Abstract:
A wear prevention system for securing compressor airfoils within a turbine engine while reducing wear of related components is disclosed. The wear prevention system may include a compressor diaphragm spring positioned in an airfoil receiving channel between a radially outer surface of a diaphragm base and a radially inner surface of the airfoil receiving channel. The spring may bias the diaphragm base and airfoil attached thereto radially inward against upstream and downstream arms formed from upstream and downstream recesses extending axially from the airfoil receiving channel in the compressor case. The compressor diaphragm spring may dampen vibration and increase service life of the diaphragm base.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention is directed generally to turbine engines, and more particularly to compressor vane attachment systems in turbine engines. 
       BACKGROUND 
       [0002]    Typically, gas turbine engines include a compressor for compressing air, a combustor for mixing the compressed air with fuel and igniting the mixture, and a turbine blade assembly for producing power. The compressor blade assembly typically includes a rotor assembly rotatable positioned in a turbine compressor case and having a plurality of compressor blades extending radially outward from the rotor assembly. The turbine engine also includes a plurality of stationary compressor vanes, which are also referred to as diaphragm airfoils  4  attached to diaphragms  2 , extending radially inward from the turbine compressor case  6 . The compressor blades and compressor vanes  4  are aligned into rows, or stages, and are positioned in alternating rows of vanes and blades. The compressor vanes  4  are typically attached to a turbine combustion case  6  via a hook fit  8 , as shown in cross-section in  FIGS. 1 and 2 . The hook fit releasably and securely attaches the compressor vanes  4  within a turbine engine. During operation, the hooks fits  8  are susceptible to wear due to vibration, heat, and other factors. For instance, a hook fit  8  is typically worn in the areas  7  shown in  FIG. 2 . Such wear negatively affects the safety and efficiency of a turbine engine in which the wear occurs. 
         [0003]    Typically, such wear regions  7  are repaired on turbine engines during outages in which other aspects of the turbine engine are repaired. Repairing the diaphragm  2  and related components generally takes weeks because of the time needed to remove half of the compressor case  6  to gain access. Thus, a need exists for extending the useful life of the diaphragm and relevant portions of the compressor case forming the hook fit of a turbine engine. 
       SUMMARY OF THE INVENTION 
       [0004]    This invention is directed to a wear prevention system for securing compressor airfoils within a turbine engine to reduce wear on diaphragm components used to secure the compressor airfoils. Diaphragm bases may be configured to support airfoils, such as compressor vanes, extending radially inward. The diaphragm bases may be contained within one or more airfoil receiving channels in the compressor case. The diaphragm bases may be biased radially inward within the airfoil receiving channel though use of a compressor diaphragm spring to dampen vibration. Use of the compressor diaphragm spring reduces wear on the inner surfaces of the airfoil receiving channel of the compressor case, thereby increasing the time between servicing. 
         [0005]    The wear prevention system for securing compressor airfoils within a turbine engine may include a generally cylindrical compressor case having at least one airfoil receiving channel. The airfoil receiving channel may be positioned in an inner surface the generally cylindrical compressor case such that the inner surface includes an opening for receiving a diaphragm supporting an airfoil. The least one airfoil receiving channel may include an upstream recess and a downstream recess. The upstream recess may be formed from a generally curved, upstream arm that extends axially downstream and has an inner surface that is aligned with and forms a portion of the inner surface of the generally cylindrical compressor case. The downstream recess may be formed from a generally curved, downstream arm that extends axially upstream and has an inner surface that is aligned with and forms a portion of the inner surface of the generally cylindrical compressor case. The wear prevention system may include at least one diaphragm base that is curved about a longitudinal axis and that extends from the upstream recess to the downstream recess with an upstream radially outward support surface and a downstream radially outward support surface. An airfoil may extend radially inward from the diaphragm base. A compressor diaphragm spring may be positioned in the airfoil receiving channel between a radially outer surface of the diaphragm base and a radially inner surface of the at least one airfoil receiving channel. The compressor diaphragm spring may impart a force radially inward on the diaphragm base to dampen vibration of the diaphragm base and the airfoil. 
         [0006]    In one embodiment, the compressor diaphragm spring may extend axially from the upstream radially outward support surface of the diaphragm base to the downstream radially outward support surface of the diaphragm base. The compressor diaphragm spring may include an upstream inner support pad that is configured to mate with the upstream radially outward support surface and may include a downstream inner support pad that is configured to mate with the downstream radially outward support surface. The upstream and downstream inner support pads may extend radially inward further than other aspects of the compressor diaphragm spring. A radially outward engagement pad may extend radially outward from the compressor diaphragm spring. The radially outward engagement pad may extend radially outward from the compressor diaphragm spring further than other aspects of the compressor diaphragm spring, contact the radially inner surface of the airfoil receiving channel, and deflect radially inward. The compressor diaphragm spring may be curved about a longitudinal axis and may be curved about an axis orthogonal to the longitudinal axis. 
