Domed tip cap and related method

Abstract

A bucket for a turbine includes a dovetail mounting portion, a shank portion defined at a radially outer end thereof by a platform, and an airfoil portion extending radially outward of the platform. The airfoil portion has a radially outer end closed by a tip cap having a non-planar shape that reduces stress in the tip cap during use. A related method of reducing stress in a tip cap of a turbine bucket includes providing an airfoil portion of the turbine bucket with a radially outer end; and closing the radially outer end with a tip cap having a non-planar shape that reduces stress in the tip cap during use.

1 . A bucket for a turbine comprising a dovetail mounting portion, a shank portion defined at a radially outer end thereof by a platform, and an airfoil portion extending radially outward of said platform, said airfoil portion having a radially outer end closed by a tip cap wherein one or both of an interior and exterior surface of the tip cap is formed of a non-planar shape that reduces stress in the tip cap during use. 
   
   
       2 . The bucket of  claim 1  wherein said non-planar shape is domed in a radially inward direction. 
   
   
       3 . The bucket of  claim 2  wherein said tip cap is cast-in with said airfoil portion. 
   
   
       4 . The bucket of  claim 1  wherein said tip cap is welded to said airfoil portion. 
   
   
       5 . The bucket of  claim 4  wherein said tip cap is formed with a peripheral flange seated on a shoulder formed in said airfoil portion. 
   
   
       6 . The bucket of  claim 1  wherein said tip cap is formed with one or more internal ribs. 
   
   
       7 . A bucket for a turbine comprising a dovetail mounting portion, a shank portion defined at a radially outer end thereof by a platform, and an airfoil portion extending radially outward of said platform, said airfoil portion having a radially outer end closed by a tip cap;
 wherein at least an exterior surface of said tip cap is domed in a radially inward direction; and   wherein said tip cap is formed with one or more internal ribs.   
   
   
       8 . The bucket of  claim 7  wherein said tip cap is cast-in with said airfoil portion. 
   
   
       9 . The bucket of  claim 7  wherein said tip cap is welded to said airfoil portion. 
   
   
       10 . The bucket of  claim 9  wherein said tip cap is formed with a peripheral flange seated on a shoulder formed in said airfoil portion. 
   
   
       11 . A method of reducing stress in a tip cap of a turbine bucket comprising providing an airfoil portion of the turbine bucket with a radially outer end; and
 closing the radially outer end with a tip cap having a non-planar shape that reduces stress in the tip cap during use.   
   
   
       12 . The method of  claim 11  including welding the tip cap to the airfoil portion. 
   
   
       13 . The method of  claim 12  wherein the tip cap is seated on an internal flange in the airfoil portion. 
   
   
       14 . The method of  claim 11  wherein the tip cap is cast in with the airfoil portion. 
   
   
       15 . The method of  claim 11  wherein said tip cap is formed with one or more internal ribs. 
   
   
       16 . The method of  claim 11  wherein interior and exterior surfaces of said tip cap are domed in a radially inward direction. 
   
   
       17 . The method of  claim 11  wherein an exterior surface of said tip cap is domed in a radially inward direction.