Patent Publication Number: US-8974186-B2

Title: Coupling element segments for a rotor of a turbomachine

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention is directed to a rotor of a turbomachine. 
     2. Description of the Related Art 
     A rotor of a turbomachine, particularly of a gas turbine or steam turbine, has a rotor base body and a plurality of rotor blades that are fastened to the rotor base body. The rotor blades of the turbomachine rotor have a blade root and a blade body. Every rotor blade is fastened by its blade root to the rotor base body in a slot of the rotor base body in a mounting direction defined by the blade roots, and every rotor blade has in the region of its blade body at least one coupling element segment constructed as an outer shroud segment when this coupling element segment is positioned on the radially outer side of the blade body. The coupling element segments, particularly the outer shroud segments, of all of the rotor blades of a turbomachine rotor of this kind together form at least one circumferentially closed coupling element of the rotor, particularly an outer shroud. 
     Considered in circumferential direction of a turbomachine rotor, a width of a coupling element segment, particularly an outer shroud segment, of every rotor blade is defined by edges extending substantially in axial direction. A depth in axial direction of the coupling element segment, particularly of the outer shroud segment, of every rotor blade is defined by edges extending substantially in circumferential direction. Aside from the width in circumferential direction and the depth in axial direction, a coupling element segment, particularly an outer shroud segment, of every rotor blade is also characterized by a thickness in radial direction. 
     Turbomachine rotors whose rotor blades have coupling element segments of the type mentioned above for forming at least one coupling element can be installed in the region of the compressor as well as in the region of a turbine of the turbomachine. 
     Turbomachine rotors having rotor blades are fastened to their rotor base body and have at the radially outer side of the blade body a coupling element segment formed as an outer shroud segment are known, for example, from DE 1 159 965 C, DE 40 15 206 C1, U.S. Pat. No. 4,400,915 A, and GB 2 072 760 A. It is known from EP 1 134 359 A1 and DE 1 122 551 C to fasten the rotor blades by the blade roots to the rotor base body in a slot of the rotor base body in a mounting direction defined by the blade roots. The blade roots can have a fir-tree contour, a hammerhead contour, or a contour of another kind. A separate slot can be provided at the rotor base body for each blade root. Further, it is possible for all of the blade roots to be fastened in a common slot and to be threaded into this common slot through an insertion opening and, in this way, mounted at the rotor base body. 
     The coupling elements of turbomachine rotors of the type mentioned above formed as outer shroud segments are exposed to high loads in operation because they rotate at maximum radius with respect to an axis of rotation of the turbomachine rotor and are therefore exposed to high centrifugal forces. As a result of the centrifugal load, corners and edges of the coupling element segments of the rotor blades bend outward so that on the one hand stress peaks are caused in the coupling element and on the other hand a desired contact between adjacent coupling element segments of adjacent rotor blades is reduced to punctiform contact or disappears entirely. This reduces or eliminates a desired coupling between adjacent coupling element segments so that the vibration behavior of the turbomachine rotor eventually deteriorates. 
     SUMMARY OF THE INVENTION 
     An object of one embodiment of the present invention is to provide a rotor of a turbomachine in which coupling of the coupling element segments of the rotor blades is ensured during operation and the rotor is easily mounted. 
     According to one embodiment of the invention, the coupling element segment of every rotor blade is contoured in such a way at a first side to which a coupling element segment of a first directly adjacent rotor blade is connected considered in circumferential direction and at a second side which is located opposite the first side and to which a coupling element segment of a second directly adjacent rotor blade is connected considered in circumferential direction that, at the first side and at the second side, a radially outer edge of the respective coupling element segment extending substantially in axial direction and a radially inner edge of the respective coupling element segment extending substantially in axial direction respectively delimit two surfaces separated from one another by a separating line, wherein, in at least one circumferential position of the rotor between two directly adjacent rotor blades, the separating lines of these directly adjacent rotor blades formed at directly adjacent sides of the coupling element segments run approximately parallel to, or in alignment with, the mounting direction of the rotor blades at the rotor base body, which mounting direction is defined by the blade roots, whereas in every other circumferential position between two directly adjacent rotor blades, the separating lines of these directly adjacent rotor blades formed at directly adjacent sides of the coupling element segments are oblique relative to the mounting direction of the rotor blades at the rotor base body. 
