Abstract:
An annular shroud surrounding tip ends of turbine blades is fitted on an inner peripheral surface of an open end of a turbine case. In order to prevent the shroud from being dropped off in an axial direction by a retaining part provided on a retaining ring fitted on an outer peripheral surface of the open end of the turbine case, an annular groove formed in the outer peripheral surface of the turbine case and an annular groove formed in an inner peripheral surface of the retaining ring are opposed to each other, and a connection wire is inserted so as to straddle the two annular grooves, thereby connecting the retaining ring to the turbine case. Accordingly, it is possible to easily perform attachment/detachment of the retaining ring with respect to the turbine case only by inserting the connection wire into or pulling it out from the two annular grooves, thereby facilitating maintenance of the shroud and the turbine blades. Therefore, this can improve ease of attachment/detachment of the retaining ring retaining the shroud of a gas turbine engine to the turbine case.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a shroud supporting structure for a gas turbine engine, in which: an annular shroud surrounding tip ends of a plurality of turbine blades which are attached to a turbine disk in a radial arrangement is fitted on an inner peripheral surface of an open end of a turbine case; and a retaining ring fitted on an outer peripheral surface of the open end of the turbine case has a retaining part provided thereon to prevent the shroud from being dropped off in an axial direction. 
       DESCRIPTION OF THE RELATED ART 
       [0002]    Such a shroud supporting structure for a gas turbine engine is known from Japanese Patent Application Laid-open No. 2001-303907. This invention has a configuration in which the shroud is divided into eight parts in the circumferential direction and is fitted on the inner peripheral surface of the turbine case, and in this state, the retaining ring fitted on the outer periphery of the turbine case is connected to the turbine case with eight rivets; and thereby the retaining part of the retaining ring is placed in engagement with the front end of the shroud, so that the shroud is prevented from dropping off from the turbine case. 
         [0003]    Meanwhile, the above conventional configuration has the following problem: since the retaining ring is connected to the turbine case with the rivets, when the retaining ring is to be attached/detached at the time of assembling or doing maintenance on the gas turbine engine, the work to hammer or cut the rivets is necessary, thereby requiring a lot of time and labor for this work. 
       SUMMARY OF THE INVENTION 
       [0004]    The present invention has been made in view of the foregoing situation, and an object thereof is to enhance attachment/detachment capability of a retaining ring retaining a shroud for a gas turbine engine to a turbine case. 
         [0005]    In order to achieve the object, according to the present invention, there is provided a shroud supporting structure for a gas turbine engine, in which: an annular shroud surrounding tip ends of a plurality of turbine blades which are attached to a turbine disk in a radial arrangement is fitted on an inner peripheral surface of an open end of a turbine case; and a retaining ring fitted on an outer peripheral surface of the open end of the turbine case has a retaining part provided thereon to prevent the shroud from being dropped off in an axial direction, characterized in that an annular groove formed in the outer peripheral surface of the turbine case and an annular groove formed in an inner peripheral surface of the retaining ring are opposed to each other, and a connection wire is inserted so as to straddle both of the annular grooves, thereby connecting the retaining ring to the turbine case. 
         [0006]    According to the above configuration, the annular shroud which surrounds the tip ends of the turbine blades is fitted on the inner peripheral surface of the open end of the turbine case; and, in order to prevent the shroud from being dropped off in the axial direction by the retaining part provided on the retaining ring fitted on the outer peripheral surface of the open end of the turbine case, the annular groove formed in the outer peripheral surface of the turbine case and the annular groove formed in the inner peripheral surface of the retaining ring are opposed to each other, and the connection wire is inserted so as to straddle the two annular grooves, thereby connecting the retaining ring to the turbine case. Accordingly, it is possible to easily perform attachment/detachment of the retaining ring with respect to the turbine case only by inserting the connection wire into or pulling it out from the two annular grooves, thereby improving ease of attachment/detachment of the shroud and the turbine blades. 
         [0007]    The above description, other objects, characteristics and advantages of the present invention will be clear from detailed descriptions which will be provided for the preferred embodiment referring to the attached drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    Attached drawings show an embodiment of the present invention: 
           [0009]      FIG. 1  is a longitudinal cross-sectional view of a part of a gas turbine engine showing a neighboring portion of a turbine blade; 
           [0010]      FIG. 2  is a sectional view taken along a line  2 - 2  in  FIG. 1 ; 
           [0011]      FIG. 3  is a view seen from a direction of an arrow  3  in  FIG. 2 ; 
           [0012]      FIG. 4  is a sectional view taken along a line  4 - 4  in  FIG. 3 ; 
           [0013]      FIG. 5  is a sectional view taken along a line  5 - 5  in  FIG. 3 ; 
           [0014]      FIG. 6  is a sectional view taken along a line  6 - 6  in  FIG. 3 ; and 
           [0015]      FIG. 7  is a perspective view of a connection wire. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0016]    An embodiment of the present invention will be described below based on  FIG. 1  to  FIG. 7 . 
