Patent Publication Number: US-10781700-B2

Title: Turbine rotor blade assembly

Description:
TECHNICAL FIELD 
     The present invention relates to a turbine rotor blade assembly. 
     BACKGROUND ART 
     A steam turbine that converts, for example, thermal energy generated by thermal power into mechanical energy through working gas has been operated. The steam turbine includes stationary blades and rotor blades in casings. As the rotor blades, a plurality of ISBs (Integral Shroud Blades) provided on an outer periphery of a rotor disk are coupled (e.g., Patent Literatures 1 to 3). The rotor blades configured by the ISBs (hereinafter, ISB rotor blades) contribute to improvement of vibration strength of the rotor blades through coupling of the blades. 
     Each of the ISBs includes a platform, a blade root, a profile, and a shroud. The blade root extends from the platform inward in a radial direction of the rotor disk and is embedded in and fixed to the rotor disk. The profile extends from the platform outward in the radial direction. The shroud is provided at a top end of the profile. 
     The ISBs are coupled with use of centrifugal force loaded during operation of the steam turbine. In other words, the rotor blades are each inclined in a predetermined direction at the time of assembling; however, the rotor blades rise due to the centrifugal force loaded during operation. As a result, the shrouds are brought into a pseudo-integrated structure with use of contact reactive forces that are caused by firm contact of the shrouds adjacent to one another. In the ISB, with respect to a circumferential direction, a pitch of each of the shrouds in an inclined state is set larger than that in a raised state. Accordingly, in a case where an increasing amount of the pitch geometrically obtained is larger than a separating amount of contact surfaces due to the centrifugal force and heat in rotation, the contact surfaces of the shrouds of the ISB adjacent to one another are not separated and the coupled state is maintained during rotation. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: JP 2001-200703 A 
     Patent Literature 2: JP 2002-349204 A 
     Patent Literature 3: JP 2014-101880 A 
     SUMMARY OF INVENTION 
     Technical Problem 
     To surely realize the coupled state during operation, it is important to secure a contact reactive force from the adjacent shroud to be a contact counterpart. However, nonuniform contact in which the contact surfaces of the contact counterparts to each other are in partial contact with each other may occur due to the shapes, an assembled state, a shape error, etc. of the ISB. This makes the contact reactive forces nonuniform as the whole of the rotor blades, and it is difficult to secure vibration strength. 
     In consideration of the above, an object of the present invention is to provide a turbine rotor blade assembly that makes it possible to improve uniformity of contact reactive forces between each of shrouds and the shroud as the contact counterpart. 
     Solution to Problem 
     The present invention is a turbine rotor blade assembly provided with a plurality of turbine rotor blades in a circumferential direction of a turbine disk. Each of the turbine rotor blades includes a platform having a blade root to be embedded in the turbine disk, a profile rising from the platform, and a shroud provided at a top end of the profile. 
     The shroud according to the present invention includes a first contact end part that comes into contact with an adjacent shroud adjacent to one end side of the shroud in the circumferential direction, a second contact end part that comes into contact with an another adjacent shroud adjacent to the other end side of the shroud in the circumferential direction, and a main body part disposed between the first contact end part and the second contact end part. In the present invention, one or both of the first contact end part and the second contact end part of the shroud are lower in rigidity than the main body part. 
     The present invention includes at least the following two modes as a mode in which one or both of the first contact end part and the second contact end part are lower in rigidity than the main body part. 
     In a first mode, one or both of the first contact end part and the second contact end part include a contact surface that protrudes from the main body part in the circumferential direction and comes into contact with the adjacent shroud, and an area of the contact surface is smaller than an area of a cross-section of the main body part in a width direction. 
     The contact surface according to the present invention is preferably symmetrical in the width direction, and further preferably protrudes more than concave parts that are provided on both sides of the contact surface in the width direction. 
     In a second mode, one or both of the first contact end part and the second contact end part communicate with the main body part through a thickness-reducing part. 
     The thickness-reducing part is preferably formed to extend in the width direction or a height direction. 
     Advantageous Effects of Invention 
     According to the present invention, one or both of the first contact end part and the second contact end part are lower in rigidity than the main body part. Therefore, one or both of the first contact end part and the second contact end part elastically deform following the surface shape of a counterpart shroud when coming into contact with the shroud to be the counterpart shroud. This makes it possible to suppress nonuniform contact. Therefore, according to the present invention, it is possible to improve uniformity of the contact reactive force between each of the shrouds and the shroud as the contact counterpart. On the other hand, only a small part of the shroud is enough to contribute to improvement of uniformity of contact, which makes it possible to secure rigidity required as the shroud. As a result, it is possible to obtain a necessary contact reactive force through contact with the adjacent shroud. 
