Abstract:
A seal plate assembly for a turbine rotor includes at least one inner shiplap seal plate disposed on the rotor; and at least one outer seal plate adapted to engage the at least one inner shiplap plate. The thickness of the at least one outer seal plate is different than the thickness of the at least one inner shiplap plate causing either the at least one inner shiplap plate or the at least one outer seal plate to come into contact first under centrifugal load.

Description:
TECHNICAL FIELD 
       [0001]    The subject matter disclosed herein relates to gas turbine rotors and, more particularly, is concerned with a seal assembly for sealing coolant passageways in turbine rotor blades disposed in the periphery of a turbine rotor disc. 
       BACKGROUND 
       [0002]    A typical gas turbine has a rotor (wheel) with a number of blades (buckets) distributed around the circumference of the rotor. The blades may be secured to the rotor using a conventional dovetail configuration. The blades are driven by hot gas from the combustion chamber and are cooled using a coolant that flows through passages in the blades. It is important to avoid the hot gases from coming into contact with the rotor. 
         [0003]    A variety of seal configurations have been developed to prevent the hot gases from coming into contact with the rotor. In some cases a full hoop coverplate may be positioned about the rim of rotor to seal off the hot gases. The seal assembly may also seal a cavity between the blades and the rotor disc that allows air to flow to the blades for cooling purposes. In some applications a wire seal may be disposed in a groove in the rotor to provide a more effective seal. Another approach is to provide a seal plate comprising of a number of seal plate segments each having seal wings that isolate the rim cavity from the hot gas path. The seal plate segments may be connected to the rotor using hooks and locking pins that capture the seal plates and prevent them from slipping out of the bladed rotor assembly when the turbine is not spinning, respectively. Wire seals can be used around the seal plates. The segmented seal plates usually rely on tight tolerances to control leakage area. 
         [0004]    Full hoop coverplates provide effective seals, but can rarely be used in heavy duty gas turbines due to field maintenance requirements and the difficulty of unstacking the unit rotor in the field. Segmented seals facilitate field maintenance. Segmented seals have the problem that in some cases the seal performance is not satisfactory. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0005]    In accordance with one exemplary non-limiting embodiment, the invention relates to a seal plate assembly for a turbine rotor including at least one inner shiplap seal plate disposed on the rotor, and at least one outer seal plate adapted to engage the at least one inner shiplap plate. The seal plates and shiplaps are dimensioned such that when the shiplaps are in contact there is either a gap between the outer seal plate and the rotor or a gap between the at least one inner shiplap plate and rotor or bucket hook. 
         [0006]    In another embodiment, a sealing system for a turbine rotor is provided and includes a plurality of inner shiplap seal plates disposed on the rotor. Each inner shiplap seal plate is provided with a first rabbet edge and a second rabbet edge. The system also includes a plurality of outer seal plates where each outer seal plate is adapted to engage the rabbet edge of one of the plurality of inner shiplap seal plates and the rabbet edge of an adjacent one of the plurality of inner shiplap seal plates. The seal plates and shiplaps are dimensioned such that when the shiplaps are in contact there is either a gap between the outer seal plate and the rotor or a gap between the at least one inner shiplap plate and rotor or bucket hook. 
         [0007]    Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a cross sectional view of an embodiment of a rotor assembly incorporating a seal assembly. 
           [0009]      FIG. 2  is a cross sectional view of an embodiment of a seal assembly. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0010]    Illustrated in  FIG. 1  is an embodiment of a rotor assembly  9  that may be used in a turbine system. The rotor assembly  9  rotates about an axis  10 , and may include at least one turbine blade  11  having a blade flange  12 . The blade flange  12  protrudes from the turbine blade  11  and angles towards the axis of rotation of the rotor assembly  9 . The turbine blade  11  is secured to a rotor  13  by conventional means, such as for example a dovetail structure. The rotor  13  may be provided with a rotor flange  14  that protrudes from the rotor  13  and angles away from the axis of rotation of the rotor assembly  9 . The blade flange  12  and the rotor flange  14  define an opening  15  and a chamber  16 . 
