Abstract:
A sealing system includes a bolt and a cover plate for sealing a joint between a rotor disk and a blade root of a rotor blade, the blade root being disposed in a blade root slot in the rotor disk. The sealing arrangement is used in particular in a gas turbine.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the US National Stage of International Application No. PCT/EP2014/072817 filed Oct. 24, 2014, and claims the benefit thereof. The International Application claims the benefit of European Application No. EP13193327 filed Nov. 18, 2013. All of the applications are incorporated by reference herein in their entirety. 
     
    
     FIELD OF INVENTION 
       [0002]    The present invention relates to a bolt and to a sealing system with the bolt and with a cover plate for sealing a joint between a rotor disk and a blade root, arranged in a blade root groove of the rotor disk, of a rotor blade. The sealing arrangement is provided in particular in a gas turbine. 
       BACKGROUND OF INVENTION 
       [0003]    It is known in the prior art to seal the joint between the rotor disk and the blade root by means of plate-like sealing elements. In order to axially secure such sealing plates, WO 2007/028703 A1 discloses an arrangement of rotor blades in a rotor with a shaft collar, on the outer circumference of which rotor blade retaining grooves extending in the axial direction of the rotor are provided. A projection in which a circumferential groove open radially toward the outside is provided is arranged in the region of the retaining grooves on an end side face of the shaft collar. A securing groove is associated with each rotor blade. In order to axially secure the rotor blade, a sheet-like sealing element engaging in the circumferential groove and in the securing groove is in each case provided. All sealing elements form an end sealing ring in the circumferential direction. In order to secure the sealing elements against displacement in the circumferential direction, at least one of the sealing elements comprises a metal strip fastened to the latter. The metal strip is attached to the radially inner end of the sealing element, is L-shaped, and bears against the rotor disk. 
         [0004]    In addition, other arrangements are known in the prior art which are intended to secure the sealing plates against displacement in the circumferential direction. GB 2 258 273 A thus discloses a locking arrangement for rotor blades of an axial turbo engine in which the sealing plate has a rectangular piece which fits into a recess of the blade root in the mounted state. 
         [0005]    U.S. Pat. No. 3,656,865 A discloses plates which are fixed by means of screws in the circumferential direction. 
         [0006]    EP 1 944 471 A1 discloses an arrangement with a one-piece bolt, seated in a hole, which is likewise at the same time positively connected to a sealing element associated with it, wherein the bolt is in turn secured against becoming detached by a securing plate. 
         [0007]    In U.S. Pat. No. 2,971,744 A, in order to fasten rotor blades, a washer is retained on a blade root arranged in a rotor by means of two superposed strip pins which, after passing through an open gap below the blade root, are flange-mounted between the blade root and the rotor. 
         [0008]    U.S. Pat. No. 3,887,298 A discloses a sealing device with two sealing plates, arranged opposite each other on a rotor disk, the protrusions of which, projecting into a cavity of the rotor disk, overlap, wherein the protrusion of one sealing plate has an inclined plane, as a result of which this protrusion presses radially against the other protrusion during the rotation of the rotor disk and the sealing plate is pressed against the rotor disk. 
       SUMMARY OF INVENTION 
       [0009]    An object of the present invention is to provide an improved arrangement for sealing the joint between the rotor disk and the blade root. 
         [0010]    This object is achieved with a bolt, a sealing system, and a gas turbine. Advantageous developments of the invention are given in the dependent claims and described in the description. 
         [0011]    The bolt according to the invention has a bolt length which extends from a bolt front side to a bolt rear side. The bolt has an upper part and a lower part, wherein the bolt is split into the upper part and the lower part over its entire bolt length. According to the invention, the bolt has a lug. 
         [0012]    By virtue of the structure consisting of multiple parts, the bolt can have a contour with a different shape over its bolt length but can nevertheless be mounted because the parts can be placed in their assembled position one after the other. There is more space available for the part inserted first during insertion. 
         [0013]    In its assembled position, the upper part can engage, with its lug, positively behind a cover plate. Undesired displacement of the upper part in the assembled position is thereby prevented. 
         [0014]    In an advantageous embodiment of the bolt according to the invention, the upper part has an upper part underside and the lower part has a lower part upper side. The upper part underside is shaped so that it corresponds with the lower part upper side in such a way that the upper part and the lower part can be displaced relative to each other in the direction of the bolt length. For this purpose, the upper part and the lower part are in particular provided with a groove/spring combination. 
         [0015]    The positioning of the lower part relative to the upper part is hence facilitated because the lower part is guided under the upper part by the corresponding contours when it is inserted. Lateral deviation is not possible. Correct positioning of the bolt parts in the desired end position is thus additionally ensured. 
         [0016]    In a further advantageous embodiment of the bolt according to the invention, the upper part or the lower part has a depression on the bolt front side. 
