Abstract:
The disclosure concerns a wire seal for sealing a gap between two components of a gas turbine, the wire seal including a first core and a second core spaced apart from one another, a wire pack extending around the first core and the second core, and a fastener for securing the wire pack to the first core and the second core, wherein the wire seal is curved. Various embodiments are disclosed, including various types of fastener. A method of manufacturing a wire seal is also disclosed.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to wire seals, and particularly to wire seals for sealing a gap between a picture frame and a first vane of a gas turbine. 
       BACKGROUND OF THE INVENTION 
       [0002]    In a gas turbine, there is a sealing interface between combustor outlet and the first vane of the turbine. Movement of the two parts relative to one another can be considerable, and a gap must be left between the parts to avoid contact. The gap is generally purged with cooling air. It has been appreciated that it would be advantageous to improve the design around this gap to, for example, reduce the cooling air requirements. 
       SUMMARY OF THE INVENTION 
       [0003]    The invention is defined in the appended independent claims to which reference should now be made. Advantageous features of the invention are set forth in the dependent claims. 
         [0004]    A first aspect of the invention provides a wire seal for sealing a gap between two components of a gas turbine, the wire seal comprising a first core and a second core spaced apart from one another, a wire pack extending around the first core and the second core, and a fastener for securing the wire pack to the first core and the second core, wherein the wire seal is curved. The plate can provide extra sealing in addition to the wire pack, for example if a gap opens in the wire pack during use. The wire pack can help protect the plate, thereby increasing the lifetime of the plate in a high temperature environment. The wire seal can cope with the large relative axial and radial movements of the picture frame and first vane (first turbine vane). 
         [0005]    In one embodiment, the wire seal comprises a plate with a first face, a second face, a first edge comprising the first core, a second edge comprising the second core and two end edges, wherein the first edge is opposite the second edge, wherein the wire pack extends around the first face, the first edge, the second face and the second edge of the plate, and wherein the fastener secures the wire pack around the plate. The plate can improve the seal. 
         [0006]    In one embodiment, the fastener comprises a first clamp for securing the wire pack to the first core and a second clamp for securing the wire pack to the second core. 
         [0007]    In one embodiment, the fastener comprises at least one end piece attached at each end first core and the second core, to hold the wire pack in place adjacent to the first core and the second core. In one embodiment, the fastener extends around the wire pack from the first core to the second core, to hold the wire pack in place adjacent to the plate. In one embodiment, the wire seal comprises a first core wire attached to the first edge and a second core wire attached to the second edge. In one embodiment, the wire seal is a conical wire seal. In one embodiment, the first core is a first core wire and the second core is a second core wire. 
         [0008]    A second aspect of the invention provides a gas turbine comprising a wire seal as described above. In one embodiment, the gas turbine comprises a combustor and a first vane separated by a gap, and wherein the wire seal is arranged to seal the gap. Leakage reduction through this gap can thereby be achieved. In one embodiment, the combustor comprises a picture frame and wherein the gap is between the first vane and the picture frame. In one embodiment, the gas turbine comprises a socket in the picture frame, and wherein the wire seal is seated in the socket. This can hold the wire seal in place. 
         [0009]    A third aspect of the invention provides a method of manufacturing a wire seal for sealing a gap between two components of a gas turbine, the wire seal comprising a first core and a second core spaced apart from one another, a wire pack extending around the first core and the second core, and a fastener for securing the wire pack to the first core and the second core, wherein the wire seal is curved, comprising the steps of placing the wire pack around the plate and fastening the wire pack to the plate with the fastener. In one embodiment, the wire pack is made of wire and is placed around the first core and the second core by winding the wire repeatedly around the first core and the second core. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    An embodiment of the invention will now be described by way of example only and with reference to the accompanying drawings in which: 
           [0011]      FIG. 1  shows a perspective view of a wire seal; 
           [0012]      FIG. 2  shows a schematic top view of the wire seal of  FIG. 1 ; 
           [0013]      FIGS. 3, 4 and 5  show cross-sections of part of a gas turbine comprising a wire seal, during different phases in gas turbine operation; 
           [0014]      FIG. 6  shows a perspective view of another wire seal; and 
           [0015]      FIG. 7  shows a perspective view of a further wire seal. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0016]      FIG. 1  shows a wire seal  10  comprising a first core wire  12 , a second core wire  14 , a plate  16 , a first clamp  18 , a second clamp  20  and a wire pack  22 . 
