Patent Publication Number: US-9890653-B2

Title: Gas turbine bucket shanks with seal pins

Description:
TECHNICAL FIELD 
     The present application and the resultant patent relate generally to gas turbine engines and more particularly relate to gas turbine bucket shanks with seal pins and the like for reducing leakage flow between components of a gas turbine engine. 
     BACKGROUND OF THE INVENTION 
     Generally described, turbo-machinery such as gas turbine engines and the like include a main gas flow path extending therethrough. Gas leakage, either out of the gas flow path or into the gas flow path, may lower overall gas turbine efficiency, increase fuel costs, and possibly increase emission levels. Secondary flows also may be used within the gas turbine engine to cool the various heated components. Specifically, cooling air may be extracted from the later stages of the compressor for use in cooling the heated components and for purging gaps and cavities between adjacent components. For example, seals may be placed at wheel space cavities between turbine components such as bucket wheels and the like to limit air leakage. Seals, however, may have different configurations, which may result in leakage flow escaping through gaps created by certain seals. Leakage flow may result in reduced efficiency of the gas turbine. 
     There is thus a desire for improved seal configurations for use with gas turbine components, such as bucket wheel components and other components of heavy duty gas turbine engines. Such seals may be configured to reduce or remove gaps between gas turbine components, resulting in reduced leakage flow therethrough, as well as increased overall efficiency and/or increased component lifetime. 
     SUMMARY OF THE INVENTION 
     The present application and the resultant patent provide a gas turbine component shank assembly including a shank with a platform having a first slash face. The gas turbine component shank assembly includes a seal pin slot extending into the first slash face, the seal pin slot having a slot length and a depth, and a seal pin disposed in the seal pin slot, the seal pin having a rounded end positioned adjacent to an end of the seal pin slot. 
     The present application and the resultant patent also provide a method of reducing a leakage flow in a gas turbine component. The method includes providing a first bucket shank with a first platform having a first slash face, and providing a second bucket shank with a second platform having a second slash face. The second slash face may be substantially planar and positioned adjacent to the first slash face. The method includes positioning a seal pin in a seal pin slot disposed within the first slash face, the seal pin slot having a slot length and a depth, where the seal pin has a rounded end positioned adjacent to an end of the seal pin slot. The method includes flowing hot gas in between the first slash face and the second slash face, where a hot gas path of the hot gas is occluded by the seal pin. 
     The present application and the resultant patent further provide a gas turbine seal assembly including a first shank having a first platform and a first dovetail extending from the first platform, where the first platform includes a first slash face on a first side of the first platform and a second slash face on a second side of the first platform opposite the first side. The gas turbine seal assembly may include a seal pin slot extending into the first slash face, the seal pin slot having a length defined along a major axis of the first slash face, a width defined along a minor axis of the first slash face, and a depth defined into the first slash face. The gas turbine seal assembly may include a seal pin disposed in the seal pin slot, the seal pin having a dome portion and a central portion disposed adjacent to the dome portion, where the central portion has a constant diameter, and the dome portion has a first end adjacent to the central portion and a second end forming an end of the seal pin. The first end has the constant diameter of the central portion, and the second end has a diameter less than the constant diameter. The gas turbine seal assembly may include a second shank positioned adjacent to the first shank having a second platform with a third slash face positioned such that the seal pin is retained in the seal pin slot. 
     These and other features and improvements of the present application and the resultant patent will become apparent to one of ordinary skill in the art upon review of the following detailed description when taken in conjunction with the several drawings and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  schematically depicts an example of a gas turbine engine. 
         FIG. 2  schematically depicts an example cross-sectional view of a turbine bucket. 
         FIG. 3  schematically depicts an example perspective cross-sectional view of a turbine near flow path seal with a seal pin, according to one or more embodiments of the disclosure. 
         FIG. 4  schematically depicts a detailed cross-sectional view of a seal pin positioned in a seal slot of a gas turbine component shank, according to one or more embodiments of the disclosure. 
         FIGS. 5-7  schematically depict portions of a seal pin positioned in a seal slot in perspective and detail views, according to one or more embodiments of the disclosure. 
