component, and engaging a hook located at a third location on the first static component with a second static structure whereby the second static structure supports at least a part of the weight of the first static component. A reaction mount system provides support for a stator vane, comprising a stator hanger located on an outer band at a first location and a stator stopper located at a second location that is located circumferentially apart from the first location. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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, may be best understood by reference to the following description taken in conjunction with the accompanying drawing figures in which: 
         FIG. 1  is a longitudinal cross sectional illustration of a portion of a gas turbine showing the rotors and stators including an exemplary embodiment of the present invention. 
         FIG. 2  is a longitudinal cross sectional illustration of the stator components in the gas turbine shown in  FIG. 1 , including an exemplary embodiment of the present invention. 
         FIG. 3  shows an isometric view of a stator assembly having an exemplary embodiment of a stator mounting system according to the present invention. 
         FIG. 4  shows an isometric view of a stator vane having a reaction mount system according to an exemplary embodiment of the present invention. 
         FIG. 5  shows an isometric view of a stator assembly having an alternative embodiment of a stator mounting system according to the present invention. 
         FIG. 6  shows an isometric view of a stator vane having a reaction mount system according to an alternative embodiment of the present invention. 
         FIG. 7  shows an isometric view of a shroud hanger shown in  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the drawings wherein identical reference numerals denote the same elements throughout the various views,  FIG. 1  shows a longitudinal cross sectional illustration of a portion of an exemplary gas turbine  10  showing the rotors and stators including an exemplary embodiment of the present invention. The exemplary gas turbine  10  shown in  FIG. 1  comprises a Stage  1  turbine rotor  21 , a Stage  2  turbine rotor  22 , and a Stage  2  turbine nozzle  23  located axially in between them. Turbine blades  20  and  24  are circumferentially arranged around turbine centerline  11  on the rims of the Stage  1  and Stage  2  rotors respectively. The exemplary embodiments shown herein show support systems  300  in turbines for supporting static components, such as turbine nozzles  23 , using adjacent static structures  91 ,  92  such as shroud hangers  32 ,  90 . 
       FIG. 2  shows an enlarged view of the Stage  2  turbine nozzle that is shown in  FIG. 1 . The stage  2  turbine nozzle  23  comprises an inner band  51 , an outer band  52  and an airfoil  50  that extends between the inner band  51  and the outer band  52 . The turbine nozzles shown herein have one airfoil between the inner band and the outer band. However, in other embodiments of the present invention, it is possible to have a plurality of airfoils in a turbine nozzle segment, between the inner band and the outer band. The inner band  51  and the outer band  52  form the flow path for the combustion gases. The turbine nozzle airfoil  50  may be hollow (such as, for example, shown in  FIG. 5 ) so that cooling air supplied from a spoolie  100  can be circulated through the hollow airfoil  50 . The nozzle segment  23  including the outer band may be made of a single piece of casting having the vane airfoils, the outer band and the inner band. Alternatively the nozzle segment may be made by suitable conventional methods of joining, such as brazing, individual sub-components such as vane airfoils, the outer band and the inner band. 
     The outer band  52  and inner band  51  of each nozzle segment  23  have an arcuate shape so as to form an annular flow path when multiple nozzle segments are assembled around the turbine centerline  11 . The turbine nozzle segments  23 , when assembled in the engine, form an annular turbine nozzle assembly, with the inner and outer bands  51 ,  52  forming the annular flow path through which the hot gases pass. In the turbine  10  shown in  FIG. 1 , Stage  2  turbine nozzle receives the flow coming out of the stage  1  turbine and reorients its direction and flows it into the stage  2  turbine. 
     Referring to  FIGS. 2 and 3 , the exemplary embodiment of the stage  2  nozzle shown therein is held in position by a stator support system  300 . An exemplary outer band cantilever mount system is shown in  FIGS. 1 and 2 . In the exemplary embodiments shown, the axially forward end  61  of the outer band  52  has a forward hook  56  which extends in the circumferential direction along the circumferential length of the nozzle segment  23 . The forward hook  56  sits on an arcuate rail  40  which protrudes axially from the aft end of the stage  1  shroud hanger  32 . 