         [0017]    The first core wire  12  is attached to one edge (a first edge) of the plate  16  and the second core wire  14  is attached to the opposite edge (a second edge) of the plate  16 . The wire pack  22  extends around the first and second core wires  12 ,  14  and the plate  16 . The wire pack is held in place by a fastener, in this case the first and second clamps  18 ,  20 . The first clamp extends around the portion of the wire pack closest to the first core wire, with the second clamp arranged in the same way close to the second core wire. As the plate is thinner than the diameter of the first and second core wires, the effective width (the width including the plate/core wires) of the cross-section of the wire pack  22  perpendicular to the plate  16  is greater at the core wires  12 ,  14  than in the main portion of the wire pack  22  at the plate  16 . 
         [0018]      FIG. 2  shows a top view of the wire seal  10  in  FIG. 1 . In contrast to  FIG. 1 , where only a short portion of seal is shown and curvature is not shown,  FIG. 2  shows the curvature of the wire seal  10 . 
         [0019]      FIG. 3  shows a cross-section of the wire seal  10  in a gas turbine. The gas turbine comprises a first vane  30 , a picture frame  32  and a bulkhead  34 . The bulkhead  34  may be an integral part of the picture frame  32  or a separate component attached to the picture frame  32 , as is shown in  FIG. 3 . The wire seal  10  extends across a gap  36  between the first vane  30  and the picture frame  32 /bulkhead  34 . The first clamp  18  of the wire seal  10  contacts the first vane  30 , and the second clamp  20  of the wire seal  10  fits within a socket  38  in the bulkhead  34  (or in the picture frame  32 ). 
         [0020]    In a gas turbine, a plurality of picture frames (sequential liner outlets) are arranged around the longitudinal axis of the gas turbine in a ring, with the picture frames typically being attached to sequential liners (combustor linings) and the sequential liners typically surrounding can combustors. The picture frames generally all intersect a plane perpendicular to the gas turbine longitudinal axis. The wire seal discussed in this application can be applied on either the inner or outer diameters of the picture frames (the edge of the picture frames closest to the gas turbine longitudinal axis). This can allow for single vane/blade assembly and/or disassembly during manufacture, maintenance and repair. 
         [0021]    In  FIG. 3 , the gas turbine is shown during a heating phase. In  FIG. 4 , the gas turbine is shown in a running phase during normal operation, and in  FIG. 5 , the gas turbine is shown in a forced cool down phase. During the different phases, the first vane  30  moves relative to the picture frame  32 , varying the shape and width of the gap  36 . The movement of the first vane  30  relative to the picture frame  32  includes both axial and radial movement relative to the gas turbine longitudinal axis (also the wire seal longitudinal axis, in wire seal longitudinal direction  40 ). It is this movement that the wire seal  10  can be designed to withstand, maintaining a seal across the gap  36 . 
         [0022]      FIG. 6  shows an alternative wire seal  10 . As with the wire seal of  FIG. 1 , this wire seal comprises a plate  16  and a wire pack  22 , but does not comprise first and second core wires. Optionally, core wires could be added to this embodiment. The embodiment of  FIG. 6  comprises a fastener that differs from the fastener shown in  FIG. 1 . In the embodiment of  FIG. 6 , four end pieces  60  are provided as a fastener. These end pieces are attached to the four corners of the plate  16  and, as with the clamps shown in  FIG. 1 , the end pieces  60  are arranged to hold the wire pack  22  on the plate  16 . The plate  16  extends beyond the wire pack  22  at the sides to provide a surface for attachment of the clamps, although this is not essential. Similarly, slots are provided in the end pieces in which the plate is placed, and these slots are also optional. Providing a larger contact surface for the end pieces  60  on the plate  16  can allow for a better join between the end pieces  60  and the plate  16 . 
         [0023]      FIG. 7  shows another alternative wire seal  10 . As in  FIG. 6 , four end pieces  60  are provided. In addition to the end pieces  60 , a further fastener in the form of a central clamp is provided across the wire seal  10 , extending across the wire seal  10  from one end edge of the plate to the other end edge, with the central clamp extending in the same direction as the first edge and the second edge. The central clamp comprises two central clamp end pieces  72  and at least one connecting bar  74 . 
