Abstract:
A shroud ( 22 ) comprises shroud bodies ( 22 ) fixed to blade tips of blades ( 18 ) mounted to a rotor body to extend in a radial direction, the shroud bodies ( 22 ) being disposed adjacent to one another in a circumferential direction, wherein each of the shroud bodies ( 22 ) includes a circumferential end surface ( 27, 28 ) that includes an abutting end surface where adjacent shroud bodies ( 22 ) abut, and an opposing surface ( 34 ) where adjacent shroud bodies ( 22 ) face one another with a clearance ( 32 ) therebetween, the opposing surface ( 34 ) being contiguous with the abutting end surface; and an outer surface ( 24 ) that includes a radially outward protruding protrusion ( 40 ) formed to extend along the opposing surface ( 34 ).

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a shroud fixed to a blade tip of a blade of a rotary machine, a blade member with the shroud, and a rotary machine. 
         [0002]    This application claims priority based on Japanese Patent Application No. 2014-050599 filed in Japan on Mar. 13, 2014, of which the contents are incorporated herein by reference. 
       BACKGROUND ART 
       [0003]    In recent years, gas turbines have been designed to operate at higher temperatures and with increased efficiency. This has led to a trend of increasing the length of the turbine blades (providing long blades). Such blades, while having a reduced vibration frequency due to the increased blade length, have an increased susceptibility to the occurrence to flutter and other unstable vibrations. 
         [0004]    To combat this, tip shrouds have been disposed on the tips of blade bodies that constitute the turbine blades to increase the natural frequency and/or structural damping of the turbine blades, thus suppressing the occurrence of vibrations. Adjacent tip shrouds of such turbine blades abut one another to reduce leakage flow between blade tips. Vibrations are also dampened by the adjacent tip shrouds abutting one another. To prevent damage caused by heterogeneous contact and stress concentration at corner portions however, tip shrouds have been provided with a portion with a gap via which adjacent tip shrouds do not abut one another (see, for example, Patent Document 1). 
       CITATION LIST 
     Patent Documents 
       [0005]    Patent Document 1: Japanese Unexamined Patent Application Publication No. H10-317905A 
       SUMMARY OF THE INVENTION 
     Technical Problem 
       [0006]    Through such a gap, combustion gas from the main flow may leak out into a cavity located radially outward from the tip shrouds causing loss and the reduction in performance of the turbine. 
         [0007]    An object of the present invention is to provide shrouds capable of reducing the amount of fluid that leaks out through the clearance between the shrouds. Such shrouds are disposed adjacent to one another in the circumferential direction, each of the shrouds being fixed to a blade tip of a blade mounted to a rotor body to extend in the radial direction. 
       Solution to Problem 
       [0008]    A first embodiment of the present invention is a shroud comprising: 
         [0009]    shroud bodies fixed to blade tips of blades mounted to a rotor body to extend in a radial direction, the shroud bodies being disposed adjacent to one another in a circumferential direction, wherein 
         [0010]    each of the shroud bodies includes 
         [0011]    a circumferential end surface that includes 
         [0012]    an abutting end surface where adjacent shroud bodies abut, and 
         [0013]    an opposing surface where adjacent shroud bodies face one another with a clearance therebetween, the opposing surface being contiguous with the abutting end surface; and 
         [0014]    an outer surface that includes a radially outward protruding protrusion formed to extend along the opposing surface. 
         [0015]    According to such a configuration, the protrusion acts as a dam and the fluid that convects in the radially outer region of the shroud stagnates. As a result, pressure rises at the radially outward outlet of the clearance causing the flow of the fluid flowing at these locations to be inhibited. In other words, the amount of fluid that leaks out from the clearance is reduced. 
         [0016]    The shroud described above may further have a configuration wherein the protrusion is disposed at a position on the outer surface furthest to a leading side in a rotational direction of the blades. 
         [0017]    According to such a configuration, a pressure rise occurs at the proximity of the outlet of the clearance due to the stagnation. This allows the amount of fluid that leaks out from the clearance to be further reduced. 
         [0018]    The shroud described above may further have a configuration wherein 
         [0019]    the clearance has a distance between the adjacent opposing surfaces that is greater at a side approximate to the abutting end surface; and 
         [0020]    the protrusion protrudes from the outer surface to a greater degree at the side approximate to the abutting end surface. 
         [0021]    According to such a configuration, the shape of the protrusion can be optimized. In other words, the height of the protrusion can be made appropriate depending on the size of the clearance. 
