Abstract:
A steam turbine with at least two steam chambers which are enclosed by a basically tubular casing and which are separated from each other by means of at least one partition which is arranged in the casing, is characterized according to the invention in that the partition is formed from at least two flat partial surfaces which are formed in an inclined manner relatively to each other.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the US National Stage of International Application No. PCT/EP2005/053954, filed Aug. 11, 2005 and claims the benefit thereof. The International Application claims the benefits of European application No. 04019959.8 filed Aug. 23, 2004, both of the applications are incorporated by reference herein in their entirety. 
     
    
     FIELD OF INVENTION 
       [0002]    The invention relates to a steam turbine with two steam chambers which are enclosed by a basically tubular casing and which are separated from each other by means of at least one partition which is arranged in the casing. 
       BACKGROUND OF THE INVENTION 
       [0003]    In steam turbines of the aforesaid type, individual steam chambers, in cylindrical turbine casings, are separated by partitions. Connections are provided on the casing for feed and exhaust of steam in the steam chambers. 
         [0004]    The partitions, which separate the steam chambers from each other, at the same time must be producible simply and yet permanently withstand the compression stress which occurs. The connections must be formed with cross sectional areas which, in proportion to the fluid volumes which are to be guided through the steam chambers, are often dimensioned comparatively large. 
         [0005]    Furthermore, the thermal expansion stresses, which arise in steam turbines on account of the high temperature differences, pose a large problem in the design of the casing and the associated partitions. 
         [0006]    In known steam turbines, the individual steam chambers are separated by rotationally symmetrical, cone-shaped walls, on which the cone angles widen during temperature influence as a result of thermal expansion. This leads to relatively high expansion stresses on the partitions. 
         [0007]    Furthermore, in known casings, the external surfaces of the individual steam chambers are partially only relatively narrow strips, on which space for arranging said connections is not adequately available. 
       SUMMARY OF INVENTION 
       [0008]    The invention is based on the object of making available a steam turbine of this generic type in which especially low thermal stresses arise on the partitions but which at the same time is formed especially compactly. 
         [0009]    The object according to the invention is achieved by a steam turbine of the type mentioned in the introduction, in which the partition is formed from at least two flat partial surfaces which are formed in an inclined manner relative to each other. 
         [0010]    According to the invention, the partition which is to be provided in a casing of a steam turbine is not formed alone as a flat surface or as a curved surface, but there are creases or kinks, as the case may be, purposefully formed in the partition, by means of which flat partial surfaces adjoin each other. The walls which are creased in such a way can actually be produced by means of a creasing process or by means of connecting two flat pieces, for example by welding, depending upon size and thickness of the partition. By means of the creases, the partitions according to the invention, and especially their flat partial surfaces, expand uniformly, without particular change of shape, and no additional stresses are created on the associated casing. Furthermore, the creases lead to a stiffening of the walls and, as is subsequently explained in more detail, enable a more flexible partitioning of the steam chambers. With a corresponding design, a flat partial surface of a partition can be extended from the actual casing section and, therefore, can form a part of a wall of a connector on the casing. In this way, a more favorable introduction of external connection forces into the casing structure results. 
         [0011]    The creases according to the invention are especially advantageously formed as straight crease edges, by which partial surfaces adjoin each other. Such straight crease edges can be inexpensively produced by means of simple kinking or by means of welding of straight plate edges. 
         [0012]    Furthermore, it is advantageous if the partial surfaces which are formed with crease edges according to the invention, adjoin each other on crease edges which are asymmetrically arranged with regard to a longitudinal axis of the tubular casing. This has the effect that the partitions according to the invention not being constructed in an especially rotationally symmetrical manner. Such a design is especially of advantage with regard to the thermal expansion stresses which arise while the temperature is being maintained. 
         [0013]    Furthermore, it is additionally advantageous, with regard to the development of stresses on the casing structure of the steam turbine according to the invention, if the partial surfaces are also asymmetrically arranged, especially not rotationally symmetrically arranged, in their inclination with regard to a longitudinal axis of the tubular casing. By means of a flexible design over the circumference of the casing, such partial surfaces, which are asymmetrically inclined with regard to the longitudinal axis of the tubular casing, especially also enable an improved location of entry openings, so-called manholes, through which the relevant regions inside the casing are better reachable over the operating period of the steam turbine. 
