Abstract:
A passive flow modulation device according to an embodiment includes: a temperature sensitive element disposed within a first area; a piston coupled to the temperature sensitive element, the piston extending through a wall to a second area, wherein the first area is at a higher temperature than the second area; and a valve arrangement disposed in the second area and actuated by a distal end portion of the piston, the valve arrangement tangentially injecting a supply of cooling air through an angled orifice from the second area into the first area in response an increase in temperature in the first area.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is related to co-pending US application numbers: ______, GE docket numbers 280848-1 and 283683-1, filed on ______. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The disclosure relates generally to turbomachines, and more particularly, to passive flow modulation of cooling flow into a cavity. 
         [0003]    Turbines are widely used in a variety of aviation, industrial, and power generation applications to perform work. Such turbines generally include alternating stages of peripherally mounted stator vanes and rotating blades. The stator vanes may be attached to a stationary component such as a casing that surrounds the turbine, and the rotating blades may be attached to a rotor located along an axial centerline of the turbine. A compressed working fluid, such as steam, combustion gases, or air, flows along a gas path through the turbine to produce work. The stator vanes accelerate and direct the compressed working fluid onto a subsequent stage of rotating blades to impart motion to the rotating blades, thus turning the rotor and performing work. 
         [0004]    Various components (e.g., blades, nozzles, shrouds, etc.) and areas wheelspaces between stator and rotor) of turbines are typically cooled in some fashion to remove heat transferred by the hot gas path. A gas such as compressed air from an upstream compressor may be supplied through at least one cooling circuit including one or more cooling passages to cool the turbine. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0005]    A first aspect of the disclosure provides a passive flow modulation device, including: a temperature sensitive element disposed within a first area; a piston coupled to the temperature sensitive element, the piston extending through a wall to a second area, wherein the first area is at a higher temperature than the second area; and a valve arrangement disposed in the second area and actuated by a distal end portion of the piston, the valve arrangement tangentially injecting a supply of cooling air through an angled orifice from the second area into the first area in response an increase in temperature in the first area. 
         [0006]    A second aspect of the disclosure provides a passive flow modulation device, including: a temperature sensitive element; a piston coupled to the temperature sensitive element, the piston including a head section, wherein the temperature sensitive element and the piston are disposed in a first area; and an orifice, extending from a second area into the first area, for supplying a flow of cooling air from the second area to the first area, wherein the first area is at a higher temperature than the second area; wherein the temperature sensitive element enlarges or contracts to selectively position the head of the piston over a portion of the aperture to control the flow of cooling air from the second area into the first area. 
         [0007]    A third aspect of the disclosure provides a cooling system for a turbine, including: an orifice located between a first area and a second area of the turbine, wherein the first area of the turbine is at a higher temperature than the second area of the turbine; a passive flow modulation device disposed adjacent the orifice for directing a flow of cooling air through the orifice from the second area of the turbine to the first area of the turbine, the passive flow modulation device including: a temperature sensitive element disposed within the first area; a piston coupled to the temperature sensitive element, the piston extending through a wall to the second area; and a valve arrangement disposed in the second area and actuated by a distal end portion of the piston, the valve arrangement selectively directing the flow of cooling air through the orifice from the second area into the first area in response a change in temperature in the first area; or a temperature sensitive element; and a piston coupled to the temperature sensitive element, the piston including a head section, wherein the temperature sensitive element and the piston are disposed in the first area; 
         [0008]    wherein the temperature sensitive element enlarges or contracts in response to a change in temperature in the first area to selectively position the head of the piston over a portion of the aperture to control the flow of cooling air from the second area into the first area. 
         [0009]    The illustrative aspects of the present disclosure are designed to solve the problems herein described and/or other problems not discussed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    These and other features of this disclosure will be more readily understood from the following detailed description of the various aspects of the disclosure taken in conjunction with the accompanying drawing that depicts various embodiments of the disclosure. 
           [0011]      FIG. 1  is a schematic diagram of a gas turbine system according to embodiments. 
           [0012]      FIG. 2  is a cross-sectional view of a rotor, stator, and a plurality of passive flow modulation (PFM) devices according to embodiments. 
           [0013]      FIG. 3  depicts a PFM device in a closed position according to embodiments. 
           [0014]      FIG. 4  depicts the PFM device of  FIG. 3  in an open position according to embodiments. 
           [0015]      FIG. 5  depicts a graph of the flow modulation provided by the PFM device of  FIGS. 3 and 4  according to embodiments. 
           [0016]      FIG. 6  depicts a PFM device in a reduced flow position according to embodiments. 