         [0022]    The shroud described above may further have a configuration wherein the protrusion includes a canopy portion that at least partially covers a radially outward side of the clearance when viewed in the radial direction. 
         [0023]    According to such a configuration, by the fluid that leaks out from the clearance coming into contact with the canopy portion, the amount of fluid that directly leaks out can be reduced. 
         [0024]    The shroud described above may further have a configuration wherein the protrusion is formed continuously with the opposing surface of the adjacent opposing surfaces that is located closer to where the blade is mounted. 
         [0025]    According to such a configuration, a shroud can be formed which minimizes increases in bending loads due to centrifugal force. 
         [0026]    A second embodiment of the present invention is a blade member comprising: 
         [0027]    a blade body, which is a blade mounted to a rotor body to extend in a radial direction; and 
         [0028]    the shroud described above. 
         [0029]    Another embodiment of the present invention is a rotary machine comprising: the blade member described above. 
       ADVANTAGEOUS EFFECTS OF INVENTION 
       [0030]    According to the present invention, the amount of fluid that leaks out through the clearance between the shrouds can be reduced by the shrouds being disposed adjacent to one another in the circumferential direction, with each of the shrouds being fixed to a blade tip of a blade mounted to a rotor body to extend in the radial direction. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0031]      FIG. 1  is a schematic view of the configuration of a gas turbine of the first embodiment according to the present invention. 
           [0032]      FIG. 2  is a view from a position radially outward of the turbine of a turbine blade of the first embodiment of the present invention. 
           [0033]      FIG. 3  is a cross-sectional view taken along A-A of  FIG. 2  and illustrates the cross-sectional shape of a protrusion of the first embodiment of the present invention. 
           [0034]      FIG. 4  is a cross-sectional view taken along B-B of  FIG. 2  to facilitate explanation of the height of the protrusion of the first embodiment of the present invention. 
           [0035]      FIG. 5  is a diagram illustrating the cross-sectional shape of the protrusion according to a modified example of the first embodiment of the present invention. 
           [0036]      FIG. 6  is a diagram illustrating the cross-sectional shape of the protrusion according to a modified example of the first embodiment of the present invention. 
           [0037]      FIG. 7  is a diagram illustrating the cross-sectional shape of the protrusion of the second embodiment of the present invention. 
           [0038]      FIG. 8  is a diagram illustrating the cross-sectional shape of the protrusion according to a modified example of the second embodiment of the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
       [0039]    A gas turbine  1 , which is a rotary machine of the first embodiment of the present invention, will be described below in detail with reference to the attached drawings.  FIG. 1  is a schematic view of the gas turbine  1  of the first embodiment of the present invention. 
         [0040]    As illustrated in  FIG. 1 , a gas turbine  1  includes a compressor  2  that compresses outside air to generate compressed air, a combustor  3  that combusts fuel in the presence of compressed air to generate combustion gas, and a turbine  4  that is driven by high-temperature high-pressure combustion gas. 
         [0041]    Hereinafter, the axial direction of the compressor  2  and the turbine  4  may be simply referred to as “axial direction” or “axial”; the circumferential direction of the compressor  2  and the turbine  4  may be simply referred to as “circumferential direction” or “circumferential”; and the radial direction of the compressor  2  and the turbine  4  may be simply referred to as “radial direction” or “radial”. 
         [0042]    The compressor  2  includes a compressor rotor  6  and a compressor casing  7  that covers the compressor rotor  6 . The compressor rotor  6  includes a compressor rotor shaft  8  that rotates about the rotation central axis and a plurality of compressor blade arrays  9  fixed on the periphery of the compressor rotor shaft  8  disposed at intervals in the axial direction. 
         [0043]    Each of the compressor blade arrays  9  includes a plurality of compressor blades  10  disposed on the periphery of the compressor rotor shaft  8  arranged at equal intervals in the circumferential direction. The compressor blades  10  extend toward the inner surface of the compressor casing  7 . 
         [0044]    A plurality of compressor vane arrays  11  are disposed and fixed at the inner surface of the compressor casing  7  at intervals in the axial direction. Each of the compressor vane arrays  11  includes a plurality of compressor vanes  12  disposed on the inner surface of the compressor casing  7  arranged at equal intervals in the circumferential direction. The compressor vanes  12  extend toward the compressor rotor shaft  8 . 
         [0045]    The compressor vane arrays  11  and the compressor blade arrays  9  are disposed in stages in the compressor casing  7 , the compressor vane arrays  11  and the compressor blade arrays  9  alternating in the axial direction. 