       FIG. 3  shows an isometric view of a stator assembly  200  having an exemplary embodiment of a stator components mounting system  300  according to the present invention. For illustration purposes, only two outer bands  52  that are circumferentially to each other are shown in  FIG. 3 . Each outer band  52  has a reaction mount system  205  comprising a stator hanger  210  located at a first location  221 , such as near the aft end location shown in  FIG. 3 , and a stator stopper  220  at a second location  222 . The stator stopper  220  is shown located circumferentially apart from the stator hanger  210 , near the aft end on the outer bands  52 . The support system  300  further comprises a hook  56  that is located at a third location  223 , shown in  FIGS. 2 and 3  near the axially forward end  61 . As shown in  FIG. 3 , the forward hook may be have arcuate shape that engages with an arcuate rail  40  on a static structure  92  located near the forward hook  56 . As shown in the figures herein, the arcuate rail  40  forms a part of a shroud hanger  32  located axially forward from the outer band  52 . 
       FIG. 4  shows an isometric view of a stator vane  53  having a reaction mount system  205  according to an exemplary embodiment of the present invention. The stator hanger  210  and the stator stopper  220  are located near the aft end  60  and the forward hook  56  is located near the forward end  61  of the outer band  52 . The stator hanger  210  comprises a stem  64 , having a block of material shaped like a hammer (herein referred to as “hammer”, identified as item  68 ) located at its radially outer end. The stator hanger has a hanger claw  71  located near the radially outer end of the stem  64 . The stator stopper  220  is located circumferentially apart from the stator hanger  210 . The stator stopper  220  comprises a paddle  80  having a paddle aft face  83  and an end face  86 . 
     During assembly, hanger claw  71  engages with a post  96  that is located on a first support structure  91 , such as for example, a shroud hanger  90 . The stator stopper  220  located on an outer band  52  engages, as shown in  FIG. 3 , with the stator hanger  210  located on the circumferentially adjacent outer band  52 . Specifically the paddle aft face  83  is located adjacent to the stem  64  of the stator hanger  210 . A portion of the top of the stator stopper  220  engages with a radially inner portion of the hammer  68 . When the turbine is not operating, the hanger claw  71  rests on the post  96 , providing support for the nozzle in the cold condition. In  FIGS. 3 and 4 , an anti-rotation tab  72  is shown located near an end of the hanger claw  71 . The anti-rotation tab  72  engages with the post  96  to prevent rotation of the nozzle segments  23  during assembly. 
     During turbine operation the stem  64  of the hammer  68  reacts the nozzle tangential loads against the post  96 . The top of the stator stopper  220  located at the second location  222  on the opposite slash face of the outer band  52  reacts the radial moment into the hammer  68  of the circumferentially adjacent outer band  52  of the adjacent nozzle segment  23 . The top  70  of the hammer  68  reacts radially against a 360 degree shroud support. In addition to the hammer  68 , the radial load is also reacted into supporting structure  92  by the nozzle forward hook  56 . The axial moments are reacted by the paddle  80 , into the hammer stem  64  of the adjacent nozzle segment, and into the adjacent supporting structure  91 . Axial loads are reacted against the adjacent static structures such as the stage  2  shroud hanger. When the nozzle segments  23  are assembled into a full nozzle assembly, all of the nozzle segments will react the radial moment against the 360 degree shroud support and all of the axial loads and moments, and circumferential loads against the adjacent supporting structures. This feature of support system  300  improves the roundness of the nozzle assembly around the turbine axis  11  and results in a reduction of the relative gap between nozzle segments and is an improvement over prior art. 
       FIG. 5  shows a stator assembly  200  having an alternative embodiment of a stator mounting system  300  according to the present invention. Three nozzle segments are shown, each segment having a single vane. The nozzle vanes  53  shown have hollow cavities through which cooling flow air is passed through. An alternative embodiment of the stator hanger  210  is shown in  FIGS. 5 and 6 . The hanger claw engages with a post  96  located on an adjacent supporting structure  91 , such as a shroud hanger. In this alternative embodiment, the reaction mount system  205  has an anti-rotation tab  172  that is located on the reaction mount  63  (see  FIG. 6 ). The engagement of the stator hanger  210  and the stator stopper  220  with the support structure  91  is as described previously. 
       FIG. 7  shows a shroud hanger  90  that can be used in the static component mount system  300  described herein. The shroud hanger  90  has an inner rail  94  that is arcuate in shape. The inner rail can support a conventional turbine shroud. The shroud hanger  90  has an outer rail that is also arcuate in shape. The outer rail engages with a casing  34  and reacts the loads against the casing  34 . The shroud hanger has at least one post  96  that extends generally in an axial direction, as shown in  FIGS. 3 ,  5  and  7 . The post provides support for the stator vanes  23  as described previously and transmits the loads through the post  96  to the shroud hanger and the casing. The shroud hangers, and nozzles and other components shown herein are made of conventional turbine materials such as for example Rene 80 and Inconel 718 that have high temperature capabilities. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to make and use the invention. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.