     With the inventive rotor of a turbomachine, an optimal support and, therefore, an optimal coupling of the coupling element segments forming the coupling element or every coupling element is ensured by the contour of the coupling element segments of the rotor blades and the rotor is easily mounted. In this way, stress peaks in the coupling element of the rotor, or in every coupling element of the rotor, can be appreciably reduced in operation and the rotor can be mounted easily. Further, the resonant frequency behavior and, therefore, the vibration behavior of the rotor according to the invention are improved and the rotor can be mounted easily. 
     Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiment examples of the invention will be described in more detail with reference to the drawings without the invention being limited to these embodiment examples. In the drawings: 
         FIG. 1  is a schematic sectional top view of a coupling element, constructed as an outer shroud, of a rotor of a turbomachine viewed from the radially outer side according to one embodiment of the invention; 
         FIG. 2  is a schematic top view of a rotor blade of the rotor in  FIG. 1 , namely, of a coupling element segment of the rotor blade of the rotor in  FIG. 1 , which coupling element segment is formed as an outer shroud segment, viewed from the radially outer side; 
         FIG. 3  is a perspective section from the rotor blade of  FIG. 2  viewed in circumferential direction I of  FIG. 2 ; 
         FIG. 4  is another perspective section from the rotor blade of  FIG. 2  viewed in circumferential direction II of  FIG. 2 ; and 
         FIG. 5  is a schematic sectional top view of a coupling element, constructed as an outer shroud, of a rotor according to the invention of a turbomachine viewed from the radially outer side. 
     
    
    
     DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS 
     The present invention is directed to a rotor of a turbomachine, particularly a rotor of a compressor or of a turbine of a turbomachine constructed as a gas turbine or steam turbine. However, the invention is not limited to these applications; rather, the invention can be put to use in all turbomachine rotors. 
     A rotor of a turbomachine basically has a rotor base body and a plurality of rotor blades fastened by blade roots to the rotor base body. The rotor base body and the blade roots of rotor blades are not shown in detail in  FIGS. 1 to 5  because those skilled in the art will be familiar with these details. However, it should be noted in this connection that every rotor blade is fastened by its blade root to the rotor base body in a slot of the rotor base body in a mounting direction defined by the blade roots. For this purpose, a separate slot can be provided at the rotor base body for every rotor blade or blade root of every rotor blade. Further, it is possible for all of the rotor blades to be fastened by their blade roots in a common slot and threaded into this common slot through an insertion opening and, in this way, mounted at the rotor base body. 
     The mounting direction M of the rotor blades at the rotor base body defined by the blade roots is shown schematically by dashed lines in  FIGS. 1 and 5 . In  FIGS. 1 and 5 , a separate slot is provided at the rotor base body for the blade root of every rotor blade. In  FIG. 1 , the mounting direction M extends in a straight line, and in  FIG. 5  the mounting direction M extends in a curved line. In both cases, viewed in axial direction A of the rotor, the mounting direction M of the rotor blades inclines in a first orientation in circumferential direction U relative to axial direction A. The mounting direction M and the axial direction A enclose a rhomboid angle which changes in axial direction A when the mounting direction M is curved. Aside from axial direction A and circumferential direction U of the rotor, a radial direction R is also shown. 
       FIGS. 1 to 4  show different detailed views of a rotor according to one embodiment of the invention of a turbomachine.  FIG. 1  shows a section from a coupling element formed as an outer shroud which comprises coupling element segments  10 ,  10 ′,  10 ″ of a plurality of rotor blades, these coupling element segments  10 ,  10 ′,  10 ″ being constructed as outer shroud segments. As can be seen most clearly from  FIGS. 3 and 4 , the outer shroud segments  10 ,  10 ′,  10 ″ are associated with a radially outer end of a blade body  11  of the respective rotor blade. The blade body  11  has a flow inlet edge  12 , a flow outlet edge  13 , a suction side  14 , and pressure side  15  extending between the flow inlet edge  12  and the flow outlet edge  13 . 
     The outer shroud segment  10 ,  10 ′,  10 ″ associated with the blade body  11  of every rotor blade on the radially outer side has a width in circumferential direction U which is defined by edges extending substantially in axial direction A. Accordingly, a radially outer edge  18  and  19 , respectively, extending substantially in axial direction A and a radially inner edge  20  and  21 , respectively, which likewise extends substantially in axial direction A extend, respectively, at two opposite sides  16  and  17  of the outer shroud segment  10 ,  10 ′,  10 ″. The distance between this radially outer edge  18  and  19 , respectively, and this radially inner edge  20  and  21 , respectively, determines the thickness of the outer shroud segment  10 ,  10 ′,  10 ″ at sides  16  and  17  in radial direction R. 
