Abstract:
A tubular housing for a turbomachine is provided. The tubular housing includes two half-tube shells which, lying against one another in two connecting regions overlap partially in each case in the tangential direction of the tubular housing. In order to specify a particularly reliable and permanent connection of the two half-tube shells which additionally develop a particularly satisfactory sealing action, it is proposed that, in order to interlock the half-tube shells in the tangential direction, in relation to the tube axis of the housing, at least one eccentric pin is provided in one or both connecting regions.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the US National Stage of International Application No. PCT/EP2011/069103 filed Oct. 31, 2011 and claims benefit thereof, the entire content of which is hereby incorporated herein by reference. The International Application claims priority to the European Patent Office application No. 10194762.0 EP filed Dec. 13, 2010, the entire contents of which is hereby incorporated herein by reference. 
     
    
     FIELD OF INVENTION 
       [0002]    The invention relates to a tubular housing for a section of the housing of a turbomachine, comprising two half-tube shells which, when in mutual abutment in two connection regions, overlap in each case in the tangential direction of the tubular housing. 
       BACKGROUND OF INVENTION 
       [0003]    Particularly in the context of turbomachines provided for generating electrical energy, it is known to form the housing thereof from two housing halves. Both housing halves are thus in the shape of a half-tube, so that an upper housing half and a lower housing half are present. At the circumferential ends of each housing half, flanges extend in the radial direction of the housing of annular cross section. A joint, which divides the housing, exists between the flanges of the housing halves which are in mutual abutment. On account of dividing the housing into halves, one can also refer to a dividing plane, with the axis of the machine lying in this plane. The diameter and axial direction of the housing thus span the dividing plane. A multiplicity of bores, through which in each case individual expansion screws screwed tight on both sides of the flanges extend, are provided in the flanges. The expansion screws press the flanges, which are in mutual abutment in the dividing plane, tightly against each other under high prestress in order to prevent as far as possible—or if at all to allow to only an extremely small extent—a leakage flow of the medium, which is conducted inside and is under high pressure, to the outside. The above-described housing arrangement, which is also known for example from EP 1 387 706 A1, is employed in particular in the context of stationary gas turbines and gas turbines provided for generating energy and also in the context of steam turbines. 
         [0004]    In order to seal the flanges which are in mutual abutment to the greatest possible extent, it is necessary to provide as many screw connections as possible at comparatively small intervals along the axial extent of the tubular housing. However, the flanges mean that the concentration of housing material varies along the circumference of the housing. Locally varying rapid heating of the housing occurs in connection with the temperatures which arise during operation of the aforementioned turbomachines, depending on whether there is more or less material to be heated by the hot working medium flowing inside. This leads to different thermal expansion at different positions on the housing, whereby the housing becomes oval in shape. This ovalization can lead to radial gaps of irregular size between the rotor blade tips and the wall lying opposite these and can, in extreme cases, lead to the rotor blade tips rubbing against the wall. The gaps of irregular size can lead to performance losses. The rubbing endangers the integrity of the blades on the one hand and the operation of the gas turbine on the other. To that extent, the aim is to avoid ovalization as far as possible. In addition, there is a delay in the flanges heating from the inside outwards, such that the screw connections which are arranged perpendicular to the flanges are also subject to a certain flexural tension, which can lead to plastic deformations of the flange screw connections which are usually already expanded as far as the elastic limit. Following plastic deformation, the prestress provided by the expansion screw in question for the flanges in mutual abutment is reduced, thus negatively affecting the sealing of the dividing joint. In addition, creep effects reduce the lifespan of the screw connections. 