         FIGS. 8-9  schematically depict a gas turbine shank assembly and a dome-ended seal pin in partial cross-sectional perspective view, according to one or more embodiments of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     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 engine  10  as may be used herein. The gas turbine engine  10  may include a compressor  15 . The compressor  15  compresses an incoming flow of air  20 . The compressor  15  delivers the compressed flow of air  20  to a combustor  25 . The combustor  25  mixes the compressed flow of air  20  with a pressurized flow of fuel  30  and ignites the mixture to create a flow of combustion gases  35 . Although only a single combustor  25  is shown, the gas turbine engine  10  may include any number of combustors  25 . The flow of combustion gases  35  is in turn delivered to a turbine  40 . The flow of combustion gases  35  drives the turbine  40  so as to produce mechanical work. The mechanical work produced in the turbine  40  drives the compressor  15  via a shaft  45  and an external load  50  such as an electrical generator and the like. Other configurations and other components may be used herein. 
     The gas turbine engine  10  may use natural gas, various types of syngas, and/or other types of fuels. The gas turbine engine  10  may be any one of a number of different gas turbine engines offered by General Electric Company of Schenectady, N.Y., including, but not limited to, those such as a 7 or a 9 series heavy duty gas turbine engine and the like. The gas turbine engine  10  may have different configurations and may use other types of components. Other types of gas turbine engines also may be used herein. Multiple gas turbine engines, other types of turbines, and other types of power generation equipment also may be used herein together. Although the gas turbine engine  10  is shown herein, the present application may be applicable to any type of turbo machinery. 
       FIG. 2  schematically depicts one example embodiment of a portion of the turbine  40 . The turbine  40  may include a rotor  52  positioned about a longitudinal axis. A number of buckets  54  may be mounted to the rotor  52 . For example, the buckets  54  may be circumferentially position adjacent to one another and extend radially outward from the rotor  52 . The buckets  54  may form one or more stages in the turbine  40 . For example, the buckets  54  may form a first stage, a last stage, or any stage therebetween. The buckets  54  may include a platform  56 , a shank portion  58 , an airfoil  60 , and a dovetail  62 . The dovetail  62  may be configured to mate with a corresponding dovetail  64  of the rotor  52 . 
     The shank portion  56  may include a slash face  66 . The slash face  66  may be defined as a circumferential edge or edge surface of the shank portion  58 . In some instances, the leading edge of the shank portion  58  may include a forward trench cavity  68 . The forward trench cavity  68  may be formed between an angle wing seal  70  and a leading edge  72  of the platform  56 . The forward trench cavity  68  may provide an area where purge air from a wheel space  74  interfaces with the hot combustion gases. The wheel space  74  may include a wheel space cavity formed between the rotor  52  and one or more stators positioned adjacent to the rotor  52 . Other components and other configurations may be used herein. 
     Referring to  FIGS. 3-7 ,  FIG. 3  depicts an example embodiment of a portion of a near flow path seal  100  and a seal pin  200  as may be used herein. Near flow path seal  100  may be mounted to a shaft via a seal member rotor, and may be configured to prevent an exchange of gases between a gas path and a wheel space of a turbomachine. The near flow path seal  100  may be mounted to a rotor of the turbomachine. The near flow path seal  100  may be one of multiple near flow path seals mounted to a rotor. The near flow path seal  100  may include may include a platform  102 , a shank portion  104 , and a dovetail  108  configured to mate with a rotor, or in some embodiments, a seal member rotor. The shank portion  104  may extend radially inward from the platform  102 , and an airfoil may extend radially outward from the platform  102 . The shank portion  104  may include a first slash face  110 . The first slash face  110  may be the circumferential edge of the shank portion  104 . Depending on the orientation of the airfoil, the first slash face  110  may be a pressure side slash face or a suction side slash face. For example, a slash face positioned about a pressure side of an airfoil may be a pressure side slash face, while a slash face positioned about a suction side of an airfoil may be a suction side slash face. While  FIG. 3  illustrates a near flow path seal, embodiments of the disclosure include other gas turbine components with shanks, such as turbine buckets. 
