Patent Publication Number: US-8540486-B2

Title: Apparatus for cooling a bucket assembly

Description:
FIELD OF THE INVENTION 
     The subject matter disclosed herein relates generally to turbine buckets, and more specifically to cooling apparatus for bucket assembly components. 
     BACKGROUND OF THE INVENTION 
     Gas turbine systems are widely utilized in fields such as power generation. A conventional gas turbine system includes a compressor, a combustor, and a turbine. During operation of the gas turbine system, various components in the system are subjected to high temperature flows, which can cause the components to fail. Since higher temperature flows generally result in increased performance, efficiency, and power output of the gas turbine system, the components that are subjected to high temperature flow must be cooled to allow the gas turbine system to operate at increased temperatures. 
     Various strategies are known in the art for cooling various gas turbine system components. For example, a cooling medium may be routed from the compressor and provided to various components. In the turbine section of the system, the cooling medium may be utilized to cool various turbine components. 
     Turbine buckets are one example of a hot gas path component that must be cooled. Imperfectly sealed bucket shanks may allow hot gas to enter the shanks, and the hot gas can cause the bucket to fail. For example, in some shanks, when the hot gas entering the shank is above approximately 1900° F., the hot gas can cause shank seal pins to creep and deform, and may cause the seal pins to extrude from the shanks. Further, the hot gas can damage the shank damper pins and the shanks themselves, resulting in failure of the buckets. 
     Various strategies are known in the art for cooling bucket shank components and preventing hot gas ingestion. For example, one prior art strategy utilizes a high pressure flow of the cooling medium to pressurize the shank cavities, providing a positive back-flow margin for all hot gas ingestion locations on the shank. This positive back-flow margin prevents the hot gas from entering and damaging the shanks. However, the amount of cooling medium that must be routed from the compressor to pressurize the shank cavities is substantial, and this loss of flow through the compressor results in losses in performance, efficiency, and power output of the gas turbine system. Further, a substantial amount of the cooling medium provided to pressurize the shank cavities is leaked and emitted from the shank cavities into the hot gas path, resulting in a waste of this cooling medium. 
     Thus, a cooling apparatus for a bucket shank would be desired in the art. For example, a cooling apparatus that minimizes the amount of cooling medium routed from the compressor and the amount of cooling medium wasted and lost during cooling of the bucket shank would be advantageous. Further, a cooling apparatus that maximizes the performance, efficiency, and power output of the gas turbine system while effectively cooling the bucket shank would be advantageous. 
     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 embodiment, a bucket assembly is provided that includes a platform, an airfoil, and a shank. The airfoil may extend radially outward from the platform. The shank may extend radially inward from the platform. The shank may include a pressure side sidewall, a suction side sidewall, an upstream sidewall, and a downstream sidewall. The sidewalls may at least partially define a cooling circuit. The cooling circuit may be configured to receive a cooling medium and provide the cooling medium to the airfoil. The upstream sidewall may at least partially define an interior cooling passage and at least partially define an exterior ingestion zone. The cooling passage may be configured to provide a portion of the cooling medium from the cooling circuit to the ingestion zone of an adjacent bucket assembly. 
     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  is a schematic illustration of a gas turbine system; 
         FIG. 2  is a sectional side view of the turbine section of a gas turbine system according to one embodiment of the present disclosure; 
         FIG. 3  is a perspective view of a bucket assembly according to one embodiment of the present disclosure; 
         FIG. 4  is a side view of a bucket assembly according to one embodiment of the present disclosure; 
         FIG. 5  is an opposite side view of a bucket assembly according to one embodiment of the present disclosure; 
         FIG. 6  is a cross-sectional view of a partial rotor assembly according to one embodiment of the present disclosure; and 
         FIG. 7  is a perspective view of a partial rotor assembly according to one embodiment of the present disclosure. 
     
    
    
     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. 
