Cooled turbine blade tip shroud with film/purge holes

Abstract

A cooled turbine blade shroud with purge holes located proximate regions of the tip shroud cooling cavity that experience cooling air flow recirculation or stagnation. The purge holes may be oriented radially from the cooling cavity to a surface, such as the outer top surface and/or inner/bottom surface, of the tip shroud, and may provide improved heat transfer and consequent cooling and enhanced tip shroud life.

What is claimed: 
     
         1 . A turbine blade comprising:
 a blade attachment portion;   a radially extended turbine airfoil integral with said blade attachment portion, said turbine airfoil comprising one or more internal cooling passages;   a tip shroud proximate a top portion of said turbine airfoil, said tip shroud comprising an internal cooling cavity in communication with said one or more internal cooling passages, said internal cooling cavity comprising at least one high velocity region and at least one low velocity region, said at least one high velocity region and at least one low velocity region configured to pass cooling air therethrough;   at least one exit port in communication with said internal cooling cavity configured to exhaust spent cooling air from said at least one high velocity region; and   at least one purge hole in communication with said internal cooling cavity configured to exhaust spent cooling air from said at least one low velocity region.   
     
     
         2 . The turbine blade of  claim 1  wherein said at least one exit port exits through a shroud edge of said tip shroud. 
     
     
         3 . The turbine blade of  claim 1  wherein said at least one purge hole exits through an outer top surface and/or bottom surface of said tip shroud. 
     
     
         4 . The turbine blade of  claim 1  comprising a plurality of said at least one low velocity regions and at least one of said at least one purge hole in communication with each said at least one low velocity region and an outer top surface and/or inner surface of said tip shroud. 
     
     
         5 . The turbine blade of  claim 4  comprising a plurality of said at least one high velocity regions and at least one said at least one exit port in communication with each said at least one high velocity region. 
     
     
         6 . The turbine blade of  claim 5  wherein each said purge hole exits through an outer top portion and/or bottom portion of said tip shroud and each said at least one exit port exits through a shroud edge of said tip shroud. 
     
     
         7 . A method comprising:
 providing a turbine blade comprising a radially extended turbine airfoil comprising one or more internal cooling passages;   providing a tip shroud affixed to a top portion of said airfoil, said tip shroud comprising an internal cooling cavity in communication with said one or more internal cooling passages, said internal cooling cavity comprising at least one high velocity region and at least one low velocity region, both said at least one high velocity region and at least one low velocity region configured to pass cooling air therethrough;   passing cooling air through said one or more internal cooling passages and said internal cooling cavity;   exhausting spent cooling air through at least one exit port in communication with said at least one high velocity region; and   exhausting spent cooling air through at least one purge hole in communication with said at least one low velocity region.   
     
     
         8 . The method of  claim 7  wherein exhausting spent cooling air through said at least one exit port further comprises exhausting said spent cooling air through an exit of said at least one exit port on a shroud edge of said tip shroud. 
     
     
         9 . The method of  claim 7  wherein exhausting spent cooling air through said at least one purge hole further comprises exhausting said spent cooling air through an exit of said at least one purge hole on an outer top surface and/or inner surface of said tip shroud. 
     
     
         10 . The method of  claim 7  further comprising providing a plurality of said at least one low velocity regions and further providing at least one said purge hole in communication with each said at least one low velocity region and an outer top surface and/or inner surface of said tip shroud. 
     
     
         11 . The method of  claim 10  further comprising providing a plurality of said at least one high velocity regions and at least one of said at least one exit port in communication with each said at least one high velocity region. 
     
     
         12 . The method of  claim 11  further comprising exhausting spent cooling air from an exit of each said at least one purge hole through a top portion and/or bottom portion of said tip shroud and exhausting said cooling air from an exit of each said at least one exit port through a shroud edge of said tip shroud. 
     
     
         13 . A tip shroud configured for being disposed at a tip portion of an airfoil, comprising an internal cooling cavity, said internal cooling cavity comprising a plurality of high flow velocity regions and a plurality of low flow velocity regions, each of said plurality of low flow velocity regions configured to pass cooling air therethrough; at least one exit port in communication with each said at least one of the plurality of high flow velocity regions configured to exhaust spent cooling air therefrom to a side edge of said tip shroud; and at least one purge hole in communication with each said at least one low flow velocity region configured to exhaust spent cooling air therefrom to an outer top surface and/or bottom surface of said tip shroud. 
     
     
         14 . The tip shroud of  claim 13  wherein at least one of said plurality of low flow velocity regions is substantially elongated, and comprises a plurality of said at least one purge hole disposed therealong. 
     
     
         15 . The tip shroud of  claim 14  wherein said at least one purge hole are disposed substantially linearly along said plurality of low flow velocity regions. 
     
     
         16 . The tip shroud of  claim 15  wherein said at least one purge hole is disposed substantially along a line substantially bisecting a width of said plurality of low flow velocity regions. 
     
     
         17 . The tip shroud of  claim 13  wherein at least one of said plurality of low flow velocity regions comprises a narrow end transitioning to a wider opposing end. 
     
     
         18 . The tip shroud of  claim 17  comprising a plurality of said at least one purge hole wherein said at least one purge hole increase in size from said narrow end to said wider opposing end. 
     
     
         19 . The tip shroud of  claim 17  wherein said at least one purge hole decreases in relative spacing from said narrow end to said wider opposing end. 
     
     
         20 . The tip shroud of  claim 13  wherein at least one of said plurality of low flow velocity regions includes a plurality of said at least one purge hole disposed in a matrix configuration.