         [0017]    As shown in  FIG. 1 , an axial-flow type gas turbine engine includes a turbine disk  11  fixed to a turbine shaft, which is not illustrated, and a plurality of turbine blades  12  are supported in a radial arrangement on an outer periphery of the turbine disk  11  via an attachment part  12   a.  A nozzle  13  in which combustion gas from a combustor, which is not illustrated, flows is disposed on an upstream side (left side in the drawing) of the turbine blade  12 . The nozzle  13  is formed of an annular shape having an outer peripheral wall  13   a  and an inner peripheral wall  13   b,  and a downstream end of the nozzle  13  faces a front surface of a main part  12   b  of the turbine blade  12 . The outer peripheral wall  13   a  and the inner peripheral wall  13   b  of the nozzle  13  are connected by a plurality of stator vanes  13   c  which are disposed in a radial arrangement. An exhaust passage  14  disposed on a downstream side (right side in the drawing) of the turbine blade  12  is formed of an annular shape having an outer peripheral wall  14   a  and an inner peripheral wall  14   b,  and an upstream end of the exhaust passage  14  faces a rear surface of the main part  12   b  of the turbine blade  12 . 
         [0018]    A shroud  15  which faces a tip end (outer end in a radial direction) of the turbine blade  12  with a slight gap g interposed therebetween is disposed so as to close a space interposed between the outer peripheral wall  13   a  of the nozzle  13  and the outer peripheral wall  14   a  of the exhaust passage  14 . A tubular turbine case  16  covering an outer periphery of the exhaust passage  14  and extending toward the front (left side in the drawing) surrounds an outer periphery of the shroud  15 , and an open end of the turbine case  16  and a front end of the shroud  15  are covered by an integrally formed annular retaining ring  17 . A sealing member  19  is supported in an annular groove  13   d  provided in a projecting manner on the outer peripheral surface of the outer peripheral wall  13   a  of the nozzle  13  for sealing a space between an inner peripheral surface of a front part of the retaining ring  17  and the annular groove  13   d,  and a sealing member  20  is supported in an annular groove  14   c  provided in a projecting manner on the outer peripheral surface of the outer peripheral wall  14   a  of the exhaust passage  14  for sealing a space between an inner peripheral surface of the turbine case  16  and the annular groove  14   c.    
         [0019]    Next, referring to  FIG. 2  to  FIG. 7  together, a structure of the shroud  15  and a structure for supporting the shroud  15  to the turbine case  16  with the retaining ring  17  will be explained. 
         [0020]    As is clear from  FIG. 1  and  FIG. 2 , the shroud  15  disposed annularly with an axis L of the gas turbine engine being a center is configured such that eight segments  21  of the same structure each having a center angle of 45° are connected in a circumferential direction. Here, adjacent segments  21  simply abut each other and have no special connecting structure, and the shroud  15  is retained annularly by the turbine case  16  being engaged with the retaining ring  17 . 
         [0021]    The segment  21  of the shroud  15  comprises a shroud main body  22  curved in a circular arc shape, a first flange  23  rising from a front end of the shroud main body  22  outward in the radial direction, and a second flange  24  rising from a rear end of the shroud main body  22  outward in the radial direction. A width in the radial direction of the first flange  23  is formed to be larger than a width in the radial direction of the second flange  24 . A part of the segment  21  which is exposed to combustion gas, that is, a radially inner surface of the shroud main body  22 , and a part of a front surface of the first flange  23  are covered by a liner  25  having a heat resistance. 
         [0022]    On a radially outer end of the first flange  23  of each of the segments  21 , a first engaging part  23   a  protruding rearward is formed over its entire length. On a radially outer end of the second flange  24  of the segment  21 , a second engaging part  24   a  protruding rearward is formed over its entire length. 
         [0023]    An annular first engaged part  16   a  opened toward the front and an annular second engaged part  16   b  formed at a position radially inward and rearward of the first engaged part  16   a  and opened toward the front are formed in the inner peripheral surface of the turbine case  16 . The first engaging part  23   a  and the second engaging part  24   a  of each segment  21  of the shroud  15  are engaged, from the front, with the first engaged part  16   a  and the second engaged part  16   b  of the turbine case  16 , respectively. 
         [0024]    The retaining ring  17  fitted, from the front, on an outer peripheral surface of a front end of the turbine case  16  has an annular groove  17   a  of a rectangular section formed in the inner peripheral surface of a rear end thereof. An annular groove  16   c  of a rectangular section facing this annular groove  17   a  is formed in the outer peripheral surface of the front end of the turbine case  16 . And both of the annular grooves  17   a,    16   c  form a square section in cooperation with each other and are engaged with a connection wire  26  having flexibility and a circular section, so that the retaining ring  17  is fixed so as not to drop off from the turbine case  16  to the front side. In a state in which the retaining ring  17  is connected to the turbine case  16 , a retaining part  17   e  provided, in a protruding manner, radially inward on the inner peripheral surface of the retaining ring  17  is engaged with a front surface of the first flange  23  of the shroud  15 , so that the shroud  15  is retained so as not to drop off from the turbine case  16  to the front side. 
