Patent Publication Number: US-8966906-B2

Title: System for supplying pressurized fluid to a cap assembly of a gas turbine combustor

Description:
FIELD OF THE INVENTION 
     The present subject matter relates generally to gas turbines and, more particularly, to a system for supplying pressurized fluid to a cap assembly of a gas turbine combustor. 
     BACKGROUND OF THE INVENTION 
     Gas turbines often include a compressor, a number of combustors, and a turbine. Typically, the compressor and the turbine are aligned along a common axis, and the combustors are positioned between the compressor and the turbine in a circular array about the common axis. In operation, the compressor creates compressed air, which is supplied to the combustors. The combustors combust the compressed air with fuel to generate hot gases of combustion, which are then supplied to the turbine. The turbine extracts energy from the hot gases to drive a load, such as a generator. 
     To increase efficiency, modern combustors are operated at temperatures that are high enough to impair the combustor structure and to generate pollutants such as nitrous oxides (NOx). These risks are mitigated by directing pressurized air supplied from the compressor over the combustor exterior, which cools the combustor, before premixing the air with fuel to form an air-fuel mixture, so as to generate lower levels of NOx during combustion. 
     For these reasons, the combustor typically includes a flow sleeve that defines an annular passageway configured to receive the pressurized air discharged from the compressor. Specifically, the air impinges against the transition duct and combustion liner for cooling purposes. The air then travels in a reverse direction through the annular passageway toward the combustor cap assembly, which houses at least a portion of the fuel nozzles. Often, a portion of this air may be diverted from the annular passageway and into the cap assembly to provided cooling to such assembly. For example, a downstream plate of the cap assembly may be exposed to the high temperatures of the combustion chamber. Thus, the downstream plate is normally cooled with air diverted from the annular passageway through openings in an outer wall of the cap assembly. The diverted air impinges against and passes through the downstream plate into the combustion chamber. Thus, the diverted air is not pre-mixed with fuel, which exacerbates NOx generation. 
     Typically, the air traveling through the annular passageway experiences pressure loses. Due to these pressure losses, an increased amount of air is needed to cool the cap assembly, resulting in a lower percentage of premixed air in the combustor. Also, the air pressure through the downstream wall may not be sufficient to overcome a dynamic pressure wave that is present in the combustion chamber due to flame instability and/or other combustion dynamics. Specifically, this dynamic pressure wave may exert a pressure on the downstream wall that impedes or stops the cooling flow, causing the downstream wall to overheat and potentially fail. 
     Accordingly, a system for supplying pressurized air to the cap assembly that allows the pressure within the cap assembly to be increased would be welcomed in the technology. 
     BRIEF DESCRIPTION OF THE INVENTION 
     Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention. 
     In one aspect, the present subject matter discloses a combustor including an end cover and a fuel nozzle extending from the end cover. The fuel nozzle may include a downstream end. Additionally, the combustor may include a cap assembly configured to receive at least a portion of the fuel nozzle. The cap assembly may include an upstream wall spaced apart from the downstream end, a downstream wall disposed proximate to the downstream end and a cap chamber defined between the upstream and downstream walls. A conduit may extend through the end cover and the upstream wall and may include a discharge end terminating within the cap chamber. The conduit may be configured to direct pressurized fluid with the cap chamber. 
     In another aspect, the present subject matter discloses a system for supplying pressurized fluid to a combustor of a gas turbine. The system may include an end cover and a fuel nozzle extending from the end cover. The fuel nozzle may include a downstream end. Additionally, the system may include a cap assembly configured to receive at least a portion of the fuel nozzle. The cap assembly may include an upstream wall spaced apart from the downstream end, a downstream wall disposed proximate to the downstream end and a cap chamber defined between the upstream and downstream walls. Moreover, a conduit may extend through the end cover and the upstream wall such that a discharge end of the conduit is in flow communication with the cap chamber. 
