Abstract:
A seal strip assembly for use in a turbomachine having a plurality of stages including rotationally driven disks, and arms on opposed portions of adjoining disks to define paired arms with a space therebetween. The seal strip assembly includes a seal strip positioned in the space between the paired arms and having opposing edges for locating in slots formed in opposed faces of the paired arms. An anti-rotation block is provided, where a portion of the anti-rotation block is removably located in opposed openings formed in the paired arms and is engaged with the seal strip to resist movement of the seal strip relative to the paired arms. A detachable engagement member is detachably fastened to the anti-rotation block for maintaining the anti-rotation block in engagement with the seal strip.

Description:
FIELD OF THE INVENTION 
     This invention relates in general to seals for multistage turbomachines and, more particularly, to an anti-rotation structure for a seal provided between adjoining disks in a multistage turbomachine. 
     BACKGROUND OF THE INVENTION 
     In various multistage turbomachines used for energy conversion, such as turbines, a fluid is used to produce rotational motion. In a gas turbine, for example, a gas is compressed through successive stages in a compressor and mixed with fuel in a combustor. The combination of gas and fuel is then ignited for generating combustion gases that are directed to turbine stages to produce the rotational motion. The turbine stages and compressor stages typically have stationary or non-rotary components, e.g., vane structures, that cooperate with rotatable components, e.g., rotor blades, for compressing and expanding the operational gases. 
     The rotor blades are typically mounted to disks that are supported for rotation on a rotor shaft. Annular arms extend from opposed portions of adjoining disks to define paired annular arms. A cooling air cavity is formed on an inner side of the paired annular arms between the disks of mutually adjacent stages, and a labyrinth seal may be provided on the inner circumferential surface of the stationary vane structures for cooperating with the annular arms to effect a gas seal between a path for the hot combustion gases and the cooling air cavity. The paired annular arms extending from opposed portions of adjoining disks define opposing end faces located in spaced relation to each other. Typically the opposing end faces may be provided with a slot for receiving a seal strip, known as a “belly band seal”, which bridges the gap between the end faces to prevent cooling air flowing through the cooling air cavity from leaking into the path for the hot combustion gases. The seal strip may be formed of multiple segments, in the circumferential direction, that are interconnected at lapped or stepped ends, as is described in U.S. Pat. No. 6,315,301, which patent is incorporated herein by reference. 
     When the seal strip comprises plural segments positioned adjacent to each other, in the circumferential direction, the seal strips may shift circumferentially relative to each other. Shifting may cause one end of a seal strip segment to increase the overlap with an adjacent segment, while the opposite end of the seal strip segment will move out of engagement with an adjacent segment, opening a gap for passage of gases through the seal strip. In order to prevent rotation of the seal strip segments, the segments may be provided with pins or anti-rotation blocks to cooperate with an adjacent disk surface for holding the segments stationary relative to the disk. 
     For example, one known anti-rotation device comprises an anti-rotation block  2  that includes extensions  4 ,  5  positioned in engagement with notches formed in the seal strip  6  and located within an opening  7  in the end face of an annular arm  8  of the disk. The extensions  4 ,  5  are welded to the seal strip  6  to maintain the anti-rotation block  2  in position on the seal strip  6 , see  FIG. 5 . Such an anti-rotation structure may experience cracking and failures at the weld locations. In particular, failure of the weld attaching the anti-rotation block to the seal strip may result in pieces of the seal strip becoming liberated and causing damage within the turbine. Further, applying this configuration of anti-rotation structure as a field repair requires a difficult field weld to be performed, making the quality of the repair difficult to control. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect of the invention, a seal strip assembly is provided for use in a turbomachine having a plurality of stages comprising rotationally driven disks, and arms on opposed portions of adjoining disks to define paired arms with a space therebetween, the paired arms comprising end faces including slots. The seal strip assembly comprises a seal strip for positioning in the space between the paired arms and having opposing edges for locating in respective slots of the paired arms. An anti-rotation block is also provided, where a portion of the anti-rotation block is formed for removably locating in an opening formed in at least one of the paired arms and is engaged with the seal strip to resist movement of the seal strip relative to the at least one arm. A detachable engagement member is detachably fastened to the anti-rotation block for maintaining the anti-rotation block in engagement with the seal strip. 
     In accordance with a further aspect of the invention, a seal strip assembly is provided in a turbomachine having a plurality of stages comprising rotationally driven disks, and arms on opposed portions of adjoining disks to define paired arms with a space therebetween, the paired arms comprising end faces including slots. The seal strip assembly comprises a seal strip located in the space between the paired arms and includes opposing edges located in respective slots of the paired arms. An anti-rotation block is also provided, where a portion of the anti-rotation block is removably located in opposed openings formed in the paired arms and is engaged with the seal strip to resist movement of the seal strip relative to the paired arms. A detachable engagement member is detachably fastened to the anti-rotation block for maintaining the anti-rotation block in engagement with the seal strip. 