         [0046]    The turbine  4  includes a turbine rotor  14  co-rotatably coupled to the compressor rotor  6  and a turbine casing  15  that covers the turbine rotor  14 . The turbine rotor  14  includes a turbine rotor shaft  16  (rotor body) that rotates about the rotation central axis and a plurality of turbine blade arrays  17  fixed on the periphery of the turbine rotor shaft  16  at intervals in the axial direction. 
         [0047]    Each of the turbine blade arrays  17  includes a plurality of turbine blades  18  (blade members) disposed on the periphery of the turbine rotor shaft  16  arranged at equal intervals in the circumferential direction. The turbine blades  18  extend toward the inner surface of the turbine casing  15 . 
         [0048]    A plurality of turbine vane arrays  19  are disposed and fixed at the inner surface of the turbine casing  15  at intervals in the axial direction. Each of the turbine vane arrays  19  includes a plurality of turbine vanes  20  disposed on the inner surface of the turbine casing  15  arranged at equal intervals in the circumferential direction. The turbine vanes  20  extend toward the turbine rotor shaft  16 . 
         [0049]    The turbine vane arrays  19  and the turbine blade arrays  17  are disposed in stages in the turbine casing  15 , the arrays  19 ,  17  alternating in the axial direction. 
         [0050]    The turbine rotor  14  may, for example, be connected to a generator that generates electricity by the rotation of the turbine rotor  14 . 
         [0051]    Of the turbine blade arrays  17  of the multiple stages, at least the turbine blade arrays  17  of one stage are constituted by turbine blades  18 , each of the turbine blades  18  includes a blade body  21  and a tip shroud  22  fixed to the blade tip of the blade body  21 . The tip shrouds  22  are disposed adjacent in the circumferential direction with a portion of adjacent tip shrouds  22  abutting. In other words, each tip shroud  22  is in contact with another tip shroud  22  of the gas turbine  1  blade adjacent in the circumferential direction. The adjacent tip shrouds  22  also push against one another. 
         [0052]    As illustrated in  FIG. 2  and  FIG. 3 , the tip shrouds  22  are planar members that act together to suppress vibrations that occur upon rotation of the turbine blades  18 . The tip shroud  22  is integrally formed with the blade body  21  at the radially outward side of the turbine blade  18 . 
         [0053]    Though not illustrated, at the radially inward side of the blade body  21 , the turbine blade  18  further includes a platform that protrudes out from the blade body  21  and a blade root that protrudes from the platform further radially inward. The turbine blades  18  are integrally fixed to the turbine rotor shaft  16  by the blade roots being mounted to the outer surface of the turbine rotor shaft  16 . 
         [0054]    As illustrated in  FIG. 2 , the blade body  21  has a curved airfoil-shaped cross section that is convex to one side in the circumferential direction (the leading side of the rotational direction R of the turbine rotor  14 , the lower side of  FIG. 2 ) from the leading edge corresponding to upstream of the combustion gas flow direction F through to the trailing edge corresponding to downstream along the axial direction. This cross section has an airfoil shape that extends toward the other side in the circumferential direction (the trailing side of the rotational direction R of the turbine rotor  14 , the upper side of  FIG. 2 ) while extending downstream in the combustion gas flow direction F (right side of  FIG. 2 ). 
         [0055]    As illustrated in  FIG. 3 , the tip shroud  22  has a planar shape with a predetermined thickness in the radial direction and is integrally fixed to the blade body  21  protruding in the circumferential direction at the radially outward side of the blade body  21 . The surface of the tip shroud  22  that faces radially outward corresponds to an outer surface  24  of the tip shroud  22 . 
         [0056]    The tip shroud  22  includes an upstream end surface  25 , which is the surface that faces one side in the axial direction corresponding to the upstream side (upstream side of combustion gas flow direction F, left side of  FIG. 2 ) and extends conforming to the circumferential direction, and a downstream end surface  26 , which is the surface that faces the other side in the axial direction corresponding to the downstream side and extends conforming to the circumferential direction. 
         [0057]    Additionally, the tip shroud  22  includes a first circumferential end surface  27 , which is the surface that faces the leading side of the rotational direction R, i.e. one side in the circumferential direction, and a second circumferential end surface  28 , which is the surface that faces the trailing side of the rotational direction R, i.e. the other side in the circumferential direction. 
         [0058]    Two minute clearances  31 ,  32  are disposed between adjacent tip shrouds  22  taking into account deformation of the tip shroud  22  upon operation. The first clearance  31  is disposed to the upstream side and the second clearance  32  is disposed downstream. 
