Method to augment heat transfer using chamfered cylindrical depressions in cast internal cooling passages

Abstract

An air-cooled turbine blade is provided having an airfoil shape defined by a convex suction side wall, a concave pressure side wall, a leading edge, a trailing edge, a root and a tip, each wall including an interior surface that defines an interior with the edges, root and tip. The blade includes a plurality of independent cooling circuit flow paths within the blade interior and a roughened surface. The roughened surface is formed on an interior surface of at least one of the convex suction side wall and the concave pressure side wall, the roughened surface comprising a plurality of cylindrical depressions. Each depression includes a cylindrical wall coupled to a bottom wall by a chamfered edge formed therebetween, and the roughened surface defines at least a portion of one of the flow paths of the plurality of independent cooling circuit flow paths. Methods for forming the blade are also provided.

1 . A method of forming an airfoil having walls and structures extending therebetween that define an internal cooling circuit, the internal cooling circuit including a flow path, the method comprising the steps of: 
 forming an array of cylindrical pins on a selected portion of an outer surface of a core, each pin includes a top wall, a cylindrical side wall, and a chamfered edge therebetween, the core shaped substantially similarly to the internal cooling circuit, and the selected portion of the core shaped substantially similarly to the flow path;    forming the airfoil around the core; and    removing the core from the airfoil to expose a roughened surface comprising a plurality of cylindrical depressions on a surface of the airfoil from which the selected core portion is removed, each depression including a cylindrical sidewall coupled to a bottom wall by a chamfered edge formed therebetween, and the roughened surface defining at least a portion of the flow path.    
   
   
       2 . The method of  claim 1 , wherein the step of forming an array of cylindrical pins includes the step of determining a chamfering angle between the top wall and the side wall.  
   
   
       3 . The method of  claim 2 , wherein the core includes an outer surface and the cylindrical walls of each cylindrical pin is angled relative to the core outer surface.  
   
   
       4 . The method of  claim 1 , wherein the step of forming an array of cylindrical pins comprises: 
 forming a core die and end-milling depressions into the core die that have shapes that are complementary to the cylindrical pins; and    injecting the core die with ceramic material to form the core.    
   
   
       5 . The method of  claim 1 , wherein the step of forming an array of cylindrical pins comprises: 
 forming a core die and electro-discharge machining depressions into the core die that have shapes that are complementary to the cylindrical pins; and    injecting the core die with ceramic material to form the core.    
   
   
       6 . The method of  claim 1 , wherein the step of forming the airfoil around the core comprises: 
 placing the core in a wax die;    injecting wax around the core and in the wax die to form a wax pattern of the airfoil;    contacting the wax pattern with ceramic slurry to form a mold;    removing the wax pattern from the ceramic mold;    depositing molten metal material into the mold and around the core; and    cooling the molten metal material to form the airfoil.    
   
   
       7 . The method of  claim 1 , wherein the step of removing comprises chemically removing the core.  
   
   
       8 . The method of  claim 1 , wherein the step of removing comprises physically removing the core.  
   
   
       9 . The method of  claim 1 , wherein the airfoil includes a tip portion and the flow path is disposed adjacent the tip portion.  
   
   
       10 . The method of  claim 1 , further comprising forming the core from ceramic material.  
   
   
       11 . The method of  claim 1 , wherein the step of forming the core comprises injecting the ceramic material into a core die and curing the ceramic material.  
   
   
       12 . A method of forming an airfoil having walls and structures extending therebetween that define an internal cooling circuit, the internal cooling circuit including a flow path, the method comprising the steps of: 
 determining a chamfering angle between a top wall and a side wall of a cylindrical pin to be formed in a core;    forming an array of the cylindrical pins on a selected portion of an outer surface of the core, the core shaped substantially similarly to the internal cooling circuit, and the selected portion of the core shaped substantially similarly to the flow path;    forming the airfoil around the core; and    removing the core from the airfoil to expose a roughened surface comprising a plurality of cylindrical depressions on a surface of the airfoil from which the selected core portion is removed, each depression including a cylindrical wall coupled to a bottom wall by a chamfered edge formed therebetween, and the roughened surface defining at least a portion of the flow path.    
   
   
       13 . The method of  claim 12 , wherein the core includes an outer surface and the cylindrical walls of each cylindrical pin is angled at a predetermined angle relative to the core outer surface.  
   
   
       14 . The method of  claim 11 , wherein the step of forming the airfoil around the core comprises: 
 placing the core in a wax die;    injecting wax around the core and in the wax die to form a wax pattern of the airfoil;    contacting the wax pattern with ceramic slurry to form a mold;    removing the wax pattern from the ceramic mold;    depositing molten metal material into the mold and around the core; and    cooling the molten metal material to form the airfoil.    
   
   
       15 . The method of  claim 11 , wherein the step of removing comprises chemically removing the core.  
   
   
       16 . The method of  claim 11 , wherein the step of removing comprises physically removing the core.  
   
   
       17 . An air-cooled turbine blade having an airfoil shape defined by a convex suction side wall, a concave pressure side wall, a leading edge, a trailing edge, a root and a tip, each wall including an interior surface that defines an interior with the edges, root and tip, the turbine blade comprising: 
 a plurality of independent cooling circuit flow paths within the blade interior; and    a roughened surface formed on an interior surface of at least one of the convex suction side wall and the concave pressure side wall, the roughened surface comprising a plurality of cylindrical depressions, each depression including a cylindrical wall coupled to a bottom wall by a chamfered edge formed therebetween, and the roughened surface defining at least a portion of one of the flow paths of the plurality of independent cooling circuit flow paths.    
   
   
       18 . The turbine blade of  claim 17 , wherein the plurality of cylindrical depressions is formed on the interior surface of the convex suction side wall and at least one cylindrical depression has a cylindrical wall that is angled at a predetermined angle relative to the convex suction side wall interior surface.  
   
   
       19 . The turbine blade of  claim 17 , wherein the plurality of cylindrical depressions is formed on the interior surface of the concave pressure side wall and at least one cylindrical depression has a cylindrical wall that is angled at a predetermined angle relative to the concave pressure side wall interior surface.