           [0017]      FIG. 7  depicts the PFM device of  FIG. 6  in a full flow position according to embodiments. 
           [0018]      FIG. 8  depicts a graph of the flow modulation provided by the PFM device of  FIGS. 6 and 7  according to embodiments. 
           [0019]      FIG. 9  depicts a binary PFM device in a non-flow position according to embodiments. 
           [0020]      FIG. 10  depicts a binary PFM device in a full-flow position according to embodiments. 
           [0021]      FIG. 11  depicts a graph of the flow modulation provided by the binary PFM device of  FIGS. 9 and 10  according to embodiments. 
           [0022]    It is noted that the drawing of the disclosure is not to scale. The drawing is intended to depict only typical aspects of the disclosure, and therefore should not be considered as limiting the scope of the disclosure. In the drawing, like numbering represents like elements between the drawings. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    The disclosure relates generally to turbomachines, and more particularly, to passive flow modulation of cooling flow into a cavity. 
         [0024]    In the Figures, for example in  FIG. 1 , the “A” axis represents an axial orientation. As used herein, the terms “axial” and/or “axially” refer to the relative position/direction of objects along axis A, which is substantially parallel with the axis of rotation of the turbomachine (in particular, the rotor section). As further used herein, the terms “radial” and/or “radially” refer to the relative position/direction of objects along an axis (r), which is substantially perpendicular with axis A and intersects axis A at only one location. Additionally, the terms “circumferential” and/or “circumferentially” refer to the relative position/direction of objects along a circumference (c) which surrounds axis A but does not intersect the axis A at any location. 
         [0025]    Referring now to the drawings, in which like numerals refer to like elements throughout the several views,  FIG. 1  shows a schematic view of a gas turbine system  2  as may be used herein. The gas turbine system  2  may include a compressor  4 . The compressor  4  compresses an incoming flow of air  6 . The compressor  4  delivers a flow of compressed air  8  to a combustor  10 . The combustor  10  mixes the flow of compressed air  8  with a pressurized flow of fuel  12  and ignites the mixture to create a flow of combustion gases  14 . Although only a single combustor  10  is shown, the gas turbine system  2  may include any number of combustors  10 . The flow of combustion gases  14  is in turn delivered to a turbine  16 . The flow of combustion gases  14  drives the turbine  16  to produce mechanical work. The mechanical work produced in the turbine  16  drives the compressor  4  via a shaft  18 , and may be used to drive an external load  20 , such as an electrical generator and/or the like. 
         [0026]    A cross-sectional view of a turbine rotor  22  rotating within a stator  24  (e.g., along axis A) during operation of a gas turbine system  2  ( FIG. 1 ) is depicted in  FIG. 2 . A rotating flow of air  28  is produced in a wheelspace cavity  30  within the stator  24  during rotation of the rotor  22 . A plurality of orifices  34  are circumferentially positioned about the stator  24 . Cooling air  32  is tangentially injected via the plurality of orifices  34  into the wheelspace cavity  30  in a direction of rotation of the rotor  22  from a “cold” area (e.g., outside of the stator  24  in this example) to a “hot” area (e.g., the wheelspace cavity  30 ). The cooling air  32  may be generated for example by a compressor  4  of a gas turbine system  2  ( FIG. 1 ). The orifices  34  may be used, for example, as pre-swirl orifices and/or flow inducers in manner known in the art. According to embodiments, at least one of the plurality of orifices  34  is provided with a passive flow modulation (PFM) device  36 ,  38 , or  40  for selectively controlling the amount of cooling air  32  that is allowed to pass through the orifice  34  into the wheelspace cavity  30 . 
         [0027]    According to embodiments, a PFM device  36 ,  38  may be used in series with an orifice  34  to variably control the flow of cooling air  32  passing through the orifice  34  into the wheelspace  30  (e.g., from a cold area to a hot area). For example, the PFM device  36 ,  38  may initiate the flow of cooling air through the orifice  34 , and then increase and accelerate the flow of cooling air  32  exiting the orifice  34  into the wheelspace cavity  30  to or close to the speed of rotation of the rotor  22 . Each orifice  34  includes a defined effective throat area Ae and exit angle a to provide a flow path such that the exit velocity and orientation of the air flow provides optimal heat transfer efficiency in the wheelspace cavity  30 . The PFM device  36 ,  38  provides cooling flow savings across the operating range of the turbine  16  and improves the output and efficiency of the turbine  16 . 