         [0007]    In another embodiment, the compressor diaphragm spring may be formed from a rod extending radially inward from the compressor case into the airfoil receiving channel and wherein the compressor diaphragm spring is biased radially inward. A releasable housing that contains at least a portion of the rod may be releasably attached to the compressor case. A spring may be positioned between the releasable housing and a radially outer surface of the rod. In one embodiment, the spring may be a coil spring. The releasable housing may include a plurality of threads extending axially outward that engage corresponding threads on a side wall forming a chamber within the compressor case. A sacrificial wear material may be positioned on a radially inner surface of the rod. 
         [0008]    An advantage of this invention is that the restoration system compressor diaphragm spring may be positioned in the airfoil receiving channel between a radially outer surface of the diaphragm base and a radially inner surface of the airfoil receiving channel to impart a force radially inward on the diaphragm base. As such, the rate of wear on the diaphragm base and compressor case may be reduced, thereby extending the usable life between servicing outages. 
         [0009]    These and other embodiments are described in more detail below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The accompanying drawings, which are incorporated in and form a part of the specification, illustrate embodiments of the presently disclosed invention and, together with the description, disclose the principles of the invention. 
           [0011]      FIG. 1  is cross-sectional side view of a compressor with a conventional turbine vane attachment system. 
           [0012]      FIG. 2  is a detailed, cross-sectional view of a prior art airfoil attached to a diaphragm, which is attached to a compressor case at detail line  2 . 
           [0013]      FIG. 3  is a detailed, cross-sectional view of an airfoil extending from a diaphragm base attached to a compressor case with a compressor diaphragm spring. 
           [0014]      FIG. 4  is cross-sectional side view taken along section line  4 - 4  in  FIG. 3 . 
           [0015]      FIG. 5  is an axial view of stage four compressor airfoils in a compressor of the turbine engine. 
           [0016]      FIG. 6  is a cross-sectional side view of a compressor diaphragm spring. 
           [0017]      FIG. 7  is a cross-sectional side view of the compressor diaphragm spring shown in  FIG. 6  with a load applied. 
           [0018]      FIG. 8  is a cross-sectional side view of a compressor with another embodiment of the compressor diaphragm spring. 
           [0019]      FIG. 9  is a detailed cross-sectional side view of the compressor diaphragm spring shown in  FIG. 8  at detail line  9 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    As shown in  FIGS. 3-9 , this invention is directed to a wear prevention system  10  for securing compressor airfoils  12  within a turbine engine  14  to reduce wear on diaphragm components  16  used to secure the compressor airfoils  12 . Diaphragm bases  18  may be configured to support airfoils  12 , such as compressor vanes, extending radially inward. In at least one embodiment, the wear prevention system  10  may be used in connection with compressor vanes  12  stage four through stage six. The diaphragm bases  18  may be contained within one or more airfoil receiving channels  20  in the compressor case  22 . The diaphragm bases  18  may be biased radially inward within the airfoil receiving channel  20  though use of a compressor diaphragm spring  24 . Use of the compressor diaphragm spring  24  reduces wear on the inner surfaces  26  of the airfoil receiving channel  20  of the compressor case  22  by dampening vibrations, thereby increasing the time between servicing outages. 
         [0021]    The wear prevention system  10  may include a generally cylindrical compressor case  22  having one or more airfoil receiving channels  20 . The airfoil receiving channel  20  may be positioned in an inner surface  28  of the generally cylindrical compressor case  22  such that the inner surface  28  includes an opening  30 . The airfoil receiving channel  20  may extend at least partially around and in at least one embodiment, entirely around the compressor case  22 . The airfoil receiving channel  20 , thus, may be generally cylindrical and extend radially outward into the inner surface  28  of the compressor case  22 . The airfoil receiving channel  20  may include one or more upstream recesses  32  and one or more downstream recess  34 . The upstream recess  32  may be formed from a generally curved, upstream arm  36  that extends axially downstream and has an inner surface  38  that is aligned with and forms a portion of the inner surface  28  of the generally cylindrical compressor case  22 . The downstream recess  34  may be formed from a generally curved, downstream arm  40  that extends axially upstream and has an inner surface  42  that is aligned with and forms a portion of the inner surface  28  of the generally cylindrical compressor case  22 . 
