Abstract:
Systems involving feather seals are provided. A representative vane assembly for a gas turbine engine includes: a first mounting platform having a first slot; a first airfoil extending from the first mounting platform; and a feather seal having opposing faces, a first side extending between the faces, and a first tab, the first tab extending outwardly beyond the first side; the first slot being sized and shaped to receive the feather seal including the first tab.

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPEMENT 
     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-303 awarded by the United States Air Force. 
    
    
     BACKGROUND 
     1. Technical Field 
     The disclosure generally relates to seals used in gas turbine engines. 
     2. Description of the Related Art 
     Various gas turbine engine components are subjected to heating and cooling cycles that cause the components to expand and contract. Expansion and contraction causes challenges in forming seals between components to prevent gas leakage. 
     Turbine vane assemblies are examples of components that typically experience expansion and contraction during use. In order to prevent gas leakage between adjacent vanes of a vane assembly, feather seals have been used. A feather seal, which is typically configured as a strip of metal, is positioned between opposing slots of adjacent vanes. Notably, when the vanes are cold, the feather seal typically floats loosely within the opposing slots. However, after the vanes expand due to heating, the feather seal tends to fit more tightly within the opposing slots. 
     Designing a feather seal can be quite challenging. In particular, the width of a feather seal may be established so that the seal will not fall out of the slots when the vanes cool and contract. However, the width should be narrow enough so that the vanes do not crush the feather seal when the vanes heat and expand. 
     SUMMARY 
     Systems involving feather seals are provided. In this regard, an exemplary embodiment of a vane assembly for a gas turbine engine comprises: a first mounting platform having a first slot; a first airfoil extending from the first mounting platform; and a feather seal having opposing faces, a first side extending between the faces, and a first tab, the first tab extending outwardly beyond the first side; the first slot being sized and shaped to receive the feather seal including the first tab. 
     An exemplary embodiment of a feather seal for a gas turbine engine comprises: opposing faces; a first side extending between the faces; and a first tab extending outwardly beyond the first side, the first tab being located in a plane defined by the opposing faces. 
     An exemplary embodiment of a gas turbine engine comprises: a compressor; a combustion section; and a turbine operative to drive the compressor responsive to energy imparted thereto by the combustion section, the turbine having a vane assembly, the vane assembly having a first vane comprising: a first mounting platform having a first slot; a first airfoil extending from the first mounting platform; and a feather seal having opposing faces, a first side and a first tab, the first side extending between the faces, the first tab extending outwardly beyond the first side; the first slot being sized and shaped to receive the feather seal including the first tab. 
     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 
       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. 
         FIG. 1  is a schematic diagram of an embodiment of a system involving a feather seal. 
         FIG. 2  is a schematic, cut-away of the embodiment of  FIG. 1 , showing the vane and an adjacent vane engaging the feather seal when the engine is cold or being assembled. 
         FIG. 3  is a schematic, cut-away of the embodiment of  FIG. 1 , showing the vane and an adjacent vane engaging the feather seal when the engine is hot. 
         FIG. 4  is a schematic, cut-away of another embodiment of a system involving a feather seal. 
         FIG. 5  is a schematic, cut-away of another embodiment of a system involving a feather seal. 
     
    
    