     In embodiments of the disclosure, the near flow path seal  100  may include one or more seals mounted thereon configured to seal a wheel space cavity  250  from a hot gas path  260 . In the embodiment of  FIG. 3 , the near flow path seal  100  may include a seal pin slot  118 , which may be an axial seal pin slot or a radial seal pin slot in some embodiments, formed in the first slash face  110 . The near flow path seal  100  may have a second slash face  120  on an opposite side of the first slash face  110  that is substantially planar or does not otherwise include the seal pin slot  118 . The seal pin slot  118  may form a groove or cavity in the first slash face  110  configured to receive the seal pin  200 . The seal pin slot  118  may extend at least partially from an aft end  122  of the platform  102  and/or first slash face  110  to a forward end  124  of the platform  102  and/or first slash face  110 . More specifically, the seal pin slot  118  may have a first end  126  adjacent to the aft end  122  of the platform  102  and a second end  128  adjacent to the forward end  124  of the platform  102 . The seal pin slot  118  may have a slot length  130  defined as an axial length of the seal pin slot  118  along the slash face. In some embodiments, the seal pin slot  118  may have a slot length  130  substantially equal to, or equal to, a length  132  of the first slash face  110 . In other embodiments, the seal pin slot  118  may have a slot length  130  greater than half of a length of the first slash face  110 . The seal pin slot  118  may have a depth  134  measured into the first slash face  118  and/or platform  102  from the first slash face surface. The seal pin slot  118  may have a constant depth or may have a varied depth, for example the seal pin slot  118  may have one or more chamfered edges at one or both ends of the seal pin slot  118 . The seal pin slot  118  may have a width  136  or a height  138  measured radially along the platform  102  of the near flow path seal  100 . 
     The seal pin  200  may be positioned within, or partially within, the seal pin slot  118  of the near flow path seal  100 . The seal pin slot  118  may be sized and/or shaped to receive the seal pin  200  therein, in order to facilitate sealing between adjacent shank portions  104  when a number of turbine buckets  100  are coupled to the rotor. In some instances, only the pressure side slash face and/or the suction side slash face may include the seal pin slot  118 , while an opposite side slash face may be substantially planar. In such embodiments, a substantially planar slash face that does not include the seal pin slot  118  and/or the seal pin  200  may form a seal with an adjacent turbine bucket that includes the seal pin slot  118  and the seal pin  200  by preventing the seal pin  200  from exiting the seal pin slot  118 . While the seal pin  200  is illustrated as being positioned along the first slash face  110  of the platform  102 , in other embodiments, the seal pin slot  118  may be positioned radially along, or substantially vertically along, the shank portion  104  of the near flow path seal  100 . For example, in  FIG. 3 , the near flow path seal  100  may include a radial seal pin slot  270  along the shank portion  104  of the near flow path seal  100 , and a vertical seal pin  280  positioned therein. Some embodiments may include either, or both, the seal pin slot  118  and the radial seal pin slot  270 , and the respective seal pins  200 ,  280 . 
     Referring to  FIG. 4 , in some embodiments, the seal pin  200  may sit freely or otherwise unfixed in the seal pin slot  118 , and may be held in position by the mating flat surface or a mating slash face  240  of an adjacent turbine bucket  230 . The embodiment of  FIG. 4  may be a turbine bucket or a near flow path seal. As the rotor and/or turbine buckets  100 ,  230  rotate when the gas turbine is in operation, the seal pin  200  may be forced radially outward and may roll against a slot roof  140  of the seal pin slot  118  until the seal pin  200  is forced against the flat surface or mating slash face  240  of the adjacent turbine bucket  230 . As the turbine buckets  100 ,  230  rotate, the seal pin  200  may slide forward into a pocket  142  at the axially forward end  124  of the seal pin slot  118 . Purge flow  150  may flow radially outward along a slash gap  152  in between the two adjacent turbine buckets  100 ,  230 , creating a high pressure pocket underneath the seal pin  200  to prevent the hot gas from passing through the seal pin  200 . In other embodiments, the seal pin  200  may be fixed in the seal pin slot, for example via a friction fit or a securing mechanism. 