         [0059]    The first clearance  31  and the second clearance  32  run substantially parallel to the chord direction of the blade body  21 . The first clearance  31  is disposed offset to the trailing side of the rotational direction R of the turbine rotor  14 . 
         [0060]    The first circumferential end surface  27  and the second circumferential end surface  28  include first opposing surfaces  33  ( 33   a,    33   b ), which are opposing surfaces intermediated by the first clearance  31 ; second opposing surfaces  34  ( 34   a,    34   b ), which are opposing surfaces intermediated by the second clearance  32 ; and abutting end surfaces  35  disposed between the first opposing surfaces  33  and the second opposing surfaces  34 . 
         [0061]    The abutting end surface  35  is disposed between the first clearance  31  and the second clearance  32  and runs substantially orthogonal to the extending direction thereof. At at least one end of the abutting end surface  35  (in the present embodiment, to the side of the second clearance  32 ), a relief hole  36  with a width greater than that of the clearance is provided to help prevent contact. In other words, the second clearance  32  has a distance between the second opposing surfaces  34  that is greater at the side approximate to the abutting end surface  35 . 
         [0062]    A fin  38  is formed on the outer surface  24  of the tip shroud  22 . The fin  38  protrudes radially outward and extends in the circumferential direction. The fin  38  is formed continuously on adjacent tip shrouds  22 . The fin  38  has a planar shape with the dominant surface thereof formed to run orthogonal to the axial direction. 
         [0063]    A protrusion  40  is formed on the outer surface  24  of the tip shroud  22 . The protrusion  40  reduces the amount of fluid, i.e. combustion gas, that leaks out from the second clearance  32 . The protrusion  40  is formed to extend along the second opposing surface  34 . Specifically, the protrusion  40  is formed along the second opposing surface  34 , which defines the second clearance  32 , at a position furthest to the leading side in the rotational direction R of the turbine rotor  14 . 
         [0064]    As illustrated in  FIG. 3 , the protrusion  40  includes a fluid contact surface  41 , which shares a surface with the second opposing surface  34 , and a gently inclined surface  42  connecting the radially outward end of the fluid contact surface  41  and the outer surface  24  of the tip shroud  22 . The radial height H of the protrusion  40  is a maximum of approximately five times dimension C of the second clearance  32  and preferably from approximately two to three times. 
         [0065]    As illustrated in  FIG. 4 , the protrusion  40  is formed with a height that modestly increases in the proximity of the relief hole  36 . In other words, the protrusion  40  protrudes from the outer surface  24  to a greater degree at the side approximate to the abutting end surface  35 . Note that the height of the protrusion  40  does not need to be increased in the proximity of the relief hole  36  and may be a uniform height in the extending direction. 
         [0066]    According to the embodiment described above, the protrusions  40  act as a dam and the fluid that convects in the radially outer region of the tip shroud  22  stagnates. As a result, pressure rises at the radially outward outlet of the second clearance  32  causing the flow of the combustion gas flowing at these locations to be inhibited. In other words, the amount of combustion gas that leaks out from the second clearance  32  can be reduced, thus improving the efficiency of the turbine  4 . 
         [0067]    In addition, by the protrusion  40  being provided at a position on the outer surface  24  furthest to the leading side of the rotational direction R of the turbine rotor  14 , a pressure rise occurs at the proximity of the outlet of the second clearance  32  due to stagnation. This allows the amount of combustion gas that leaks out from the second clearance  32  to be further reduced. 
         [0068]    By forming the protrusion  40  protruding from the outer surface  24  to a greater degree at the side approximate to the abutting end surface  35 , the shape of the protrusion  40  can be optimized. In other words, the height of the protrusion  40  can be made appropriate depending on the size of the second clearance  32 . 
         [0069]    Note that the protrusion  40  is not limited to a shape such as the one described above and can be changed as appropriate depending on the method of manufacturing the turbine blades  18  and the like. As illustrated in  FIG. 5  for example, a portion of the circumferential end surface  27  of the tip shroud  22  may bend radially outward. In consideration of forming the protrusion  40  on an existing tip shroud  22 , such a shape is preferable. 
         [0070]    In addition, the protrusion  40  is not limited to a position in proximity to the clearance  32 . In other words, the fluid contact surface  41  of the protrusion  40  does not need to be disposed sharing a surface with the opposing surface  34  and may be disposed at a distance from the opposing surface  34 , as illustrated in  FIG. 6 . 
         [0071]    The protrusion  40  is also not limited to being formed on the side of the second clearance  32  and may be formed on the side of the first clearance  31 . 
