Turbine Blade Having Platform Cooling Holes

Abstract

A turbine blade having a plurality of cooling holes which extend from an outside edge of the platform to a cooling passage formed within the turbine blade and a method of limiting the formation of cracks in the platform of the blade are provided. The plurality of cooling holes in the platform are formed at an approximate angle of 45° to the outside edge of the platform and are formed at the approximate mid-point of the thickness of the platform. The cooling holes are generally cylindrical in shape and have a diameter of approximately 50% of the platform thickness.

1 . A turbine blade having an airfoil connected to a platform in a root region, the airfoil and platform having a common cooling passage formed therein, the platform comprising at least one cooling hole which extends from an outside edge of the platform to the common cooling passage. 
     
     
         2 . The turbine blade according to  claim 1 , wherein a plurality of cooling holes are formed in the platform which extend from the outside edge of the platform to the common cooling passage. 
     
     
         3 . The turbine blade according to  claim 2 , wherein four cooling holes are formed in the platform which extend from the outside edge of the platform to the common cooling passage. 
     
     
         4 . The turbine blade according to  claim 3 , wherein the plurality of cooling holes are formed at an angle to the outside edge of the platform which is less than 90°. 
     
     
         5 . The turbine blade according to  claim 4 , wherein the angle at which the plurality of cooling holes are formed to the outside edge of the platform is approximately 45°. 
     
     
         6 . The turbine blade according to  claim 5 , wherein the common cooling passage includes a serpentine cooling circuit. 
     
     
         7 . The turbine blade according to  claim 6 , wherein each of the cooling holes extends to a distinct pathway within the serpentine cooling circuit. 
     
     
         8 . The turbine blade according to  claim 5 , wherein the common cooling passage includes a plurality of generally parallel cooling veins extending through the platform and airfoil. 
     
     
         9 . The turbine blade according to  claim 8 , wherein each of the cooling holes extends to a distinct parallel cooling vein. 
     
     
         10 . The turbine blade according to  claim 1 , wherein the platform has a defined thickness and the at least one cooling hole is formed at the approximate mid-point of the thickness. 
     
     
         11 . The turbine blade according to  claim 1 , wherein the at least one cooling hole is generally cylindrical in shape. 
     
     
         12 . The turbine blade according to  claim 1 , wherein the platform has a defined thickness, and the at least one cooling hole has a diameter of approximately 50% of the platform thickness. 
     
     
         13 . A method of limiting damage to a platform of a turbine blade having an airfoil connected to the platform in a root region of the airfoil blade, the airfoil and platform having a common cooling passage formed therein, the method comprising the step of forming at least one cooling hole in the platform which extends from an outside edge of the platform to the common cooling passage. 
     
     
         14 . The method according to  claim 13 , wherein a plurality of cooling holes are formed in the platform which extend from the outside edge of the platform to the common cooling passage. 
     
     
         15 . The method according to  claim 14 , wherein four cooling holes are formed in the platform which extend from the outside edge of the platform to the common cooling passage. 
     
     
         16 . The method according to  claim 15 , wherein the plurality of cooling holes are formed at an angle to the outside edge of the platform which is less than 90°. 
     
     
         17 . The method according to  claim 16 , wherein the angle at which the plurality of cooling holes are formed to the outside edge of the platform is approximately 45°. 
     
     
         18 . The method according to  claim 17 , wherein the cooling passage includes a serpentine cooling circuit. 
     
     
         19 . The method according to  claim 18 , wherein each of the cooling holes extends to a distinct pathway within the serpentine cooling circuit. 
     
     
         20 . The method according to  claim 17 , wherein the cooling passage includes a plurality of generally parallel cooling veins extending through the platform and airfoil. 
     
     
         21 . The method according to  claim 18 , wherein each of the cooling holes extends to a distinct parallel cooling vein. 
     
     
         22 . The method according to  claim 13 , wherein the platform has a defined thickness and the at least one cooling hole is formed at the approximate mid-point of the thickness. 
     
     
         23 . The method according to  claim 13 , wherein the platform has a defined thickness and the at least one cooling hole is generally cylindrical in shape and has a diameter of approximately 50% of the platform thickness. 
     
     
         24 . The method according to  claim 13 , wherein the at least one cooling hole is formed by an EDM process. 
     
     
         25 . The method according to  claim 13 , wherein the step of forming at least one cooling hole is performed in the course of forming a new turbine blade. 
     
     
         26 . The method according to  claim 13 , wherein the step of forming at least one cooling hole is performed in the course of repairing a turbine blade that has previously been in service. 
     
     
         27 . The method according to  claim 25 , wherein the step of forming at least one cooling hole is performed without removing any TBC layer formed on the turbine blade.