       FIG. 1  is a schematic diagram of a gas turbine system  10 . The system  10  may include a compressor  12 , a combustor  14 , and a turbine  16 . 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 shaft  18 . 
     The turbine  16  may include a plurality of turbine stages. For example, in one embodiment, the turbine  16  may have three stages, as shown in  FIG. 2 . For example, a first stage of the turbine  16  may include a plurality of circumferentially spaced nozzles  21  and buckets  22 . The nozzles  21  may be disposed and fixed circumferentially about the shaft  18 . The buckets  22  may be disposed circumferentially about the shaft  18  and coupled to the shaft  18 . A second stage of the turbine  16  may include a plurality of circumferentially spaced nozzles  23  and buckets  24 . The nozzles  23  may be disposed and fixed circumferentially about the shaft  18 . The buckets  24  may be disposed circumferentially about the shaft  18  and coupled to the shaft  18 . A third stage of the turbine  16  may include a plurality of circumferentially spaced nozzles  25  and buckets  26 . The nozzles  25  may be disposed and fixed circumferentially about the shaft  18 . The buckets  26  may be disposed circumferentially about the shaft  18  and coupled to the shaft  18 . The various stages of the turbine  16  may be disposed in the turbine  16  in the path of hot gas flow  28 . It should be understood that the turbine  16  is not limited to three stages, but may have any number of stages known in the turbine art. 
     Each of the buckets  22 ,  24 ,  26  may comprise a bucket assembly  30 , as shown in  FIG. 3 . The bucket assembly  30  may include a platform  32 , an airfoil  34 , and a shank  36 . The airfoil  34  may extend radially outward from the platform  32 . The shank  36  may extend radially inward from the platform  32 . 
     The bucket assembly  30  may further include a dovetail  38 . The dovetail  38  may extend radially inward from the shank. In an exemplary aspect of an embodiment, the dovetail  38  may be configured to couple the bucket assembly  30  to the shaft  18 . For example, the dovetail  38  may secure the bucket assembly  30  to a rotor disk (not shown) disposed on the shaft  18 . A plurality of bucket assemblies  30  may thus be disposed circumferentially about the shaft  18  and coupled to the shaft  18 , forming a rotor assembly  20 , as partially shown in  FIGS. 6 and 7 . 
     If desired, the dovetail  38  may be configured to supply a cooling medium  95  to a cooling circuit  90  defined within the bucket assembly  30 . For example, inlets  92  of the cooling circuit  90  may be defined by the dovetail  38 . The cooling medium  95  may enter the cooling circuit  90  through the inlets  92 . The cooling medium  95  may exit the cooling circuit  90  through, for example, film cooling holes, or through any other bucket assembly exit holes, passages, or aperatures. 
     The cooling medium  95  is generally supplied to the turbine  16  from the compressor  12 . It should be understood, however, that the cooling medium  95  is not limited to a cooling medium supplied by a compressor  12 , but may be supplied by any system  10  component or external component. Further, the cooling medium  95  is generally cooling air. It should be understood, however, that the cooling medium  95  is not limited to air, and may be any cooling medium. 
     The airfoil  34  may include a pressure side surface  52  and a suction side surface  54 . The pressure side surface  52  and the suction side surface  54  may be connected at a leading edge  56  and a trailing edge  58 . The airfoil  34  may at least partially define the cooling circuit  90  therein. For example, the pressure side surface  52  and the suction side surface  54  may at least partially define the cooling circuit  90 . The cooling circuit  90  may be configured to receive cooling medium  95  and provide the cooling medium to the airfoil  34 . For example, the cooling medium  95  may pass through the airfoil  34  within the cooling circuit  90 , cooling the airfoil  34 . 
     The shank  36  may include a pressure side sidewall  42 , a suction side sidewall  44  (see  FIG. 5 ), an upstream sidewall  46 , and a downstream sidewall  48 . The upstream sidewall  46  of the shank  36  may include an exterior surface  62 , an interior surface  64 , a pressure side surface  66 , and a suction side surface  68  (see  FIG. 5 ). 
