Patent Publication Number: US-2019170017-A1

Title: Supporting device for a casing of a turbomachine, casing for a turbomachine, and turbomachine

Description:
This claims the benefit of German Patent Application DE102017221669.7, filed Dec. 1, 2017 and hereby incorporated by reference herein. 
     The present invention relates to a supporting device for a casing of a turbomachine, for bracing against forces acting on the casing that occur during operation of the turbomachine, including at least one hub element and at least one supporting element for holding the hub element on the casing. Other aspects of the present invention relate to a casing for a turbomachine, and to a turbomachine. 
     BACKGROUND 
     The U.S. Patent Application 2017/0030223 A1 describes a gas turbine where a metallic structure is formed by a plurality of struts via which load is transmittable from a hub to a turbine casing of the gas turbine. The hub supports a rotor and transmits static and dynamic loads through the struts to the casing. The struts are formed in one piece with a surface of the hub and welded or brazed to the surface thereof, for example. A gas turbine of this type is also discussed in the British Patent Application GB 2 280 484 A. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a supporting device, a casing, as well as a turbomachine of the type mentioned at the outset in a way that will make possible an especially beneficial load distribution of forces during operation of the turbomachine. 
     A first aspect of the present invention relates to a supporting device for a casing of a turbomachine, for bracing against forces acting on the casing that occur during operation of the turbomachine, including at least one hub element and at least one supporting element for holding the hub element on the casing. The hub element may have a rotationally symmetric configuration, at least in some regions, and, for example, have a periphery where the supporting element or a plurality of supporting elements may support the casing. The supporting element may have a casing-side element end where it is joined to the casing, preferably in a material-to-material bond, thus, for example, welded thereto. 
     In accordance with the present invention, the supporting device includes at least one rotary joint for rotatably connecting the hub element to the supporting element. This is advantageous since it is hereby possible to prevent bending moments, which may be induced by forces that occur during operation of the turbomachine, from being transmitted between the supporting element and the hub element. By preventing the transfer of bending moments, unacceptably high, bending moment-induced tensile stresses are able to be effectively prevented at a join region where the supporting element is connected to the hub element. Instead, an especially favorable load distribution and load application are achieved by using at least one rotary joint to connect the hub element to the supporting element. 
     During operation of the turbomachine, the at least one rotary joint makes possible an operationally induced displacement of the hub element, for example, along a central axis of a casing opening which extends through the casing. Since the rotary joint permits relative rotation between the hub element and the supporting element, a critical deformation may be prevented whereby the supporting element is subject to critical bending moment-induced stresses. Instead, the rotary joint promotes an uncritical deformation of the supporting element. 
     Thus, in contrast to a rigid connection, for example, in the form of a welded or brazed joint, between the supporting element and the hub element, the at least one rotary joint permits at least one relative rotation about at least one axis of rotation between the at least one hub element and the at least one supporting element in response to forces, in particular axial forces, acting on the at least one hub element during operation of the turbomachine. This makes possible an especially low-stress loading of the supporting device during operation of the turbomachine. 
     Another advantageous embodiment of the present invention provides that the at least one rotary joint be in the form of an articulated joint. This is advantageous since the articulated joint makes possible a controlled rotational movement (relative rotation) about an axis of rotation. Accordingly, the articulated joint makes possible an especially controlled load distribution, respectively load application of operationally induced forces. 
     In another advantageous embodiment of the present invention, the at least one rotary joint is in the form of a spherical joint. This is advantageous since the spherical joint makes possible a plurality of rotational movements about a plurality of axes of rotation. Accordingly, the spherical joint permits a plurality of rotational degrees of freedom, whereby it is possible to even completely prevent the transfer of bending moments resulting from operationally induced forces from the hub element to the supporting element. An especially low-stress load distribution is thereby made possible. 
     In another advantageous embodiment of the present invention, the at least one rotary joint has at least one joint element that is rotatably received in a recess of the at least one supporting element or of the at least one hub element. This is advantageous since the rotary joint hereby makes possible an especially space-saving coupling between the supporting element and the hub element. Another advantage is that the rotational positioning of the joint element in the recess not only makes possible a rotational motion between the supporting element and the hub element, but a pivoting angle between the supporting element and the hub element may also be limited very economically. This is because the joint element is received in the recess, allowing it at the same time to form a limit stop where it may be braced against a plurality of locations on the supporting element upon reaching a maximally permissible pivoting angle. 
