Abstract:
The turbine casing as described herein may include a first section flange, a second section flange, the first section flange and the second section flange meeting at a joint, and a heat sink positioned about the joint.

Description:
TECHNICAL FIELD 
       [0001]    The present application relates generally to gas turbines and more particularly relates to flange joint features for a turbine casing that reduce “out of roundness” caused by thermal gradients. 
       BACKGROUND OF THE INVENTION 
       [0002]    Typical turbine casings generally are formed with a number of sections that are connected to each other. The sections may be connected by bolted flanges in any orientation and similar arrangements. During a transient startup of a gas turbine, the horizontal joints may remain colder than the rest of the casing due to the additional amount of material required to accommodate the bolt. This thermal difference may cause the casing to be “out of roundness” due to the fact that the time to heat up the horizontal joint may be slower than that of the surrounding casing. This condition is also called ovalization or “pucker”. On shutdown, an opposite condition may occur where the horizontal joint remains hot while the casing around it cools off so as to cause the opposite casing movement or ovalization. 
         [0003]    There is therefore a desire to reduce or eliminate the presence of thermal gradients that may cause an “out of roundness” about the joints of a casing for a rotary machine such as a turbine. Elimination of these thermal gradients should promote a longer lifetime for the equipment with increased operating efficiency due to the maintenance of uniform clearances therein. 
       SUMMARY OF THE INVENTION 
       [0004]    The present application thus describes for a turbine casing. The turbine casing as described herein may include a first section flange, a second section flange, the first section flange and the second section flange meeting at a joint, and a heat sink positioned about the joint. 
         [0005]    The present application further describes a turbine casing. The turbine casing may include an upper half flange, a lower half flange, the upper half flange and the lower half flange meeting at a joint, and a number of heat sink fins positioned about the joint. 
         [0006]    The present application further describes a method of stabilizing a turbine casing having a number of sections meeting at flange joints. The method as described herein includes the steps of determining the average radial deflection of each section, subtracting the minimum radial deflection of each section, and adding a heat sink to each of the flange joints to reduce the average radial deflection of each section. 
         [0007]    These and other features of the present application will become apparent to one of ordinary skill in the art upon review of the following detailed description when taken in conjunction with the several drawings and the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a perspective view of a bolted joint of a casing as is described herein. 
           [0009]      FIG. 2  is a side plan view of an alternative embodiment of a casing as is described herein. 
           [0010]      FIG. 3  is a side perspective view of the bolted joint of the casing of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    Referring now to the drawings, in which like numerals refer to like elements throughout the several views,  FIG. 1  shows a turbine casing  100  as is described herein. The turbine casing  100  includes an upper half  110  and a lower half  120 . Other configurations also may be used herein. The upper half  110  may include a pair of upper half flanges  130  while the lower half  120  may include a pair of lower half flanges  140 . When positioned adjacent to each other, the upper half  110  and the lower half  120  of the casing  100  meet at a joint  125 . An aperture  150  extends through the flanges  130 ,  140  at the joints  125 . The upper half  110  and the lower half  120  are connected via a bolt  160  that extends through the apertures  150  of the flanges  130 ,  140 . Other connection means may be used herein. 
         [0012]    The thermal responsiveness of the joints  125  of the casing  100  may be improved with the addition of a heat sink  170  positioned about the joints  125 . Specifically, the heat sink  170  may be any parameterized geometric feature. The heat sink  170  may vary in any parameter such as height, width, length, elevation, taper, acuity, thickness, warpage, shape, etc. 
         [0013]    In this example, the heat sinks  170  each may include an upper fin  180  positioned on the upper half  110  of the casing  100  opposite the upper half flange  130  and a lower fin  190  positioned on the lower half  120  opposite the lower half flange  140 . The fins  180 ,  190  may extend slightly within the casing  110 . The fins  180 ,  190  may be in contact or they may be separated by a predetermined distance. Separating the fins  180 ,  190  may reduce the possibility of the fins  180 ,  190  binding and stressing each other during thermal expansion or otherwise. The fins  180 ,  190  may be made of the same or a different material as that of the turbine casing  100 . The fins  180 ,  190  may be welded, cast, or mechanically or otherwise attached to the casing  100 . The fins  180 ,  190  serve to increase the surface area about the joints  125  so as to enhance the heat transfer by increasing the effective surface area. The fins  180 ,  190  may take any desired shape. 
         [0014]    The use of the fins  180 ,  190  may reduce the “out of roundness” of the casing  100  for at least a portion of the startup time. Specifically, “out of roundness” is the average radial deflection minus the minimum radial reflection of the halves  110 ,  120  of the casing  100 . Although the fins  180 ,  190  may reduce the “out of roundness” for a portion of the startup time, the fins  180 ,  190 , however, may slightly increase the steady state “out of roundness”. The fins  180 ,  190  again reduce the “out of roundness” during cool down. The size of the fins  190  and the heat sink  170  may be balanced against the thermal gradients and the “out of roundness” experienced by the casing  100 . Larger heat gradients may require a larger heat sink  170  such that different sizes of the heat sinks  170  may be used. 
         [0015]      FIGS. 2 and 3  show a further embodiment of a turbine casing  200  as is described herein. As described above, the turbine casing  200  may include an upper half  210  and a lower half  220 . Other configurations also may be used herein. Because the upper half  210  and the lower half  220  are substantially identical, only the upper half  210  is shown. Each end of the upper half  210  and the lower half  220  meet and are connected at a joint  225 . The halves  210 ,  220  at the joints  225  may include a pair of upper half flanges  230  and a pair of lower half flanges  240 . The flanges  230 ,  240  include a number of apertures  250  positioned therein. The halves  210 ,  220  of the casing  200  may be connected via the bolts  160  extending through the apertures  250  as described above or by other types of connection means. 
         [0016]    The halves  210 ,  220  of the casing  200  may include a number of slots  260  positioned therein. The slots  260  may accommodate a shroud, a blade, a bucket, or other structures as may be desired. The halves  210 ,  220  of the casing  200  also may include a number of voids  265  positioned therein. These voids  265  may take the form of a recess along an outer edge of the casings  200  or the voids  265  may be positioned internally as may be desired. 
         [0017]    The halves  210 ,  220  of the casing  200  also may include one or more heat sinks  270  positioned about the voids  265  adjacent to the joint  225 . The heat sinks  270  may take the form of a set of upper fins  280  positioned about the upper half  210  of the turbine casing  200  and/or a set of lower fins  290  positioned about the lower half  220  of the casing  200 . The fins  280 ,  290  may be positioned adjacent to the flanges  230 ,  240  of the joints  225 . As is shown, the fins  280 ,  290  may vary in size with a larger area adjacent to the joints  225  and then decreasing in area as moving away from the joints  225 . Alternatively, the fins  280 ,  290  may have substantially uniform shape. Any number of fins  280 ,  290  may be used. Any shape of the fins  280 ,  290  may be used. As described above, the heat sinks  270  as a whole may take any desired form. 
         [0018]    The use of the heat sinks  170 ,  270 , thus allows more heat to enter or leave the colder or hotter area about the joints  125 ,  225  and therefore improves the thermal response of the joints  125 ,  225  in relation to the remainder of the casing  100 ,  200 . As a result, increased gas turbine and/or compressor/turbine efficiency may be provided due to better and more uniform clearances about the casing  100 ,  200 . Reduction of the “out of roundness” also may mean less rubbing and repair costs on compressor blades, turbine blades, or other components. 
         [0019]    It should be apparent that the foregoing relates only to the preferred embodiments of the present application and that numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the general spirit and scope of the invention as defined by the following claims and the equivalents thereof.