         [0028]    According to other embodiments, a binary PFM device  40  may be used in series with an orifice  34  to binarily control the flow of cooling air  32  passing through the orifice  34  into the wheelspace cavity  30 . In a closed position, cooling air  32  is prevented from flowing through the orifice  34  into the wheelspace cavity  30 . In an open position, the binary PFM device  40  delivers a specific flow of cooling air to the wheelspace cavity  30 . Turbine performance is improved, since the binary PFM device  40  is closed during most turbine operating modes except when high temperatures are predicted or measured in the wheelspace cavity  30 . 
         [0029]    One or more of the orifices  34  may provide a continuous (e.g., unmodulated) flow of cooling air  32  into the wheelspace cavity  30 . Such an orifice  34  is depicted in the lower section of  FIG. 2 . 
         [0030]    The PFM device  36  according to embodiments is depicted in  FIGS. 3 and 4 . The PFM device  36  is in a closed position in  FIG. 3  and in an open position in  FIG. 4 . In embodiments, some of the components of the PFM device  36  are located in a cold area (e.g., outside of the stator  24 ), while other components are disposed within a hot area (e.g., the wheelspace cavity  30 ). 
         [0031]    The PFM device  36  includes a valve system  42  positioned in a cold area  44 . The valve system  42  includes at least one gas inlet port  46  ( FIG. 4 ) and a gas outlet port  48 . A conduit  50  fluidly couples the gas outlet port  48  of the valve system  42  to the orifice  34 . An adapter/connector  52  couples the conduit  50  to the stator  24 . 
         [0032]    A temperature sensitive element  54  disposed within a hot area (e.g., the wheelspace cavity  30 ) may be used for actuating the PFM device  36 . In embodiments, the temperature sensitive element  54  may include a housing  56  containing a thermally expandable material  58 . The thermally expandable material  58  may include, for example, a silicon heat transfer fluid or any other suitable thermally expandable material that is stable at the operating temperatures of the turbine  16  (e.g., up to 1300° F.). In other embodiments, the temperature sensitive element  54  may include, for example, a bimetallic element or other type of arrangement that changes size and/or shape in response to a change in temperature. 
         [0033]    The thermally expandable material  58  within the housing  56  engages a head  59  of a piston  60 , which extends through the stator  24  to a cold area  44 . In embodiments, the valve system  42  includes a valve disc  62  that is attached to a distal end of the piston  60 . Opposing outer side surfaces  64  ( FIG. 4 ) of the valve disc  62  are configured to mate with corresponding surfaces of a valve seat  66  of the valve system  42 . In further embodiments, other valve mechanisms such as, for example, a spring-loaded pintle, a ball and stopper, a butterfly plate valve, and/or the like may be used. 
         [0034]    The PFM device  36  is shown in a closed configuration in  FIG. 3 . That is, in the closed configuration, at least a portion of the outer side surfaces  64  ( FIG. 4 ) of the valve disc  62  engage the valve seat  66  of the valve system  42 . In the closed configuration, cooling air  32  is prevented from flowing from a colder area  44 , outside of the stator  24 , through the conduit  50  and the orifice  34  into a hotter area (e.g., the wheelspace cavity  30 ). 
         [0035]    Referring now to  FIG. 4 , an increase in temperature in the wheelspace cavity  30  causes an enlargement of the thermally expandable material  58  within the housing  56 . As a result, the thermally expandable material  58  expands and forces the head  59  of the piston  60  downward. The displacement of the piston  60  forces the valve disc  62  attached to the end of the piston  60  away from the valve seat  66  as indicated by arrow  70 . When the outer side surfaces  64  of the valve disc  62  no longer contact the valve seat  66 , a flow of cooling air  32  begins to flow from the gas inlet port  46  through the gas outlet port  48 , conduit  50 , and orifice  34 , into the wheelspace cavity  30 . The flow of cooling air  32  increases as the valve disc  62  moves farther away from the valve seat  66  (as the temperature increases further) as more flow area is provided between the outer side surfaces  64  of the valve disc  62  and the valve seat  66 . 
         [0036]    A graph of the flow modulation provided by the PFM device  36  is illustrated in  FIG. 5 . As shown, the ratio of the pressure (P 3 ) in the orifice  34  and the pressure (P 2 ) in the wheelspace cavity  30 , as well as the air mass flow (qm) through the orifice  34 , increases as the temperature (T 1 ) and turbine load (GT load) increase. Arrow  74  indicates a target pressure ratio (P 3 /P 2 ) and air mass flow (qm) for optimized cooling efficiency for an illustrative turbine (e.g., turbine  16 ). As indicated by arrow  76 , the PFM device  36  provides a substantial cooling flow savings across much of the operating range of the turbine as compared to a fixed flow, which improves the output and efficiency of the turbine. 