     In accordance with another aspect of the invention, an anti-rotation structure is provided for use with a seal strip in a turbomachine. The anti-rotation structure comprises an anti-rotation block including a surface for engaging a first side of the seal strip and including a pair of spaced extensions extending from the surface for locating in a pair of respective notches formed in opposed edges of the seal strip. A detachable engagement member is also provided comprising an engagement block extending between the spaced extensions, the engagement block being removably mounted to the anti-rotation block. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       While the specification concludes with claims particularly pointing out and distinctly claiming the present invention, it is believed that the present invention will be better understood from the following description in conjunction with the accompanying Drawing Figures, in which like reference numerals identify like elements, and wherein: 
         FIG. 1  is diagrammatic section view of a portion of a gas turbine engine; 
         FIG. 2  is an exploded perspective view illustrating a seal strip assembly including an anti-rotation structure in accordance with the present invention; 
         FIG. 3  is a perspective view of the seal strip assembly shown assembled in relation to a section of a pair adjoining disks; 
         FIG. 4  is a cross-sectional view of the assembled seal strip assembly shown in  FIG. 3 ; and 
         FIG. 5  is a cross-sectional view illustrating a prior art seal assembly including a welded anti-rotation block. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following detailed description of the preferred embodiment, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration, and not by way of limitation, a specific preferred embodiment in which the invention may be practiced. It is to be understood that other embodiments may be utilized and that changes may be made without departing from the spirit and scope of the present invention. 
     Referring to  FIG. 1 , a portion of a turbine engine  10  is illustrated diagrammatically including adjoining stages  12 ,  14 , each stage  12 ,  14  comprising an array of stationary vane assemblies  16  and an array of rotating blades  18 , where the vane assemblies  16  and blades  18  are positioned circumferentially within the engine  10  with alternating arrays of vane assemblies  16  and blades  18  located in the axial direction of the turbine engine  10 . The blades  18  are supported on rotor disks  20  secured to adjacent disks with spindle bolts  22 . The vane assemblies  16  and blades  18  extend into an annular gas passage  24 , and hot gases directed through the gas passage  24  flow past the vane assemblies  16  and blades  18  to remaining rotating elements. 
     Disk cavities  26 ,  28  are located radially inwardly from the gas passage  24 . Purge air is preferably provided from cooling gas passing through internal passages in the vane assemblies  16  to the disk cavities  26 ,  28  to cool blades  18  and to provide a pressure to balance against the pressure of the hot gases in the gas passage  24 . In addition, interstage seals comprising labyrinth seals  32  are supported at the radially inner side of the vane assemblies  16  and are engaged with surfaces defined on paired annular disk arms  34 ,  36  extending axially from opposed portions of adjoining disks  20 . An annular cooling air cavity  38  is formed between the opposed portions of adjoining disks  20  on an inner side  80  of the paired annular disk arms  34 ,  36 . The annular cooling air cavity  38  receives cooling air passing through disk passages to cool the disks  20 . 
     Referring to  FIG. 2 , an exploded view showing a segment of two adjoining disks  20  is illustrated for the purpose of describing the seal strip assembly  46  of the present invention, it being understood that the disks  20  and associated disk arms  34 ,  36  define an annular structure extending the full circumference about the rotor centerline. The disk arms  34 ,  36  define respective opposed end faces  48 ,  50  located in closely spaced relation to each other. A circumferentially extending slot  52 ,  53  is formed in each end face  48 ,  50 , and at least one radial opening  54 ,  55  extends from an inner surface  56 ,  57  to an outer surface  58 ,  59  of respective disk arms  34 ,  36 , extending axially inwardly from the end faces  48 ,  50  and intersecting the slots  52 ,  53 . 
     The seal strip assembly  46  includes a seal strip  60  forming a belly band seal. The seal strip  60  is positioned within the slots  52 ,  53  defined in the opposed end faces  48 ,  50 . The seal strip  60  spans the gap between the end faces  48 ,  50  and defines a seal for preventing or substantially limiting flow of gases between the cooling air cavity  38  and the disk cavities  26 ,  28 . The seal strip  60  preferably includes a pair of notches  62 ,  64  formed in opposed edges  66 ,  68  of the seal strip  60  for alignment with the radial openings  54 ,  55  formed in the disk arms  34 ,  36 . 
