Turbine bucket for use in gas turbine engines and methods for fabricating the same

Abstract

A turbine bucket for use with a turbine engine. The turbine bucket includes a dovetail that is coupled to a rotor assembly that is positioned within a turbine casing. A platform extends from the dovetail. An airfoil extends from the platform. The airfoil includes a root end and a tip end. The tip end extends outwardly from the root end towards the turbine casing. A tip shroud extends from the tip end. The tip shroud includes a shroud plate. A first shroud rail extending a first radial distance from the shroud plate towards the turbine casing. A second shroud rail extends a second radial distance from the shroud plate towards the turbine casing that is different than the first radial distance.

1 . A turbine bucket for use with a turbine engine, said turbine bucket comprising:
 a dovetail coupled to a rotor assembly positioned within a turbine casing;   a platform extending from said dovetail;   an airfoil extending from said platform, said airfoil comprising a root end and a tip end, said tip end extending outwardly from said root end towards the turbine casing; and   a tip shroud extending from said tip end, said tip shroud comprising:
 a shroud plate; 
 a first shroud rail extending a first radial distance from said shroud plate towards the turbine casing; and 
 a second shroud rail extending a second radial distance from said shroud plate towards the turbine casing that is different than said first radial distance. 
   
     
     
         2 . A turbine bucket in accordance with  claim 1 , wherein said shroud plate extends generally between a leading surface and a trailing surface, said first shroud rail positioned closer to said leading surface than said second shroud rail such that an axial flow path is defined between the turbine casing and said tip shroud. 
     
     
         3 . A turbine bucket in accordance with  claim 2 , wherein said first radial distance is longer than said second radial distance. 
     
     
         4 . A turbine bucket in accordance with  claim 2 , wherein said first radial distance is shorter than said second radial distance. 
     
     
         5 . A turbine bucket in accordance with  claim 1 , wherein said first radial distance is between about 40% to 60% of said second radial distance. 
     
     
         6 . A turbine bucket in accordance with  claim 3 , wherein said first shroud rail is positioned a distance from said leading surface such that a cavity is defined between said leading surface and the turbine casing, said cavity facilitates reducing a formation of vortices within said cavity. 
     
     
         7 . A turbine bucket in accordance with  claim 4 , wherein said second shroud rail is positioned a distance from said trailing surface such that a cavity is defined between said trailing surface and the turbine casing, said cavity facilitates reducing a formation of vortices within said cavity. 
     
     
         8 . A turbine bucket in accordance with  claim 1 , wherein said first and second shroud rails define an tangential rail surface that is oriented at an oblique angle with respect to an outer surface of said shroud plate. 
     
     
         9 . A turbine engine system comprising:
 a casing;   a compressor;   a turbine coupled in flow communication with said compressor to receive at least some of the air discharged by said compressor, said turbine positioned within said casing;   a rotor shaft rotatably coupled to said turbine, said rotor shaft defining a centerline axis; and   a plurality of circumferentially-spaced turbine buckets coupled to said rotor shaft, each of said plurality of turbine buckets comprising:
 a platform; 
 an airfoil extending from said platform, said airfoil comprising a root end and a tip end, said tip end extending outwardly from said root end towards said casing; and 
 a tip shroud extending from said tip end, said tip shroud comprising:
 a shroud plate; 
 a first shroud rail extending a first radial distance from said shroud plate towards said casing; and 
 a second shroud rail extending a second radial distance from said shroud plate towards said casing that is different than said first radial distance. 
 
   
     
     
         10 . A turbine engine system in accordance with  claim 9 , wherein said shroud plate extends generally between a leading surface and a trailing surface, said first shroud rail positioned closer to said leading surface than said second shroud rail such that an axial flow path is defined between said casing and said tip shroud. 
     
     
         11 . A turbine engine system in accordance with  claim 10 , wherein said first radial distance is longer than said second radial distance. 
     
     
         12 . A turbine engine system in accordance with  claim 10 , wherein said first radial distance is shorter than said second radial distance. 
     
     
         13 . A turbine engine system in accordance with  claim 9 , wherein said first radial distance is between about 40% to 60% of said second radial distance. 
     
     
         14 . A turbine engine system in accordance with  claim 11 , wherein said first shroud rail is positioned a distance from said leading surface such that a cavity is defined between said leading surface and said casing, said cavity facilitates reducing a formation of vortices within said cavity. 
     
     
         15 . A turbine engine system in accordance with  claim 12 , wherein said second shroud rail is positioned a distance from said trailing surface such that a cavity is defined between said trailing surface and said casing, said cavity facilitates reducing a formation of vortices within said cavity. 
     
     
         16 . A method for fabricating a turbine bucket for use with a turbine engine, said method comprising:
 forming a substantially solid ceramic turbine bucket core;   inserting the core into a die; and   casting the turbine bucket with an airfoil extend from a platform, wherein the airfoil includes a tip shroud extending from a tip end of the airfoil, the tip shroud including a shroud plate, a first shroud rail extending a first radial distance from the shroud plate, and a second shroud rail extending a second radial distance from the shroud plate that is different than the first radial distance.   
     
     
         17 . A method in accordance with  claim 16 , wherein casting the turbine bucket further comprises casting the turbine bucket such that the first shroud rail is positioned closer to a leading surface of the shroud plate than the second shroud rail such that an axial flow path is defined from the first shroud rail to the second shroud rail. 
     
     
         18 . A method in accordance with  claim 17 , wherein casting the turbine bucket further comprises casting the turbine bucket such that the first radial distance is longer than the second radial distance. 
     
     
         19 . A method in accordance with  claim 17 , wherein casting the turbine bucket further comprises casting the turbine bucket such that the first radial distance is shorter than said second radial distance. 
     
     
         20 . A method in accordance with  claim 16 , wherein casting the turbine bucket further comprises casting the turbine bucket such that the first radial distance is between about 40% to 60% of the second radial distance.