Abstract:
A diversion station is provided. The diversion station makes it possible to particularly effectively cool diverted water vapor by mixing it with water. The diversion station includes a mixing device, which comprises a so-called static mixer that is substantially made of a wire mesh. The wire mesh is produced by at least one wire that is substantially interlaced into loops. In the intended installation situation, the mixer is installed upstream of a water injection with regard to a flow direction specified by the water vapor such that the mixture of water and water vapor flows through the loops.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the US National Stage of International Application No. PCT/EP2010/050122, filed Jan. 8, 2010 and claims the benefit thereof. The International Application claims the benefits of European Patent Office application No. 09001085.1 EP filed Jan. 27, 2010. All of the applications are incorporated by reference herein in their entirety. 
     
    
     FIELD OF INVENTION 
       [0002]    The invention relates to a device which, in connection with a diversion station, makes it possible to particularly effectively cool diverted water vapor by mixing it with water. According to the invention, a mixing device is provided, which comprises a so-called static mixer that is substantially made of a wire mesh. 
       BACKGROUND OF INVENTION 
       [0003]    In the context of a steam turbine plant, a diversion station serves the purpose, as bypass, of feeding the water vapor formed in a steam generator directly to a condenser past a (steam) turbine. Such a bypass is required, for example, when the running times of steam generator and turbine are not mutually synchronized. By way of example, as early as before the start up of the turbine or still during the shutdown of the turbine, water vapor is generated that cannot be used by the turbine in these operating states. 
         [0004]    In order not to damage the condenser when introducing the “unused” water vapor, as a rule in the diversion station the steam pressure is throttled, on the one hand, and the water vapor is cooled by injection of water, on the other hand. The water injected into the water vapor is heated and evaporated, the water vapor conversely being cooled. 
         [0005]    In what follows here the term “water” always denotes water in its liquid aggregate state, particularly in drop form, while the term “water vapor” denotes water in its gaseous aggregate state. 
         [0006]    The water is frequently injected through a plurality of nozzle stocks aligned transverse to the flow direction and mixed with the water vapor. In an alternative to this, the water is injected into the water vapor in a (single) jet, the mixing usually being implemented by an orifice. It is disadvantageous that comparatively large mixing lengths are required in both variants for mixing—and therefore for successful cooling. In addition, mixing orifices used are subject to relatively high wear from so-called drop impact. 
       SUMMARY OF INVENTION 
       [0007]    It is the object of the invention to specify an apparatus that, in conjunction with a diversion station, enables diverted water vapor to be particularly effectively cooled by mixing with water. 
         [0008]    Accordingly, provided as apparatus is a mixing device that comprises a so-called static mixer that is substantially made from a wire mesh. The wire mesh is produced in this case from at least one wire substantially interlaced to form loops. In the intended installed situation, the mixer is mounted downstream of a water injection in such a way with reference to a flow direction prescribed by the water vapor that the loops are flowed through by the mixture of water and water vapor. 
         [0009]    The loops are formed substantially by a knitted wire or a wire knitting. The wire mesh is denoted as knitted wire or wire knitting, when the loops are knitted in the literal sense. That is to say, when in a way analogous to knitting in textile technology, the loops are formed by respectively guiding a plurality of loops arranged in a row through a loop of an adjacent row. This lends the wire mesh a particularly high stability. In this case, the wire mesh can, in particular, be fabricated from a single wire. 
         [0010]    Here, the term “loop” respectively denotes a wire frame, and an opening enclosed by this wire frame. The designation is used, in particular, irrespective of whether the loop is produced in the narrower sense as a so-called knitted fabric (for example being knitted, crocheted etc.), or whether the loop is produced by another way of linking or interlacing a wire or a plurality of wires. 
         [0011]    The term “wire” denotes a thin, longitudinal, flexible piece of metal, in particular having a circular cross section. However, other cross-sectional shapes are also possible in principle. 
         [0012]    In a preferred refinement, the wire is fabricated from stainless steel. 
         [0013]    Owing to its being produced from wire, the wire mesh differs, in particular, from a perforated sheet, in the case of which a plurality of mostly substantially round openings which are introduced into a sheet. 
         [0014]    In the indented installed situation, the loops of the wire mesh are flowed through by the mixture of water drops and water vapor. In this process, the respective wire frames produce vortices which force a transverse mixing of the water vapor flow, and thus a mixing of the water drops with the water vapor. As a result, the water advantageously penetrates to a very large extent to the core of the steam flow. In addition, the water drops are separated on the wire frame, resulting in a quicker evaporation of the water and therefore a more effecting cooling. However, heat is dissipated via the thermally conductive metal owing to the wire mesh. The installation of the mixer made from wire mesh gives an especially effective cooling of the water vapor overall. 
         [0015]    By being produced from wire, the mixer has a comparatively high stability, in particular the wire is particularly resistive to tensile loads. In addition, the mixer advantageously has a high thermal endurance. 
         [0016]    An additional advantage of the mixer formed from a wire mesh consists in its filter effect: from time to time, during maintenance work on the diversion station it can happen that relatively large parts are forgotten. Said parts can cause greater damage when they pass into the condenser. They are intercepted by the wire mesh should this happen. 