         [0017]    It is thus made possible to easily press-fit the upper part and the lower part to each other, wherein the press-fitting represents a cost-effective method step. It is thus made possible to mount the bolt simply and cost-effectively. 
         [0018]    In an advantageous embodiment, the lower part of the bolt has an inclined face on the bolt front side. 
         [0019]    As a result of the inclined face, it is ensured that the bolt parts can be mounted better and the lower part can be pushed more easily under the upper part. 
         [0020]    The sealing system according to the invention for sealing a joint between a rotor disk and a blade root, arranged in a blade root groove of the rotor disk, of a rotor blade comprises a cover plate and an above described bolt. The cover plate has an upper cover plate end side for insertion into an upper groove of the rotor blade, a lower cover plate end side arranged opposite the upper cover plate end side for insertion into a lower groove of the rotor disk, a projection arranged on the upper cover plate end side for engagement in a pocket of the upper groove, and a recess arranged on the lower cover plate end side. 
         [0021]    Circumferential securing of the cover plate is advantageously provided by the projection. The cover plate is secured against displacement simply and effectively by the projection which engages positively in the pocket of the upper groove. 
         [0022]    The cover plate can be additionally secured to the bolt by the recess. 
         [0023]    The covering system according to the invention with the bolt according to the invention is in particular integrated in a gas turbine. 
         [0024]    The gas turbine thus moreover comprises a rotor disk, a rotor blade arranged in the rotor disk. The rotor blade is provided with a blade platform, a blade leaf arranged above the blade platform, and a blade root arranged below the blade platform. A protrusion is formed by the blade platform which protrudes, at a blade root end side of the rotor blade, beyond the blade root. An upper groove, which runs along the blade root end side and is open at the bottom in the direction of the space below the blade platform, is arranged in the protrusion. The upper groove has a pocket by means of which a groove width of the upper groove is enlarged along a pocket length of the pocket. The rotor disk has a circumferential surface provided with at least one blade root groove for receiving the blade root of the rotor blade, and a circumferential lower groove which is radially open to the outside and arranged in the circumferential surface. A projection with a bolt hole for receiving the bolt is arranged on the blade root groove, adjoining the lower groove. The cover plate is arranged with its upper cover plate end side in the upper groove of the rotor blade, and with its lower cover plate end side in the lower groove of the rotor disk, and with its projection in the pocket of the upper groove. The cover plate is fixed by means of the bolt arranged in the bolt hole of the rotor disk and in the recess of the cover plate. The lug of the bolt is here arranged between the cover plate and the blade root end side. 
         [0025]    The rotor blade of the gas turbine thus has a form which corresponds to the cover plate. The projection of the cover plate projects into the pocket of the rotor blade and displacement of the cover plate in the circumferential direction is prevented. 
         [0026]    The bolt hole in the rotor disk offers the possibility of positioning the bolt and the cover plate is additionally secured against undesired displacement in the circumferential direction. In addition, a more stable seating of the cover plate is achieved by the mounting of the bolt, as a result of which the sealing is improved too. 
         [0027]    The gas turbine thus benefits from the advantages of the individual components. By means of the sealing system according to the invention, a gas turbine with securely and stably seated cover plates is provided. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]    Exemplary embodiments of the invention are explained in detail with the aid of the following description and the drawings, in which: 
           [0029]      FIG. 1  shows a gas turbine according to the invention, 
           [0030]      FIG. 2  shows a rotor blade of the gas turbine, 
           [0031]      FIG. 3  shows a cover plate of the gas turbine, 
           [0032]      FIG. 4  shows a bolt according to the invention, 
           [0033]      FIG. 5  shows an upper part of the bolt according to the invention, 
           [0034]      FIG. 6  shows a lower part of the bolt according to the invention, and 
           [0035]      FIG. 7  shows an assembled situation. 
       
    
    
     DETAILED DESCRIPTION OF INVENTION 
       [0036]    A gas turbine  10  according to the invention is illustrated in  FIG. 1  in an exemplary embodiment. The gas turbine  10  shown comprises a turbine  11  in which at least one row of rotor blades with multiple rotor blades  14  is arranged. The turbine  11  shown has four rows of rotor blades. The rotor blades  14  are part of a rotor  12  which is arranged rotatably about an axis of rotation  13 . The rotor blades  14  are fastened to a rotor disk  17 . 
         [0037]    A rotor blade  14  of the gas turbine  10  is illustrated in  FIG. 2  in an exemplary embodiment. The rotor blade  14  comprises a blade platform  43 , a blade leaf  16 , and a blade root  15 . The blade leaf  16  is here arranged above the blade platform  43 , and the blade root  15  is here arranged below the blade platform  43 . The blade leaf  16  and the blade root  15  are fastened to the blade platform  43 . The blade leaf  16  and the blade platform  43  and the blade root  15  are together formed in particular as a monolithic body. 
