Abstract:
A turbine exhaust diffuser includes a diffuser component disposed within the turbine exhaust diffuser and having an outer surface. Also included is a suction path extending between the outer surface and an interior compartment of the diffuser component, wherein the suction path is configured to ingest a fluid. Further included is an actuating path extending between the outer surface and the interior compartment of the diffuser component, wherein the actuating path is configured to expel the fluid. Yet further included is a flow manipulating device disposed within the interior compartment of the diffuser component.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The subject matter disclosed herein relates to turbine systems, and more particularly to boundary layer flow control of turbine exhaust diffuser components. 
         [0002]    Typical turbine systems, such as gas turbine systems, for example, include an exhaust diffuser coupled to a turbine section of the turbine system to increase efficiency of a last stage bucket of the turbine section. The exhaust diffuser is geometrically configured to rapidly decrease the kinetic energy of flow and increase static pressure recovery within the exhaust diffuser. 
         [0003]    Commonly, the exhaust diffuser is designed for full load operation, however, the turbine system is often operated at part load. Therefore, part load performance efficiency is sacrificed, based on the full load design. Such inefficiency is due, at least in part, to flow separation on exhaust diffuser components, such as an inner barrel and radially extending struts, for example. Flow separation often is caused, in part, by swirling of the flow upon exit of the last bucket stage of the turbine section and entry into the exhaust diffuser. The magnitude of swirl may be quantified as a “tangential flow angle,” and such an angle may be up to about 40 degrees, which leads to a higher angle of attack on the exhaust diffuser components, such as the radially extending struts, for example. Such a flow characteristic leads to boundary layer growth and flow separation and eventually reduced pressure recovery. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0004]    According to one aspect of the invention, a turbine exhaust diffuser includes a diffuser component disposed within the turbine exhaust diffuser and having an outer surface. Also included is a suction path extending between the outer surface and an interior compartment of the diffuser component, wherein the suction path is configured to ingest a fluid. Further included is an actuating path extending between the outer surface and the interior compartment of the diffuser component, wherein the actuating path is configured to expel the fluid. Yet further included is a flow manipulating device disposed within the interior compartment of the diffuser component. 
         [0005]    According to another aspect of the invention, a turbine exhaust diffuser includes a strut extending between, and operably coupled to, an annular inner barrel extending in a longitudinal direction of the turbine exhaust diffuser and an outer wall disposed radially outwardly from the inner barrel, the strut comprising a leading edge, a trailing edge and a suction side. Also included is a suction path extending from a first aperture in the suction side to an interior compartment of the strut. Further included is an actuating path extending from a second aperture in the suction side to the interior compartment of the strut. Yet further included is a flow manipulating device disposed within the interior compartment of the strut. 
         [0006]    According to yet another aspect of the invention, a turbine system includes a turbine casing that surrounds a portion of a turbine section of the turbine system. Also included is an exhaust diffuser that includes an inner barrel extending from proximate a diffuser inlet to a location downstream of the diffuser inlet. The exhaust diffuser also includes an outer wall disposed radially outwardly from the inner barrel. The exhaust diffuser further includes a strut extending between, and operably coupled to, the inner barrel and the outer wall, the strut comprising a leading edge, a trailing edge and a suction side. The exhaust diffuser yet further includes a suction path extending from the suction side to an interior compartment of the strut and an actuating path extending from the suction side to the interior compartment of the strut. The exhaust diffuser also includes a flow manipulating device disposed within the interior compartment of the strut. 
         [0007]    These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0008]    The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0009]      FIG. 1  is a schematic illustration of a turbine system; 
           [0010]      FIG. 2  is a cross-sectional view of a turbine exhaust diffuser of the turbine system; and 
           [0011]      FIG. 3  is a schematic, side view of a strut of the turbine exhaust diffuser. 