     A depth in axial direction A of the outer shroud segment  10 ,  10 ′,  10 ″ of every rotor blade is defined by edges extending substantially in circumferential direction U, namely, again, by radially outer edges  22  and  23 , respectively, and radially inner edges  24  and  25 , respectively. Edges  22  and  24  are edges on the flow inlet side, and edges  23  and  25  are edges on the flow outlet side. Also, the distance between these edges determines the thickness of the outer shroud segment  10 ,  10 ′,  10 ″ in radial direction R, namely, on the flow inlet side and flow outlet side. 
     Viewed from the radially outer side, the contour of the outer shroud segment  10 ,  10 ′,  10 ″ of every rotor blade is carried out in such a way in the region of a first side  16  at which an outer shroud segment of a first directly adjacent rotor blade adjoins a second side thereof in circumferential direction U that, adjacent on the flow inlet side to the flow inlet edge  12  of the blade body  11  of each respective rotor blade, the radially outer edge  18  of the outer shroud segment  10 ,  10 ′,  10 ″ extending essentially in axial direction A projects out in circumferential direction U relative to the radially inner edge  20  of the outer shroud segment  10 ,  10 ′,  10 ″ extending substantially in axial direction A. 
     At this first side  16  facing the flow outlet edge  13  on the flow outlet side, the radially inner edge  20  of the outer shroud segment  10 ,  10 ′,  10 ″ extending substantially in axial direction A projects out in circumferential direction U relative to the radially outer edge  18  which likewise extends substantially in axial direction A. 
     At the opposite, second side  17  of the outer shroud segment  10 ,  10 ′,  10 ″ to which a directly adjacent second rotor blade is connected with its outer shroud segment, namely with a first side thereof, the contour of this outer shroud segment is carried out such that, adjacent on the flow outlet side to the flow outlet edge  13  of the blade body  11 , the radially outer edge  19  of the outer shroud segment  10 ,  10 ′,  10 ″ extending essentially in axial direction A projects out in circumferential direction U relative to the radially inner edge  21  which likewise extends substantially in axial direction A. 
     At this second side  17  remote of the flow inlet edge  12  on the flow inlet side, the radially inner edge  21  of the outer shroud segment  10 ,  10 ′,  10 ″, extending substantially in axial direction A, projects out in circumferential direction U relative to the radially outer edge  19  which likewise extends substantially in axial direction A. 
     At the first side  16  of the outer shroud segment  10 ,  10 ′,  10 ″ that faces toward the flow inlet edge  12  of the blade body  11  and faces away from the flow outlet edge  13  of the same, and at the second side  17  of the outer shroud segment  10 ,  10 ′,  10 ″ that faces toward the flow inlet edge  13  of the blade body  11  and faces away from the flow inlet edge  12 , the radially outer edges  18  and  19 , respectively, which extend substantially in axial direction A, together with the radially inner edges  20  and  21 , respectively, which likewise extend substantially in axial direction A, respectively delimit two surfaces separated from one another by a separating line  26  and  27 , respectively, namely, a surface  28  and  29 , respectively, which is concealed considered from the radially outer side and a surface  30  and  31 , which is visible viewed from the radially outer side. 
     At the first side  16  of the outer shroud segment  10 ,  10 ′,  10 ″, the surface  28  is concealed from the radially outer side is positioned on the flow inlet side and the surface  30  which is visible from the radially outer side is positioned on the flow outlet side. In the region of the opposite second side  17  of the outer shroud segment  10 ,  10 ′,  10 ″, on the other hand, the surface  29 , which is concealed from the radially outer side, is positioned on the flow outlet side and the surface  31  is visible from the radially outer side and is positioned on the flow inlet side. 
     According to one embodiment of the invention, in at least one circumferential position of the rotor between two directly adjacent rotor blades, the separating lines  26 ,  27  of these directly adjacent rotor blades formed at directly adjacent sides of the respective coupling element segments  10 ′ and  10 ″ run approximately parallel to, or in alignment, with the mounting direction M of the rotor blades at the rotor base body, which mounting direction M is defined by the blade roots, whereas, in every other circumferential position between two directly adjacent rotor blades, the separating lines  26 ,  27  of these directly adjacent rotor blades formed at directly adjacent sides of the respective coupling element segments  10 ,  10 ′ and  10 ″ are oblique to the mounting direction M. 
