Patent Publication Number: US-10309246-B2

Title: Passive clearance control system for gas turbomachine

Description:
BACKGROUND 
     The subject matter disclosed herein relates to the art of turbomachines and, more particularly, to a passive clearance control system for a turbine portion of a gas turbomachine. 
     Gas turbomachines typically include a compressor portion, a turbine portion, and a combustor assembly. The combustor assembly mixes fluid from the compressor portion with a fuel to form a combustible mixture. The combustible mixture is combusted forming hot gases that pass along a hot gas path of the turbine portion. The turbine portion includes a number of stages having airfoils mounted to rotors that convert thermal energy from the hot gases into mechanical, rotational energy. Additional fluid from the compressor is passed through a shell of the gas turbomachine for cooling purposes. 
     BRIEF DESCRIPTION 
     According to one aspect of an exemplary embodiment, a turbomachine includes a compressor portion, and a turbine portion operatively connected to the compressor portion. The turbine portion includes a turbine casing, a plurality of stators fixedly mounted to the turbine casing, and a plurality of rotating airfoils rotatably supported in the turbine casing. A combustor assembly, including at least one combustor, fluidically connects the compressor portion and the turbine portion. At least one of the compressor portion, turbine portion, and combustor assembly includes a sensing cavity configured to contain a fluid having a fluid parameter indicative of a desired operational mode of the turbomachine. A passive clearance control system is operatively arranged in the turbomachine. The passive clearance control system includes at least one passive flow modulating device mounted in the sensing cavity and is responsive to the fluid parameter, and at least one cooling channel extending from the sensing cavity through the casing. The at least one passive flow modulating device selectively passes the fluid from the sensing cavity through the at least one cooling channel to adjust a clearance between the plurality of stators and the plurality of rotating airfoils. 
     According to another aspect of an exemplary embodiment, a turbomachine system includes a compressor portion and a turbine portion operatively connected to the compressor portion. The turbine portion includes a turbine casing, a plurality of stators fixedly mounted to the turbine casing, and a plurality of rotating airfoils rotatably supported in the turbine casing. An intake system is fluidically coupled to the compressor portion. The intake system is operative to condition a flow of intake air to the compressor portion. An exhaust system is fluidically connected to the turbine portion. The exhaust system is operative to condition a flow of exhaust gases passing from the turbine portion. A load is operatively connected to one of the turbine portion and the compressor portion. A combustor assembly, including at least one combustor, fluidically connects the compressor portion and the turbine portion. At least one of the compressor portion, turbine portion, and combustor assembly includes a sensing cavity configured to contain a fluid having a fluid parameter indicative of a desired operational mode of the turbomachine. A passive clearance control system is operatively arranged in the turbomachine. The passive clearance control system includes at least one passive flow modulating device mounted in the sensing cavity and is responsive to the fluid parameter, and at least one cooling channel extends from the sensing cavity through the turbine casing. The at least one passive flow modulating device selectively passes the fluid from the sensing cavity through the at least one cooling channel to adjust a clearance between the plurality of stators and the plurality of rotating airfoils. 
     According to yet another aspect of an exemplary embodiment, a method of adjusting rotor blade-to-stator clearance in a turbomachine includes sensing a fluid parameter of a fluid in a sensing cavity of the turbomachine indicative of a desired operating mode of the turbomachine, and actuating at least one passive flow modulating device in response to the fluid parameter, and passing the fluid from the sensing cavity to one or more cooling channels extending through a casing of a turbine portion to passively adjust rotor blade-to-stator clearance in the turbine portion. 
     These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The subject matter, which is regarded as the disclosure, 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 disclosure are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is schematic view of a gas turbomachine including a passive clearance control system, in accordance with an exemplary embodiment; 
         FIG. 2  is a partial cross-sectional side view of the turbomachine of  FIG. 1 ; 
         FIG. 3  is a partial cross-sectional side view of a portion of a turbine casing of the turbomachine of  FIG. 2 ; 
         FIG. 4  is a schematic representation of an array of coolant channels of the passive clearance control system, in accordance with an aspect of an exemplary embodiment; 
         FIG. 5  is a schematic representation of an array of coolant channels of the passive clearance control system, in accordance with another aspect of an exemplary embodiment; 
         FIG. 6  is a schematic representation of an array of coolant channels of the passive clearance control system, in accordance with yet another aspect of an exemplary embodiment; 
         FIG. 7  is a schematic representation of coolant channels having a generally circular cross-section, in accordance with an aspect of an exemplary embodiment; 
         FIG. 8  is a schematic representation of coolant channels having a generally rectangular cross-section, in accordance with an aspect of an exemplary embodiment; 
         FIG. 9  is a schematic representation of coolant channels arranged in clusters, in accordance with an aspect of an exemplary embodiment; and 
         FIG. 10  is a schematic representation of a first plurality of coolant channels and a second plurality of coolant channels arranged radially outwardly of the first plurality of coolant channels, in accordance with an aspect of an exemplary embodiment. 
