Gas turbine engines and related systems involving variable vanes

1. A vane assembly for a gas turbine engine comprising:

a first inner diameter platform having an outer diameter surface and a recess located in the outer diameter surface;

a first outer diameter platform spaced from the first inner diameter platform; and

a variable vane airfoil rotatably attached to and extending between the first inner diameter platform and the first outer diameter platform such that at least a portion of the vane airfoil extends beyond a periphery of at least one of the first inner diameter platform and the first outer diameter platform, wherein a root of the vane airfoil extends into the recess, and wherein the root comprises an airfoil cross-sectional geometry.

2. The assembly of claim 1 , wherein:

each of the first inner diameter platform and the first outer diameter platform has a front edge, an aft edge and a side edge extending between the front edge and the aft edge; and

at least a portion of the vane airfoil extends beyond the side edge of at least one of the first inner diameter platform and the first outer diameter platform.

3. The assembly of claim 1 , wherein:

the recess is a suction-side recess; and

at least a portion of the root associated with a suction side of the vane airfoil extends into the suction-side recess.

4. The assembly of claim 1 , further comprising:

a second inner diameter platform; and

a second outer diameter platform spaced from the second inner diameter platform;

the second inner diameter platform being positioned adjacent to the first inner diameter platform such that an inner platform gap is formed therebetween;

the second outer diameter platform being positioned adjacent to the first outer diameter platform such that an outer platform gap is formed therebetween; and

the vane airfoil spanning across at least a portion of the inner platform gap and across at least a portion of the outer platform gap.

5. The assembly of claim 4 , wherein:

the second inner diameter platform has a pressure-side recess; and

at least a portion of the root associated with a pressure side of the vane airfoil extends into the pressure-side recess.

6. The assembly of claim 1 , wherein:

the vane airfoil is a first vane airfoil; and

the assembly further comprises a second vane airfoil extending between the first inner diameter platform and the first outer diameter platform.

7. The assembly of claim 6 , wherein the second vane airfoil is a stationary airfoil fixed in position with respect to the first inner diameter platform and the first outer diameter platform.

8. The assembly of claim 1 , wherein the vane airfoil is a portion of a variable vane assembly having a shaft, the vane airfoil being attached to the shaft such that the airfoil rotates with the shaft.

9. The assembly of claim 8 , wherein:

the first inner diameter platform supports an inner diameter bearing; and

a free end of the shaft is received by the inner diameter bearing.

10. The assembly of claim 8 , wherein the shaft is a hollow shaft operative to receive cooling air for cooling the vane airfoil.

11. The assembly of claim 8 , wherein the shaft has a tapered spline.

12. A vane assembly for a gas turbine engine comprising:

a first inner diameter platform;

a first outer diameter platform spaced from the first inner diameter platform; and

a variable vane airfoil rotatably attached to and extending between the first inner diameter platform and the first outer diameter platform such that at least a portion of the vane airfoil extends beyond a periphery of at least one of the first inner diameter platform and the first outer diameter platform;

wherein the vane airfoil is a portion of a variable vane assembly having a shaft, the vane airfoil being attached to the shaft such that the airfoil rotates with the shaft;

wherein the variable vane assembly further comprises a pillow block attached to the shaft; and

wherein the first outer diameter platform is operative to mount the pillow block.

13. A gas turbine engine comprising:

a compressor;

a combustion section operative to receive compressed air from the compressor; and

a turbine operative to drive the compressor, the turbine having a vane assembly;

the vane assembly comprising:

a first inner diameter platform;

a first outer diameter platform spaced from the first inner diameter platform, which first outer diameter platform has an inner diameter surface and a recess located in the inner diameter surface; and

a variable vane airfoil rotatably attached to and extending between the first inner diameter platform and the first outer diameter platform such that at least a portion of the vane airfoil extends beyond a periphery of at least one of the first inner diameter platform and the first outer diameter platform, wherein a tip of the vane airfoil extends into the recess, and wherein the tip comprises an airfoil cross-sectional geometry.

14. The engine of claim 13 , wherein:

the vane airfoil is a first vane airfoil; and

the assembly further comprises a second vane airfoil extending between the first inner diameter platform and the first outer diameter platform.

15. The engine of claim 14 , wherein the vane airfoil is removably attached to the vane assembly.

16. A gas turbine engine comprising:

a compressor;

a combustion section operative to receive compressed air from the compressor;

a turbine operative to drive the compressor, the turbine having a vane assembly comprising:

a first inner diameter platform;

a first outer diameter platform spaced from the first inner diameter platform, which first outer diameter platform has an inner diameter surface and a recess located in the inner diameter surface; and

a variable vane airfoil rotatably attached to and extending between the first inner diameter platform and the first outer diameter platform such that at least a portion of the vane airfoil extends beyond a periphery of at least one of the first inner diameter platform and the first outer diameter platform wherein a tip of the vane airfoil extends into the recess, and wherein the tip comprises an airfoil cross-sectional geometry;

a second inner diameter platform; and

a second outer diameter platform spaced from the second inner diameter platform;

the second inner diameter platform being positioned adjacent to the first inner diameter platform such that an inner platform gap is formed therebetween;

the second outer diameter platform being positioned adjacent to the first outer diameter platform such that an outer platform gap is formed therebetween; and

the vane airfoil spanning across at least a portion of the inner platform gap and across at least a portion of the outer platform gap.

17. A variable vane for a gas turbine engine comprising:

a hollow shaft extending between a first end and a second end, and including a tapered spline; and

a vane airfoil attached to the shaft between the first end and the second end;

wherein the tapered spline is located between the airfoil and the second end, and is configured such that a narrow portion of the spline is located toward the second end.