     As was already stated, the mounting direction M of the rotor blades at the rotor base body, viewed in axial direction A of the rotor, is inclined by the rhomboid angle relative to the axial direction A in a first orientation in circumferential direction U. At the circumferential position, or at every circumferential position, of the rotor at which the separating lines  26 ,  27  formed at the directly adjacent rotor blades extend approximately parallel to, or in alignment with, the mounting direction M of the rotor blades at the rotor base body defined by the blade roots, the separating lines  26 ,  27  are inclined in circumferential direction U relative to the axial direction A in the same first orientation as the mounting direction. On the other hand, at the circumferential position, or at every circumferential position, of the rotor between two directly adjacent rotor blades, the separating lines  26 ,  27  are inclined in circumferential direction relative to the axial direction in a second orientation opposite to the first orientation as the mounting direction M. 
     Due to the above-mentioned contours of the coupling element segments  10 ,  10 ′ and  10 ″ of the rotor blades, an optimal support and, therefore, an optimal coupling of the coupling element segments forming the coupling element, or every coupling element, is ensured while facilitating the mounting of the rotor. Accordingly, the separating lines  26  and  27 , which are oblique to the mounting direction M at directly adjacent sides of the coupling element segments  10 ,  10 ′ and  10 ″, ensure an optimal support and, therefore, an optimal coupling of the coupling element segments. The separating lines  26  and  27  that extend approximately parallel to, or in alignment with, the mounting direction M at directly adjacent sides of the coupling element segments  10 ′ and  10 ″ facilitate the mounting of the last rotor blade to be mounted at the rotor base body in particular. It is sufficient when the separating lines  26 ,  27  formed at directly adjacent sides of the respective coupling element segments  10 ′ and  10 ″ extend approximately parallel to, or in alignment with, the mounting direction M of the rotor blades at the rotor base body at one individual circumferential position of the rotor between two directly adjacent rotor blades. But this can also be the case at a plurality of circumferential positions of the rotor for improving the vibration behavior. 
     Stress peaks can be appreciably reduced in the coupling element, or every coupling element, of the rotor in operation by the above-mentioned contours of the coupling element segments  10 ,  10 ′ and  10 ″ of the rotor blades, and the rotor can be mounted easily. Further, the resonant frequency behavior and, therefore, the vibration behavior of the rotor according to the invention can be improved while facilitating mounting. 
     The separating lines  26 ,  27  enclose an angle of at most about 10°, preferably at most 5°, with the mounting direction M at the circumferential position, or at every circumferential position, of the rotor at which the separating lines  26 ,  27  formed at the coupling element segments  10 ,  10 ′ and  10 ″ of directly adjacent rotor blades run approximately parallel to the mounting direction M of the rotor blades at the rotor base body, which mounting direction M is defined by the blade roots. 
     The radially outer edges  18  and  19 , respectively, which extend substantially in axial direction A and the radially inner edges  20  and  21 , respectively, which likewise extend substantially in axial direction A and which delimit the surfaces  28 ,  29 ,  30  and  31 , respectively, together with the separating lines  26 ,  27  preferably also run in the same orientation as the separating lines  26 ,  27 . 
     When a separating line  26  or  27  runs approximately parallel to, or in alignment with, the mounting direction M of the rotor blades, the respective edges  18 ,  20  and  19 ,  21 , respectively, also run approximately parallel to, or in alignment with, the mounting direction M. 
     When a separating line  26  or  27  is oblique to the mounting direction M of the rotor blades, the respective edges  18 ,  20  and  19 ,  21 , respectively, are also oblique to the mounting direction M, namely in the same orientation as the respective separating line  26  or  27 . 
     The separating lines  26  and  27  which separate the surfaces  28  and  30  and surfaces  29  and  31  from one another, respectively, at the first side  16  and at the second side  17  are constructed according to a preferred further development of the invention so as to be without an inflection point, these separating lines  26  and  27  extending in a straight line in the embodiment example shown in  FIGS. 1 to 4  and in a curved line in  FIG. 5 . This allows an especially simple manufacture. The edges  18 ,  19 ,  20  and  21  extending substantially in axial direction A are likewise constructed without an inflection point. 
     In the embodiment example in  FIGS. 1 to 4 , the separating line  26  of the first side  16  is visible viewed from the radially outer side, whereas the separating line  27  of the second side  17  is concealed considered from the radially outer side. According to  FIGS. 3 and 4 , the separating lines  26  and  27  of the two sides  16 ,  17  run from the radially outer side to the radially inner side, respectively, proceeding from edges on the flow inlet side to edges on the flow outlet side. 