     Another advantageous embodiment of the present invention provides that the at least one joint element be received form-fittingly in the recess of the at least one supporting element or of the at least one hub element. This is advantageous since an especially captive coupling between the joint element and the supporting element or the hub element is made possible by the form-fitting receiving. Moreover, the form-fitting receiving provides an especially loadable rotary connection, where an especially large-area force distribution may be implemented between the joint element and the supporting element. 
     In another advantageous embodiment of the present invention, the at least one supporting element is in the form of a strut. This is advantageous since such a strut has an especially simple design and makes it possible to support the hub element, respectively brace against operationally induced forces acting on the casing in the presence of an especially favorable force flow. 
     In another advantageous embodiment of the present invention, the at least one hub element has a passageway for receiving a shaft element, in particular a rotor shaft, of the turbomachine. This is advantageous since the hub element renders possible an especially favorable support of the shaft element, as well as a low-stress force flow of operationally induced forces between the shaft element and the casing. 
     The hub element may preferably be designed to at least indirectly support the shaft element. A bearing element, in the form of a rolling bearing, for example, mounted on the hub element, in particular fixed thereto, may provide an indirect supporting, for example. In the post-assembly position of the supporting device and thus during normal operational use thereof, the bearing element may be mounted, in particular fixed between the hub element and the shaft element. 
     A second aspect of the present invention relates to a casing for a turbomachine, having at least one supporting device in accordance with the first aspect of the present invention. A casing of this kind makes possible an especially favorable load distribution of forces during operation of the turbomachine. 
     In an advantageous embodiment of the present invention, the casing is designed as a turbine center frame. This is advantageous since the turbine center frame may constitute an especially favorable interface between a high-pressure turbine side and a low-pressure turbine side of the turbomachine. Hot gas having a temperature of more than 1000° C. may flow through the turbine center frame from the high-pressure turbine side to the low-pressure turbine side. Because of the favorable load distribution that is attainable using the supporting device, the turbine center frame that is equipped therewith, thus that includes the same, features an especially low-stress deformation behavior, even when hot gas having such a high temperature passes through the turbine center frame. 
     A third aspect of the present invention relates to a turbomachine, having at least a supporting device in accordance with the first aspect of the present invention and/or having a casing in accordance with the second aspect of the present invention. Working with a turbomachine of this kind makes possible an especially favorable load distribution of forces that occur during operation thereof. 
     In an advantageous embodiment of the present invention, the turbomachine is a gas turbine. A gas turbine is exceptionally efficient. Moreover, a gas turbine equipped with the supporting device features an especially favorable deformation behavior, even at high gas temperatures, respectively high operationally induced forces. 
     The explanations regarding one of the aspects of the present invention, in particular regarding individual features thereof, also apply analogously to the other aspects of the present invention. 
     Other features of the present invention will become apparent from the claims, the figures, and the detailed description. The features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the detailed description and/or shown in isolation in the figures may be used not only in the indicated combination, but also in other combinations without departing from the scope of the present invention. Thus, embodiments of the present invention that are not explicitly shown and described in the figures, but derive from and can be produced from the explained embodiments using separate feature combinations, are also considered to be included and disclosed herein. Embodiments and feature combinations are also considered to be disclosed herein that, therefore, do not include all of the features of an originally formulated independent claim. Moreover, variants and feature combinations are also considered to have been disclosed herein, in particular by the above explanations that go beyond or deviate from the feature combinations described. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawing, 
         FIG. 1  shows a portion of a turbomachine; 
         FIG. 2  schematically illustrates a casing of the turbomachine, in some regions, as well as a supporting device attached to the casing in accordance with an area A shown in  FIG. 1 ; 
         FIG. 3  is a schematic representation of a hub-strut connection known from the related art. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a portion of a turbomachine  100  which is merely shown in some regions here and is in the form of a gas turbine. Turbomachine  100  includes a casing  12  which is designed here as a turbine center frame. During operation of turbomachine  100 , a shaft element  102  of turbomachine  100  rotates within a casing opening  14  of casing  12 . In addition, hot gas  104  flows through casing opening  14  of casing  12  and thereby from a high-pressure turbine side of turbomachine  100  to a low-pressure turbine side of turbomachine  100 . In the present case, casing opening  14  is in the form of a channel-type passageway. 
       FIG. 2  schematically depicts some regions of a portion of casing  12  in accordance with an outlined area A shown in  FIG. 1 , a supporting device  10  being mounted in passageway  14  of casing  12 . Supporting device  10  is used for bracing against forces that occur during operation of turbomachine  100 , such as, for example, an axial force F_A that acts on casing  12  illustrated by an arrow in  FIG. 2 . Supporting device  10  includes a hub element  40 , upon which axial force F_A acts in the present case. 