     
    
    
     The detailed description explains embodiments of the disclosure, together with advantages and features, by way of example with reference to the drawings. 
     DETAILED DESCRIPTION 
     A turbomachine system, in accordance with an exemplary embodiment, is indicated generally at  2 , in  FIGS. 1 and 2 . Turbomachine system  2  includes a turbomachine  4  having a compressor portion  6  and a turbine portion  8  operatively connected through a common compressor/turbine shaft  10 . A combustor assembly  12  is fluidically connected between compressor portion  6  and turbine portion  8 . Combustor assembly  12  includes at least one combustor  14  that directs products of combustion toward turbine portion  8  through a transition piece  15 . An intake system  16  is fluidically connected to an inlet (not separately labeled) of compressor portion  6 . In addition, a load  18  is mechanically linked to turbomachine  4  and an exhaust system  20  is operatively connected to an outlet (also not separately labeled) of turbine portion  8 . 
     In operation, air is passed through intake system  16  into compressor portion  6 . Intake system  16  may condition the air by, for example, lowering humidity, altering temperature, and the like. The air is compressed through multiple stages of compressor portion  6  and is passed to turbine portion  8  and combustor assembly  12 . The air is mixed with fuel, diluents, and the like, in combustor  14  to form a combustible mixture. The combustible mixture is passed from combustor  14  into turbine portion  8  via transition piece  15  as hot gases. The hot gases flow along a hot gas path  22  of turbine portion  8 . The hot gases interact with one or more stationary airfoils, such as shown at  24 , and rotating airfoils, such as shown at  25 , to produce work. The hot gases then pass as exhaust into an exhaust system  20 . The exhaust may be treated and expelled to ambient or used as a heat source in another device (not shown). 
     In accordance with an exemplary embodiment, turbomachine  4  includes a casing or shell  30  having a compressor section  32  that surrounds compressor portion  6  and a turbine section  34  that surrounds turbine portion  8 . Compressor section  32  includes a compressor discharge cavity (CDC)  38  that leads a portion of the compressed air into turbine portion  8  as cooling gas. In the exemplary embodiment shown, CDC  38  may take the form of a sensing cavity  40  that may contain a fluid having a fluid parameter, such as for example, pressure and/or temperature, indicative of a desired operational mode of turbomachine  4 . 
     In accordance with an aspect of an exemplary embodiment illustrated in  FIG. 3 , turbine section  34  of casing  30  includes an outer surface  43  and an inner surface  45 . Inner surface  45  includes a plurality of hook members  47 . Hook members  47  may take the form of first stage shroud supports  49  and second stage shroud supports  50 . First and second stage shroud supports  49  and  50  retain stators or shrouds, such as indicated at  52 , to turbine section  34  of casing  30 . 
     In addition, casing  30  includes a plurality of cooling channels  54  extending through turbine section  34  and arranged in a heat exchange relationship with hook members  47 . As each of the plurality of cooling channels  54  is substantially similar, a detailed description will follow to one of the plurality of cooling channels indicated at  56  with an understanding that others of the plurality of cooling channels may be similarly formed. Cooling channel  56  includes a first end  59  exposed to sensing cavity  40 , a second end  60  and an outlet  62 . Outlet  62  may be fluidically connected with stationary airfoil  24 . A baffle member  64  may be arranged in cooling channel  56  to establish a desired residence time of cooling air along hook members  47 . 
     In accordance with an aspect of an exemplary embodiment, turbomachine  4  includes a passive clearance control system  70  that passively adjusts a clearance between tip portions (not separately labeled) of rotating airfoils  25  and shrouds (also not separately labeled) supported from hook members  47 . By “passive” it should be understood that clearances are autonomously adjusted based solely on turbomachine parameters without the intervention of external programmed control systems and/or personnel. 