     These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which: 
         FIG. 1  illustrates a schematic diagram of one embodiment of a gas turbine; 
         FIG. 2  illustrates a cutaway, perspective view of one embodiment of a gas turbine combustor; 
         FIG. 3  illustrates an enlarged, perspective view of a portion of the combustor shown in  FIG. 2 , particularly illustrating a portion of a flow conduit extending into a cap assembly of the combustor; and 
         FIG. 4  illustrates a cross-sectional view of a portion of the flow conduit shown in  FIG. 3 , particularly illustrating a seal defined between the flow conduit and an upstream plate of the cap assembly. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
     In general, the present subject matter is directed to a system for supplying pressurized fluid to a cap assembly of a gas turbine combustor. In particular, the present subject matter discloses a system including one or more flow conduits extending through an end cover of the combustor and into a cap chamber of the cap assembly. Each flow conduit may be in flow communication with a pressurized fluid source such that a pressurized fluid may be directed through each flow conduit and into the cap chamber. As a result, the pressure within the cap chamber may be increased, thereby increasing the pressure drop between the cap chamber and the combustion chamber. Such an increased pressure drop may generally enhance the cooling provided to a downstream wall of the cap assembly and may also prevent hot gases from being forced into and/or through the downstream wall during periods of high combustion dynamics. 
     Referring now to the drawings,  FIG. 1  illustrates a schematic depiction of one embodiment of a gas turbine  10 . In general, the gas turbine  10  includes a compressor  12 , a combustion section  14 , and a turbine  16 . The combustion section  14  may include a plurality of combustors  100  (one of which is illustrated in  FIG. 2 ) disposed around an annular array about the axis of the gas turbine  10 . The compressor  12  and turbine  16  may be coupled by a shaft  18 . The shaft  18  may be a single shaft or a plurality of shaft segments coupled together to form the shaft  18 . During operation, the compressor  12  supplies compressed air to the combustion section  14 . The compressed air is mixed with fuel and burned within each combustor  100  ( FIG. 2 ) and hot gases of combustion flow from the combustion section  14  to the turbine  16 , wherein energy is extracted from the hot gases to produce work. 
     Referring now to  FIGS. 2 and 3 , one embodiment of a combustor  100  having a plurality of flow conduits  102  installed therein is illustrated in accordance with aspects of the present subject matter. In particular,  FIG. 2  illustrates a cutaway, perspective view of the combustor  100 . Additionally,  FIG. 3  illustrates an enlarged view of a portion of a cap assembly  104  of the combustor  100  shown in  FIG. 2 , particularly illustrating one of the flow conduits  102  extending into the cap assembly  104 . 
     As shown, the combustor  100  generally includes a substantially cylindrical combustion casing  106  secured to a portion of a gas turbine casing  108 , such as a compressor discharge casing or a combustion wrapper casing. The gas turbine casing  108  may generally define a plenum (not shown) configured to receive pressurized air discharged from the compressor  12  ( FIG. 1 ). Additionally, the combustor  100  may include an end cover  110  secured to an upstream end of the combustion casing  106  and a plurality of fuel nozzles  112  secured to and extending from the end cover  110 . Each fuel nozzle  112  may generally be configured to intake fuel supplied through the end cover  110  and mix the fuel with the pressurized air supplied from the compressor  12 . For purposes of clarity, the fuel nozzles  112  are illustrated in  FIGS. 2 and 3  as cylinders without any detail with respect to the type, configuration and internal components of the nozzles  112 . It should be readily appreciated by those of ordinary skill in the art that the disclosed combustor  100  is not limited to any particular type, shape and/or configuration of the fuel nozzles  112  and, thus, any suitable fuel nozzle known in the art may be utilized within the scope of the present subject matter. Moreover, it should be appreciated that the combustor  100  may include any suitable number of fuel nozzles  112 . 