     Moreover, supporting device  10  includes a plurality of supporting elements in the form of respective struts, of which only one single supporting element  20  is shown in the present case. The supporting elements may, for example, each be joined in a material-to-material bond to casing  12 , thus, for example, welded thereto. Supporting element  20 , in the form of a strut, is used for holding hub element  40  on casing  12 . The following explanations that relate to supporting element  20  also apply analogously to the further supporting elements, which are not shown in  FIG. 2 , are disposed circumferentially along casing  12  in casing opening  14 , and are each rotatably connected to hub element  40 . 
     Hub element  40  has a passageway  42  for receiving shaft element  102  which, in the present case, is in the form of the rotor shaft of turbomachine  100 . Axial force F_A may occur, for example, in response to temperature-induced changes in the length of shaft element  102 , to name just one example. 
     Supporting device  10  includes a plurality of rotary joints, each one of which is connected to a respective supporting element, as well as to hub element  40 . In the present case,  FIG. 2  shows only one single rotary joint  30 . Rotary joints rotatably connect hub element  40  to supporting element  20 . In the present case, the rotary joints are in the form of respective articulated joints. Alternatively, the rotary joints could also be designed as respective spherical joints. The following explanations that relate to rotary joint  30  also apply analogously to the further rotary joints, which are not shown in  FIG. 2  and are each coupled to hub element  40 . 
     Rotary joint  30  may at least permit relative rotation between hub element  40  and supporting element  20  in response to axial force F_A acting on hub element  40 . 
     During operation of turbomachine  100 , rotary joint  30  (and thus all rotary joints) makes possible, for example, an operationally induced axial displacement of hub element  40 , for example, along a central axis  16  of the casing opening which extends through casing  12  and in which supporting device  10  is mounted in the present case. This central axis  16  also corresponds here to an element central axis of hub element  40 , as well as to a shaft axis of shaft element  102 . A displacement of hub element  40  causes an uncritical deformation  28  in the form of an at least slight deflection of supporting element  20 . Critical stresses are thereby at least largely prevented from occurring in supporting device  10  and, in particular, in supporting element  20 . 
     Rotary joint  30  has a joint element  32  that is rotatably received in a recess  22  of supporting element  20 . Alternatively, recess  22  could also be provided in hub element  40  and, correspondingly, joint element  32  be introduced into hub element  40 . Joint element  32  is received form-fittingly in recess  22  of the at least one supporting element  20 . 
       FIG. 3  shows a hub-strut connection  110  known from the related art that includes a strut  114  and a hub  116 . Strut  114  and hub  116  are joined to one another rigidly, for example, by a welded connection, at a join region  118 . Strut  114  is thereby welded to a casing component  112 . Axial force F_A acting on hub  116  displaces the same, causing a critical stress region  120  to occur, as denoted in  FIG. 3  by a dashed line, where unacceptably large stresses can take place. Moreover, an unfavorable, S-shaped deformation of torsionally rigid hub-strut connection  110  occurs in the area of strut  114 , as can be inferred from  FIG. 3 . 
     In contrast, in the case of supporting device  10 , the rotary joint ensures that no unfavorable stress region  120  shown in  FIG. 3 , nor S-shaped deformation occurs. Accordingly, the rotary joints also effectively prevent unacceptably high tensile stresses from occurring in supporting device  10 . The rotary joints provide a respective point of articulation which makes possible a load-oriented stress distribution that is improved over hub-strut connection  110  known from the related art. 
     Since rotary joint  30  permits relative rotation between hub element  40  and supporting element  20 , it is possible in other words to prevent the critical S-shaped deformation which leads to critical bending moment-induced stresses. Instead, rotary joint  30  promotes uncritical deformation  28  of respective supporting element  20 . In the case of uncritical deformation  28 , instead of the S-shaped deformation shown in  FIG. 3 , the result is that supporting element  20  is merely deflected, as shown in  FIG. 2 . 
     REFERENCE NUMERAL LIST 
       10  supporting device 
       12  casing 
       14  casing opening 
       16  central axis 
       20  supporting element 
       22  recess 
       28  deformation 
       30  rotary joint 
       32  joint element 
       40  hub element 
       42  passageway 
       100  turbomachine 
       102  shaft element 
       104  hot gas 
       110  hub-strut connection 
       112  casing component 
       114  strut 
       116  hub 
       118  join region 
       120  stress region 
     F_A axial force