       
    
    
       [0012]    The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0013]    Referring to  FIG. 1 , a turbine system, such as a gas turbine system, for example, is schematically illustrated with reference numeral  10 . The gas turbine system  10  includes a compressor section  12 , a combustor section  14 , a turbine section  16 , a shaft  18  and a fuel nozzle  20 . It is to be appreciated that one embodiment of the gas turbine system  10  may include a plurality of compressors  12 , combustors  14 , turbines  16 , shafts  18  and fuel nozzles  20 . The compressor section  12  and the turbine section  16  are coupled by the shaft  18 . The shaft  18  may be a single shaft or a plurality of shaft segments coupled together to form the shaft  18 . 
         [0014]    The combustor section  14  uses a combustible liquid and/or gas fuel, such as natural gas or a hydrogen rich synthetic gas, to run the gas turbine system  10 . For example, fuel nozzles  20  are in fluid communication with an air supply and a fuel supply  22 . The fuel nozzles  20  create an air-fuel mixture, and discharge the air-fuel mixture into the combustor section  14 , thereby causing a combustion that creates a hot pressurized exhaust gas. The combustor section  14  directs the hot pressurized gas through a transition piece into a turbine nozzle (or “stage one nozzle”), and other stages of buckets and nozzles causing rotation of turbine blades within an outer casing  24  of the turbine section  16 . Subsequently, the hot pressurized gas is sent from the turbine section  16  to an exhaust diffuser  26  that is operably coupled to a portion of the turbine section, such as the outer casing  24 , for example. 
         [0015]    Referring now to  FIG. 2 , a side, cross-sectional view of the exhaust diffuser  26  is illustrated. The exhaust diffuser  26  includes an inlet  28  configured to receive an exhaust fluid  30  from the turbine section  16 . An outlet  32  is disposed at a downstream location relative to the inlet  28 . Extending relatively axially along a longitudinal direction of the exhaust diffuser  26  at least partially between the inlet  28  and the outlet  32  is an inner barrel  34  that includes an outer surface  36 . Spaced radially outwardly from the inner barrel  34 , and more specifically radially outwardly from the outer surface  36 , is an outer wall  38  having an inner surface  40 . The outer wall  38  is arranged in a relatively diverging configuration, such that kinetic energy of the exhaust fluid  30  is lessened subsequent to entering the inlet  28  of the exhaust diffuser  26 . More particularly, a transfer of dynamic pressure to static pressure occurs within the exhaust diffuser  26  due to the diverging configuration of the outer wall  38 . The exhaust fluid  30  flows through the area defined by the outer surface  36  of the inner barrel  34  and the inner surface  40  of the outer wall  38 . 
         [0016]    Also disposed between the outer surface  36  of the inner barrel  34  and the inner surface  40  of the outer wall  38  is a strut  42 . Although only a single strut will be described herein, it is to be appreciated that the exhaust diffuser  26  typically includes a plurality of struts, with exemplary embodiments including a number of struts ranging from four (4) to twelve (12) struts. The strut  42  serves to hold the inner barrel  34  and the outer wall  38  in a fixed relationship to one another, as well as providing bearing support. As the strut  42  is disposed within the area between the inner barrel  34  and the outer wall  38 , the exhaust fluid  30  passes over the strut  42 . Therefore, the strut  42  influences the flow characteristics of the exhaust fluid  30 , and hence the overall exhaust diffuser performance. 
         [0017]    Referring now to  FIG. 3 , the strut  42  is shaped as a cambered airfoil, and it is to be appreciated that the precise geometry and dimensions of the strut  42  may vary from that illustrated, based on the application. The strut  42  includes a leading edge  44 , a trailing edge  46 , a suction side  48  and a pressure side  50 . Extending from the leading edge  44  to the trailing edge  46  is an imaginary line referred to as a chord length  52 . Although described as having a cambered airfoil shape, it is to be understood that a generally symmetrical configuration may be employed. 