         [0038]    The blade platform  43  protrudes on a blade root end side  44  beyond the blade root  15 . As a result, a protrusion  45  is formed. The rotor blade  14  has an upper groove  20  in this protrusion  45 . The upper groove  20  runs essentially parallel to the blade root end side  44 . The upper groove  20  has a groove width  47  and is open at the bottom. The upper groove  20  is open in the direction of the space below the blade platform  43 . In the mounted state, the upper groove  20  is open radially, in the direction of the axis of rotation  13 . The upper groove  20  is closed above, in the direction of the space above the blade platform  43 , and to the rear  49  and the front  50 . In the mounted state of all the rotor blades  14  in the rotor disk  17 , the upper groove  20  is designed so that it is radially circumferential. In the regions between the individual rotor blades  14 , the circumferential upper groove  20  may be formed by the rotor disk  17 . In the mounted state, the groove width  47  runs lengthwise with respect to the axis of rotation  13 . The upper groove  20  has in particular an essentially rectangular cross-section. 
         [0039]    The directions to the front  50  and to the rear  49  run lengthwise with respect to the axis of rotation  13  in the mounted state. In the assembled state in the gas turbine  10 , to the rear  49  corresponds to downstream, and to the front  50  corresponds to upstream. 
         [0040]    The rotor blade  14  has a pocket  21  in the upper groove  20 . The pocket is in particular formed in the center of the blade root end side  44 . The pocket  21  can be formed to the rear  49  (cold air side) or to the front  50  (hot gas side). 
         [0041]    In the embodiment shown, the pocket is formed to the rear  49 . The pocket  21  has a specific pocket length  48 . The pocket length  48  is designed parallel to the upper groove  20 . The upper groove  20  has an increased groove width  47  in the region of the pocket  21 . 
         [0042]    A cover plate  18  of the gas turbine  10  is illustrated in  FIG. 3  in an exemplary embodiment. The cover plate  18  is in particular a metal plate. The cover plate  18  serves to seal a joint between the rotor disk  17  and the blade root  15 . 
         [0043]    The cover plate  18  has an upper cover plate end side  25  and a lower cover plate end side  26 , arranged opposite the upper cover plate end side  25 . The upper cover plate end side  25  is designed for insertion into the upper groove  20  of the rotor blade  14 , and the lower cover plate end side  26  is designed for insertion into a lower groove  41  of the rotor disk  17 . 
         [0044]    The cover plate  18  has a projection  23  on the upper cover plate end side  25 . The projection  23  has a form which corresponds to the form of the pocket  21 . The projection  23  and the pocket  21  are designed in such a way that the pocket  21  can receive the projection  23 . The pocket  21  has essentially a negative form of the projection  23 . In the embodiment shown, the projection  23  is formed in the direction of a cover plate rear side  27 , corresponding to the embodiment of the pocket  21  of the upper groove  20 , which is formed according to  FIG. 2  to the rear  49 . The pocket  21  can likewise be formed to the front  50 , and the projection  23  is then formed correspondingly in the direction of a cover plate front side  42 . 
         [0045]    The cover plate  18  shown has strengthening ribs  24  on the cover plate rear side  27  in order to increase the rigidity of the cover plate  18 . In addition, the cover plate  18  shown has a recess  28  on the lower cover plate end side  26 . 
         [0046]    As a result of this recess  28 , the cover plate  18  can be fixed in its assembled location by means of a bolt  19  according to the invention. 
         [0047]    The bolt  19  according to the invention is illustrated in  FIG. 4  in an exemplary embodiment. An upper part  29  of the bolt  19  according to the invention is shown in detail in  FIG. 5  and a lower part  30  in  FIG. 6 , in each case in an exemplary embodiment. 
         [0048]    The bolt  19  has a bolt front side  35  and a bolt rear side  36 . A bolt length  46  extends from the bolt front side  35  to the bolt rear side  36 . 
         [0049]    The bolt  19  consists according to the invention of multiple parts  29 ,  30 . The bolt  19  comprises the upper part  29  and the lower part  30 . Thus both the upper part  29  and the lower part  30  have the bolt length  46 . The upper part  29  and the lower part  30  split the bolt  19  shown into two parts over the whole bolt length  46 . The upper part  29  and the lower part  30  are thus arranged relative to each other in the mounted state in such a way that the upper part  29  bears with an upper part underside  37  on a lower part upper side  38  of the lower part  30 . The upper part underside  37  is in particular shaped to correspond with the lower part upper side  38  in such a way that the upper part  29  and the lower part  30  can be displaced relative to each other in the direction of the bolt length  46 . This is achieved in particular by a groove/spring combination. In the case of the bolt  19  shown, the upper part  29  is provided with a bolt groove  31  according to  FIG. 5 , and the lower part  30  is provided with a bolt spring  32  according to  FIG. 6 . According to the invention, other contours of the upper part underside  37  and the lower part upper side  38  are also conceivable which are formed in the same fashion along the bolt length  46  in order to be able to ensure displaceability along the bolt length  46 . 