     The combustor  100  may also include a flow sleeve  114  and a combustion liner  116  substantially concentrically arranged within the flow sleeve  114 . As such, an annular passageway  118  may be defined between the flow sleeve  114  and the combustion liner  116  for directing the pressurized air flowing within the turbine casing  108  along the combustion liner  116 . For example, the flow sleeve  114  (and/or an impingement sleeve  120  of the combustor  100 ) may define a plurality of holes configured to permit the pressurized air contained within the turbine casing  108  to enter the annular passageway  118  and flow upstream along the combustion liner  116  toward the fuel nozzles  112 . Additionally, the combustion liner  116  may generally define a substantially cylindrical combustion chamber  122  downstream of the fuel nozzles  112 , wherein the fuel and pressurized air mixed within the fuel nozzles  112  are injected and combusted to produce hot gases of combustion. Further, the downstream end of the combustion liner  116  may generally be coupled to a transition piece  124  extending to a first stage nozzle (not shown) of the turbine  16  ( FIG. 1 ). As such, the combustion liner  116  and transition piece  124  may generally define a flowpath for the hot gases of combustion flowing from the combustor  100  to the turbine  16 . 
     As indicated above, the combustor  100  may also include a cap assembly  104  disposed upstream of the combustion chamber  122 . For example, in several embodiments, a portion of the cap assembly  104  may be secured to an upstream end of the combustion liner  116  in order to seal the hot gases of combustion within the combustion chamber  122 . As such, the cap assembly  104  may generally serve to shield or protect the upstream components of the combustor  100  (e.g., the end cover  110  and portions of the fuel nozzles  112 ) from the hot gases of combustion generated within the combustion chamber  122 . Additionally, at least a portion of each fuel nozzle  112  may be configured to be received within and extend through the cap assembly  104 . Thus, as shown in.  FIG. 3 , a downstream end  126  of each fuel nozzle  112  (shown in a cut-away portion of  FIG. 3 ) may generally be in flow communication with the combustion chamber  122 , thereby allowing the fuel and air mixed within each fuel nozzle  112  to be injected into the combustion chamber  122 . 
     As shown in  FIGS. 2 and 3 , the cap assembly  104  may generally include a radially outer wall  128 , an upstream wall  130  and a downstream wall  132 . In general, the walls  128 ,  130 ,  132  of the cap assembly  104  may be spaced apart from one another so as to define a plenum or cap chamber  134 . Specifically, as shown in the illustrated embodiment, the cap chamber  134  may extend axially a distance  136  ( FIG. 3 ) defined between the upstream and downstream walls  130 ,  132  and may extend radially a distance  138  ( FIG. 2 ) defined between opposed sides of the radially outer wall  128 . As is generally understood, a portion of the pressurized air flowing within the annular passageway  118  may be diverted into the cap chamber  134  to provide cooling to the downstream wall  132  of the cap assembly  104 . For example, in several embodiments, a plurality of openings (not shown) may be defined through the radially outer wall  126  to permit pressurized air flowing within the annular passageway  118  to enter the cap chamber  134 . 
     The upstream wall  130  of the cap assembly  104  may generally comprise a plate (e.g., a baffle plate) defining a plurality of openings  140  ( FIG. 4 ) for receiving the fuel nozzles  112 . As such, at least a portion of each fuel nozzle  122  may extend through the upstream wall  130  and into the cap chamber  134 . Additionally, as shown in the illustrated embodiment, the upstream wall  130  may generally be positioned upstream of the downstream wall  132  of the cap assembly  104 . Accordingly, the upstream wall  130  may be spaced axially apart from both the combustion chamber  122  and the downstream ends  126  of the fuel nozzles  112 . 
     The downstream wall  132  of the cap assembly  104  may generally define the upstream end of the combustion chamber  122  and, thus, may be disposed proximate to both the combustion chamber  122  and the downstream ends  126  of the fuel nozzles  112 . For example, in several embodiments, the downstream wall  132  may define a plurality of openings  142  ( FIG. 3 ) configured to receive the downstream end  126  of each fuel nozzle  112 . As such, the downstream ends  126  of the fuel nozzles  112  may extend through the downstream wall  132  to permit the nozzles  112  to be in direct flow communication with the combustion chamber  122 . 