         [0024]    In a method of manufacturing a wire seal  10  as shown in  FIG. 1 , the first and second core wires  12 ,  14  are first attached to the plate  16 . The wire pack  22  is then placed around the first and second core wires  12 ,  14  and the plate  16 , for example by wrapping a wire repeatedly around the first and second core wires  12 ,  14  and the plate  16  to create the wire pack  16 . Before the wire is wrapped around, one end of it may be attached, for example by welding, to one of the first and second core wires  12 ,  14  and/or the plate  16 . After the wire pack  22  is in place, the first and second clamps  18 ,  20  are attached. 
         [0025]    The wire that makes up the wire pack  22  is described above as being attached to another part of the wire seal before being wrapped around the plate, but one or both ends of the wire may be attached either before or after the wire is wrapped around the plate. 
         [0026]    To manufacture the wire seal  10  as shown in  FIG. 6 , the plate  16  is first attached to the end pieces  60  and the wire pack  22  is then placed around the plate  16 , for example by wrapping a wire repeatedly around the plate  16 . The end pieces  60  may alternatively be attached after the wire pack  22  is placed around the plate  16 . 
         [0027]    To manufacture the wire seal  10  as shown in  FIG. 7 , the same method of manufacture for the embodiment in  FIG. 6  can again be used, with the addition of adding a central clamp. The central clamp can be added in two ways. Firstly, the central clamp can be made in pieces and joined together once it is in place around the wire pack  22 , in which case the central clamp can be attached at any time after the wire pack  22  is in place. Secondly, the central clamp can be made as a single piece (or made in pieces and then assembled before attachment to the wire pack) and then slid onto the wire pack from the first edge (or from the second edge, in the case of a straight wire seal). In this case, the central clamp must be attached after the wire pack  22  is in place and before the end pieces have been attached, in embodiments such as that of  FIG. 7  where the end pieces have a diameter larger than the effective width of the wire pack at the point on the wire pack where the central clamp is attached (as explained in more detail below). 
         [0028]    The wire seal  10  is described above as sealing the gap between a picture frame and a first vane of a gas turbine, but more generally the wire seal may also seal the gap between two components, for example between the first vane and another part of the combustor such as the combustor lining. The components to be sealed would normally both be static (static-to-static sealing). 
         [0029]    The wire seal  10  may be straight as shown in the small portions shown in  FIGS. 1, 6 and 7 , or may be curved in a circumferential direction (relative to the wire seal longitudinal axis), as shown in  FIG. 2 . A curved wire seal is preferable for the wire seals used in a gas turbine as described in  FIGS. 3 to 5 . The wire seal may also be a full ring. Generally though, multiple wire seals will be used in a ring. In one example, 20 wire seals are placed around a 360° annular joint, each extending 15° around the gas turbine circumference in the circumferential direction  42 . Each picture frame around the gas turbine circumference preferably has at least one wire seal on the inner diameter (inner platform), as this can help enable single vane/blade assembly/disassembly. 
         [0030]    The wire seal can be annular. In the case of an annular wire seal, the wire seal describes (a section of) a ring in which the first edge and the second edge are at the same distance from the gas turbine longitudinal axis (wire seal longitudinal axis); that is, the radius of curvature of the first edge and the second edge are the same. A radial wire seal could also be used, in which the second edge is further from the gas turbine longitudinal axis than the first edge and in the same plane perpendicular to the gas turbine longitudinal axis direction. 
         [0031]    Preferably though, the wire seal is a conical wire seal. The conical wire seal has a second edge that is further from the gas turbine longitudinal axis than the first edge and in a different plane perpendicular to the gas turbine longitudinal axis direction. 
         [0032]    For completeness, it is noted that a cone is a three-dimensional geometric shape that tapers smoothly from a flat base; the base may be circular or may be another shape. Mathematically, a conical wire seal is conical frustum, being in the shape of the surface of the frustum of a cone (i.e. a section of the cone not including the apex, also known as a truncated cone), in contrast to an annular wire seal in which the wire seal follows the shape of the surface of a cylinder. 
         [0033]    The first and second core wires  12 ,  14  are optional, and one or both may be omitted, such as in the embodiments in  FIGS. 6 and 7 . For example, one of both of the core wires of the embodiment of  FIG. 1  may be omitted, and one or two core wires may be added to the embodiments of  FIG. 6  and  FIG. 7 . Alternatively, one or two core wires may be included as an integral part of plate  16 , or may simply be the first edge  25  and second edge  26  of the plate  16  respectively. The two core wires preferably have the same diameter, but may also have different diameters. 