         [0050]    In the embodiment of the bolt  19  shown, the upper part has a lug  34 . The lug  34  projects from the cylindrical contour of the bolt  19 . The lug  34  forms in particular a part of the bolt rear side  36 . The lug  34  has a lug length  51 . The lug length  51  runs lengthwise relative to the bolt length  46 . In particular, the lug length  51  is less than half the bolt length  46 . 
         [0051]    In order to press-fit the two bolt parts  29 ,  30  together in the mounted position of the bolt  19 , the upper part  29  shown has a depression  33  on the bolt front side  35 . It is also conceivable that the depression  33  is arranged on the lower part  30 . By means of local plastic projection, a positive connection can be created by press-fitting between the two parts  29 ,  30  along the bolt length  46 . 
         [0052]    In the embodiment shown, the upper part  29  and the lower part have multiple inclined faces  39 . The inclined faces  39  serve to improve the ability to mount the bolt parts  29 ,  30 . The lower part  30  which is to be pushed under the upper part  29  thus has an inclined face  39  on the bolt front side  36 . An inclined face  39  at the rear end of the bolt spring  32  serves to receive the material of the upper part  29  which is deformed during press-fitting. 
         [0053]    An assembled position is illustrated in an exemplary embodiment in  FIG. 7 . The rotor disk  17 , the rotor blade  14 , the cover plate  18 , and the bolt  19  are shown in the mounted state in a cross-sectional view. The cross-section here runs lengthwise with respect to the axis of rotation  13  over the width of the pocket  21  of the upper groove  20 . 
         [0054]    The rotor disk  17  has a circumferential surface in which multiple blade root grooves for receiving the blade roots  15  of the rotor blades  14  are provided. The rotor disk  17  has one blade root groove per rotor blade  14 . The blade root grooves are thus, as is common in the prior art, introduced in the circumferential surface essentially transversely to the circumferential direction of the rotor disk  17 . In order to mount the rotor blade  14  on the rotor disk  17 , the blade root  15  with the blade root end side  44  is pushed into the blade root groove. In the mounted state of the rotor blade  14 , the blade platform upper side is preferably flush with the circumferential surface of the rotor disk  17 . 
         [0055]    The lower groove  41  is arranged in the circumferential surface of the rotor disk  17 . The lower groove  41  is designed to be circumferential and open radially outwards. The direction radially outwards here means directed away from the center point of the rotor disk  17 . In the mounted state, the lower groove  41  is arranged opposite the upper groove  20 . The open sides of the lower groove  41  and the upper groove  20  face each other. 
         [0056]    The rotor disk  17  has, at least on one of the blade root grooves, adjoining the lower groove  41 , a projection  40  which is provided with a bolt hole  22 . 
         [0057]    The bolt hole  22  serves to receive the bolt  19  according to the invention in order to fix the cover plate  18  in its assembled position. To do this, the cover plate  18  is first brought into its end position and then the upper part  29  of the bolt  19  is passed through the bolt hole  22  of the rotor disk  17  and through the recess  28  of the cover plate  18  so that the lug  34  engages behind the cover plate  18 . The lug  34  fills the space between the cover plate rear side  27  and the blade root end side  44  lengthwise with respect to the bolt length  46 . After the upper part  29 , the lower part  20  is pushed under the upper part  29  through the bolt hole  22  of the rotor disk  17  and through the recess  28  of the cover plate  18 . The groove/spring combination of the bolt  19  here helps to position the upper part  29  and the lower part  30  relative to each other. The bolt parts  29 ,  30  are then fixed, in particular by press-fitting. The bolt  19  is fastened positively. The upper part  29  is fastened positively to the front  50  by the lug  34 . The lower part  30  is fastened positively to the front  50  by the press-fitting. The positive connection is produced in the other directions by the blade root  15  and the rotor disk  17 . 
         [0058]    In the assembled state, all the cover plates  18 , lined up one after the other, form a sealing band. It is possible that the cover plates  18  have overlapping regions (not shown here) on their sides, as a result of which the sealing effect between the cover plates  18  is increased because there is no straight continuous joint between two cover plates  18 . 
         [0059]    Although the invention has been described and illustrated in detail by the preferred exemplary embodiment, the invention is not limited by the disclosed examples, and other variants can be derived by a person skilled in the art without going beyond the scope of the invention.