         [0017]    In an alternative embodiment, the wire mesh is formed from a wire netting. As netting, the wire mesh is distinguished in that a plurality of wires are respectively substantially interlaced obliquely to one another to form loops. In a further alternative, it is also conceivable to produce the wire mesh as cloth in the case of which a plurality of wires are interwoven to form at least two units. In this case, the wires of one unit are substantially at right angles to the wires of the second unit. 
         [0018]    In principle, the mixer can be designed substantially in the form of a round disk that can be mounted in the cross section of a (round) pipeline. In a preferred embodiment, the mixer or its wire mesh is, however, shaped overall substantially as an elliptic paraboloid. In this case, the mesh is intentionally mounted in the pipeline in such a way that it has substantially the shape of a parabola open in the upstream direction in a longitudinal section (with reference to the pipeline). The mesh thereby becomes particularly highly stable against the steam flow. 
         [0019]    The wire mesh is preferably dimensioned in such a way that a loop width is selected in relation to the diameter of the wire in such a way that a free flowed-through surface is at least 50% of the total surface of the wire mesh. In this case, the free flowed-through surface is substantially formed by the loop openings, while the total surface is formed both by the loop openings and by the respectively assigned wire frames. 
         [0020]    Since the wire frames of the loops of the water vapor flow then advantageously oppose only a comparatively slight cross-sectional surface, on the one hand the pressure loss caused by the installation of the mixer is comparatively slight. On the other hand, the wire frames are also thereby subject to a comparatively slight extent to erosion by drop impact. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    Exemplary embodiments of the invention are explained in more detail below with the aid of a drawing, in which: 
           [0022]      FIG. 1  shows a schematic sectional illustration of a mixing device mounted in a diversion station and having a mixer, formed from a wire mesh, for mixing water and water vapor, 
           [0023]      FIG. 2  shows a schematic illustration of the wire mesh in a first embodiment in accordance with  FIG. 1 , and 
           [0024]      FIG. 3  and  FIG. 4  respectively show the wire mesh in a further embodiment in a representation in accordance with  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION OF INVENTION 
       [0025]      FIG. 1  indicates a part of a diversion station  1  in a highly schematic fashion in longitudinal section. The diversion station  1  comprises a pipeline  2 , aligned horizontally here, for transferring water vapor  3 , starting from a steam generator (not illustrated here, and arranged on the left of the diversion station  1  in the representation) to a condenser (likewise not illustrated, and to the right of the diversion station). A flow direction  4 , indicated by arrows, of the water vapor  3  therefore runs from left to right. 
         [0026]    Upward in the flow direction  4 , a Laval nozzle  5  is positioned upstream of the pipeline  2  and serves, on the one hand, to throttle the steam pressure and, on the other hand, as a measuring point for the flow rate. 
         [0027]    An introduction nozzle  7  for injecting water  8  into the flowing water vapor  3  is arranged in a conically expanding outlet area  6  of the Laval nozzle  5 . 
         [0028]    The introduced water  8  serves the purpose of cooling down the water vapor  3  before the transfer to the condenser. To this end, the water  8  is mixed with the water vapor  3 , the water  8  evaporating. The cooling of the water vapor  3  is performed, on the one hand, by the lower temperature level of the water  8  by comparison with the water vapor  3 , and, on the other hand, by taking the evaporation enthalpy absorbed during the evaporation of the water  8  away from the water vapor  3 . 
         [0029]    In order to improve the mixing of the water  8  with the water vapor  3 —and thus for a more effective cooling—a mixing device  10  is mounted in the pipeline  2  in the flow direction  3  downstream of the introduction nozzle  7  or downstream of the Laval nozzle  5 . 
         [0030]    In a first embodiment illustrated here, the mixing device  10  comprises, on the one hand, a roughly indicated fastening ring  11  and, on the other hand, a mixer  12 , likewise roughly indicated, which is fabricated from a wire mesh  13 . The wire mesh  13  is fabricated in the manner of a wire net fence in this embodiment ( FIG. 2 ). 
         [0031]    The mixer  12  has approximately the form of an (overdimensioned) thimble or of a rounded hollow cone. The mixer  12  is rounded at its closed end  14 . The mixer is mounted, here screwed, on the fastening ring  11  in an approximately concentric fashion with an annular edge  16  facing its open end  15 . Here, the fastening ring  11  projects radially beyond the edge  16  radially on both sides. 
         [0032]    In a mounted state illustrated here, the fastening ring  11  is mounted between a flange  17  of the Laval nozzle  5  and a flange  18  of the pipeline  2 . Here, the mixer  12  is aligned in such a way that its open end  15  faces the introduction nozzle  7  or—approximately in the fashion of a funnel to be filled—faces the flow direction  4 . 
         [0033]    Vortices are produced in the flow owing to the mesh structure of the mixer  12 , thus dictating a mixing transverse to the flow direction  4 . In addition, the water  8  present in the flow as drops is separated by the wire mesh  13 . 