         [0034]    Although most of the plate  16  is not directly visible in the Figures, the plate  16  can be described in more detail as follows, with reference to  FIGS. 1 and 2 . The plate  16  has a first face  23 , a second face  24  and four edges  25 ,  26 ,  27 . Of these four edges, the wire pack  22  extends around a first edge  25  and a second edge  26 , the first edge  25  and the second edge  26  being opposite one another. In  FIG. 1 , the first edge  25  and the second edge  26  are adjacent to the first core wire  12  and the second core wire  14  respectively. Two end edges  27  complete the plate  16 , and it is one of these end edges  27  that is visible in  FIGS. 1, 6 and 7 . Typically, the first edge and the second edge are longer than the two end edges. Typically, the two end edges are the same length. Typically, in the case of a wire seal extending in a circumferential direction (relative to the wire seal longitudinal axis), the second edge is (slightly) longer than the first edge and the radius of curvature of the second edge is (slightly) larger than the radius of curvature of the first edge. The plate  16  may be a solid sheet or may be a mesh. In embodiments with a plate, the first core and the second core are part of the plate, at the first and second edges respectively. First and second core wires may additionally be attached to the first and second cores respectively in such cases. The plate is optional and may be omitted in some embodiments. When no plate is present, the first and second cores correspond to the first and second core wires. 
         [0035]    In embodiments comprising core wires, the plate is preferably thinner than the diameter of the first and second core wires, but in some embodiments the plate may be the same width as or wider than the diameter of the first and second core wires. The plate and the first and second core wires are described as separate components in the examples described above, but they may be one integrated component. The core wires may also be omitted entirely, as in the embodiments of  FIGS. 6 and 7 . 
         [0036]    The attachment between the first and second core wires and the plate  16  can be a physical attachment such as a weld. Alternatively or additionally, a slot can be provided in the first and second core wires, and the plate is arranged in the slot. If a slot is provided, a physical attachment between the first and second core wires and the plate is optional, as the wire pack can hold the first and second core wires and the plate together. 
         [0037]    The wire pack  22  may be made up of one or more wires repeatedly wound around the plate (and the first and second core wires in embodiments with core wires). Alternative wire packs are also possible; for example, a mesh or a chain could be wound around instead of a wire. The wire pack wire, mesh, chain or the like is typically attached at each end to stop it from unravelling, and can be attached to any appropriate part of the wire seal, for example a fastener, the plate or another part of the wire pack. 
         [0038]    The wire pack is held on to the plate by a fastener or fasteners. Without appropriate fastening, the wire pack can unravel and/or slide off the end edges of the plate, and the clamps are designed to restrict the movement of the wire pack relative to the plate. The wire pack can also be fastened directly to the plate and/or to the clamps. 
         [0039]    Various fasteners are described in this application, but other types of fastener and modifications to the described fasteners are possible. Any combination of the described fasteners is also possible in addition to those combinations already described. For example, the fasteners of the wire seals of  FIGS. 1 and 6  could both be used on the same wire seal, to improve the clamping of the wire pack. 
         [0040]    The first and second clamps  18 ,  20  can vary in shape but are each typically designed to encircle an end edge of the plate. The first and second clamps may be made as a spring so that the first and second clamps are in tension and are pushing on the wire pack to keep the wire pack against the plate. This can also help ensure that the first and second clamps do not slip off the wire pack, and may be particularly useful in cases without core wires. The first and second clamps could be attached to one another by one or more connecting bars extending across the surface of the wire pack (in the direction perpendicular to the first and second edges of the plate), in a similar manner to the connecting bar  74  between the central clamp end pieces  72  in the embodiment of  FIG. 7 . The first and second clamps can also be attached to the wire pack or the plates. The first and second clamps are shown in  FIG. 1  with a rounded cross-section in a plane perpendicular to the first and second edges of the plate, but the clamp could also have a square or rectangular cross-section, similar to the shape of the central clamp end piece  72 . 
         [0041]    The end pieces  60  in the wire seal of  FIG. 6  are cylindrical with circular faces, but clamps of a different shape could be provided, such as square- or hexagonal-faced clamps. Two or more of the clamps could also be connected together; for example, the two end pieces at either end of one end edge of the plate could be connected or could be a single plate extending along part or all of the extent of the end edge. 