     Further, according to the first mode of the present invention, a region coming into contact with the counterpart shroud is specified, which makes it possible to more surely suppress nonuniform contact. In addition, according to the first mode, the area of the contact surface where the adjacent shroud is contacted is smaller than the area of the cross-section of the main body part. This makes it possible to enhance surface accuracy of the contact surface, and thereby it is possible to contribute to suppression of nonuniform contact. 
     In addition, according to the second mode, because the thickness-reducing portion is lower in rigidity than the main body part, the first contact end part located on the top end side of the thickness-reducing part comes into contact with the adjacent shroud. And then, the first contact end part easily elastically deforms following the contact surface of the adjacent shroud. Thereby, nonuniform contact between the contact surfaces of the shrouds adjacent to each other is possible to be surely suppressed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a partial cross-sectional view illustrating a turbine rotor blade assembly according to an embodiment of the present invention. 
         FIG. 2A  illustrates an assembled state of the turbine rotor blade assembly according to the embodiment of the present invention. 
         FIG. 2B  illustrates an operating state of the turbine rotor blade assembly according to the embodiment of the present invention. 
         FIG. 3  is a perspective view illustrating a single turbine rotor blade according to the embodiment of the present invention. 
         FIG. 4A ,  FIG. 4B  and  FIG. 4C  are respectively perspective views each illustrating a single turbine rotor blade according to another embodiment of the present invention. 
         FIG. 5A  and  FIG. 5B  are respectively partial plan views each illustrating the turbine rotor blades according to another embodiment of the present invention. 
         FIG. 6A  is a plan view of the turbine rotor blade according to another embodiment of the present invention. 
         FIG. 6B ,  FIG. 6C  and  FIG. 6D  are respectively cross-sectional views taken along a line A-A of  FIG. 6A  of the turbine rotor blade according to the another embodiment of the present invention. 
         FIG. 7A ,  FIG. 7B  and  FIG. 7C  are respectively plan views, each illustrating the turbine rotor blade according to another embodiment of the present invention, and illustrate different embodiments from each other. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present invention will be described below with reference to accompanying drawings. 
     As illustrated in  FIG. 1 , a turbine rotor blade assembly  1  according to the present embodiment includes a turbine disk  30  and a plurality of turbine rotor blades  10 . The turbine disk  30  includes a plurality of blade grooves  31  on an outer periphery thereof. The plurality of turbine rotor blades  10  are respectively held by the blade grooves  31  of the turbine disk  30  and are provided along a circumferential direction C of the turbine disk  30 . The turbine rotor blade assembly  1  is used for, for example, a steam turbine that converts thermal energy generated by thermal power into mechanical energy. Although only a part of the turbine rotor blade  1  is illustrated in  FIG. 1 , the turbine disk  30  has a disk shape, and the plurality of turbine rotor blades  10  are provided over an entire region of the turbine disk  30  in the circumferential direction. 
     Each of the turbine rotor blades  10  includes a platform  11 , a profile  13 , and a shroud  14 . The platform  11  has a blade root  12  that is inserted into and fixed to the corresponding blade groove  31  of the turbine disk  30 . The profile  13  rises from the platform  11  on a side opposite to the side provided with the blade root  12 . The shroud  14  is provided at a top end of the profile  13 . The platform  11 , the blade root  12 , the profile  13 , and the shroud  14  of each of the turbine rotor blades  10  may be integrally formed. Further, for example, the shroud  14  that is separately fabricated may be joined with the platform  11 , the blade root  12 , and the profile  13  that are integrally formed. 
     The platform  11  is a member whose appearance is a substantially rectangular in a planar view. The blade root  12  extends from a rear surface of the platform  11  toward a center in a radial direction in a state where each of the turbine rotor blades  10  is assembled to the turbine disk  30 . The blade root  12  according to the present embodiment includes teeth  12 A,  12 B, and  12 C in three stages that are formed toward a top end from a base communicating with the platform  11 . The teeth  12 A,  12 B, and  12 C each protrude toward both sides in the circumferential direction C of the turbine disk  30 . Further, a tooth space  12 D that is recessed more than the platform  11  and the tooth  12 A is provided therebetween. A tooth space  12 E that is recessed more than the tooth  12 A and the tooth  12 B is provided therebetween. A tooth space  12 F that is recessed more than the tooth  12 B and tooth  12 C is formed therebetween. Each of the blade grooves  31  of the turbine disk  30  is formed in a shape so as to be engaged with the teeth  12 A,  12 B, and  12 C, and the tooth spaces  12 D,  12 E, and  12 F. 