         [0037]    The PFM device  38  according to embodiments is depicted in  FIGS. 6 and 7 . The PFM device  38  is in a reduced flow position in  FIG. 6  and in a full flow position in  FIG. 6 . In embodiments, the PFM device  38  is disposed within the wheelspace cavity  30  (e.g., a hot area). 
         [0038]    The PFM device  38  includes a temperature sensitive element  78  disposed within the wheelspace cavity  30 . In embodiments, the temperature sensitive element  78  includes a housing  80  partially filled with a thermally expandable material  84 . The thermally expandable material  84  may include, for example, a silicon heat transfer fluid or any other suitable thermally expandable material that is stable at the operating temperatures of the turbine  16 . In other embodiments, the temperature sensitive element  78  may include, for example, a bimetallic element or other type of arrangement that changes size and/or shape in response to a change in temperature. 
         [0039]    A piston  86  is coupled to a movable shelf  88 . A head  90  of the piston  86  extends at least partially over an exit  92  of an orifice  34 . The distal end surface  94  of the head  90  of the piston  86  may have an angled configuration corresponding to the flow angle a of cooling air  32  through the orifice  34  into the wheelspace cavity  30 . The angled configuration of the distal end surface  94  of the head  90  of the piston  86  helps to direct the flow of, and maintain the exit angle of, cooling air  32  into the wheelspace cavity  30 . Other configurations of the end surface  94  of the head  90  of the piston  86  (e.g., perpendicular to the displacement direction of the piston  86 ) may also be used. 
         [0040]    A biasing member  96  (e.g., a spring) biases the movable shelf  88  and piston  86  towards the exit  92  of the orifice  34  as indicated by arrow  98 . In the configuration depicted in  FIG. 6 , the head  90  of the piston  86  extends at least partially over the exit  92  of the orifice  34 . This reduces the flow of cooling air  32  that can pass through the orifice  34  into the wheelspace cavity  30 . 
         [0041]    Referring now to  FIG. 7 , an increase in temperature in the wheelspace cavity  30  causes an expansion of the thermally expandable material  84  within the housing  80  and a corresponding displacement of the piston  86  in direction  100 . The force applied by the piston  86  counteracts the biasing force applied by the biasing member  96  and forces the movable shelf  88  and piston  86  in direction  100 . As indicated by arrow  102 , the expansion of the thermally expandable material  84  displaces the head  90  of the piston  86  away from the exit  92  of the orifice  34 . Since the head  90  of the piston  86  is now blocking less of the exit  92  of the orifice  34 , a larger flow of cooling air  32  can pass from the cold area outside of the stator  24  through the orifice  34  into the wheelspace cavity  30 . The flow of cooling air  32  continues to increase as the temperature within the wheelspace cavity  30  increases, which causes additional displacement of the head  90  of the piston  86  away from the exit  92  of the orifice  34 . In  FIG. 7 , the exit  92  of the orifice  34  is fully open. 
         [0042]    A graph of the flow modulation provided by a PFM device  38  is illustrated in  FIG. 8 . As shown, the effective flow area (Ae) and the air mass flow (qm) of the cooling air  32  through the orifice  34  increase as the temperature (T 1 ) and turbine load (GT load) increase. Arrow  174  indicates a target effective flow area (Ae) and air mass flow (qm) for optimized cooling efficiency for an illustrative turbine (e.g., turbine  16 ). As indicated by arrow  176 , the PFM device  38  provides a substantial cooling flow savings across much of the operating range of the turbine as compared to a fixed flow, which improves the output and efficiency of the turbine. 
         [0043]    The binary PFM device  40  according to embodiments is depicted in  FIGS. 9 and 10 . The PFM device  40  is in non-flow position in  FIG. 9  and in a full-flow position in  FIG. 10 . In embodiments, the PFM device  40  is disposed in a cold area (e.g., outside the stator  24 ). 
         [0044]    As depicted in  FIGS. 9 and 10 , the binary PFM device  40  includes a temperature sensitive pilot valve  100  and a pressure sensitive main valve  102 . The temperature sensitive pilot valve  100  is configured to open at a predetermined temperature, which causes a pressurization of the pressure sensitive main valve  102 . The pressurization of the pressure sensitive main valve  102  actuates the pressure sensitive main valve  102  to a full open position. To this extent, the pressure sensitive main valve  102  is either full open or full closed. 
