Abstract:
A flow manipulating arrangement for a turbine exhaust diffuser includes a strut having a leading edge and a trailing edge, the strut disposed within the turbine exhaust diffuser. Also included is a plurality of rotatable guide vanes disposed in close proximity to the strut and configured to manipulate an exhaust flow, wherein the plurality of rotatable guide vanes is coaxially aligned and circumferentially arranged relative to each other. Further included is an actuator in operative communication with the plurality of rotatable guide vanes and configured to actuate an adjustment of the plurality of rotatable guide vanes. Yet further included is a circumferential ring operatively coupling the plurality of rotatable guide vanes, wherein the actuator is configured to directly actuate rotation of one of the rotatable guide vanes, and wherein the circumferential ring actuates rotation of the plurality of rotatable guide vanes upon rotational actuation by the actuator.

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 or on a cold day. Therefore, part load performance efficiency is sacrificed, based on the full load design. Inefficiency is due, at least in part, to flow separation on exhaust diffuser components, such as walls and 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 60 degrees during part load and 20 degrees during a cold day, which leads to a higher angle of attack on the exhaust diffuser components, such as the 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 flow manipulating arrangement for a turbine exhaust diffuser includes a strut having a leading edge and a trailing edge, the strut disposed within the turbine exhaust diffuser. Also included is a plurality of rotatable guide vanes disposed in close proximity to the strut and configured to manipulate an exhaust flow, wherein the plurality of rotatable guide vanes is coaxially aligned and circumferentially arranged relative to each other. Further included is an actuator in operative communication with the plurality of rotatable guide vanes and configured to actuate an adjustment of the plurality of rotatable guide vanes. Yet further included is a circumferential ring operatively coupling the plurality of rotatable guide vanes, wherein the actuator is configured to directly actuate rotation of one of the rotatable guide vanes, and wherein the circumferential ring actuates rotation of the plurality of rotatable guide vanes upon rotational actuation by the actuator. 
         [0005]    According to another aspect of the invention, a flow manipulating arrangement for a turbine exhaust diffuser includes an inner barrel extending in a longitudinal direction of the turbine exhaust diffuser. Also included is an outer wall disposed radially outwardly of the inner barrel. Further included is a strut extending between, and operatively coupled to, the inner barrel and the outer wall, wherein the strut comprises a leading edge and a trailing edge. Yet further included is at least one guide vane disposed axially upstream of the leading edge or downstream of the trailing edge of the strut, the at least one guide vane selectively circumferentially displaceable relative to the strut. 
         [0006]    According to yet another aspect of the invention, a flow manipulating arrangement for a radial turbine exhaust diffuser includes an inner wall. Also included is an outer wall. Further included is a strut operatively coupled to at least one of the inner wall and the outer wall. Yet further included is at least one rotatable guide vane disposed proximate the strut, wherein the at least one rotatable guide vane is selectively rotatable over a range of angular positions and displaceable in at least one of an axial direction and a radial direction. 
         [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 DRAWINGS 
         [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 perspective view of a flow manipulation arrangement according to a first embodiment; 
           [0011]      FIG. 3  is a side, schematic view of the flow manipulation arrangement of  FIG. 2 ; 
           [0012]      FIG. 4  is top view of guide vanes and struts of the flow manipulation arrangement of  FIG. 2 ; 
           [0013]      FIG. 5  is a top view of a plurality of guide vanes operatively coupled; 
           [0014]      FIG. 6  is a perspective, schematic view of the plurality of guide vanes operatively coupled; 
           [0015]      FIG. 7  is a perspective view of the flow manipulation arrangement according to a second embodiment; 
           [0016]      FIG. 8  is a front elevational view of the flow manipulation arrangement of  FIG. 7 ; 
           [0017]      FIG. 9  is a top view of the flow manipulation arrangement of  FIG. 7 ; 
           [0018]      FIG. 10  is a top view of the flow manipulation arrangement according to a third embodiment illustrating guide vanes in a first position; 
           [0019]      FIG. 11  is a top view of the flow manipulation arrangement of  FIG. 10  illustrating guide vanes in a second position; 
           [0020]      FIG. 12  is a schematic illustration of a control mechanism of the flow manipulation arrangement of  FIG. 10 ; and 
           [0021]      FIG. 13  is a schematic illustration of the flow manipulation arrangement according to a fourth embodiment. 
       
    
    
       [0022]    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 
       [0023]    Referring to  FIG. 1 , a turbine system, such as a gas turbine system, for example, is schematically illustrated with reference numeral  10 . The 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 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 . 
         [0024]    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 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. 
         [0025]    Although illustrated and described above as a gas turbine system, it is to be appreciated that the turbine system  10  may alternatively be a steam turbine system. As will be described below, various embodiment of the exhaust diffuser  26  are contemplated, such as an axial exhaust diffuser and a radial exhaust diffuser. 