         [0025]    As is clear from  FIG. 3  and  FIG. 5 , a recess  16   d  depressed radially inward is formed in a part of the turbine case  16  which faces a cutout  17   b  formed in a rear edge of the retaining ring  17  and extending in the peripheral direction. The annular groove  16   c  of the turbine case  16  and the annular groove  17   a  of the retaining ring  17  are opened in an end of the cutout  17   b  of the retaining ring  17 . 
         [0026]    As is clear from  FIG. 3  and  FIG. 6 , a rotation-preventing pin  27  is engaged with a pin hole  17   c  formed in the retaining ring  17  in the vicinity of the other end of the cutout  17   b  and a pin hole  16   e  formed in the turbine case  16 , so that the retaining ring  17  is restrained against rotation relative to the turbine case  16 . 
         [0027]    As is clear from  FIG. 3  and  FIG. 7 , the connection wire  26  is formed by curving a wire having an elasticity to form an annular shape over substantially 360°, and includes a small-loop-shaped grip part  26   a  at one end thereof and a retaining part  26   b  curved so as to continue with the grip part  26   a.  And the retaining ring  17  includes a recess  17   d  which is formed in an end edge thereof adjacent to the cutout  17   b,  with which recess the retaining part  26   b  of the connection wire  26  can be engaged. 
         [0028]    Next, operations of the embodiment of the present invention having the above configuration will be explained. 
         [0029]    When the shroud  15  and the retaining ring  17  are assembled to the turbine case  16 , the eight divided segments  21  of the shroud  15  are moved from the front to the rear in  FIG. 1  (left side to right side in the drawing); and the first engaging part  23   a  formed on the first flange  23  of each segment  21  is engaged with the first engaged part  16   a  of the turbine case  16  and, concurrently, the second engaging part  24   a  formed on the second flange  24  of each segment  21  is engaged with the second engaged part  16   b  of the turbine case  16 . Accordingly, the eight segments  21  are integrally connected together, thereby forming the annular shroud  15 . 
         [0030]    Next, in a state in which the retaining ring  17  is fitted on the open end of the turbine case  16 , the retaining ring  17  is positioned in the rotational direction so as to place the pin hole  17   c  of the retaining ring  17  in alignment with the pin hole  16   e  of the turbine case  16 , and the positioning pin  27  is inserted into both of the pin holes  17   c,    16   e . Subsequently, while elastically deforming the annular connection wire  26  into an elongated state, a tip end of the connection wire  26  on a side opposite from the grip part  26   a  is inserted from the cutout  17   b  of the retaining ring  17  into both of the annular grooves  16   c ,  17   a  opened in the recess  16   d  of the turbine case  16 . As a result, the connection wire  26  is fitted, over substantially 360°, on both of the annular grooves  16   c,    17   a,  and, finally, the retaining part  26   b  provided continuously with the grip part  26   a  is engaged with the recess  17   d  of the retaining ring  17 , so that the grip part  26   a  is housed in the recess  16   d  of the turbine case  16  (see  FIG. 3 ). 
         [0031]    In this state, as shown in  FIG. 4 , the connection wire  26  is engaged so as to straddle both of the annular groove  17   a  of the retaining ring  17  and the annular groove  16   c  of the turbine case  16 . Accordingly, the retaining ring  17  is connected to the turbine case  16 , and the shroud  15  is prevented from dropping off form the inside of the turbine case  16  to the front side by the engaging part  17   e  of the retaining ring  17 . 
         [0032]    When the retaining ring  17  is to be separated from the turbine case  16 , only the following work is required: the grip  26   a  of the connection wire  26  within the recess  16   d  of the turbine case  16  is gripped and pulled; and the entire connection wire  26  is pulled out from the annular groove  17   a  of the retaining ring  17  and the annular groove  16   c  of the turbine case  16 . And, when the retaining ring  17  is separated from the turbine case  16 , the shroud  15  can be freely attached to or detached from the open end of the turbine case  16 , thereby improving the assemblability and ease of maintenance of the shroud  15 . Further, since the shroud  15  can be fixed to the turbine case  16  only by the retaining function of the retaining ring  17 , any special fixing member is not required, thereby reducing number of parts and cost. 
         [0033]    One embodiment of the present invention is explained above, but the present invention may be modified in a variety of ways as long as the modifications do not depart from the gist of the present invention. 
         [0034]    For example, in the embodiment, the shroud  15  is divided into eight segments  21 , but the divided number is arbitrary. 
         [0035]    Further, in the embodiment, when the eight segments  21  of the shroud  15  is assembled to the turbine case  16 , the first and second engaging parts  23   a,    24   a  of the segments  21  are engaged with the first and second engaged parts  16   a,    16   b  of the turbine case  16 , but it is possible to employ other arbitrary assembling structure.