       Second Embodiment 
       [0072]    Hereinafter, the tip shroud  22  of a second embodiment of the present invention will be described with reference to the drawings.  FIG. 7  illustrates a cross-sectional shape of a protrusion  40 B of the second embodiment of the present invention.  FIG. 7  correlates to  FIG. 3  of the first embodiment. Note that, in the present embodiment, points that are different from the above-described first embodiment will be mainly described, and a description will be omitted of the portions that are the same. 
         [0073]    As illustrated in  FIG. 7 , the protrusion  40 B of the present embodiment is disposed at a position on the outer surface  24  of the tip shroud  22  furthest to the trailing side in the rotational direction R. In other words, the protrusion  40  is formed continuously with the opposing surface  34  of the pair of opposing surfaces  34  that is located closer to where the blade body  21  is mounted. 
         [0074]    In addition, the protrusion  4013  includes a canopy portion  44  formed covering the radially outward side of the clearance  32 . The canopy portion  44  may be formed covering all of the clearance  32  or may be formed at least partially covering the clearance  32 . In other words, the canopy portion  44  is formed at least partially overlapping the clearance  32  when the clearance  32  is viewed from a position radially outward thereof. 
         [0075]    In addition, a space D between the radially outward surface of the canopy portion  44  and the outer surface  24  is at most equal to the dimension C of the clearance. 
         [0076]    According to embodiment described above, by forming the canopy portion  44  on the protrusion  40 B, the combustion gas that leaks out from the second clearance  32  comes into contact with the canopy portion  44 . Thus, the amount of combustion gas that leaks out can be reduced. 
         [0077]    Additionally, by forming the protrusion  40 B with the canopy portion  44  continuously with the opposing surface  34  of the pair of opposing surfaces  34  that is located closer to where the blade body  21  is mounted, the tip shroud  22  which minimizes increases in bending loads due to centrifugal force can be formed. 
         [0078]    Note that in the embodiment described above, the protrusion  40  with the canopy portion  44  is formed continuously with the opposing surface  34  of the pair of opposing surfaces  34  that is located closer to where the blade body  21  is mounted. However the protrusion  40  is not limited to being formed as such. As illustrated in  FIG. 8  for example, the protrusion  40 B may be formed continuously with the opposing surface  34  of the pair of opposing surfaces  34  that is located further away from where the blade body  21  is mounted. 
         [0079]    While the above has described embodiments of the present invention in detail with reference to the drawings, each configuration of each embodiment and the combinations thereof are merely examples, and additions, omissions, substitutions, and other changes may be made without deviating from the spirit and scope of the present invention. The present invention is not to be considered as being limited by the foregoing description but is only limited by the scope of the appended claims. 
         [0080]    For example, the embodiment described above had a configuration in which one tip shroud  22  is provided with one turbine blade  18 . However the present invention is not limited thereto and one tip shroud  22  may be provided with a plurality of turbine blades  18 . 
       INDUSTRIAL APPLICABILITY 
       [0081]    According to this shroud, the protrusion acts as a dam and the fluid that convects in the radially outer region of the shroud stagnates. As a result, pressure rises at the radially outward outlet of the clearance causing the flow of the fluid flowing at these locations to be inhibited. In other words, the amount of fluid that leaks out from the clearance is reduced. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           1  Gas turbine 
           2  Compressor 
           3  Combustor 
           4  Turbine 
           6  Compressor rotor 
           7  Compressor casing 
           8  Compressor rotor shaft 
           9  Compressor blade array 
           10  Compressor blade 
           11  Compressor vane array 
           12  Compressor vane 
           14  Turbine rotor 
           15  Turbine casing 
           16  Turbine rotor shaft (rotor body) 
           17  Turbine blade array 
           18  Turbine blade (blade body, blade member) 
           19  Turbine vane array 
           20  Turbine vane 
           21  Blade body 
           22  Tip shroud (shroud, shroud body) 
           24  Outer surface 
           25  Upstream end surface 
           26  Downstream end surface 
           27  First circumferential end surface 
           28  Second circumferential end surface 
           31  First clearance 
           32  Second clearance 
           33  First opposing surface 
           34  Second opposing surface 
           35  Abutting end surface 
           36  Relief hole 
           38  Fin 
           40  Protrusion 
           41  Fluid contact surface 
           42  Inclined surface 
           44  Canopy portion 
         C Dimension of second clearance 
         D Space between radially outward surface of canopy portion and outer surface 
         H Radial height of protrusion 
         F Combustion gas flow direction 
         R Rotational direction