         [0018]    As the exhaust fluid  30  exits the turbine section  16 , the last stage bucket exit tangential flow angle (referred to herein as “swirl”) of the exhaust fluid  30  increases based on the diverging configuration of the outer wall  38  of the exhaust diffuser  26 , thereby leading to flow separation in regions proximate the outer surface  36  of the inner barrel  34 , as well as regions proximate the various outer surfaces of the strut  42 , such as the suction side  48  and the pressure side  50 , for example. To reduce flow separation and the increase in swirl, a flow manipulating device  54 , such as a rotating impeller, is disposed within the strut  42  to promote ingestion, or suction, of a portion of the exhaust fluid  30  passing over the suction side  48  of the strut  42  through a suction path  56 . Subsequently, a portion of the exhaust fluid  30  is expelled, or blown, to a region proximate the suction side  48  of the strut  42  through an actuating path  58 . The flow manipulating device  54  is generally fully enclosed by surrounding surfaces of the strut  42 , with the exception of the suction path  56  and the actuating path  58 . The flow manipulating device  54  may be driven by various actuation structures, such as one or more motors. The one or more motors may be mounted proximate the outer wall  38 , the inner barrel  34 , and/or the strut  42 . 
         [0019]    The suction path  56  extends from a first aperture  60  disposed within the suction side  48  of the strut  42  to an interior compartment  62  of the strut  42 , where the flow manipulating device  54  is located. The suction path  56  may be arranged at numerous angles, as the embodiment shown is merely for illustrative purposes only. The first aperture  60 , and therefore at least a portion of the suction path  56 , is disposed proximate the leading edge  44  of the strut  42 , however, it is contemplated that the first aperture  60  may be located substantially downstream of the leading edge  44 . Similarly, the actuating path  58  extends from a second aperture  64  disposed within the suction side  48  of the strut  42  to the interior compartment  62 . As with the suction path  56 , the actuating path  58  may be arranged at numerous angles other than that illustrated. The second aperture  64 , and therefore at least a portion of the actuating path  58 , may be disposed at various locations downstream of the first aperture  60 . In an exemplary embodiment, the second aperture  64  is located about  60 % downstream of the leading edge  44 , with respect to the chord length  52  extending from the leading edge  44  to the trailing edge  46 , however, the precise location may vary based on overall characteristics of the exhaust diffuser  26 . Similarly, the first aperture  60  may be located proximate the trailing edge  46 , rather than proximate the leading edge  44 , as illustrated. 
         [0020]    It should be understood that although the preceding description has referred to an embodiment having a suction path  56  disposed at an upstream location of the actuating path  58 , it is contemplated that the actuating path  58  is disposed upstream of the suction path  56 , such that the exhaust fluid  30  is ingested downstream and blown through the actuating path  58  to an upstream location. Furthermore, it is to be appreciated that although the suction path  56  and the actuating path  58  are illustrated and described above as being disposed at locations between the suction side  48  and the interior compartment  62 , it is also contemplated that the suction path  56  and the actuating path  58  may be disposed at locations between the pressure side  50  and the interior compartment  62  in other embodiments. Alternatively, a plurality of suctions paths  56  and actuating paths  58  may be employed proximate both the suction side  48  and the pressure side  50 . 
         [0021]    In addition or alternatively to disposition of the flow manipulating device  54  within the strut  42 , the flow manipulating device  54  may be included within the inner barrel  34  to reduce flow separation and swirl proximate regions along the outer surface  36  of the inner barrel  34 . Such an embodiment is similar in structure and operation as that of an embodiment comprising the flow manipulating device  54  in the strut  42 . Irrespective of whether the flow manipulating device  54  is included in the strut  42  or the inner barrel  34 , or both, the flow manipulating device  54 , used in conjunction with the suction path  56  and the actuating path  58 , reduces flow separation proximate the outer surface  36  of the inner barrel  34  and the suction side  48  of the strut  42 . 
         [0022]    While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.