         [0005]    As an alternative solution to the flange connections of housing parts, an inner housing of a steam turbine which is designed substantially as a hollow cylinder is known from laid-open application DE 10 2006 038 021 A1. The two housing parts which form the housing have in the region of the separation plane two overlapping regions which are positioned opposite each other and have wall sections which are in each case in mutual abutment and overlap in the circumferential direction. The overlapping wall sections each have only half the wall thickness that is otherwise present, such that the wall thickness as seen in the circumferential direction is always constant. The two mutually overlapping wall sections of the housing parts are then screwed to each other. It is thus possible to avoid the above-mentioned drawbacks with respect to the differential concentrations of mass at different positions on the circumference, resulting in reduced ovalization of the housing. It is disadvantageous, however, that the screw connections do not make it possible to generate adequate contact pressure between the wall sections in mutual abutment. This can result in relative movements of the wall sections pressed against each other, whereby it is possible for the screws to experience an additional shear load. This additional load can lead to premature failure of the screws, endangering the safe operation of a turbomachine equipped therewith and possibly causing leaks. To that extent, efforts focus on solutions which reliably exclude these shortcomings. 
         [0006]    Notwithstanding this, the aim is to continuously raise both the working temperature of the working medium of the turbomachine and the pressure thereof, in order to achieve greater power and greater efficiency of the turbomachine. This too leads to an increased requirement with respect to the leaktightness of the connection regions and long-term reliability of tubular turbomachine housings which have been divided into halves. 
         [0007]    Furthermore, screw-connecting two overlapping elements using eccentric screws is known both from U.S. Pat. No. 1,097,185 and from U.S. Pat. No. 3,006,443. The eccentrics of US 1,097,185 serve to tension the two overlapping elements. U.S. Pat. No. 3,006,443 provides a countersunk arrangement of the eccentric screw in order to reduce flow resistance. 
       SUMMARY OF INVENTION 
       [0008]    The invention is based on the object of providing a tubular housing for a turbomachine which consists of two halves of a tube and, while avoiding the drawbacks known from the prior art, is additionally designed so as to be especially reliable, long-lived and extremely leaktight. 
         [0009]    The object is achieved by a tubular housing according to the features of the claims Advantageous configurations are respectively the subject of subclaims. 
         [0010]    A housing according to the invention is distinguished by the fact that at least one eccentric bolt is provided in one or both connection regions for tensioning the half-tube shells which partially overlap each other in the tangential direction with respect to the tube axis of the housing. 
         [0011]    The invention has recognized that the screw connections, known from the prior art, of the wall sections which overlap one another in the tangential direction can transmit transverse forces only by means of friction. In order to remedy this and so as to be able to take up larger transverse forces, the invention combines, in a previously unknown manner, two functional and operational principles for the separable connection of divided housings. The invention proposes transmitting the transverse forces which arise in the tangential direction according to the principle of bearing surfaces within the hole. A bolt seated without play in correspondingly dimensioned bores is provided for this purpose, which bores are in each case arranged in an overlap section of the corresponding half-tube shell. At the same time, a relative displacement of the two half-tube shells should be possible in order to be able to better adjust the centricity of the housing and tension the two half-tube shells with respect to each other in the tangential direction. To that end, a section of the bolt is designed as an eccentric, such that the bolt which is then formed as an eccentric bolt allows for the two half-tube shells to be tensioned or displaced with respect to each other during assembly following the lever principle. 
         [0012]    The transverse forces are de facto taken up and/or transmitted with the aid of a plurality of eccentric bolts. To this end, a plurality of eccentric bolts are preferably provided distributed in the axial direction in the connection region, by means of which bolts the two half-tube shells of the housing can be moved with respect to each other and thereby tensioned in the circumferential direction during assembly. The two half-tube shells are thus connected to one another without play as seen in the circumferential direction with the aid of the eccentric bolts. 
         [0013]    During operation, the eccentric bolts are loaded as shear bolts, without also being subjected to a tensile load. It is thereby possible for these to take up larger forces, as a result of which the housing according to the invention can in particular take up and house further increased pressures inside the housing without unusually great or impermissibly high leakage rates arising through the partial joint present in the connection region. The use of the eccentric bolts capable of higher loading thus also leads to safe operation of a turbomachine equipped with a housing according to the invention. 
         [0014]    The eccentric bolt has a head for turning the eccentric bolt, an eccentric section and a shaft section, wherein the eccentric section is arranged in the connection region in one of the two half-tube shells and the shaft section is arranged in the connection region in the other of the two half-tube shells. The eccentric bolt thus extends transversely to the two partially mutually overlapping half-tube shells and is oriented substantially radially with respect to the tube axis of the housing. 