     Because the seal pin  200  may be sized and/or shaped differently than the seal pin slot  118  or due to other gaps, hot gas, cooling air, and/or purge air may leak about the seal pin  200  when the seal pin  200  is positioned in the seal pin slot  118 . For example, in  FIG. 7 , example leakage paths about the seal pin  200  are illustrated. A first leakage path  154  may be through the seal pin contact area  156  with the seal pin  200  and the seal pin slot  118 , and a second leakage path  158  may be through the forward end gap or aft end gap  160  of the seal pin slot  118 . The seal pins described herein may reduce the leakage flow about the seal pin  200 , and in particular the leakage flow about the forward end and/or aft end gaps  160 ,  164  by reducing the effective clearance between the seal pin  200  and the respective ends of the seal pin slot  118 . The seal pins described herein may also enhance the sealing of the slash gap  152 , thereby resulting in a decreased amount of purge flow needed to maintain a desired differential pressure. 
     Referring now to  FIGS. 5-7 , one embodiment of the seal pin  200  is depicted. The seal pin  200  may have a seal pin length  202  and a seal pin width  204 . The seal pin length  202  may be measured from a first outer end  206  of the seal pin  200  to a second outer end  208  of the seal pin  200 . The seal pin length  202  may be less than the seal pin slot length  132  so as to accommodate thermal growth. The seal pin width  204  may be measured as a height of the seal pin  200  or a diameter  210  of the seal pin  200  in embodiments where the seal pin  200  has a cylindrical portion. The seal pin width  204  may vary or may otherwise be non-uniform, for example, a diameter of the seal pin at the first outer edge may be different than the seal pin width at a middle portion of the seal pin. The seal pin width  204  may be less than the slot width  136  of the seal pin slot  118 , such that the seal pin  200  can move within the seal pin slot  118 . 
     The seal pin  200  may include a central portion  212  in between and adjacent to the first and second outer ends  206 ,  208 . The central portion  212  of the seal pin  200  may be substantially cylindrical in some embodiments. The central portion  212  may have a constant radius  214  or diameter. One or both of the first and second outer ends  206 ,  208  of the seal pin  200  may be rounded seal pin ends. The rounded seal pin ends may be positioned in the seal pin slot  118  so as to correspond to the first end  126  and the second end  128  of the seal pin slot  118 , respectively. In embodiments where one or both of the first end  126  and the second end  128  of the seal pin slot  118  are chamfered or otherwise shaped, the rounded seal pin ends may be configured to fit within the seal pin slot  118  with a rounded geometry or configuration to facilitate positioning of the seal pin  200  in the seal pin slot  200 . The seal pin  200  may be hollow in some embodiments, in that the seal pin  200  includes an inner diameter and an outer diameter, where the inner diameter defines a hollow portion of the seal pin  200  and the outer diameter defines an outer surface of the seal pin  200 . The seal pin  200  may be formed from any suitable material. 
     The seal pin ends  206 ,  208  may have a specific geometry. Each respective seal pin end  206 ,  208  may have an identical or different geometry and/or configuration. For example, as illustrated in  FIG. 5 , the first seal pin end  206  of the seal pin  200  may have a first portion  216  adjacent to the central portion  212  that has the constant radius  214  of the central portion  212  so as to achieve a flush outer surface  218  at the interface between the central portion  212  and the first seal pin end  206 . The first seal pin end  206  may further have a second portion  220  opposite the first portion  216  that has a radius  222  less than the constant radius  214  of the first portion  216  of the first seal pin end  206  and the central portion  212 , such that the first seal pin end  206  forms a dome-like shape or dome-ended configuration at the outer end of the seal pin  200 . The seal pin ends  206 ,  208  may reduce the effective clearance between the seal pin  200  and the seal pin slot end, as well as between adjacent turbine buckets, thereby reducing operation costs associated with the gas turbine, increasing lifespan of gas turbine components, and/or increasing overall efficiency of the gas turbine engine. 
     In  FIG. 6 , a detailed view of the dome portion  300  of the seal pin is illustrated. The dome portion  300  may have a dome radius  302  at an end  304  of a seal pin that is less than a radius  306  of a middle portion  308  of the seal pin, resulting in reduced leakage area, as well as a deterministic seating in a seal pin slot. The dome radius  302  of the dome portion (or dome portions for embodiments where both ends of the seal pin are dome-ended) at the end  304  of the seal pin  300  may be anywhere from hemispherical to less than substantially hemispherical. Specifically, the dome radius  302  or rounding radius of the dome portion may have a ratio with respect to a central or middle portion of the seal pin  300  to be anywhere from about 1.1 to about 1.8. In some embodiments, the dome radius  302  may be proportional to the radius  306  of the shank portion or middle portion  308  of the seal pin. For example, the dome radius  302  may have a ratio of about 1.8 with respect to the radius  306  of the middle portion  308  of the seal pin. 