         [0026]    Referring now to  FIGS. 2 and 3 , a first embodiment of a flow manipulating arrangement  50  is illustrated within the exhaust diffuser  26 . In the illustrated embodiment, the exhaust diffuser  26  is an axial exhaust diffuser disposed axially downstream of a last stage of the turbine section  16 . The exhaust diffuser  26  includes an inlet  28  configured to receive an exhaust flow  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  may be arranged in a relatively diverging configuration, such that kinetic energy of the exhaust flow  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 flow  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 . 
         [0027]    Also disposed between the outer surface  36  of the inner barrel  34  and the inner surface  40  of the outer wall  38  is at least one, but typically a plurality of struts  42 , with exemplary embodiments including a number of struts ranging from four (4) to twelve (12) struts circumferentially spaced from each other in a coaxial alignment. The plurality of struts  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 flow  30  passes over the strut  42 . Therefore, the strut  42  influences the flow characteristics of the exhaust flow  30 , and hence the overall exhaust diffuser performance. The plurality of struts  42  is shaped as or surrounded by an airfoil, and it is to be appreciated that the precise geometry and dimensions of the plurality of struts  42  may vary from that illustrated, based on the application. Each of the plurality of struts  42  includes a leading edge  44  and a trailing edge  46 . 
         [0028]    As the exhaust flow  30  exits the turbine section  16 , the last stage bucket exit tangential flow angle ( FIG. 4 ) of the exhaust flow  30  increases based on the diverging configuration of the outer wall  38  of the exhaust diffuser  26 , as well as various operating conditions, 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 plurality of struts  42 . To reduce the flow separation described above, the exhaust flow  30  is manipulated by the flow manipulating arrangement  50 , as described in detail below. 
         [0029]    Referring to  FIGS. 4 and 5 , in conjunction with  FIGS. 2 and 3 , the flow manipulating arrangement  50  comprises at least one, but typically a plurality of rotatable guide vanes  52  circumferentially spaced from each other and coaxially aligned. As described above, the plurality of struts  42  is disposed in an axial location, such that the struts are coaxially aligned. The plurality of rotatable guide vanes  52  is disposed proximate the plurality of struts  42  and at a location axially upstream of the plurality of struts  42 . The plurality of rotatable guide vanes  52  comprises an airfoil-shaped geometry and is operatively coupled to the inner barrel  34  and/or the outer wall  38  for support. One or more sealing components  41  may be disposed between the plurality of rotatable guide vanes  52  and the inner barrel  34  and/or the outer wall  38  for sealing at an interface therebetween. The plurality of rotatable guide vanes  52  each include a rotatable member  54 , such as a spindle or rod, operatively coupled thereto. In one embodiment, the rotatable member  54  extends in a radial direction through a portion of the plurality of rotatable guide vanes  52 . The rotatable member  54  is also operatively coupled to an actuator assembly  56  ( FIG. 2 ) configured to actuate rotation of the rotatable member  54 . In particular, the actuator assembly  56  may be directly coupled to the rotatable member  54 , such as via an output shaft or gear of the actuator assembly  56 , or indirectly coupled to the rotatable member  54  via a gear arrangement and/or cable arrangement, generally referred to as  58 . The actuator assembly  56  refers to various motors, including a servo motor. Alternatively, a pneumatic actuator may actuate adjustment of the rotatable member  54 . In one embodiment, the rotatable member  54  is coupled to the inner barrel  34  and/or outer wall  38  with a bushing or bearing arrangement mounted to the inner barrel  34  and/or outer wall  38 . 
         [0030]    The plurality of rotatable guide vanes  52  is rotatable about an axis defined by the rotatable member  54  over a range of angular positions. The range of angular positions advantageously provides numerous positions of the plurality of rotatable guide vanes  52 , thereby accounting for various flow angles of the exhaust flow  30 . Specifically, the plurality of struts  42  is aligned in a direction to provide efficient flow characteristics of the exhaust flow  30  within the exhaust diffuser  26  at certain operating conditions, such as a base load, or full-speed, full-load operating condition. However, flow angles of the exhaust flow  30  differ at other operating conditions, such as a part load operating condition, for example. In the alternate operating conditions, efficiency is reduced due to an increase in boundary layer formation. By rotating the plurality of rotatable guide vanes  52  to positions corresponding to appropriate flow manipulating positions, the exhaust flow  30  is manipulated in what is referred to as a “straightening” manner, which results in a desirable flow angle of the exhaust flow  30  upon passage over the plurality of struts  42 . 
         [0031]    In one embodiment, with reference to  FIGS. 5 and 6 , a circumferential segment of rotatable guide vanes  60  comprises operatively coupled rotatable guide vanes arranged in a “ganged” relationship. The circumferential segment of rotatable guide vanes  60  comprises two or more guide vanes operatively coupled by a circumferential ring  62 . It is contemplated that any number of a plurality of guide vanes may form the circumferential segment of rotatable guide vanes  60 . The ganged arrangement allows the actuator assembly  56  and the gear arrangement and/or cable arrangement  58  to directly impart rotation of a single rotatable member, while indirectly rotating the additional guide vanes of the circumferential segment of rotatable guide vanes  60  via the circumferential ring  62 . The circumferential ring  62  forms a rack and pinion arrangement with additional rotatable members to facilitate rotation of the additional guide vanes via a toothed gear arrangement between the circumferential ring  62  and the additional rotatable members of each guide vane. Alternatively, or in combination with the rack and pinion arrangement, the circumferential ring  62  may be operative coupled to one or more bearings  63  ( FIG. 6 ) that facilitate sliding of the circumferential ring  62  within a slot structure  65 , thereby driving a rotational motion of each of the rotatable guide vanes about the rotatable member  54  of the respective rotatable guide vanes. 