         [0022]    The wear prevention system  10  may include one or more diaphragm bases  18  for supporting the compressor airfoils  12  and securing the compressor airfoils  12  to the compressor case  22 . The diaphragm base  18  may be curved about a longitudinal axis  78  and may extend from the upstream recess  32  to the downstream recess  34  with an upstream radially outward support surface  44  and a downstream radially outward support surface  46 . A compressor airfoil  12  may extend radially inward from the diaphragm base  18 . The diaphragm base  18  may include an upstream foot  33  configured to fit within the upstream recess  32  and a downstream foot  35  configured to fit within the downstream recess  34 . 
         [0023]    The wear prevention system  10  may also include a compressor diaphragm spring  24  positioned in the airfoil receiving channel  20  between a radially outer surface  48  of the diaphragm base  18  and a radially inner surface  26  of the airfoil receiving channel  20 . The compressor diaphragm spring  24  may impart a force radially inward on the diaphragm base  18 . The compressor diaphragm spring  24  may be deflected when installed, thereby creating a force directed on the diaphragm base  22 . 
         [0024]    In one embodiment, as shown in  FIGS. 3 ,  4 ,  6  and  7 , the compressor diaphragm spring  24  may extend axially from the upstream radially outward support surface  44  of the diaphragm base  18  to the downstream radially outward support surface  46  of the diaphragm base  18 . The compressor diaphragm spring  24  may include an upstream inner support pad  50  that is configured to mate with the upstream radially outward support surface  44  and includes a downstream inner support pad  52  that is configured to mate with the downstream radially outward support surface  46 . The upstream and downstream inner support pads  50 ,  52  may extend radially inward further than other aspects of the compressor diaphragm spring  24 . 
         [0025]    A radially outward engagement pad  54  may extend radially outward from the compressor diaphragm spring  24 . The radially outward engagement pad  54  may extend radially outward from the compressor diaphragm spring  24  further than other aspects of the compressor diaphragm spring  24 . The radially outward engagement pad  54  may contact the radially inner surface  26  of the airfoil receiving channel  20 . The radially outward engagement pad  54  may deflect radially inward when installed in the airfoil receiving channel  20  under a diaphragm base  18 . The compressor diaphragm spring  24  may be curved about a longitudinal axis  78 , as shown in  FIG. 4 , and may be curved about an axis  80  orthogonal to the longitudinal axis  78 , as shown in  FIG. 6 . 
         [0026]    In another embodiment, as shown in  FIGS. 8 and 9 , the compressor diaphragm spring  24  may be formed from a rod  56  extending radially inward from the compressor case  22  into the airfoil receiving channel  20 . The rod  56  may bias the compressor diaphragm spring  24  radially inward, which thereby biases the diaphragm base  18  and the compressor airfoil  12  radially inward. A releasable housing  58  may contain at least a portion of the rod  56  and may be releasably attached to the compressor case  22 . The releasable housing  58  may include a plurality of threads  60  extending axially outward that engage corresponding threads  62  on a sidewall  64  forming a chamber  66  through the compressor case  22 . A sacrificial wear material  70  may be positioned on a radially inner surface  72  of the rod  56 . A spring  68  may be positioned between the releasable housing  58  and a radially outer surface of the rod  56 . The spring  68  may be, but is not limited to being, a coil spring. A jamb nut  72  may be attached to the housing  58  thereby permitting a preloaded force to be applied to the spring  68 . 
         [0027]    During use, the compressor diaphragm spring  24  may be positioned between the diaphragm base  18  and the inner surface  26  of the airfoil receiving channel  20 . The compressor diaphragm spring  24  may be loaded at horizontal joints at four locations around the compressor case  22 . The compressor diaphragm spring  24  may be deflected such that a radially inward force is imparted from the radially outward engagement pad  54  through the compressor diaphragm spring  24 , through the upstream and downstream inner support pad  50 ,  52  and into the upstream and downstream radially outward support surfaces  44 ,  46 . As such, the diaphragm base  18  and the attached compressor airfoils  12  are biased radially inward, thereby reducing the wear on the diaphragm base  18  and related components.  FIG. 5  discloses the heavy wear regions  74  in close proximity to the case torque restraints  76 . 
         [0028]    In the embodiment shown in  FIGS. 8 and 9 , the compressor spring  24  may exert a force on the radially outer surface  48  of the diaphragm base  18 . As such, the diaphragm base  18  and the attached compressor airfoils  12  are biased radially inward, thereby reducing the wear on the diaphragm base  18  and related components. 
         [0029]    The foregoing is provided for purposes of illustrating, explaining, and describing embodiments of this invention. Modifications and adaptations to these embodiments will be apparent to those skilled in the art and may be made without departing from the scope or spirit of this invention.