     The seal strip assembly  46  further includes an anti-rotation structure comprising an anti-rotation block  70  and a detachable engagement member including an engagement block  72  and a fastener  74 . The anti-rotation block  70  comprises an upper portion including an engagement surface  78  for engaging a first, radially inner surface or first side  80  of the seal strip  60 . The engagement surface  78  extends in an axial direction a distance substantially equal to the distance between the notches  62 ,  64  in the seal strip  60 , and is bounded on either axial end by radially extending walls  82 ,  84  defined on a pair of spaced extensions  86 ,  88 . The extensions  86 ,  88  are dimensioned in the circumferential direction to fit within the notches  62 ,  64 , and are dimensioned in the radial direction to include an end extending a predetermined distance above a radially outer surface or second side  90  of the seal strip  60 , opposite the first side  80 . The extensions  86 ,  88  are further dimensioned to fit within the radial openings  54 ,  55  in the disk arms  34 ,  36 . Engagement of the extensions  86 ,  88  with the notches  62 ,  64  constrains the seal strip  60  to a predetermined position relative to the anti-rotation block  70 , as well as relative to the disk arms  34 ,  36 . 
     A lower portion of the anti-rotation block  70  includes axially extending legs  92 ,  94 . The legs  92 ,  94  include respective outer surfaces  96 ,  98  for engaging the inner surfaces  56 ,  57  of the paired disk arms  34 ,  36 . The legs  92 ,  94  locate the anti-rotation block  70  in the radial direction relative the paired disk arms  34 ,  36 . 
     The engagement block  72  is dimensioned such that opposing ends or edge portions thereof may fit with the radial openings  54 ,  55 . The engagement block  72  extends between the extensions  86 ,  88  of the anti-rotation block  70  and includes an engagement surface  100  for engaging the second side  90  of the seal strip  60  in the area between the notches  62 ,  64 . Recessed areas  102 ,  104  are located at either axial end of the engagement block  72  and are dimensioned to receive the ends of the extensions  86 ,  88 . 
     Referring further to  FIGS. 3 and 4 , the engagement block  72  is removably mounted to the anti-rotation block  70 , with the seal strip  60  sandwiched therebetween, by the fastener  74 . The fastener  74  preferably comprises a threaded fastener, such as a screw or a bolt, extending through an aperture  106  in the engagement block  72 , passing through a hole  108  in the seal strip  60 , and threadably engaged in a threaded aperture  110  in the anti-rotation block  70 . An outer surface  112  of the engagement block  72  may be provided with a recess  114  for receiving a head portion  116  of the fastener  74  whereby the top of the head portion  116  is recessed substantially flush with the outer surfaces  58 ,  59  of the disk arms  34 ,  36 . It may be seen that the thickness of the engagement block  72  in the radial direction locates the outer surface  112  of the engagement block  72  substantially flush with the outer surfaces  58 ,  59  of the disk arms  34 ,  36 , as may be best seen in  FIG. 4 . 
     In addition, it should be understood that, within the scope of the present invention, other detachable engagement structures, including other fasteners or connecting structure than threaded fasteners, may be used to removably retain the anti-rotation block  70  in association with the seal strip  60 . Such alternative connecting structures may include, without limitation, removable or detachable clips, clamps, or other equivalent structures. 
     The present invention provides a structure that may be incorporated into existing gas turbine engines without requiring modification of the disk arms  34 ,  36  to incorporate the seal strip assembly  46  disclosed herein. In particular, the present seal strip assembly  46  is adapted to fit within the existing radial openings  54 ,  55  currently provided on turbine engine disk arms  34 ,  36  for receiving prior art anti-rotation blocks, such as is disclosed in  FIG. 5 . 
     In a typical application of the invention, the seal strip  60  may be provided as four separate seal strip segments having lapped ends (not shown) to form a continuous belly band seal about the circumference of the cooling air cavity  38 . An anti-rotation structure may be provided at the mid-span of each of the seal strip segments to thereby locate each seal strip segment relative to adjacent seal strip segments. 
     Field repair of the seal strip  60  is typically performed by removing and replacing seal strips through an opening (not shown) formed in the inner surfaces  56 ,  57  of the arms  34 ,  36 . The present invention permits accurate placement of the seal strip assembly  46  by providing a structure having tolerances that may be accurately machined in a shop or factory environment, prior to transport to the field. Further, the installation of the disclosed seal strip assembly  46  is simplified in that a weld connection utilized for the prior art installation is replaced by a removable fastener connection that facilitates manipulation in the field, and that permits disassembly of the seal strip assembly  46  if repositioning or removal of components of the assembly is required. 
     While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.