         [0032]    As described above, the plurality of rotatable guide vanes  52  is rotatable over a range of angular positions. The range of angular positions corresponds to a range of operating conditions of the turbine system  10 , and more specifically a range of angles of tangential flow of the exhaust flow  30 . For example, a first position corresponds to a first condition and a second position corresponds to a second condition. The first position of the plurality of rotatable guide vanes  52  is relatively parallel to the plurality of struts  42  at a first condition corresponding to a full-speed, full-load operating condition of the turbine system  10 . As the speed of the turbine system  10  is reduced to a part load condition, such as 60% speed, for example, the plurality of rotatable guide vanes  52  are rotated to an angle that provides desirable manipulation of the exhaust flow  30  to straighten for flow over the plurality of struts  42 . 
         [0033]    Referring now to  FIGS. 7-9 , a flow manipulation arrangement  100  according to a second embodiment is illustrated. The second embodiment is similar in many respects to the first embodiment described in detail above, such that duplicative description of each component is not necessary and similar reference numerals are employed where applicable. Additionally, the second embodiment is employed in conjunction with an axial exhaust diffuser, such as the exhaust diffuser  26  described in detail above. In the second embodiment, the plurality of rotatable guide vanes  52  is disposed circumferentially adjacent to, but coaxially aligned with the plurality of struts  42 . As shown, at least a portion of the plurality of rotatable guide vanes  52  is disposed at substantially the same axial location of at least a portion of the plurality of struts  42 , including the leading edge  44  and/or the trailing edge  46  of the plurality of struts  42 . It is contemplated that the rotatable guide vanes and the struts may be arranged in an alternating arrangement in a one-to-one ratio, or alternatively more than one rotatable guide vane may be disposed between the struts. Additionally, as is the case with the first embodiment, one or more sealing components  41  are disposed at an interface between the plurality of rotatable guide vanes  52  and the inner barrel  34  and/or the outer wall  38 . 
         [0034]    Referring now to  FIGS. 10-12 , a flow manipulation arrangement  200  according to a third embodiment is illustrated. The third embodiment is employed in conjunction with an axial exhaust diffuser, such as the exhaust diffuser  26  described in detail above. The third embodiment includes a plurality of guide vanes  202  circumferentially spaced from each other and coaxially aligned. Additionally, the plurality of guide vanes  202  is disposed in at least one axial stage, which may be axially upstream and/or downstream of the plurality of struts  42 . 
         [0035]    Each of the plurality of guide vanes  202  are aligned in a substantially parallel alignment with the plurality of struts  42 , but each stage of guide vanes is adjustable in a circumferentially displaceable manner. Specifically, the plurality of guide vanes  202  are “clocked” to alter their alignment with the plurality of struts  42 . For example, in a first position ( FIG. 10 ), the plurality of guide vanes  202  is circumferentially aligned with the plurality of struts  42  and in a second position ( FIG. 11 ), the plurality of guide vanes  202  is circumferentially misaligned with the plurality of struts  42 . As described above, the first position and the second position are advantageous at different operating conditions of the turbine system  10 . 
         [0036]    As is the case with the previous embodiments described, the flow manipulation arrangement  200  is actuated with an actuator arrangement  204 , such as one or more motors that directly or indirectly interact with a circumferential ring  206  that controls the position of the plurality of guide vanes  202 . 
         [0037]    Referring now to  FIG. 13 , a flow manipulation arrangement  300  according to a fourth embodiment is illustrated. The fourth embodiment is similar in many respects to the first and second embodiments described in detail above, such that duplicative description of each component is not necessary and similar reference numerals are employed where applicable. However, in contrast to the axial exhaust diffuser of the first and second embodiments, the fourth embodiment is employed in conjunction with a radial exhaust diffuser  302 . The radial exhaust diffuser  302  comprises either a steam turbine diffuser or a gas turbine diffuser. The radial exhaust diffuser  302  includes an inner wall  304  and an outer wall  306 , with at least one strut  308  operatively coupled to at least one of the inner wall  304  and the outer wall  306 . At least one guide vane  310  is operatively coupled to the at least one strut  308 , and as is the case with the previous embodiments comprising rotatable guide vanes, the at least one guide vane  310  is rotatable over a range of angular positions that corresponds to a range of exhaust flow conditions. Additionally, the at least one guide vane  310  is selectively displaceable in the axial direction and/or the radial direction. 
         [0038]    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.