     In accordance with an aspect of an exemplary embodiment, passive clearance control system  70  includes a passive flow modulating device  75  fluidically exposed to sensing cavity  40 . In an aspect of an exemplary embodiment, passive flow modulating device  75  may take the form of a valve  80  arranged in sensing cavity  40 . Valve  80  may be responsive to pressure and/or temperature of fluid in sensing cavity  40 . The pressure and/or temperature of the fluid may be indicative of a desired operational parameter of turbomachine  4 . At a predetermined temperature and/or pressure, valve  80  may open passing cooling fluid from sensing cavity  40  through cooling channels  54 . In this manner, casing  30  may adjust a desired clearance between rotating airfoils  25  and internal surfaces of casing  30 . In accordance with an aspect of an exemplary embodiment, passive flow modulating device  75  may operate as an integrated sensor, actuator and valve that controls a flow of coolant from sensing cavity  40  to cooling channels  54 . 
     In accordance with an aspect of an exemplary embodiment illustrated in  FIG. 4 , each of the plurality of cooling channels  54  may be provided with a corresponding passive flow modulating device  75 . Each passive flow modulating device  75  controls the flow of cooling fluid into a respective one of the plurality of cooling channels  54 . Passive flow modulating device  75  may open in response to pressure and/or temperature of fluid in sensing cavity  40 . In accordance with an exemplary embodiment illustrated in  FIG. 5 , a single passive flow modulating device  75  may control cooling flow to all of the plurality of cooling channels  54 . In further accordance with an aspect of an exemplary embodiment, each of the plurality of cooling channels  54  may be provided with a secondary passive flow modulating device  84  that controls fluid flow into an associated one of the plurality of cooling channels  54 . Secondary passive flow modulating device  84  may take the form of a pressure activated valve which opens in response to a predetermined coolant pressure. Passive flow modulating device  75  may be directly fluidically connected, in series, to each secondary passive flow modulating device  84  or could take the form of a piloted flow valve or actuator that is fluidically isolated from each secondary passive flow modulating device  84  and simply controls a flow of fluid from sensing cavity  40 .  FIG. 6  illustrates an exemplary aspect in which a plurality of passive flow modulating devices  75  control fluid flow to more than one of the plurality of cooling channels  54 . For example, each passive flow modulating device  75  may control cooling fluid delivery to two or more of the plurality of cooling channels  54 . 
     In accordance with an aspect of an exemplary embodiment, turbine section  34  of casing  30  defines a casing volume V C . In further accordance with an exemplary embodiment, plurality of cooling channels  54  collectively defines a channel volume V Ch . In accordance with an aspect of an exemplary embodiment, casing volume V C  and channel volume V Ch  define a volume ratio of about 0.0002&lt;V Ch /V C &lt;0.9. In accordance with another aspect of an exemplary embodiment, casing volume V C  and channel volume V Ch  define a volume ratio of about 0.01&lt;V Ch /V C &lt;0.74. The volume ratio ensures a desired cooling for casing  30  while also maintaining a desired operational efficiency of turbomachine  4 . 
       FIG. 7  illustrates plurality of cooling channels  54  arranged in an array about turbine section  34  of casing  30 .  FIG. 8  illustrates a plurality of cooling channels  100  each having a rectangular cross-section  104 .  FIG. 9  depicts a plurality of cooling channels  108  arranged in cooling channel clusters  110 .  FIG. 10  depicts a plurality of cooling channels  120 . Cooling channels  120  include first plurality of cooling channels  124  arranged in a first annular array, about and extending through, turbine portion  34  of casing  30 , and a second plurality of cooling channels  126  arranged in an annular array radially inwardly of cooling channels  124 . 
     At this point, it should be understood that exemplary embodiments describe a system for passively controlling running clearances in a turbomachine. More specifically, the system employs a valve responsive to a fluid parameter indicative of an operating condition of the turbomachine. In response to detecting a desired operating parameter, the passive flow modulating device selectively controls a flow of cooling fluid through a turbine shell. The cooling fluid passes in a heat exchange relationship with turbine casing. The casing expands and/or contracts resulting from a presence and/or absence of cooling fluid. The expansion and/or contraction of the casing causes a shifting of the turbine shrouds resulting in a change in or adjustment of turbine running clearance. 
     The term “about” is intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application. For example, “about” can include a range of ±8% or 5%, or 2% of a given value. 
     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, element components, and/or groups thereof. 
     While the disclosure is provided in detail in connection with only a limited number of embodiments, it should be readily understood that the disclosure is not limited to such disclosed embodiments. Rather, the disclosure 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 disclosure. Additionally, while various embodiments of the disclosure have been described, it is to be understood that the exemplary embodiment(s) may include only some of the described exemplary aspects. Accordingly, the disclosure is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.