     Additionally, in several embodiments, the downstream wall  132  may have a double-walled configuration. For example, as shown in  FIG. 3 , the downstream wall  132  may include a first plate  144  and a second plate  146  disposed adjacent to and directly downstream of the first plate  144 . In several embodiments, the first and/or second plates  144 ,  146  may include a plurality of holes. For instance, as particularly shown in  FIG. 3 , the first plate  144  may be configured as an impingement plate and may include a plurality of impingement holes  148  defined therein. As such, any pressurized fluid contained within the cap chamber  134  may be directed through the impingement holes  148  in order to provide impingement cooling against the second plate  146 . For example, as indicated above, pressurized air from the annular passageway  118  may be diverted into the cap chamber  134 , which may then be flow through the impingement holes  148  to providing cooling to the second plate  146 . Moreover, the second plate  146  may be configured as an effusion plate and may include a plurality of effusion holes  150  defined therein. For instance, the effusion holes  150  may be smaller than and angled with respect to the impingement holes  148 . As such, the pressurized fluid flowing through the impingement holes  148  may flow through the effusion holes  150  to provide film cooling to the combustion chamber side of the second plate  146 . 
     In alternative embodiments, it should be appreciated that the downstream wall  132  need not have double-walled configuration. For example, in one embodiment, the downstream wall  132  may simply comprise a single plate (e.g., an effusion plate) disposed proximate to both the combustion chamber  122  and the downstream ends  126  of the fuel nozzles  112 . 
     Referring still to  FIGS. 2 and 3 , as indicated above, the pressurized air flowing through the annular passageway  118  may experience pressure losses, which may result in a reduction in the maximum pressure that may be obtained within the cap chamber  134 . As such, the pressure drop between the cap chamber  134  and the combustion chamber  122  may be reduced, thereby decreasing the amount of cooling provided to the downstream wall  132  and increasing the likelihood that the hot gases contained within the combustion chamber  122  are forced into and/or through the downstream wall  132  (e.g., through the effusion holes  150 ) during periods of high combustion dynamics. Thus, in accordance with several embodiments of the present subject matter, the combustor  100  may include one or more flow conduits  102  configured to supply a pressurized fluid into the cap chamber  134  in order to increase the pressure within the chamber  134 . 
     In general, each flow conduit  102  may be configured to extend through the end cover  110  and the upstream wall  130  of the cap assembly  104  such that a discharge end  152  of each flow conduit  102  terminates within the cap chamber  134  (i.e., at a location downstream of the upstream wall  130  and upstream of the downstream wall  132 ). As such, each flow conduit  102  may generally define a fluid pathway for pressurized fluid to be directed through the end cover  110  and upstream wall  130  and into the cap chamber  134 . The pressurized fluid exiting the discharge end  152  of each conduit  102  may then be utilized to cool the downstream wall  132  (e.g., by being directed through the impingement holes  148  so as to provide impingement cooling to the second plate  146 ) and/or otherwise to increase the pressure drop between the cap chamber  134  and the combustion chamber  122 . 
     It should be appreciated that the pressurized fluid supplied to the cap chamber  134  through the flow conduits  102  may be in addition to, or as an alternative to, the pressurized air diverted into the cap chamber  134  from the annular passageway  118 . For example, in one embodiment, the flow conduits  102  may be configured to provide pressurized fluid to the cap chamber  134  at a sufficient pressure and/or flow rate so as to eliminate the need of diverting a portion of the pressurized air from the annular passageway  118 . As a result, an increased amount of the pressurized air flowing through the annular passageway  118  may be supplied to the fuel nozzles  112  and mixed with fuel for subsequent combustion. 
     It should also be appreciated any number of flow conduits  102  may be configured to extend through the end cover  110  and into the cap chamber  134 . For example, in several embodiments, the number of flow conduits  102  may correspond to the number of fuel nozzles  112  contained within the combustor  100 . However, in alternative embodiments, the number of flow conduits  112  may be more or less than the number of fuel nozzles  112  (including a single flow conduit  102 ). 
     Moreover, it should be appreciated that the flow conduits  102  may generally be configured as any suitable tube, pipe, hose, flow channel and/or the like known in the art that may be utilized to direct a pressurized fluid through the end cover  110  and into the cap chamber  134 . Similarly, the flow conduits  102  may be installed within and/or secured to a portion of the combustor  100  using any suitable means. For example, as shown in  FIG. 2 , in one embodiment, each flow conduit  102  may be mounted to the end cover  110 , such as by securing an annular flange  154  of each flow conduit  102  to an outer surface  156  of the end cover  110  using any suitable attachment means (e.g., bolts, screws, pins and/or the like). 