     The shank  36  may at least partially define the cooling circuit  90  therein. For example, the sidewalls  42 ,  44 ,  46 , and  48  may at least partially define the cooling circuit  90 . The shank  36  may further include an upstream upper angel wing  130 , upstream lower angel wing  134 , downstream upper angel wing  132 , and downstream lower angel wing  136 . The angel wings  130  and  134  may extend outwardly from the upstream sidewall  46 , and the angel wings  132  and  136  may extend outwardly from the downstream sidewall  48 . The upstream upper angel wing  130  and the downstream upper angel wing  132  may be configured to seal buffer cavities (not shown) defined within the rotor assembly  20 . The upstream lower angel wing  134  and the downstream lower angel wing  136  may be configured to provide a seal between the bucket assembly  30  and the rotor disk (not shown). 
     The shank  36  may further define an exterior ingestion zone  70 . The exterior ingestion zone  70  is a zone between adjacent bucket assemblies  30  where the hot gas flow  28  enters the bucket assemblies  30 . In an exemplary aspect of an embodiment, the ingestion zone  70  may be at least partially defined with respect to a bucket assembly  30  adjacent the suction side surface  68  of the upstream sidewall  46  and adjacent the platform  32 . The ingestion zone  70  may be further defined with respect to a bucket assembly  30  adjacent the pressure side surface  66  of the upstream sidewall  46  and adjacent the platform  32 . For example, during operation of the system  10 , pressure gradients in the hot gas flow  28  may cause at least a portion of the hot gas flow  28  to be directed into a trench cavity  75  defined by the shank  36 . The trench cavity  75  may be defined approximately adjacent the upstream upper angel wing  130 . The hot gas flow  28  may be further directed from the trench cavity  75  through the ingestion zone  70  between and into the adjacent bucket assemblies  30 . 
     The bucket assembly  30  may include an upstream seal pin  112 . The upstream seal pin  112  may be disposed adjacent the upstream sidewall  46 , as shown in  FIG. 5 . For example, the upstream seal pin  112  may be disposed adjacent the suction side surface  68  of the upstream sidewall  46 , and may be disposed in a channel  113  defined in the suction side surface  68  of the upstream sidewall  46 . Alternately, the channel  113  may be defined in the pressure side surface  66  of the upstream sidewall  46 , and the upstream seal pin  112  may be disposed in the channel  113 . Alternately, channels  113  may be defined in both the suction side surface  68  and the pressure side surface  66 , and the upstream seal pin  112  may be disposed in the channel  113  defined in the suction side surface  68  of the upstream sidewall  46  as well as in the channel  113  defined in the pressure side surface  66  of the upstream sidewall  46  of an adjacent bucket assembly  30 . The bucket assembly  30  may further include a downstream seal pin  114 , which may be disposed adjacent the downstream sidewall  48  in a channel  115 , as shown in  FIG. 5 . The channel  115  may be defined in the downstream sidewall  48  similarly to the channel  113  in the upstream sidewall  46 . The seal pins  112  and  114  may be configured to provide a seal between the bucket assembly  30  and an adjacent bucket assembly  30 . For example, during operation of the turbine  16 , rotational forces may cause the seal pins  112  and  114  of a bucket  30  to interact with the upstream sidewall  46  and downstream sidewall  48 , respectively, of the adjacent bucket  30 , providing a seal between the bucket assemblies  30 . As shown in  FIG. 6 , for example, the upstream seal pin  112  may interact with the pressure side surface  66  of the upstream sidewall  46 , providing a seal between the bucket assemblies  30 . 
