Abstract:
Gas turbine engine systems and related methods involving thermally isolated retention are provided. In this regard, a representative method for attaching a gas turbine engine component includes using a fastener, varying in diameter along a length thereof, to prevent a portion of a component from being crimped between surfaces to which the component is attached such that the component moves relative to the surfaces responsive to thermal cycling of a gas turbine engine of which the surfaces and the component are constituent parts.

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT 
       [0001]    The U.S. Government may have an interest in the subject matter of this disclosure as provided for by the terms of contract number N00019-02-C-3003 awarded by the United States Navy. 
     
    
     BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The disclosure generally relates to gas turbine engines. 
         [0004]    2. Description of the Related Art 
         [0005]    Gas turbine engines, particularly turbojet engines for military use, may incorporate augmentors (afterburners) for increasing thrust. The use of augmentors tends to increase stresses on various components, such as the components used to form the augmentors. For instance, these stresses can be manifest as thrust-induced and thermally-induced stresses. 
       SUMMARY 
       [0006]    Gas turbine engine systems and related methods involving thermally isolated retention are provided. In this regard, an exemplary embodiment of an assembly for a gas turbine engine comprises: a mounting surface having a first flange portion and a first mounting orifice, the first flange portion having a first underside, a first aperture and a first free end, the first underside being spaced from and adjacent to the mounting surface such that a first channel is formed therebetween, the first aperture being aligned with the first mounting orifice; a first component having a first body and a first leg, the first leg extending outwardly from the first body, the first leg having a first recess, the first leg being sized and shaped to be positioned at least partially within the first channel; and a first fastener having a first diameter portion and a second diameter portion, the second diameter portion being narrower than the first diameter portion, the first fastener being fastened to the mounting surface and the first flange with the first diameter portion extending through the first mounting orifice and the first recess, and the second diameter portion extending through the first aperture of the first flange such that the first fastener maintains a spacing between the first underside of the first flange and the mounting surface for permitting movement of the component relative to the mounting surface during thermal cycling of the gas turbine engine. 
         [0007]    An exemplary embodiment of a method for attaching a gas turbine engine component comprises using a fastener, varying in diameter along a length thereof, to prevent a portion of a component from being crimped between surfaces to which the component is attached such that the component moves relative to the surfaces responsive to thermal cycling of a gas turbine engine of which the surfaces and the component are constituent parts. 
         [0008]    An exemplary embodiment of a gas turbine engine comprises: a compressor section; a turbine section operative to drive the compressor section; and an exhaust section located downstream of the turbine section, the exhaust section having an augmentor assembly, the augmentor assembly having a spray bar assembly and a flame holder assembly, the spray bar assembly being operative to provide a spray of fuel for augmentation of the gas turbine engine, the flame holder assembly having a mounting surface, a fastener and a floating lug, the floating lug being operative to support the spray bar assembly, the mounting surface having a first flange portion defining a first channel, a first portion of the first lug being positioned within the first channel the fastener extending through the mounting surface and the first flange portion, the fastener being operative to prevent the portion of the floating lug located within the first channel from being crimped between the mounting surface and the first flange portion. 
         [0009]    Other systems, methods, features and/or advantages of this disclosure will be or may become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features and/or advantages be included within this description and be within the scope of the present disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    Many aspects of the disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
           [0011]      FIG. 1  is a schematic diagram depicting an exemplary embodiment of a gas turbine engine. 
           [0012]      FIG. 2  is a schematic diagram depicting a portion of the embodiment of  FIG. 1 . 
           [0013]      FIG. 3  is an assembly diagram depicting the flame holder assembly of embodiment of  FIGS. 1 and 2 . 
           [0014]      FIG. 4  depicts exemplary embodiment of a floating lug. 
           [0015]      FIG. 5  is schematic diagram depicting an embodiment of a portion of a flame holder assembly showing mounting detail of a floating lug. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Gas turbine engine systems and related methods involving thermally isolated retention are provided, several exemplary embodiments of which will be described in detail. In this regard, retention features are used to accommodate disparate thermal expansion and contraction between components that are attached to each other. In some embodiments, the components are floating lugs that are configured to move with respect to the mounting surfaces to which the lugs are attached. By way of example, the floating lugs are attached using stepped rivets, which incorporate steps (locations of diameter change) for maintaining control gaps. The control gaps facilitate movement of the floating lugs after deformation of the rivets by preventing crimping of adjacent material about the lug. In some embodiments, the floating lugs can be used in combination with fixed lugs. 
         [0017]    Reference is now made to the schematic diagram of  FIG. 1 , which depicts an exemplary embodiment of a gas turbine engine. Specifically, engine  100  is a turbofan that incorporates a compressor section  102 , a combustion section  104 , a turbine section  106  and an exhaust section  108 . Although depicted as a turbofan gas turbine engine, it should be understood that the concepts described herein are not limited to use with turbojets as the teachings may be applied to other types of gas turbine engines. 