         [0011]    Disposed in the chamber  16  is a seal assembly  18  that may include an inner shiplap seal plate  19 . The at least one inner shiplap plate  19  may include a rim  21  and an indented portion  23 . The indented portion  23  provides clearance between the at least one inner shiplap plate  19  and the rotor flange  14  when the at least one inner shiplap plate  19  is inserted into the chamber  16 . The seal assembly  18  has a radial dimension that is greater than the radial dimension of the opening  15  and smaller than the radial dimension of the chamber  16 . The seal assembly  18  may also include an outer diameter wire seal  27 , and an inner diameter wire seal  29 . The outer diameter wire seal  27  and the inner diameter wire seal  29  may be of any of a variety of cross-section such as for example circular, hexagonal, octagonal, and the like. Additionally, the outer diameter wire seal  27  and the inner diameter wire seal  29  may be a single filament or multiple filaments braided into a rope. The outer diameter wire seal  27  and the inner diameter wire seal  29  may be made of any of a number of known materials as necessary to survive in this operating environment such as high temperature steels, nickel alloys, ceramic, or a combination of any of the materials. The inner diameter seal  29  forms a seal with rim  21  when a centrifugal load is imparted on the inner diameter seal  29 . When the rotor assembly  9  is not turning, the at least one inner shiplap plate  19  may be secured to the rotor by conventional means such as, for example pin  31 . 
         [0012]      FIG. 2  illustrates a cross sectional view along axis  2 - 2  of the embodiment of  FIG. 1 . The seal assembly  18  may include at least one inner shiplap seal plate  19  having a shiplap or rabbet edge  33 . An outer seal plate  35  having at a central portion  37  and at least one projection (shiplap)  39  is disposed in contact with the shiplap  33 . The dimensions of the at least one inner shiplap plate  19  and the outer seal plate  35  are such that the shiplaps are in contact and there is a slight gap  41  between the outer seal plate  35  and the rotor flange  14  or the at least one inner shiplap plate  19  and the rotor flange  14 . The shiplap or projections  39 , if included in the design, engage the shiplap  33  and are dimensioned to minimize an air gap  43 , while maintaining appropriate clearances between seal plates for installation and thermal growth of the turbine during operation. 
         [0013]    The outer seal plate  35  may be disposed between a pair of inner shiplap seal plates  19 . Outer diameter wire seal  27  and inner diameter wire seal  29  comprise the top and bottom portion of two sides of the seal that prevents leakage of bucket cooling flow. The shiplaps  33  come into contact first under centrifugal load or due to the wedging of the seal wire between the wheel and seal plate. This system provides a nearly complete sealing circumference around the at least one inner shiplap plate  19  and the outer seal plate  35 . The shiplaps  33  are designed to contact first before the outer seal plate  35  itself contacts the turbine wheel, or in an alternate embodiment, the shiplaps  33  are designed to contact first before the at least one inner shiplap plates  19  contact the rotor flange  14 . The system can rely on the wedging force of the inner diameter wire seal  29  and the outer diameter wire seal  27  to force contact between the shiplaps  33  or centrifugal force by properly locating the center of gravity of the seal plates segments  19  and the male seal plates  35 . 
         [0014]    As one of ordinary skill in the art will appreciate, the many varying features and configurations described above in relation to the several exemplary embodiments may be further selectively applied to form the other possible embodiments of the present invention. For the sake of brevity and taking into account the abilities of one of ordinary skill in the art, all of the possible iterations is not provided or discussed in detail, though all combinations and possible embodiments embraced by the several claims below or otherwise are intended to be part of the instant application. In addition, from the above description of several exemplary embodiments of the invention, those skilled in the art will perceive improvements, changes and modifications. Such improvements, changes and modifications within the skill of the art are also intended to be covered by the appended claims. Further, it should be apparent that the foregoing relates only to the described embodiments of the present application and that numerous changes and modifications may be made herein without departing from the spirit and scope of the application as defined by the following claims and the equivalents thereof.