     The profile  13  includes a belly side part  13 A and a back side part  13 B opposite to the belly side part  13 A. The belly side part  13 A is recessed toward the back side part  13 B, and the profile  13  accordingly has a wing-shaped cross-section (see  FIG. 5 ). The turbine rotor blades  10  each receive steam at the recessed portion of the belly side part  13 A to obtain rotational driving force of the turbine disk  30 . 
     The shroud  14  is a substantially rectangular member in a planar view that is provided so as to face the platform  11  beyond the profile  13  therebetween. The shrouds  14  adjacent to one another are brought into a pseudo-integrated structure with use of contact reactive forces that are caused by firm contact of the shrouds  14  adjacent to one another. When the blade roots  12  are respectively embedded in the blade grooves  31  of the turbine disk  30  with respect to the respective turbine rotor blades  10 , the platforms  11  are arranged in the circumferential direction C along the outer periphery of the turbine disk  30 , and the profiles  13  are radially arranged in the radial direction of the turbine disk  30 . 
     As illustrated in  FIG. 2A , when the turbine rotor blade assembly  1  is assembled, the turbine rotor blade assembly  1  is inclined by a predetermined inclination angle α. The inclination angle α in the present embodiment is defined as an angle that is formed by a center line C 2  of the blade root  12  with a center line C 1  of the blade groove  31 . 
     When the turbine rotor blade assembly  1  rotates, rotation moment M occurs from the back side part  13 B toward the belly side part  13 A on each of the turbine rotor blades  10  due to centrifugal force generated on the turbine rotor blade assembly  1 . As a result, the turbine rotor blade assembly  1  is shifted from an inclined state to a raised state illustrated in  FIG. 2B . Note that  FIG. 2A  and  FIG. 2B  exaggeratingly illustrate the inclination in order to clearly show a state that the turbine rotor blades  10  are inclined. 
     In this example, a pitch P 1  ( FIG. 2A ) of the shroud  14  of each of the turbine rotor blades  10  in the circumferential direction C is set larger than a pitch P 2  ( FIG. 2B ) in the raised state during operation. Accordingly, when the turbine rotor blades  10  rise, the shrouds  14  are brought into the pseudo-integrated structure with use of the contact reactive force F that is caused by firm contact of the shrouds  14  adjacent to one another, which makes it possible to maintain a coupled state of the rotating turbine rotor blades  10 . 
     To surely realize the coupled state during operation, it is important to secure the contact reactive force from the adjacent shroud  14 . In a case where contact surfaces of the shrouds  14  adjacent to one another come into contact only partially with one another, necessary contact pressure is unobtainable. In addition, with respect to a large number of the contact surfaces, if contact regions of them are varied, the contact reactive forces easily become nonuniform. Therefore, the turbine rotor blades  10  according to the present embodiment improve uniformity of the contact reactive forces. This will be described below with reference to  FIG. 3 . 
       FIG. 3  illustrates an example of one turbine rotor blade  10  according to the present embodiment. 
     The shroud  14  of the turbine rotor blade  10  has a substantially rectangular plate shape and includes a first contact end part  15  and a second contact end part  16  that are disposed with a predetermined interval in a length direction L of the turbine rotor blade assembly  1 . Further, the shrouds  14  are provided along the circumferential direction C of the turbine rotor blade assembly  1 , each shroud  14  including a first side part  17  and a second side part  18  that are disposed with a predetermined interval in a width direction W. A portion between the first contact end part  15  and the second contact end part  16  forms a main body part of the turbine rotor blade  10 . One side of the first contact end part  15  and one side of the second contact end part  16  are connected by the first side part  17 , and the other side of the first contact end part  15  and the other side of the second contact end part  16  are connected by the second side part  18 . 
     In the shroud  14 , the first contact end part  15  is provided with a first contact surface  21  that comes into contact with the adjacent shroud  14  on one end side in the circumferential direction C during operation. The first contact end part  15  is provided with a first concave part  19  on one side in the width direction W and a second concave part  22 , which is recessed from the first contact surface  21 , on the other side of the first contact surface  21 , that the first contact surface  21  is sandwiched. Accordingly, the first contact surface  21  protrudes more than the other regions. The concave parts  19  and  22  are formed throughout a height direction H. The first contact surface  21  is formed as a flat surface, and has an area smaller than an area of a cross-section of the main body part in the width direction W. The first contact surface  21  is point-symmetrical in the width direction W. 