         [0015]    The shaft section or the eccentric section is in addition mounted in a compensating element, which is mounted such that it can be displaced axially but is fixed in rotation in or relative to one of the two half-tube shells. This makes it possible, when adjusting the eccentric bolt, to prevent a relative movement of the two half-tube shells in the axial direction and obtain only a relative movement in the tangential direction, since the compensating element can compensate for the axial relative displacement which also usually takes place when the eccentric bolt is turned. To this end, the compensating element must be mounted such that it can be displaced in the axial direction but is without play in the tangential direction with respect to the half-tube shell in which it is held. As a consequence, the two half-tube shells then perform only a tangential relative displacement, making it possible for the housing according to the invention to be rigidly attached at its axial ends to further components. 
         [0016]    In one advantageous embodiment, the two half-tube shells are tensioned—that is to say pressed against each other areally—radially with respect to the tube axis of the housing in the respective connection region by means of at least one screw connection. In combination with the eccentric bolt connection of sheet-like components, i.e. the half-tube shells, the additional use of the screw connections leads to a further improved connection, since the overlap sections can also take up friction forces at their contact surfaces which extend in the tangential direction. In addition, this ensures close areal contact between the two overlap sections. This prevents the presence of an air gap between the overlap sections which would lead to different thermal behavior of the two overlap sections and thus to different mechanical loads. Consequently, the screw connections ensure a particularly good transfer of heat between the two overlap sections. In addition, the screw connection stiffens the connection region. The use of the eccentric bolts also reliably protects the screw connections from shear forces. This ensures a screw connection between the housing halves which is reliable in the long term. 
         [0017]    Particular preference is given to that embodiment in which at least two screw connections which are adjacent in the circumferential direction are provided in each connection region. As a result, although it is necessary to have overlap sections which are relatively long in the tangential direction, this configuration increases, on the one hand, the contact surface which is relevant for friction forces and lengthens, on the other hand, the leakage path for the medium conducted inside the housing. In addition, the contact pressure in the contact surface of the half-tube shells can be increased. 
         [0018]    According to a further advantageous embodiment, a plurality of eccentric bolts are distributed along the axial direction in the respective connection region, wherein the eccentric bolts are in each case articulated, via a lever fastened thereto, to at least one rod assembly for the synchronous adjustment of the eccentric bolts. The only requirement for this is that the central axes of the eccentric bolts be parallel and the position or arrangement thereof permit the use of the rod assembly. The limited turn angle necessary for generating the prestress also means that the eccentric bolts can easily be coupled to each other using individual levers articulated to a common rod assembly. Actuating the rod assembly adjusts the eccentric bolts synchronously. This leads on one hand to an even and distributed input of force for tensioning the two half-tube shells in the tangential direction. On the other hand, assembly is then very quick. Unwanted distortion of one of the two half-tube shells by successive tightening of the eccentric bolts is hereby also precluded. In the event that the drive of the rod assembly is also self-locking, this configuration secures the eccentric bolts against unintentional independent loosening. 
         [0019]    A further advantage results from the use of seals in the partial joint surfaces. The respective connection region therefore comprises a sealing region, in which is situated a sealing means for sealing off the internal housing space with respect to the external space. The sealing means can then carry out their function optimally, as the relative movement forced by eccentric bolts during assembly can be used to accurately predict the simultaneously accompanying deformation of the sealing means. This allows the sealing means to be very well matched to the embodiment, which leads to very high leaktightness. 
         [0020]    That the housing is tubular does not necessarily mean that it is cylindrical. Rather, tubular means that the cross section is substantially circular. Accordingly, the housing can vary also in diameter along its axial direction, as necessary. It can thus also be designed conically in the axial section according to the invention. It is also possible for the housing to be designed as a guide vane carrier of a turbomachine, which guide vane carrier has on its inward facing lateral surface means for attaching guide vanes arranged in one or more rings. Of course, an outer housing of a stationary compressor or of a stationary turbine—for example a steam turbine or a gas turbine 1 &#39;can also comprise at least one axial section designed as a tubular housing in the sense of the previously described configurations. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    Further advantages, features and properties of the invention will be explained in more detail with reference to a preferred exemplary embodiment in the following drawing. Expedient configurations result from advantageous combinations of features. In the drawing: 
           [0022]      FIG. 1  shows a part of the cross section of a tubular housing according to a first configuration. 
