Multiple piece turbine airfoil
A turbine airfoil, such as a rotor blade or a stator vane, for a gas turbine engine, the airfoil formed as a shell and spar construction with a plurality of dog bone struts each mounted within openings formed within the shell and spar to allow for relative motion between the spar and shell in the airfoil chordwise direction while also forming a seal between adjacent cooling channels. The struts provide the seal as well as prevent bulging of the shell from the spar due to the cooling air pressure.
1. An air cooled turbine airfoil comprising:
a shell having an airfoil shape with a leading edge, a trailing edge, and a pressure side wall and a suction side wall extending between the leading edge and the trailing edge;
a spar forming an internal cooling air supply channel;
both the shell and the spar have a plurality of raised sections each with a circular opening on an inner side of the raised section and a narrow gap on an outer side of the raised section;
a dog bone strut mounted within opposed raised sections between the shell and the spar, the dog bone strut having a figure eight cross section shape with two ends having a circular cross section shape and a narrow neck connecting the two circular ends; and,
the circular openings within the raised sections and the dog bone struts form a seal between adjacent cooling channels, prevent bulging of the shell from the spar due to cooling air pressure within the cooling channels, and allow for thermal growth between the shell and the spar in a chordwise direction and a spanwise direction of the airfoil.
2. The air cooled turbine airfoil of claim 1 , and further comprising:
the raised sections have facing surfaces that form the narrow gap when the dog bone strut is mounted within the circular openings to allow for relative chordwise motion between the shell and the spar.
3. The air cooled turbine airfoil of claim 1 , and further comprising:
the raised sections have a narrow opening on the inner ends so that the dog bone strut can pivot within the circular openings during relative chordwise motion between the shell and the spar.
4. The air cooled turbine airfoil of claim 1 , and further comprising:
the dog bone struts are formed from a high temperature metallic material that can be extruded to form the strut.
5. The air cooled turbine airfoil of claim 1 , and further comprising:
the shell is formed from one of tungsten, molybdenum and columbium.
6. The air cooled turbine airfoil of claim 5 , and further comprising:
the shell is a thin walled shell.
7. The air cooled turbine airfoil of claim 1 , and further comprising:
the airfoil is a rotor blade for use in an industrial gas turbine engine.
8. The air cooled turbine airfoil of claim 1 , and further comprising:
the airfoil is a stator vane for use in an industrial gas turbine engine.
9. The air cooled turbine airfoil of claim 1 , and further comprising:
the raised sections of the shell and the spar extend the length of the shell; and,
the dog bone struts are each a single piece and extend the length of the raised sections of the shell and the spar.
10. The air cooled turbine airfoil of claim 1 , and further comprising:
the dog bone strut includes a cut on the outer ends to provide flexibility to the strut.