     Additionally, as particularly shown in  FIG. 2 , each of the flow conduits  102  may be in flow communication with a pressurized fluid source  158 . In general, it should be appreciated that the pressurized fluid source  158  may comprise any suitable machine, device and/or object capable of supplying pressurized fluid to the flow conduits  102 . Thus, in one embodiment, the pressurized fluid source  158  may comprise the compressor  12  of the gas turbine  10  ( FIG. 1 ). For example, a suitable coupling and/or manifold (not shown) may be utilized to couple the flow conduits  102  to a location downstream of the compressor  112  (e.g., at the compressor outlet, at a diffuser downstream of the compressor outlet or at a location on the gas turbine casing  108 ) such that a portion of the pressurized air discharged by the compressor  12  may be directed into the flow conduits  102 . In other embodiments, the pressurized fluid source  158  may comprise a separate or secondary compressor of the gas turbine  10  or any other suitable pressurized fluid source (e.g., fluid filled tank). 
     It should be appreciated that, in several embodiments, the pressurized fluid may be passively supplied from the pressurized fluid source  158  to the flow conduits  102 , such as by continuously directing the pressurized fluid between the pressurized fluid source  158  and the fluid conduits  102  at a constant flow rate and pressure. Alternatively, the pressurized fluid supplied from the pressurized fluid source  158  to the flow conduits  102  may be actively controlled. For example, as shown in  FIG. 2 , in one embodiment, one or more valves  160  may be disposed between the pressurized fluid source  158  and the discharge ends  152  of one or more of the flow conduits  102  to permit the flow rate and/or pressure of the pressurized fluid supplied to be controlled. In addition to the use of such valve(s)  160  or as alternative thereto, the pressurized fluid source  158  may be actively controlled in order to vary the characteristics of the pressurized fluid supplied to the flow conduits  102 . For example, the pressurized fluid source  158  may be controlled such that the pressure, flow rate and/or temperature of the pressurized fluid supplied to the flow conduits  102  may be varied as desired. 
     It should also be appreciated that the pressurized fluid may generally comprise any suitable fluid. For example, in several embodiments, the pressurized fluid may comprise air, steam and/or an inert gas (e.g., nitrogen). Additionally, it should be appreciated that each flow conduit  102  may be configured to supply the same fluid, or different fluids may be supplied through different flow conduits  102 , depending on operational needs and the availability of particular pressurized fluids. 
     Referring now to  FIG. 4 , there is illustrated a cross-sectional view of a portion of the flow conduit  102  shown in  FIG. 3 , particularly illustrating the portion of the flow conduit  102  extending through the upstream wall  130  of the cap assembly  104 . As shown, a seal  162  may be disposed between the upstream wall  130  and the flow conduit  102  to prevent fluid from leaking into and/or out of the cap chamber  134  through the opening  140  defined in the upstream wall  130 . It should be appreciated that the seal  162  may generally comprise any suitable sealing device and/or sealing mechanism known in the art. For example, as shown in the illustrated embodiment, the seal  162  comprises a ring seal (e.g., a piston ring seal or an O-ring seal) configured to be engaged within a seal groove  164  defined in the upstream wall  130 . 
     In another embodiment, the seal  162  may comprise a floating seal extending between the upstream wall  130  and the flow conduit  102 . In further embodiments, the seal  162  may comprise any other suitable sealing device and/or sealing mechanism, such as a face seal, a brush seal, a labyrinth seal, a friction seal, a slip joint, a compression seal, a gasket seal and/or the like. 
     It should be appreciated that a suitable seal (not shown) may also be disposed between the end cover  110  and the portion of each flow conduit  102  extending through the end cover  110 . For example, in one embodiment, a gasket seal or other suitable seal may be disposed between the end cover  110  and each flow conduit  102  to prevent the leakage of fluids through the end cover  110 . 
     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 include 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.