Impingement cooling of a turbine airfoil with large platform to airfoil fillet radius

Abstract

A method of impingement cooling a turbine airfoil with a large platform to airfoil fillet radius which includes coring the airfoil fillet such that the fillet wall is maintained at a minimum thickness. An impingement tube is used which follows the fillet contour as it transitions from airfoil to platform and supplies impingement air to the airfoil walls. The air subsequently flows across the airfoil internal wall and finally exits the airfoil through airfoil holes to provide film cooling to the airfoil fillet.

1 . A method of impingement cooling a turbine airfoil with a large platform to airfoil fillet radius which contains a plurality of cooling holes through the airfoil wall which comprises:
 (a) coring the airfoil fillet such that the fillet wall is maintained at a minimum thickness;   (b) inserting into the airfoil an impingement tube which follows the fillet contour to platform transition;   (c) applying impingent air through the impingement tube to the airfoil walls and (d) using the impinged air to subsequently flow through airfoil and fillet holes to provide film cooling to the airfoil fillet.   
     
     
         2 . The method of  claim 1  in which the fillet has been cored such that the backwall of the fillet substantially follows the exterior contour of the fillet surface. 
     
     
         3 . A system for impingement cooling a turbine airfoil with a large platform to airfoil fillet radius which contains a plurality of cooling holes through the airfoil wall which comprises:
 (a) an airfoil having an airfoil fillet which exhibits a fillet wall thickness similar to the wall thickness of the airfoil wall; and   (b) said airfoil having an impingement tube inserted internally therein said tube being configured to follow the fillet contour to platform transition and having holes for delivery of impingement air to said airfoil fillet.   
     
     
         4 . (canceled) 
     
     
         5 . A method of impingement cooling a turbine airfoil with a large platform to airfoil fillet radius which comprises:
 (a) providing an airfoil having an airfoil fillet having a defined contour and a minimum fillet wall thickness with said airfoil having a plurality of cooling holes through the airfoil wall;   (b) inserting into said airfoil an impingement tube positioned to follow the fillet contour;   (c) applying impingent air through said tube to the airfoil and fillet walls;   (d) with said impinged air thereby providing film cooling to the airfoil fillet.   
     
     
         6 . A turbine airfoil which includes:
 (a) an airfoil fillet having a fillet wall maintained at a thickness similar to that of the airfoil side walls, with said airfoil containing a plurality of cooling holes through the airfoil wall;   (b) an impingement tube inserted into said airfoil and positioned adjacent said fillet which follows the fillet contour;   (c) whereby impingent air is passed through said tube to the airfoil and fillet walls to provide film cooling to the airfoil fillet.   
     
     
         7 . The airfoil of  claim 6  in which the airfoil fillet backwall is contoured to follow the contour of the exterior fillet surface.