           [0023]      FIG. 2  shows an eccentric bolt in a side view. 
           [0024]      FIG. 3  shows a side view of a housing according to an alternative configuration. 
           [0025]      FIG. 4  shows the detail from the cross section of the housing according to  FIG. 1  with an alternative overlap. 
       
    
    
     DETAILED DESCRIPTION OF INVENTION 
       [0026]    A detail of a tubular housing  10  for a turbomachine is shown in a cross sectional representation in  FIG. 1 . The housing  10  comprises two half-tube shells  12 ,  13  which each extend over an arc length of somewhat more than 180°. Both half-tube shells  12 ,  13  here have a wall thickness d over a large portion of their arc length, this wall thickness being constant along this extent. Overlap sections  18 ,  19  of the half-tube shells  12 ,  13  respectively adjoin the latter at each circumferential end, the wall thickness of these overlap sections being just half the wall thickness d. For reasons of strength, however, the wall thicknesses of the overlap sections  18 ,  19  can also be slightly greater than half the wall thickness d. Both overlap sections  18 ,  19  end respectively at the circumferential end points  15 . The two half-tube shells  12 ,  13  thus overlap in a connection region  14 , with the overlap sections  18 ,  19  being in mutual areal abutment in a contact region  16 . In a conventional manner, the tubular housing  10  here comprises two connection regions  14 , which are situated at mutually opposite positions of the circumference of the housing  10 . 
         [0027]    The two half-tube shells  12 ,  13  are connected to each other in the connection region  14  with the aid of at least one eccentric bolt  20 . The eccentric bolt  20  is shown in a side view in  FIG. 2  and comprises, in succession, an eccentric head  22  to which are attached, in succession, an eccentric section  24 , a shaft section  26  and a threaded section  28 . The shaft section  26  has in this case a central axis  30  which coincides with the central axis of the eccentric head  22 . The central axis  32  of the eccentric section  24  is, in a known manner, offset by a distance e from the central axis  30  of the shaft section  26 . 
         [0028]    In the exemplary embodiment shown, the eccentric head  22  is designed as an external hexagon. The eccentric head  22  can of course also be designed for other forms of drive, such as an internal hexagon or radial bores for accommodating a rotary rod. 
         [0029]    A bore is provided in each of the two overlap sections  18 ,  19 . The diameter of the bore  34  located in the overlap section  19  corresponds to that of the shaft section  26  of the eccentric bolt  20 . Similarly, the diameter of the bore  36  located in the overlap section  18  is the same as that of the eccentric section  24  of the eccentric bolt  20 . As can be seen in  FIG. 1 , the eccentric bolt  20  is inserted with a snug fit from the outside into the corresponding bores  34 ,  36  of the overlap sections  18 ,  19 , such that the threaded section  28  projects into the inside of the housing  10 . A self-locking nut  38  is screwed onto the threaded section  28 , whereby the eccentric bolt is secured against loss. Turning the eccentric bolt  20  about its central axis  30  produces a force on both half-tube shells  12 ,  13  which leads to the two respective half-tube shells  12 ,  13  moving relative to each other. 
         [0030]    By so doing, the two half-tube shells  12 ,  13  can be tensioned against each other in the circumferential direction U. This is important in particular if a substantially greater pressure is present inside the housing  10  compared to the outside, or if no separate sealing means is provided for sealing the joint. At the same time, the two overlap sections  18 ,  19  of the half-tube shells  12 ,  13  are areally pressed against each other in the contact region  16  by two screw connections  40 , which are shown only schematically. As the screw connections  40  are installed from outside, they are screwed into the overlap section  19  of the half-tube shell  13 . 
         [0031]    Instead of the overlap shown in  FIG. 1 , it is also possible to use a double-section variant of the connection region  14 , as represented schematically in  FIG. 4 . This has the advantage that the contact surface in the connection region is further enlarged compared to the embodiment shown in  FIG. 1 . This lengthens the path of any leakage arising through the joint and increases the size of the sealing area. 