     In the area of the first side  16  of the outer shroud segment  10  and of the opposite, second side  17  of the outer shroud segment  10 , the surfaces  28  and  29 , respectively, are concealed from the radially outer side and the surfaces  30  and  31 , respectively, and are visible when viewed from the radially outer side are inclined by an angle relative to the radial direction R considered along the respective separating line  26  and  27 . The surfaces  28  and  29 , respectively, are concealed from the radially outer side are inclined relative to the radial direction R by a first angle and the surfaces  30  and  31 , respectively, and are visible from the radially outer side are inclined relative to the radial direction R by a second angle. At the first side  16  and second side  17 , the first angle and second angle are preferably identical with respect to degree but have different mathematical signs. This is particularly advantageous in technical respects relating to manufacture. In contrast, however, it is also possible that the first angle and the second angle at the first side  16  and second side  17  differ in degree but again have different mathematical signs. 
     According to one embodiment of the invention, the surfaces  28  and  29 , respectively, which are concealed from the radially outer side and the surfaces  30  and  31 , respectively, which are visible from the radially outer side have a surface ratio of 1:1 at the first side  16  of the outer shroud segment  10  and at the second side  17  of the outer shroud segment  10 , which means that the surfaces  28  and  29 , respectively, which are concealed from the radially outer side and the surfaces  30  and  31 , respectively, which are visible from the radially outer side are identically dimensioned at the two sides  16  and  17 . It should be noted that these surfaces can also have different dimensions at the first side  16  and at the second side  17 . Accordingly, it is possible that the surfaces  28  and  29 , respectively, which are concealed from the radially outer side and the surfaces  30  and  31 , respectively, which are visible from the radially outer side have a surface ratio of up to 1:5 or up to 5:1, particularly a surface ratio of up to 1:3 or up to 3:1, at the first side  16  and/or at the second side  17 . By deliberately increasing or decreasing the surface ratio between the surface  28  and  29 , respectively, which is concealed from the radially outer side and the surface  30  and  31 , respectively, which is visible from the radially outer side at sides  16  and  17 , it is possible to adapt the desired coupling between the outer shroud segments  10  of adjacent rotor blades in an optimal manner. This can also be carried out by the above-mentioned angles which are enclosed by these surfaces with the respective separating line  26  and  27 , respectively. 
     As can be seen most clearly from  FIG. 1 , the radially outer edges  18  and  19 , respectively, which extend substantially in axial direction A and the radially inner edges  20  and  21 , respectively, which extend substantially in axial direction A are congruent with one another exclusively in an axial position when viewed from the radially outer side at the first side  16  and at the second side  17  of the outer shroud segment  10 . 
     According to  FIGS. 1 to 4 , the surfaces  28  and  29 , respectively, and the surfaces  30  and  31 , respectively, formed at the sides  16  and  17  of the outer shroud segment  10  have a three-dimensional contour and are spatially radially curved. Edges  32  which extend substantially in radial direction and which delimit the outer shroud segment  10  together with edges  18 ,  19 ,  20 ,  21 ,  22 ,  23 ,  24  and  25  are accordingly curved. 
     In contrast, it is also possible that these surfaces  28 ,  29 ,  30  and  31  are constructed as two-dimensionally contoured, plane surfaces. Edges  32  extend substantially in radial direction and which delimit the outer shroud segment  10  together with edges  18 ,  19 ,  20 ,  21 ,  22 ,  23 ,  24  and  25  accordingly run in a straight line. 
     The embodiment example from  FIG. 5  differs from the embodiment example of  FIGS. 1 to 4  only in that the mounting direction M of the rotor blades is curved instead of running in a straight line. The embodiment example of  FIG. 5  corresponds to the embodiment example of  FIGS. 1 to 4  with respect to the rest of the details, so that the above statements may be referred to in this regard. 
     Further modifications of the invention are possible. For example, it is possible that the radially outer edges  18  and  19  and the radially inner edges  20  and  21  extend substantially in axial direction A and define the width of the outer shroud segment  10  in circumferential direction U also have a curved contour or extend in a curved manner but without an inflection point, respectively, at the two opposite sides  16  and  17  in the same way as the separating lines  26 ,  27 . Further, it is possible that a rotor according to the invention not only has a coupling element formed as an outer shroud segment  10  but also a coupling element formed as an inner coupling element. In this case, the outer shroud segments and inner coupling element segments are formed in the manner described above. Further, it is possible that a rotor according to the invention has no outer shroud segment but rather exclusively at least one coupling element segment formed as an inner coupling element segment. Further, it is possible that the separating line  26  of the first side  16  is concealed considered from the radially outer side, whereas the separating line  27  of the second side  17  is visible considered from the radially outer side. 
     Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.