     In the embodiments described herein, a seal pin with an end radius to pin radius ratio of 1 may be referred to as a hemispherical seal pin, whereas a seal pin with an end radius to pin radius of infinity may be referred to as a flat seal pin. Embodiments of the disclosure may have end radius to pin radius ratios of greater that or equal to about 1.0 and less than or equal to about 2.0, resulting in measurable reduced leakage flow. 
     Referring now to  FIGS. 8 and 9 , another embodiment of a gas turbine sealing system  310  as described herein is illustrated. The gas turbine sealing system  310  includes a first near flow path seal or bucket shank  312  (illustrated without an airfoil) with a first platform  314  and a first dovetail  316  extending from the first platform  314 . The first platform  314  includes a first slash face  318  on a first side  320  of the first platform  314  and a second slash face  322  on a second side  324  of the first platform  314  opposite the first side  320 . The gas turbine sealing system  310  includes a seal pin slot  326  extending into the first slash face  318 . The seal pin slot  326  may have a length defined along a major axis  328  of the first slash face  318 , a width defined along a minor axis  330  of the first slash face  318 , and a depth defined into the first slash face  318 . For example, the depth may be measured as a distance into the first slash face  318  from an outer surface forming the first slash face  318 . The seal pin slot  326  may have one or more chamfered ends. The gas turbine sealing system  300  may further include a seal pin  336  disposed in the seal pin slot  326 . The seal pin  336  may have a dome portion  338  and a central portion  340  disposed adjacent to the dome portion  338 , where the central portion  338  has a constant diameter  342 . The dome portion  338  may have a first end adjacent to the central portion  338  and a second end forming an outer end  344  of the seal pin, where the first end has the constant diameter  342  of the central portion  340  and the outer end  344  has a diameter  346  less than the constant diameter  342 , such that the outer end has a smaller radius than the radius of the central portion  340 . The chamfered end of the seal pin slot may correspond to the one or more dome portions  338  of the seal pin  336 , and the chamfered end may be configured such that the depth  332  of the seal pin slot  326  decreases across the first end of the seal pin slot  326 . The gas turbine sealing system  300  may further include a second bucket shank  350  positioned adjacent to the first bucket shank  312  having a second platform  352  with a third slash face  354  positioned such that the seal pin  336  is retained in the seal pin slot  326 . The third slash face  354  may be substantially planar, so as to hold the seal pin  336  in the seal pin slot  326  when the first and second bucket shanks  312 ,  350  are positioned adjacent to each other. A slash face gap  356  may be formed in between the first platform  314  and the second platform  352 , and the seal pin  336  may occlude or otherwise block a portion or all of the slash face gap  356 . The dome portion  338  may have a geometry configured to mate with the forward and aft ends of the seal pin slot  326 , resulting in reduced leakage. 
     Embodiments of the disclosure may seal turbine wheel space cavities between adjacent bucket wheels of gas turbines from a hot gas path, resulting in reduced leakage flow, as well as the capability of using different materials for gas turbine engine components that may be less resistant and/or cheaper to manufacture. The seal pin may therefore effectively seal the turbine wheel space cavity by shielding the turbine wheels from the hot gas path. As a result, different materials (e.g., less heat resistant) may be used for components in the turbine wheel space. 
     The bucket shank and seal pin assembly described herein thus provides improved systems and methods for gas turbine component sealing. The seal pins described herein may reduce the leakage flow about the seal pin, and in particular the leakage flow about the forward end gap by reducing the effective clearance between the seal pin and the forward end of the seal pin slot. The seal pins described herein may also enhance the sealing of the slash gap, thereby resulting in a decreased amount of purge flow needed to maintain a desired differential pressure. The seal pins described herein may be implemented and/or utilized with little or no change in cost, as the seal pins may be installed during routine maintenance operations. 
     It should be apparent that the foregoing relates only to certain embodiments of the present application and the resultant patent. Numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the general spirit and scope of the invention as defined by the following claims and the equivalents thereof.