         [0034]    The wire mesh  13  in accordance with the first exemplary embodiment is illustrated partially in  FIG. 2  in a greatly enlarged fashion. The wire mesh  13  is illustrated here, in particular, in a prefabricated state in which it spans a plane surface aligned parallel to the plane of the drawing. In order to produce the mixer  12 , the wire mesh  13  can then be bent into any desired spatial structure. As an alternative to this, it is also possible to shape the wire mesh  13  as early as when it is being produced into a three-dimensional formation—for example, in the dish-like shape in accordance with  FIG. 1 . 
         [0035]    In  FIG. 1 , the wire mesh  13  is produced as a wire netting in the manner of a wire net fence. The wire mesh  13  comprises a plurality of (round) wires  20 . Each wire  20  is guided in a substantially rectangular, equilateral zig-zag line such that each wire  20  has a multiplicity of corner points  21 . Lengthwise, the wires  20  are respectively arranged in a fashion aligned substantially along a longitudinal direction  22  and parallel to one another. In this case, a wire  20  is respectively arranged offset from its adjacent wire  20 ′ in such a way that in each case one of the corner points  21  of the wire  20  makes contact of a sort with one of the corner points  21 ′ of the adjacent wire  20 ′ at a contact point  23 . In this case, each wire  20  is respectively interlocked with the wire  20 ′ in the area of the contact point  23 . This gives rise to approximately square loops  24 . Here, each loop  24  is formed by a wire frame  25  that respectively encloses an opening  26 . Each wire frame  25  is defined by four contact points  23 , and the sections  27  respectively connecting them, of the wire  20  or of the adjacent wire  20 ′. The size of each opening  26 —the loop width a—is in this case substantially of greater dimension than the diameter d of the wire  20 . 
         [0036]    In order to obtain such a wire mesh  13 , it is possible, in particular, also to guide a single wire  20  substantially in serpentine lines, it then comprising a plurality of sections that, in accordance with the above description, are respectively aligned along the longitudinal direction  22  in zig-zag lines, in a fashion substantially parallel to one another, and are interlocked with one another to form loops  24 . 
         [0037]    In an alternative embodiment, it is also possible for each wire  20  to be twisted with the adjacent wire  20 ′ at the contact points  23 . This respectively lends the loops  24  an essentially hexagonal shape (as frequently employed in the case of “hare fence”). In a further alternative, it is also conceivable for the two adjacent wires  20  and  20 ′ to be knotted with one another at the contact points  23  in a manner of a fishing net. Two alternative embodiments are distinguished by a particularly high dimensional stability of the loops  24 . 
         [0038]    The wire mesh  13  in the prefabricated state in accordance with  FIG. 2  is shown in a second embodiment in  FIG. 3 . In this embodiment, the wire mesh  13  is formed by a wire cloth (a flat one here). In turn in this case, a multiplicity of the wires  20  are aligned—rather like warp wires—parallel to one another in the longitudinal direction  22 , while on the other hand a multiplicity of the wires  20 ′ are aligned, as it were as weft wires, parallel in turn to one another in a transverse direction  30 , approximately at right angles to the wires  20 . In this case, each wire  20 ′ is interwoven with the wires  20  in a transverse direction  30  by being guided alternately once over a wire  20  and once under a wire  20  adjacent thereto. In the illustrated embodiment, all the wires  20  and  20 ′ are arranged in each case at the same spacing from one another so that substantially square loops  24  are formed here. 
         [0039]    In this case, each wire frame  25  is defined in turn by four contact points  23  at which a wire  20  and a wire  20 ′ respectively cross, and by the sections  27  respectively connecting said wires. 
         [0040]    In a departure from the distribution illustrated here, an irregular distribution of the wires  20 ,  20 ′ is also conceivable. An asymmetric “web pattern” is also possible. For example, each wire  20 ′ can alternately respectively be guided over two wires  20  and in an adjacent fashion under a wire  20 . 
         [0041]    In  FIG. 4 , the wire mesh  13  is designed in turn as a knitted wire in the prefabricated state in accordance with  FIG. 2 . In a way similar to the first embodiment, each wire  20  here is guided in a meandering shape, a multiplicity of loops  40  being arranged next to one another in a longitudinal direction  22 . In a way analogous to the embodiment from  FIG. 1 , the wires  20  are aligned in this case in a fashion substantially parallel to one another overall, a wire  20  respectively being adjacent to a wire  20 ′. 
         [0042]    Each loop  40 ′ of one wire  20 ′ in this case hooks into an adjacent loop  40  of the wire  20  such that a multiplicity of loops  24  result in turn. Each loop  24  is largely formed in this case by one of the loops  40  or  40 ′. Here, the wire frame  25  of each loop  24  is formed in turn by four contact points  23  (at which the wire  20 ′ is respectively interlaced with one of the wires  20  adjacent on both sides in a transverse direction  30 ) and the section  27  connecting said loops. In a way analogous to the embodiment in accordance with  FIG. 2 , it is also possible here for the knitted wire to be formed from a single wire  20 —that is guided appropriately.