         [0014]    A partition according to the invention which is to be developed and produced particularly cost-effectively is characterized in that it is formed with a central partial surface, to which is connected a plurality of additional partial surfaces, which are distributed over the circumference and which are inclined to the central partial surface. While the central partial surface for separating the steam chambers is provided directly on a rotor which rotates in the casing, the additional partial surfaces, which are distributed around this central partial surface, can be arranged in a differently inclined manner, depending upon the space requirement in the respective steam chambers and on the enclosing tubular casing. At the same time, comparatively simple crease edges and/or connecting edges result. 
         [0015]    A further standardization of the partitions according to the invention, and a reduction of costs which is associated with it, is possible by connecting to the central partial surface inclined partial surfaces which are distributed over its circumference and which are the same size. In this case, the aforementioned asymmetrical design of the partitions according to the invention can be especially advantageously achieved by means of three inclined partial surfaces. 
         [0016]    These three inclined partial surfaces, for example, can be advantageously arranged on one side in each case of a basically rectangular central partial surface, wherein the central partial surface itself is formed on the fourth side of the basically rectangular basic shape such that it continues flat up to the casing. 
         [0017]    With regard to the partition according to the invention, it is further advantageous if the central surface is oriented basically perpendicularly to a longitudinal axis of the tubular casing and, as a result, perpendicularly to a rotor which rotates in the casing. 
         [0018]    As has already been indicated above, a connector, which serves as a connection on the casing, can also be at least partially formed by the partial surfaces which according to the invention are inclined. Furthermore, it is also advantageous if an inlet or outlet, which is funnel-shaped at least on one side, is formed by one of the inclined partial surfaces inside the casing. Such funnel-shaped inlets or outlets create the fluidically desired narrowing or widening in each case of the cross sectional areas of the associated flow paths in the steam turbine according to the invention. 
         [0019]    Furthermore, according to the invention it is proposed that in a steam turbine of this generic type at least two connections for steam are formed on the casing in such a way that one of the steam chambers has decreasing cross sectional areas or cross sectional widths, as the case may be, in the direction from an associated connection into the casing, while the steam chamber which is located on the other side of the partition has increasing cross sectional areas or cross sectional widths, as the case may be, in the direction towards an associated connection from the casing. The decreasing cross sectional areas, therefore, are arranged directly next to increasing cross sectional areas and so altogether lead to an especially compact and space-saving construction of such a steam turbine according to the invention. Especially in the case of a very limited axial constructional length of the tubular casing, adequate space for the location of connections on the external sides of the casing can be created as a result of the design of separating surfaces according to the invention. At the same time, the cross sectional progressions along the flow paths into the individual steam chambers are designed according to the reducing space requirement, for example in the case of an inlet with increasing distance from the inlet connector. According to the invention, the region with small space requirement of a steam chamber lies next to the region with large space requirement of the adjacent steam chamber. A comparatively short constructional length of the tubular casing, with an especially favorable utilization of space, ensues as a result of this. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    An exemplary embodiment of a steam turbine according to the invention is subsequently explained in detail with reference to the attached schematic drawings. In the drawings: 
           [0021]      FIG. 1  shows a half-section of an exemplary embodiment of a casing, with partitions, of a steam turbine according to the invention, 
           [0022]      FIG. 2  shows a side view of the casing according to  FIG. 1 , 
           [0023]      FIG. 3  shows the section III-III in  FIG. 1 , 
           [0024]      FIG. 4  shows the section IV-IV in  FIG. 1 , 
           [0025]      FIG. 5  shows a view of the parting joint of the bottom section of the casing and of the partitions according to  FIG. 1 , 
           [0026]      FIG. 6  shows a perspective view of the partitions of the steam turbine according to  FIG. 1 , 
           [0027]      FIG. 7  shows a broken-open perspective view of the casing with partitions according to  FIG. 1  and 
           [0028]      FIG. 8  shows a perspective view of the casing according to  FIG. 1  from the outside. 
       
    
    
     DETAILED DESCRIPTION OF INVENTION 
       [0029]    The elements of a tubular casing  12 , and partitions  14   a - d  which are arranged therein, of a steam turbine  10 , which are essential for the invention, are illustrated in the figures. The casing  12  is formed basically with a tubular shape along a longitudinal axis  16  and on its external side has a steam inlet  18  in the form of a connector. Steam outlets  20  and  22 , which serve as tappings for branching of preheated steam, are also arranged on the external side of the casing  12 . The casing  12  is divided by altogether four partitions  14   a ,  14   b ,  14   c  and  14   d  into five steam chambers  24   a  to  24   e , in which the steam inlet  18  leads into the steam chamber  24   c,  a “small” steam outlet  20  leads out of the steam chambers  24   b  and  24   d  in each case, and two “large” steam outlets  22  lead out of the steam chambers  24   a  and  24   e  in each case. 