     The bucket assembly  30  may further include a damper pin  116 . The damper pin  116  may be disposed adjacent the platform  32  and the suction side sidewall  44 , or the platform  32  and the pressure side sidewall  42 . The damper pin  116  may include a leading end  117  and a trailing end  118 . The leading end  117  may be disposed adjacent the upstream sidewall  46 . The trailing end  118  may be disposed adjacent the downstream sidewall  48 . The damper pin  116  may be configured to dampen vibrations between the bucket assembly  30  and an adjacent bucket assembly  30 . For example, during operation of the turbine  16 , rotational forces may cause the damper pin  116  of a bucket  30  to interact with the platform  32  of the adjacent bucket  30 , dampen vibrations between the bucket assemblies  30 , as shown in  FIG. 6 . 
     The shank  36  of the bucket assembly  30  may further define an interior cooling passage  80 . The cooling passage  80  may be configured to provide a portion of the cooling medium  95  from the cooling circuit  90  to the ingestion zone  70  of an adjacent bucket assembly  30 . For example, the cooling passage  80  may extend from the cooling circuit  90  through the shank  36 . In an exemplary aspect of an embodiment, the cooling passage  80  may extend from the cooling circuit  90  at least partially through the upstream sidewall  46  of the shank  36 . However, the cooling passage  80  may also extend, partially or entirely, through the pressure side sidewall  42 , the suction side sidewall  44 , or the downstream sidewall  48 . The cooling passage  80  may further include an exterior cooling passage opening  84 , as shown in  FIG. 4 . The cooling passage opening  84  may be defined by the upstream sidewall  46 , such as, for example, by the pressure side surface  66  of the upstream sidewall  46 . Alternatively, the cooling passage opening  84  may be defined by the upstream sidewall  46  such as by the suction side surface  68  of the upstream sidewall  46 . A portion of the cooling medium  95  may flow from the cooling circuit  90  through the cooling passage  80 , and the cooling medium  95  may be exhausted from the cooling passage  80  through the cooling passage opening  84 . 
     The cooling medium  95  may be provided through the cooling passage  80  and cooling passage opening  84  to the ingestion zone  70  of an adjacent bucket assembly  30 . For example, in an exemplary aspect of an embodiment, a plurality of bucket assemblies  30  may be disposed circumferentially about the shaft  18  and coupled to the shaft  18 , forming rotor assembly  20 , as partially shown in  FIGS. 6 and 7 . Each bucket assembly  30  and adjacent bucket assembly  30  may define an ingestion zone  70  therebetween, as shown in  FIG. 6 . 
     In an exemplary aspect of an embodiment, the cooling medium  95  provided to the ingestion zone  70  may interact with at least a portion of the seal pin  112  of the adjacent bucket assembly  30 , cooling the upstream seal pin  112 . For example, as shown in  FIG. 6 , an upper end  119  of the upstream seal pin  112  may be disposed adjacent to or within the ingestion zone  70 . The cooling medium  95  provided to the ingestion zone  70  may interact with the upper end  119  of the seal pin  112 , cooling the upper end  119 . 
     In one exemplary aspect of an embodiment, the exterior cooling passage opening  84  may be positioned upstream of the seal pin  112  with respect to the hot gas flow  28 . In another exemplary aspect of an embodiment, the exterior cooling passage opening  84  may be substantially aligned with the seal pin  112  with respect to the hot gas flow  28 . It should be understood, however, that the position of the exterior cooling passage opening  84  is not limited to a position upstream or in alignment with the seal pin  112 , but may be anywhere on the shank  36  where the cooling medium  95  can be provided through the cooling passage opening  84  to the ingestion zone  70  of an adjacent bucket assembly  30 . 
     In an exemplary aspect of an embodiment, the cooling medium  95  provided to the ingestion zone  70  may interact with at least a portion of the damper pin  116  of the adjacent bucket assembly  30 , cooling the damper pin  116 . For example, as shown in  FIG. 6 , the leading end  117  of the damper pin  116  may be disposed adjacent to or within the ingestion zone  70 . The cooling medium  95  provided to the ingestion zone  70  may interact with the leading end  117  of the damper pin  116 , cooling the leading end  117 . 