     In contrast, the second contact end part  16  is formed as a flat surface. A surface of the second contact end part  16 , the surface coming into contact with the first contact end part  15  of the counterpart shroud adjacent to the other end side in the circumferential direction C, is referred to as a second contact surface  23 . 
     Next, effects achieved by the turbine rotor blade assembly  1  according to the present embodiment will be described. 
     In the turbine rotor blade assembly  1 , when the inclined shrouds  14  rise at the time of operation, with respect to the shrouds  14  and  14  to be adjacent to each other, the first contact end part  15  of one of the shrouds and the second contact end part  16  of the other one face each other and come into contact with each other. At this time, the first contact end part  15  is provided with the protruding first contact surface  21 , and a part of the second contact end part  16  corresponding to the first contact surface  21  is formed as a flat surface. Accordingly, the first contact surface  21  comes into contact with the second contact surface  23  of the second contact end part  16  in preference to the other parts of the first contact end part  15 . 
     As described above, when the shrouds  14  are used, only a specific region of the first contact end part  15  always comes into contact with the second contact end part  16  of the counterpart in preference to the other regions of the first contact end part  15 . This makes it possible to make the contact regions of the plurality of shrouds  14  uniform, and to accordingly eliminate nonuniform contact between the shrouds  14  adjacent to one another. In addition, since the area of the first contact surface  21  is smaller than the area of the cross-section of the main body part of the shroud  14  in the width direction W, it is possible to enhance surface accuracy. As a result, it is possible to suppress nonuniform contact within the range of the first contact surface  21 . Moreover, the protruded part provided with the first contact surface  21  on the top end thereof is lower in rigidity than the main body part communicating the protruded part. Accordingly, when the protruded part comes into contact with the contacting shroud  14 , the protruded part elastically deforms following the surface feature of the second contact surface  23  of the second contact end part  16  of the counterpart. This also makes it possible to improve uniformity of contact. 
     On the other hand, a region which contributes to improvement of uniformity of contact is limited to a part of the shroud  14 . Accordingly, rigidity as the whole of the shroud  14  is secured, which makes it possible to obtain the necessary contact reactive force through contact with the adjacent shroud  14 . In addition, if each of the turbine rotor blades  10  is integrally molded through casting, it is unnecessary to especially add a process of manufacturing the protruding first contact surface  21 . 
     In the present invention, means for limiting the region coming into contact with the adjacent shroud  14  to a partial region of the first contact end part  15  is not limited to the mode illustrated in  FIG. 3 . As other examples thereof, modes illustrated in  FIG. 4A  to  FIG. 4C  could be applied. 
       FIG. 4A  to  FIG. 4C  each illustrate the shroud  14  whose planer shape is a rectangular. Among them,  FIG. 4A  illustrates an example in which because of a recessed part  25  which is provided along the width direction W in a predetermined region of the first contact end part  15  in the height direction H, the first contact surface  21  protrudes more than the other regions. In addition,  FIG. 4B  illustrates an example in which because of a plurality of recessed parts  26  which are formed in stripes at the first contact end part  15 , the first contact surface  21  divided into a plurality of surfaces protrudes more than the other regions. Further,  FIG. 4C  illustrates an example in which because of recessed parts  27 ,  27 , . . . arranged in a lattice shape which are formed at the first contact end part  15 , the first contact surface  21  divided into the plurality of surfaces protrudes more than the other regions. 
     In any one of  FIG. 4A  to  FIG. 4C , the surface(s) coming into contact with the adjacent shroud  14  is(are) specified and the protruded part(s) is(are) lower in rigidity than the other regions, which results in action and effects similar to those described above. 
     Note that, as with the example illustrated in  FIG. 3 , the first contact surface  21  is point-symmetrical in the examples illustrated in  FIG. 4B  and  FIG. 4C , whereas the first contact surface  21  is line-symmetrical in the example illustrated in  FIG. 4A . In the present invention, the first contact surface  21  preferably has a symmetrical shape which is a point-symmetrical shape or line-symmetrical shape in the width direction W. 
     Further, in the embodiment described above, as illustrated in  FIG. 5A , a region where the surface coming into contact with the adjacent shroud  14  is specified is provided only in the first contact surface  21  of the first contact end part  15 . The surfaces coming into contact with the adjacent shrouds  14 , however, may be specified at both of the first contact end part  15  and the second contact end part  16  respectively, as illustrated in  FIG. 5B . 