     DETAILED DESCRIPTION 
     Several exemplary embodiments of systems involving feather seals will now be described in greater detail. In this regard, at least some of these embodiments involve a feather seal that incorporates at least a first tab that effectively widens the feather seal at the location of the tab. The tab is configured to be received by a corresponding feature of a vane. By way of example, the feature can be a cavity or through-hole into which the tab is inserted. So configured, the feather seal can be designed narrow enough to limit component weight, while the tab effectively widens the feather seal. That is, the tab locally widens the feather seal so that the feather seal does not tend to fall out of place when the vane contracts during cooling. Thus, one or more tabs of a feather seal can be sized for preventing fall-out and remaining portions of the feather seal can be sized to accommodate crushing considerations. 
     In this regard, an embodiment of a system involving feather seals is depicted schematically in  FIG. 1 . In this embodiment, system  100  incorporates a vane  102  and a feather seal  104 . Specifically, vane  102  incorporates an outer mounting platform  106 , an inner mounting platform  108 , and an airfoil  110  extending between the outer mounting platform and the inner mounting platform. Notably, the outer mounting platform includes rails  112  and  114 , which define slots  116  and  118 , respectively. The slots are sized and shaped to receive a portion of the feather seal. 
     Feather seal  104  is generally elongate, exhibiting a longitudinal axis, and is planar. In this embodiment, the feather seal is formed of a strip of material, e.g. a Cobalt alloy, such as Haynes-188. The feather seal has opposing faces  120 ,  122 , sidewalls  124 ,  126  extending between the faces, and endwalls  128 ,  130  extending between the faces and between the sidewalls. In cross-section, the feather seal of this embodiment is generally rectangular. 
     Tabs  131 ,  132 ,  133  and  134  extend outwardly beyond the sidewalls of the feather seal. In particular, tabs  131  and  133  extend beyond sidewall  124 , and tabs  132  and  134  extend beyond sidewall  126 . In this embodiment, the tabs are generally rectangular and are positioned in opposing pairs along a length of the feather seal. In other embodiments, various other numbers, shapes and/or arrangements of tabs can be used. For instance, in some embodiments, one or more portions of the tabs could be tapered, such as by incorporating a chamfer. 
       FIG. 2  schematically depicts the embodiment of  FIG. 1  positioned next to an adjacent vane  202 , with the feather seal  104  installed to seal a gap formed between vane  102  and vane  202 . Specifically, when in the installed position shown in  FIG. 2 , a gap  204  is formed between the vanes when the vanes are cold. 
     In the installed position, the feather seal is held within slot  116  of vane  102  and slot  206  of vane  202 . Specifically, slot  116  is defined by a backwall  210 , and walls  212  and  214  that are spaced from each other and that extend from backwall  210 . Similarly, slot  206  is defined by a backwall  220 , and walls  222  and  224  that are spaced from each other and that extend from  220  backwall. 
     Each of the slots communicates with a corresponding through-hole that is configured to receive a tab. In this case, slot  116  communicates with through-hole  231  and slot  206  communicates with through-hole  232 . In this embodiment, the through-holes are formed by the material of the walls that define the rails. Additionally, each incorporates a recess. 
     In the configuration depicted in  FIG. 2 , the feather seal is not wide enough at non-tabbed locations to extend from the backwall of one rail to the backwall of the other. However, the tabs tend to prevent the feather seal from falling out of the slots by spanning the gap  204  between the adjacent vanes. 
       FIG. 3  depicts the embodiment of  FIG. 2  after heating; thus, the vanes have expanded. Note that, in this configuration, the gap  204  between the adjacent vanes has significantly reduced in size such that the non-tabbed locations of the feather seal are in close proximity to the backwalls of the rails. Note also that the through-holes have accommodated repositioning of the tabs by enabling more material of the tabs to be inserted through the through-holes. Thus, despite the gap between the vanes being narrowed due to heating, the feather seal is not crushed. 
     Another embodiment of a vane is depicted schematically in  FIG. 4 . As shown in  FIG. 4 , vane  400  includes an outer mounting platform  402 , a portion of which is depicted. In particular, outer mounting platform  402  includes a rail  404  and a feature for receiving a tab of a feather seal. In this embodiment, the feature is a cavity  406  that incorporates an entrance  408 . 
     In this configuration, a tab of a feather seal (not shown) can be inserted into the cavity via the entrance. In such an embodiment, any gas leakage that may occur in a vicinity of the tab can be contained by the sealed cavity. Note that in this embodiment, construction of the sealed cavity is facilitated by casting a lower portion  410  of material that defines the cavity integrally with the outer mounting platform; however, other techniques can be used in other embodiments. This casting results in an opening  412  for facilitating release and holding of the component during manufacture. Sealing of the cavity is accomplished by attaching a wall  414 , in this case a plate, to the cast portion. In some embodiments, such as here, this can accomplished by welding the plate to the outer mounting platform. 
     Another embodiment of a vane is depicted schematically in  FIG. 5 . This embodiment differs from that depicted in  FIG. 4  by incorporating a casting feature that can be sealed without the use of a wall. In particular, vane  500  includes an outer mounting platform  502 , a portion of which is depicted. In particular, outer mounting platform  502  includes a rail  504  and a cavity  506  that incorporates an entrance  508 . 
     In this embodiment, the sealed cavity is constructed by casting a lower portion  510  of the cavity integrally with the outer mounting platform. This casting results in an opening  512  for facilitating release of the component during manufacture. In contrast to the embodiment of  FIG. 4 , opening  512  can be sealed by welding the opening closed without using a wall. In other embodiments, such an opening may not be incorporated into the final component as other manufacturing methods could be used. 
       FIG. 5  also depicts recess  520  that extends from the cavity and into a wall  522  that partially defines slot  524 . In this embodiment, recess  520  is generally rectangular and extends along the floor of the cavity  506 . In some embodiments, a recess may be avoided. However, such a recess can be used to ensure that a ridge or other raised surface is not present along the intersection of the cavity and the slot as may be caused by different manufacturing techniques for forming the cavity and slot. 
     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.