Spar and shell constructed turbine blade

Abstract

A blade for a rotor of a gas turbine engine is constructed with a spar and shell configuration. The spar is constructed in an integral unit or multi-portions and includes a first wall adjacent to the pressure side and a second wall adjacent to the suction side, a tip portion extending in the spanwise direction and extending beyond the first wall and the second wall and a root portion extending longitudinally, an attachment portion having a central opening for receiving the root portion and a platform portion. The root portion fits into the central opening and is secured therein by a pin extending transversely through the attachment and the root portion. The shell fits over the spar and is supported thereto by a plurality of complementary hooks extending from the spar and shell. The ends of the shell fit into grooves formed on the tip portion and the platform. The shell is made from a high temperature resistant material, such as Molybdenum or Niobium, and is formed from a wire EDM process.

1 . A shell for use in a turbine airfoil constructed from a spar and shell; the shell comprising:
 the shell having an airfoil shape with a leading edge and a trailing edge, and a pressure side and a suction side extending between the two edges;   the shell being formed from an electric discharge machining process; and,   the shell being a thin shell wall to allow for near wall cooling of the inner surface of the shell.   
     
     
         2 . The shell of  claim 1 , and further comprising:
 the shell being formed form a relatively high temperature resistant material that cannot be cast or machined as a thin wall shell.   
     
     
         3 . The shell of  claim 2 , and further comprising:
 the shell being formed from Molybdenum or Niobium.   
     
     
         4 . The shell of  claim 1 , and further comprising:
 the electric discharge machining process is a wire electric discharge machining process.   
     
     
         5 . The shell of  claim 1 , and further comprising:
 the shell includes at least one hook extending from the inner surface of the shell to secure the shell to a spar of the turbine airfoil.   
     
     
         6 . The shell of  claim 5 , and further comprising:
 the hook extends along the spanwise length of the shell.   
     
     
         7 . The shell of  claim 5 , and further comprising:
 the hook is also formed from the electric discharge machining process and is formed as a single piece along with the shell.   
     
     
         8 . The shell of  claim 1 , and further comprising:
 the shell includes a plurality of exit cooling holes in the trailing edge region of the shell to discharge cooling air out from the shell.   
     
     
         9 . The shell of  claim 5 , and further comprising:
 the shell includes a second hook in the same side of the shell as the first hook; and,   the two hooks face in opposite directions such that a chordwise movement of the shell with respect to a spar is limited.   
     
     
         10 . The shell of  claim 1 , and further comprising:
 the shell has substantially the same thickness from the platform end to the tip end of the shell.   
     
     
         11 . A turbine blade for use in a gas turbine engine, the turbine blade comprising:
 an attachment portion forming a platform and having a central opening;   a spar having a tip on one end;   a shell secured in place between the spar tip and the attachment portion; and,   the shell being formed form a relatively high temperature resistant material that cannot be cast or machined as a thin wall shell.   
     
     
         12 . The turbine blade of  claim 11 , and further comprising:
 the shell being a thin wall shell formed from an electric discharge machining process.   
     
     
         13 . The turbine blade of  claim 12 , and further comprising:
 the electric discharge machining process is a wire electric discharge machining process.   
     
     
         14 . The turbine blade of  claim 11 , and further comprising:
 the shell being formed from Molybdenum or Niobium.   
     
     
         15 . The turbine blade of  claim 11 , and further comprising:
 the shell and the spar both include hook means extending from the shell and spar to secure the shell to a spar of the turbine airfoil.   
     
     
         16 . The turbine blade of  claim 11 , and further comprising:
 the shell has substantially the same thickness from the platform end to the tip end of the shell.   
     
     
         17 . The turbine blade of  claim 11 , and further comprising:
 the spar having an internal cooling supply passage, a plurality of exit cooling holes in the tip, and a plurality of near wall cooling holes to discharge cooling air from the internal cooling supply passage and onto the backside wall of the shell to provide near wall cooling for the blade.   
     
     
         18 . The turbine blade of  claim 17 , and further comprising:
 the plurality of near wall cooling holes are located on the pressure side and the suction side of the blade.   
     
     
         19 . The turbine blade of  claim 17 , and further comprising:
 the shell includes a row of trailing edge region exit cooling holes to discharge cooling air from a space formed between the spar and the shell.