     Next, another example in which a region coming into contact with the adjacent shroud  14  will be lowered in rigidity is described with reference to  FIGS. 6A to 6D  and  FIGS. 7A to 7C . 
     In examples illustrated in  FIGS. 6A to 6D , instead of making the area of the first contact surface  21  smaller than the area of the cross-section of the main body part, at least one gap extending in the width direction W of the shroud  14  is formed to provide a thickness-reducing part where the thickness is reduced due to formation of the at least one gap. This lowers rigidity of the thickness-reducing part and facilitates elastic deformation of a part lying on the top end side of the thickness-reducing part. Note that  FIG. 6A  illustrates a basic configuration of the turbine rotor blade  10  provided with the thickness-reducing part. 
     Among them, in  FIG. 6B , concave grooves  28 A and  28 A that continuously extend in the width direction W are respectively formed on a front surface  14 F and a rear surface  14 B of the shroud  14 , to lower the rigidity of a part where the concave grooves  28 A and  28 A are formed. This allows a part lying on the top end side of the part where the concave grooves  28 A and  28 A are provided, to elastically deform following the shape of the counterpart when the part comes into contact with the adjacent shroud  14 . 
     Likewise, in  FIG. 6C , a unfilled part  28 B that penetratingly extends in the width direction W is provided, which results in action and effects similar to those in  FIG. 6B . It is unnecessary to integrally form the unfilled part  28 B, and a plurality of divided unfilled parts may be provided as illustrated in  FIG. 6D . 
     Note that the examples of the concave grooves  28 A and  28 A continuing in the width direction W and the unfilled part  28 B penetrating in the width direction W are illustrated here; however, concave grooves or unfilled parts may be intermittently provided along the width direction W in the present invention. 
     In examples illustrated in  FIGS. 7A to 7C , a gap extending in the height direction H of the shroud  14  is formed to reduce a thickness and to lower rigidity of a part where the gap is formed, which facilitates elastic deformation of a part lying on the top end side of the part where the gap is formed. 
     Among them, in  FIG. 7A , concave grooves  29 A and  29 A that penetratingly extend in the height direction H are formed at both ends of the shroud  14  in the width direction W respectively, thereby lowering rigidity of a part where the concave grooves  29 A and  29 A are formed. As a result, a part lying on the top end side of the part where the concave grooves  29 A and  29 A are provided elastically deforms following the surface feature of the contacting shroud when the part comes into contact with the adjacent shroud  14 . 
     Likewise, in  FIG. 7B , a through hole  29 B that penetratingly extends in the height direction H is formed throughout a region of the shroud  14  except for both ends in the width direction W, thereby lowering rigidity of a part where the through hole  29  is provided. Further, as illustrated in  FIG. 7C , the through hole may be divided into a plurality of through holes  29 B. 
     Note that the examples of the concave grooves  29 A and  29 A penetrating in the height direction H and the through hole  29 B penetrating in the height direction H are illustrated here; however, concave grooves or holes may be intermittently provided along the height direction H in the present invention. 
     As described above, the first contact end part  15  communicates with the main body part through the thickness-reducing part, which facilitates elastic deformation of a part lying on the top end side of the thickness-reducing part. 
     As described above, also in the shroud  14  illustrated in  FIGS. 6A to 6D  and  FIGS. 7A to 7C , the first contact end part  15  elastically deforms according to the feature of the counterpart, which makes it possible to improve uniformity of contact. 
     Other than the above, the configurations described in the above-described embodiments may be selected or appropriately modified without departing from the scope of the present invention. 
     REFERENCE SIGNS LIST 
     
         
           1  Turbine rotor blade assembly 
           10  Turbine rotor blade 
           11  Platform 
           12  Blade root 
           12 A,  12 B,  12 C Tooth 
           12 D,  12 E,  12 F Tooth space 
           13  Profile 
           13 A Belly side part 
           13 B Back side part 
           14  Shroud 
           14 B Rear surface 
           14 F Front surface 
           15  First contact end part 
           16  Second contact end part 
           17  First side part 
           18  Second side part 
           19  First concave part 
           20  First contact surface 
           21  Second concave part 
           22  Second contact surface 
           24 ,  25 ,  26 ,  27  Recessed part 
           28 A,  29 A Concave groove 
           29 B Through hole 
           30  Turbine disk 
           31  Blade groove