         [0032]    Axially securing the eccentric bolt  20  need not necessarily be carried out from the inside by means of a self-locking nut  38 . Instead, a securing measure against loss can also be provided from the outside, which provides simpler installation of the securing measure. For example, a frame or a plate can block the axial displacement path of the eccentric bolt  20  and thus secure it. 
         [0033]    An alternative and preferred configuration of the embodiment represented in  FIG. 1  is shown in  FIG. 3  in a side view of the connection region  14 , where features which are identical to  FIG. 1  are given identical reference numbers. The configuration of  FIG. 3  differs from the configuration of  FIG. 1  in that a recess  44  of rectangular contour is provided for each eccentric bolt  20  in the overlap section  18 . The recess  44  passes right through the overlap section  18  and is represented only in  FIG. 3 . A compensating element  46  which can be displaced only in the axial direction is at least partially introduced into each recess  44  in the form of what is termed a sliding block. The compensating element  46  moreover has a bore in which the eccentric section  24  of the eccentric bolt  20  is mounted without play. The diameter of the bore of the compensating element  46  thus corresponds exactly to the diameter of the eccentric section  24  of the eccentric bolt  20 . As with the configuration of  FIG. 1 , the shaft section  26  of the eccentric bolt  20  is seated without play in the bore  34  of the overlap section  19 . The contour of the compensating element  46  corresponds substantially to that of the recess  44 , as a result of which the compensating element  46  is held fixed in rotation in the recess  44 . The axial extent of the compensating element  46  is smaller than that of the recess  44 , as a result of which the compensating element  46  is mounted in the recess  44  in an axially displaceable manner. However, as seen in the tangential direction T, the extent of the recess  44  and that of the compensating element  46  are identical, in order to ensure that the compensating element  46  is seated without play in the recess  44 , such that the eccentric bolt  20  is subjected to the shear loading. 
         [0034]    As, conventionally, both half-tube shells  12 ,  13  of the housing  10  are very limited in their axial movement, it is also possible with the aid of the compensating element  46  to use the eccentric bolt or bolts  20  to tangentially tension the two half-tube shells  12 ,  13 . This is because the axial displacement of the two half-tube shells  12 ,  13  relative to each other, which otherwise accompanies turning of the eccentric bolt  20 , can be compensated for by the compensating element  46  which can be displaced axially but is fixed in rotation. 
         [0035]    In an alternative configuration, which is not shown and has a sliding block, the recess  44  can also be arranged as a purely superficial pocket on the outward facing surface  42  (see  FIG. 1 ) of the overlap section  18 . In this case, the recess  44  has a depth which is smaller than half the wall thickness d. The bore  36  situated in the overlap section  18  of the half-tube shell  12  then has a diameter greater than the diameter of the eccentric section  24  of the eccentric bolt  20 , whereby the latter is seated with play in the overlap section  18  in order not to restrict the displaceability of the sliding block. 
         [0036]    The arrangement of the recess  44  and the compensating element  46  is of course also possible in the overlap section  19 . 
         [0037]    According to the embodiment represented in  FIG. 3 , the connection region  14  has an axial extent in which a multiplicity of eccentric bolts  20  and also a further multiplicity of pretensioned screw connections  40  are distributed along the axial direction A in a grid pattern, whereby an axial connection region can be realized. In order to mitigate warping in the individual half-tube shells  12 ,  13  when tensioning using the eccentric bolts  20 , it is provided that the respective eccentric bolts  20  be turned synchronously. To that end, a lever  48  is in each case rigidly fastened to each eccentric bolt  20 , the ends of which lever being in each case articulated to a rod assembly  50 . The two rod assemblies  50  shown in  FIG. 3  can be displaced in opposite axial directions by hydraulically actuated pistons  52 , with the result that, via the levers  48  articulated thereto, all the eccentric bolts  20  coupled thereto can be swiveled through the same angle synchronously during installation.  FIG. 3  shows two positions of the levers  48  by means of solid and dashed lines respectively.