         [0018]    As shown in the embodiment of  FIG. 1 , exhaust section  108  defines a core gas path  110  directing a core flow of gas (depicted by arrow A), and a bypass gas path  112  directing a bypass flow of gas (depicted by arrow B). Multiple vanes (e.g., vane  114 ) are positioned circumferentially about a longitudinal axis  116  of the engine, with various components of an augmentor assembly  120  being supported by the vanes. By way of example, a trailing edge box  122  of vane  114  (described in greater detail with respect to  FIG. 2 ) mounts a spray bar assembly for providing a spray of fuel for augmentation and a flame holder assembly for facilitating combustion of the spray of fuel. A tailcone  124  also is located in the exhaust section. 
         [0019]    As shown in  FIG. 2 , augmentor assembly  120  includes a flame holder assembly  130  and a spray bar assembly  132 , both of which are mounted to trailing edge box  122 . As the names imply, the spray bar assembly routes fuel to spray nozzles that provide sprays of fuel for augmentation; and the flame holder assembly provides ignition for the sprays of fuel. Flame holder assembly  130  is shown in greater detail in  FIG. 3 . 
         [0020]    As shown in  FIG. 3 , flame holder assembly  130  includes an impingement sheet assembly  140  that is elongate and which includes a base  141  and a mounting surface  142 . Mounting surface  142  mounts a series of lugs (e.g., lug  144 ) that attach the flame holder assembly to the trailing edge box  122  ( FIG. 2 ). Notably, the lugs are shown in respective mounted positions in phantom lines. 
         [0021]    In the embodiment of  FIG. 3 , two types of lugs are used. Specifically, lugs  144 ,  146  are floating lugs and lug  148  is a fixed lug. The floating lugs differ from the fixed lug in this embodiment by incorporating recesses (e.g., recesses  145 ,  147 ) for receiving fasteners, whereas the fixed lug incorporates through holes (e.g., holes  149 ,  151 ). The recesses enable the floating lugs to slide relative to the mounting surface  142  even though movement away from the mounting surface is restricted by fasteners (e.g., rivets  153 ,  155 ). Notably, the lugs are fastened to flange portions (e.g., portions  157 ,  159 ) that extend from the mounting surface  142 . 
         [0022]    As shown in greater detail in  FIGS. 4 and 5 , floating lug  144  includes a body  160 , with legs  162  and  164  extending from the body. The body incorporates a housing  166  that defines an interior cavity  168 . One or more inserts (e.g., insert  170 ) are mounted within cavity  168 . In this embodiment, insert  170  includes an internally threaded bore  172  that is sized to receive an externally threaded bolt (not shown). Such a bolt is used to attach the flame holder assembly to the trailing edge box  122  ( FIG. 2 ). A cut-out  173  is provided in an upper portion of the housing in this embodiment as a clearance feature for enabling positioning of the lug adjacent to other components. 
         [0023]    As shown in  FIG. 4 , leg  162  incorporates recess  145 , and leg  164  incorporates a recess  147 . The recesses open to contact free ends  183 ,  185 , respectively, of the legs. 
         [0024]      FIG. 5  schematically depicts lug  144  attached to mounting surface  142 , showing the interrelationship between the lug, the mounting surface and fasteners  153 ,  155 . As shown in  FIG. 5 , mounting surface  142  includes flange portions  157 ,  159 , with undersides  187 ,  188  of the flange portions defining channels  190 ,  191  that are sized to receive the legs of floating lug  144 . Additionally, each of the flange portions includes a corresponding aperture  192 ,  193 , with each of the apertures aligning with a corresponding mounting orifice ( 194 ,  195 ) formed through mounting surface  142 . 
         [0025]    Fasteners  153 ,  155  (which vary in diameter along their respective lengths) are used to secure lug  144  within channels  190 ,  191 . In this embodiment, the fasteners are rivets mounted from an underside  196  of the mounting surface. Fastener  153  includes a head  198 , a first diameter portion  199 , and a second diameter portion  200  extending between portion  199  and a tip  201 . Similarly, fastener  155  includes a head  202 , a first diameter portion  203 , and a second diameter portion  204  extending between portion  203  and a tip  205 . Notably, tip  205  of fastener  155  is crimped to provide retention of leg  164  within channel  191 . 
         [0026]    As shown in  FIG. 5 , fastener  153  extends through mounting orifice  194 , recess  145  of the lug and then through aperture  192  of flange portion  157 . In particular, a length of first diameter portion  199  is configured to maintain a desired clearance between mounting surface  142  and the underside  187  of flange portion  157 . Thus, even after crimping (as shown with respect to fastener  155 ), the desired spacing is established by the first diameter portion is preserved. As such, the lug is capable of sliding within the opposing channel  190 ,  191  as permitted by clearance between the surfaces of the legs forming the recesses  145 ,  147  and the first diameter portions of the fasteners  153 ,  157 . 
         [0027]    It should be emphasized that the above-described embodiments are merely possible examples of implementations set forth for a clear understanding of the principles of this disclosure. Many variations and modifications may be made to the above-described embodiments without departing substantially from the spirit and principles of the disclosure. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the accompanying claims.