Abstract:
A double-flow low-pressure partial turbine is provided herein, wherein the exhaust steam of the first flow and the exhaust steam of the second flow are deflected in a common direction within the outer housing and thus axial outlet flow occurs.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the US National Stage of International Application No. PCT/EP2013/065466 filed Jul. 23, 2013, and claims the benefit thereof. The International Application claims the benefit of European Application No. EP12178221 filed Jul. 27, 2012. All of the applications are incorporated by reference herein in their entirety. 
     
    
     FIELD OF INVENTION 
       [0002]    The invention relates to a low-pressure turbine comprising a first flow and a second flow and also a rotor and an inner housing arranged around the rotor and an outer housing arranged around the inner housing. The invention also relates to a method for operating a low-pressure partial turbine, the low-pressure partial turbine having a double-flow configuration. 
       BACKGROUND OF INVENTION 
       [0003]    Steam turbines are usually divided into partial turbines. Thus, by way of example, a steam turbine used in local power supply is divided into a high-pressure partial turbine, an intermediate-pressure partial turbine and a low-pressure partial turbine. Each of these individual partial turbines mentioned above is accommodated in each case in an individual housing. Moreover, designs in which the high-pressure part and the intermediate-pressure part are accommodated in a common housing are known. Designs in which the intermediate-pressure part and the low-pressure part are arranged in a common housing are similarly known. An axial arrangement of the individual partial turbines in succession requires a comparatively large amount of installation space. 
         [0004]    Since, for reasons of thermodynamics, the pressure and the temperature of the steam decrease from the high-pressure partial turbine to the low-pressure partial turbine, and as a result the volume increases greatly, in some cases a plurality of partial turbines are used. Moreover, the low-pressure partial turbines generally have a two-flow configuration. This means that the inflowing steam flows away both in one direction and also axially in the opposite direction. Low-pressure partial turbines are configured in such a manner that the exhaust steam in one flow and the exhaust steam in the second flow are carried away laterally. This is also known under the term Single Side Exhaust or Double Side Exhaust. A further embodiment provides that the low-pressure exhaust steam is carried away downward (what is termed Down Exhaust). This generally leads to an increased space requirement, since low-pressure partial turbines configured in this way have to be constructed either with a great width or with a great height. In particular, in the case of a Single Side Exhaust assembly, the pipe system is concentrated on one side, and might therefore lead to problems in terms of space. It would be desirable to have a narrow machine housing, in which the partial turbines can be arranged. Moreover, it is desirable to be able to implement a well-structured pipe system. 
       SUMMARY OF INVENTION 
       [0005]    It is an object of the invention to specify a low-pressure partial turbine which requires relatively little space. 
         [0006]    This object is achieved by a low-pressure partial turbine as claimed in the independent claim. 
         [0007]    Advantageous developments are specified in the dependent claims. 
         [0008]    An embodiment of the invention proceeds from the aspect that guidance of the low-pressure exhaust steam laterally or downward results in a high space requirement, and this can be eliminated by guiding the low-pressure exhaust steam in such a manner that it is carried away axially. To this end, it is proposed according to an embodiment of the invention to design the outer housing in such a manner that the exhaust steam chamber of the second flow is designed in such a manner that the steam is deflected in the same direction as the exhaust steam of the first flow. This means that the low-pressure exhaust steam of the second flow is deflected in the direction of the low-pressure exhaust steam of the first flow. 
         [0009]    Advantageously, an annular space is thus formed between the inner housing and the outer housing, a low-pressure exhaust steam of the second flow flowing through said annular chamber and mixing with the low-pressure exhaust steam of the first flow on the output side. 
         [0010]    An alternative embodiment would be a box-like construction of the inner housing outer wall, such that the inner housing could be positioned on the base in the thus formed chamber. 
         [0011]    It is thus proposed according to an aspect of the invention to design a new outer housing for a two-flow low-pressure partial turbine which makes an axial discharge flow possible. The machine housing costs can thereby be reduced. Moreover, it is thereby possible to harmonize the basic power plants. Accordingly, considerable cost savings are possible. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    Aspects of the invention will be explained in more detail on the basis of an exemplary embodiment. 
           [0013]    The FIGURE shows a schematic cross-sectional view of a low pressure partial turbine. 
       
    
    
     DETAILED DESCRIPTION OF INVENTION 
       [0014]    The FIGURE shows a low-pressure partial turbine  1 , which has a two-flow configuration. This means that the low-pressure partial turbine  1  has a first flow  2  and a second flow  3 . Live steam flows into the low-pressure partial turbine  1  via an admission connector  4 . A flow path  8  is formed between a rotor  6  mounted rotatably about an axis of rotation  5  and an inner housing  7  arranged around the rotor  6 . 
         [0015]    An outer housing  9  is arranged around the inner housing  7 . The rotor  6  is formed with individual rotor blades  10 . For the sake of clarity, only one rotor blade is provided with the reference sign  10 . Guide vanes  11  arranged on the inner housing  7  are arranged between the individual rotor blade stages. For reasons of clarity, only one guide vane is provided with the reference sign  11 . 
         [0016]    Live steam flows in via the admission connector  4  and is expanded in the first flow  2  to the right, as seen in the plane of the drawing, and in the second flow  3  to the left, as seen in the plane of the drawing. The steam is expanded in the flow path  8  and is cooled in the process. After the last rotor blade  10  and guide vane  11 , the low-pressure exhaust steam  12  is deflected in the second flow  3  through the inner housing  7 . For this purpose, the outer housing  9  has deflection elements  13 , which deflect the steam again in the axial direction to the first flow  2 . An annular space  14 , through which the low-pressure exhaust steam  12  of the second flow  3  flows, is formed between the outer housing  9  and the inner housing  7 . The low-pressure exhaust steam  16  of the first flow  2  is mixed with the low-pressure exhaust steam of the second flow  12  in a mixing zone  15 . In this respect, it has to be ensured that the velocity of the low-pressure exhaust steam  16  of the first flow  2  is substantially the same as the velocity of the low-pressure exhaust steam  12  of the second flow  3  in the mixing zone  15 . 
         [0017]    Then, the steam mixed from the low-pressure exhaust steam  16  of the first flow  2  and the low-pressure exhaust steam  12  of the second flow  3  flows into an exhaust steam chamber  17  and, after this exhaust steam chamber  17 , to the condenser (not shown in more detail). A base for a bearing  18 , on which the rotor  6  is mounted, is arranged in the exhaust steam chamber  17 . The site of the bearing  18  can be arranged in the steam chamber or, in alternative embodiments, can be positioned as a separate encapsulated base outside the steam chamber. 
         [0018]    The low-pressure partial turbine ( 1 ) has a double-flow configuration and the exhaust steam from the first flow ( 2 ) is deflected in the direction of the exhaust steam of the second flow ( 3 ). The direction of the exhaust steam from the first flow ( 2 ) and the direction of the exhaust steam from the second flow ( 3 ) are oriented substantially parallel to the axis of rotation ( 5 ).