     In one exemplary aspect of an embodiment, the cooling medium  95 , upon exiting the cooling passage  80  through the cooling passage opening  84 , may mix with the hot gas flow  28  in the ingestion zone  70 , cooling the hot gas flow  28 . For example, in one embodiment, the hot gas flow  28  may be at a temperature above approximately 1900° F. The cooling medium  95  may mix with the hot gas flow  28 , cooling the hot gas flow  28  to a temperature below approximately 1900° F. In another exemplary aspect of an embodiment, the cooling medium  95 , upon exiting the cooling passage  80  through the cooling passage opening  84 , may provide an ingestion barrier. The ingestion barrier may prevent the hot gas flow  28  from entering the ingestion zone  70 . For example, the cooling medium  95  may exit the cooling passage  80  at a pressure sufficient to provide a localized cooling outflow, resulting in an ingestion barrier. 
     The present disclosure is also directed to a method for cooling a bucket assembly  30 . The method may include, for example, the step of providing a cooling medium  95  to a cooling circuit  90  within the bucket assembly  30 . For example, the cooling medium  95  may be provided from the compressor  12  through the dovetail  38  or shank  36  to the cooling circuit  90 , as discussed above. The method may further include, for example, the step of providing a portion of the cooling medium  95  from the cooling circuit  90  through an interior cooling passage  80  to an exterior ingestion zone  70  of an adjacent bucket assembly  30 . The bucket assembly  30  may include a platform  32 , an airfoil  34 , a shank  36 , and a dovetail  38 , as discussed above. 
     The bucket assembly  30  may further include a seal pin  112 , as discussed above. The bucket assembly  30  and the adjacent bucket assembly  30  may further define the ingestion zone  70  therebetween, and the cooling medium  95  provided to the ingestion zone  70  may interact with at least a portion of the seal pin  112  of the adjacent bucket assembly  30 , cooling the seal pin  112 , as discussed above. 
     The cooling passage  80  may include an exterior cooling passage opening  84 , as discussed above. The cooling passage opening  84  may be positioned, for example, upstream of the seal pin  112  with respect to a hot gas flow  28 , or substantially aligned with the seal pin  112  with respect to the hot gas flow  28 , as discussed above. 
     The bucket assembly  30  may further include a damper pin  116 , as discussed above. The bucket assembly  30  and the adjacent bucket assembly  30  may further define the ingestion zone  70  therebetween, and the cooling medium  95  provided to the ingestion zone  70  may interact with at least a portion of a leading end  117  of the damper pin  116  of the adjacent bucket assembly  30 , cooling the leading end  117 , as discussed above. 
     The cooling medium  95  may mix with a hot gas flow  28  in the ingestion zone  70 , cooling the hot gas flow  28 , as discussed above. Alternatively, the cooling medium  95  may provide an ingestion barrier. The ingestion barrier may prevent a hot gas flow  28  from entering the ingestion zone  70 , as discussed above. 
     The amount of cooling medium  95  that is required to prevent ingestion of the hot gas flow  28 , cool the seal pin  112 , and cool the damper pin  116  according to the present disclosure may be a beneficially minimal amount. For example, the required amount of cooling medium  95  that is supplied to the turbine  16  and the various bucket assemblies  30  from the compressor  12  may be substantially lower than the amounts required by various other bucket component cooling devices and designs, such as pressurized shank designs. Thus, the minimal amount of cooling medium  95  that is required according to the present disclosure may provide significant decreases in the amount of cooling medium  95  wasted through leakage and emission in the turbine  16  of the gas turbine system  10 . Further, the minimal amount of cooling medium  95  that is required according to the present disclosure may provide significant increases in the performance and efficiency of the turbine  16  and the gas turbine system  10 . 
     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.