         [0030]    During operation of the steam turbine  10 , a rotor, which is not shown and which is oriented in the direction of the longitudinal axis  16 , rotates in the casing  12 . This rotor penetrates the partitions  14   a  to  14   d , for which a central opening  26  is formed in these partitions  14  in each case. The steam which is introduced through the steam inlet  18  into the steam chamber  24   c  flows in this case in an axial direction towards the two end faces of the tubular casing  12  and leaves the casing  12  there through an opening  28  in each case. The flow of steam through the casing  12  is guided in the region of the steam chambers  24   b  and  24   d  through a pipe section  30  in each case, by which pipe section the partitions  14   a  and  14   b , or  14   c  and  14   d , as the case may be, are interconnected in the region of the associated openings  26 . So that the steam turbine  10  is especially compactly formed in the axial direction, and so that a short distance, which is especially cost-effective to realize, between associated bearings (not shown) of the steam turbine rotor is achieved, and, furthermore, so that the casing  12  and also the partitions  14  are not subjected to excessively large expansion stresses during temperature changes in the steam turbine  10 , the partitions  14  are formed in each case from individual, flat, partial surfaces  32  which are arranged in an inclined manner to the longitudinal axis  16  around a central partial surface  34  in each case. The partial surfaces  32 , which lie radially on the outside in such a way on the central partial surface  34 , adjoin straight crease edges  36  on the central partial surface  34  in each case. 
         [0031]    As is especially easy to see in  FIG. 1 , the outer partial surfaces  32  of the steam chamber  24   c  on the side of the steam inlet  18  are inclined in such a way that the steam inlet  18  has reducing cross sectional widths or cross sectional areas, as the case may be, into the casing  12 . On the diametrically opposite side of the casing  12 , the outer partial surfaces  32  of the partitions  14   b  and  14   c  are inclined to each other in such a way that the cross sectional widths or cross sectional areas of the steam chamber  24   c , as the case may be, reduce more with increasing distance from the steam inlet  18 . The central partial surfaces  34  of the partitions  14   b  and  14   c , however, are oriented perpendicularly to the longitudinal axis  16 . Especially in  FIG. 6 , it is also to be seen that the central partial surfaces  34  of the partitions  14   b  and  14   c  are continued laterally from the steam inlet  18  in a flat manner up to the casing  12  in each case, and no crease edges are provided there. 
         [0032]    Unlike the partitions  14   b  and  14   c , the partitions  14   a  and  14   d  are formed in each case as “shells”, on which three outer partial surfaces  32 , which are arranged in an inclined manner, are formed on a central partial surface  34 . The outer partial surfaces  32  of the partitions  14   a  and  14   d  are inclined in the axial direction to the end face openings  28  of the associated steam chambers  24   a  and  24   e  in each case. As a result, the upper, outer partial surface  32  of the partitions  14   a  and  14   d  in each case, with regard to  FIG. 6 , extends basically parallel to the upper, outer partial surfaces  32  of the partitions  14   b  or  14   c , as the case may be (see also  FIG. 1 , top half). In the bottom region of the partitions  14 , with regard to the figures, a widening of the steam chambers  24   b  and  24   d  in the direction of the “small” steam outlets  20  is achieved by means of the outer partial surfaces  32  of the partitions  14   b  and  14   c , which are inclined in relation to each other, and by means of the central partial surface  34  of the partitions  14   a  and  14   d , which surface extends to the bottom perpendicularly to the longitudinal axis  16 . Consequently, from the top downwards there results altogether an increase of the cross sectional areas of the annular steam chambers  24   b  and  24   d , which are bounded towards the middle by means of the pipe section  30 , in the direction of the steam outlets  20 . 
         [0033]    Two steam outlets  22  are provided in each case on the steam chambers  24   a  and  24   e  at the bottom. These steam outlets  22  lie in a region of the steam chambers  24   a  or  24   e , as the case may be, in which the steam chambers  24   a  and  24   e  are especially wide in the axial direction, owing to the shape of the partitions  14   a  or  14   d , as the case may be. In the upper and side regions, the steam chambers  24   a  and  24   e , however, are comparatively narrow owing to the three outer partial surfaces  32  which are grouped on the partitions  14   a  and  14   d  in each case around the central partial surface  34 . 
         [0034]    As is shown in  FIG. 8 , entry openings or manholes  38 , as the case may he, are formed on the casing  12  just above the parting joint of the bottom section, which entry openings or manholes, on account of the selected shape of the partitions  14 , enable an especially easily accessible entry and a good access to the regions inside the casing  12  which are to be worked.