         [0045]    The temperature sensitive pilot valve  100  includes at least one gas inlet port  104  and a gas outlet port  106  ( FIG. 10 ). A temperature sensitive element  108  for actuating the temperature sensitive pilot valve  100  is located within a housing  110 . In embodiments, the housing  110  is partially filled with a thermally expandable material  114 . The thermally expandable material  114  may include, for example, a silicon heat transfer fluid or any other suitable thermally expandable material that is stable at the operating temperatures of the turbine  16 ). In other embodiments, the temperature sensitive element  114  may include, for example, a bimetallic element or other type of arrangement that changes size and/or shape in response to a change in temperature. 
         [0046]    The thermally expandable material  114  engages a head  112  of a piston  116 . A valve disc  118  is attached to a distal end of the piston  116 . In the non-flow state, opposing outer side surfaces of the valve disc  118  mate with corresponding surfaces of a valve seat  120  ( FIG. 10 ). In further embodiments, other valve mechanisms such as, for example, a spring-loaded pintle, a ball and stopper, a butterfly plate valve, and/or the like may be used. 
         [0047]    The pressure sensitive main valve  102  includes at least one gas inlet port  122  and a gas outlet port  124  ( FIG. 10 ). A pressure sensitive element  126  for actuating the pressure sensitive main valve  102  is located within a housing  128 . In embodiments, the pressure sensitive element  126  may include a bellows  130  (or other expandable element (e.g., a diaphragm)) that is fluidly coupled to the gas outlet port  106  of the temperature sensitive pilot valve  100 . 
         [0048]    The bellows  130  is coupled to a piston  132 . A valve disc  134  is attached to a distal end of the piston  132 . A weep hole  136 , which extends through the piston  132  and valve disc  134 , fluidly couples the bellows  130  and the gas outlet port  124 . The weep hole  136  releases pressure in the bellows  130  when the temperature sensitive pilot valve  100  closes. In the non-flow state, opposing outer side surfaces of the valve disc  134  mate with corresponding surfaces of a valve seat  138 , preventing cooling air  32  from flowing from the gas inlet port(s)  122  through the gas outlet port  124  into the orifice  34  and wheelspace cavity  130 . In further embodiments, other valve mechanisms such as, for example, a spring-loaded pintle, a ball and stopper, a butterfly plate valve, and/or the like may be used. 
         [0049]    Referring now to  FIG. 10 , an increase in temperature in the cold area surrounding the binary PFM device  40  causes an expansion of the thermally expandable material  114  within the housing  110 . The expansion of the thermally expandable material  114  within the housing  110  displaces the valve disc  118  attached to the end of the piston  116  away from the valve seat  120 . When the outer side surfaces of the valve disc  118  no longer contact the valve seat  120 , ambient air passes through the gas inlet port(s)  104  and the gas outlet port  106  into the bellows  130 . This pressurizes the bellows  130 . 
         [0050]    The pressurization causes the bellows  130  to expand, displacing the attached piston  132  outward toward the gas outlet port  124 . In response to the outward displacement of the piston  132 , the valve disc  134  is displaced away from the valve seat  138 , allowing cooling air  32  to pass from the gas inlet port(s)  122 , through the gas outlet port  124  and the orifice  34 , into the hot area (e.g., the wheelspace cavity  30 ). 
         [0051]    A graph of the flow modulation provided by the binary PFM device  40  is illustrated in  FIG. 11 . As shown, the air mass flow (qm) through the orifice  34  at temperatures above the actuation temperature of the temperature sensitive pilot valve  100  is the same as a fixed flow orifice  34 . At temperatures under the actuation temperature, as indicated by arrow  150 , the binary PFM device  40  provides a substantial cooling flow savings across much of the operating range of the turbine, which improves the output and efficiency of the turbine. 
         [0052]    In various embodiments, components described as being “coupled” to one another can be joined along one or more interfaces. In some embodiments, these interfaces can include junctions between distinct components, and in other cases, these interfaces can include a solidly and/or integrally formed interconnection. That is, in some cases, components that are “coupled” to one another can be simultaneously formed to define a single continuous member. However, in other embodiments, these coupled components can be formed as separate members and be subsequently joined through known processes (e.g., fastening, ultrasonic welding, bonding). 
         [0053]    When an element or layer is referred to as being “on”, “engaged to”, “connected to” or “coupled to” another element, it may be directly on, engaged, connected or coupled to the other element, or intervening elements may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to”, “directly connected to” or “directly coupled to” another element, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
         [0054]    The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof 
         [0055]    This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.