         [0042]    In embodiments with first and second core wires, the end pieces can be attached to the first and second core wires and/or the plate. The first and second core wires may extend beyond the end edges of the plate, in which case holes would be provided in the end pieces to connect with the first and second core wires. This could provide a better join between the first and second core wires and the end pieces. The end pieces may additionally be attached to the wire pack. 
         [0043]    The diameter of the end pieces in the wire seals of  FIGS. 6 and 7  is larger than the width of the wire pack (in the direction perpendicular to the plane of the plate). Alternatively, the diameter of the end pieces may be the same as the width of the wire pack. In some embodiments the diameter of the end pieces may even be slightly smaller than the width of the wire pack, as long as the diameter of the end pieces is sufficient to hold the wire pack on to the plate. The diameter of the different end pieces may vary; for example, the two end pieces adjacent to the first edge of the plate could be smaller in diameter than the two end pieces adjacent to the second edge of the plate. 
         [0044]    The first vane of the gas turbine may comprise one or more slots to accommodate the shape of fasteners such as end pieces  60 . This can improve the seal and can also ensure that the wire seal remains in the correct place in the gap. In some of the embodiments the fastener contacts the first vane and/or the bulkhead/picture frame, and in other embodiments the wire pack contacts the first vane and/or the bulkhead/picture frame. 
         [0045]    The central clamp  70  may be one integral part, or may be two or more parts. In the embodiment of  FIG. 7 , the central clamp  70  is three connected parts, namely two central clamp end pieces  72  and one connecting bar  74 . Various other central clamp arrangements are possible. For example, the connecting bar is narrower than the central clamp end pieces (in the direction across the seal perpendicular to the first and second edges of the plate) in the embodiment of  FIG. 7 , but could be the same width or wider than the central clamp end pieces. The T-clamp could have more than two central clamp end pieces and/or more than one connecting bar. Subsequent connecting bars could be on the same face of the wire seal as the first connecting bar and/or on the opposite face (i.e. on the face that is not shown in  FIG. 7 ). The T-clamp could be used without any other form of fastener, or in combination with another fastener. The point of the T-clamp is generally to hold the wire pack on the plate, both so that the wire pack does not slide off the end edges and also so that the wires making up the wire pack are kept close to the faces of the plate  16 . This stops the wire pack from expanding or bending away from the plate. 
         [0046]    The picture frame  32 , bulkhead  34  and first vane  30  may all vary in shape compared to the embodiments shown above, and the design can depend on variables such as the shape of the wire seal and the relative motion of the picture frame/bulkhead and the first vane. 
         [0047]    The socket  38  in the picture frame/bulkhead is optional, and in some embodiments is not necessary. For example, a socket could alternatively be provided in the first vane to hold the wire seal in place. Sockets could also be provided on both the first vane and the picture frame/bulkhead. Other connecting components could also be provided to pivotally attach the wire seal to the first vane or the picture frame/bulkhead. 
         [0048]    Typically, the gap is also purged with a cooling fluid such as cooling air, and there can therefore be a higher pressure on the side of the wire seal further from the hot gas path than on the side of the seal closer to the hot gas path. This pressure differential could hold the seal in place, and can also improve the quality of the seal. 
         [0049]    The wire seals described herein are preferably for sealing gaps between two stationary parts, rather than gaps between a rotor and a stator. 
         [0050]    Various modifications to the embodiments described are possible and will occur to those skilled in the art without departing from the invention which is defined by the following claims. 
       REFERENCE SIGNS 
       [0051]      10  wire seal 
         [0052]      12  first core wire 
         [0053]      14  second cord wire 
         [0054]      16  plate 
         [0055]      18  first clamp 
         [0056]      20  second clamp 
         [0057]      22  wire pack 
         [0058]      23  first face 
         [0059]      24  second face 
         [0060]      25  first edge 
         [0061]      26  second edge 
         [0062]      27  end edge 
         [0063]      30  first vane 
         [0064]      32  picture frame 
         [0065]      34  bulkhead 
         [0066]      36  gap 
         [0067]      38  socket 
         [0068]      40  wire seal longitudinal direction (gas turbine longitudinal direction) 
         [0069]      42  circumferential direction 
         [0070]      60  end piece 
         [0071]      70  central clamp 
         [0072]      72  central clamp end piece 
         [0073]      74  connecting bar