Bellcrank assembly for gas turbine engine and method

1. A bellcrank assembly for variable vane assembly of a gas turbine engine, the bellcrank assembly comprising:

a first bellcrank segment;

a second bellcrank segment;

a bolt extending through respective interior barrels defined by the first and second bellcrank segments to couple the first and second bellcrank segments to each other within the axial direction;

a torsion spring having an end including a keyed geometry, the end engaged with one of the first and second bellcrank segments, the torsion spring extending from the first bell crank segment to the second bell crank segment, wherein the torsion spring has a spring coefficient sufficient to maintain a rigid connection between the first and second bellcrank segments during a normal operating condition of the compressor, the torsion spring allowing relative rotation of the first bellcrank segment and the second bellcrank segment during a surge condition; and

a torque frame wall defining an aperture, the bolt and torsion spring extending through the aperture.

2. The bellcrank assembly of claim 1 , wherein the torque frame is a single plate or multiple stacked plates.

3. The bellcrank assembly of claim 2 , wherein the torque frame wall is located proximate a longitudinal midpoint of the bellcrank assembly.

4. The bellcrank assembly of claim 3 , wherein the keyed geometry comprises at least one protrusion received within a recess defined by at least one of the first and second bellcrank segments.

5. The bellcrank assembly of claim 3 , further comprising a shear bushing disposed within the aperture defined by the torque frame wall.

6. The bellcrank assembly of claim 1 , wherein the interior barrels extend along a longitudinal axis of the bellcrank assembly.

7. A gas turbine engine comprising:

a compressor section;

a combustor fluidly coupled to the compressor section via a primary flowpath;

a turbine section fluidly coupled to the combustor section via the primary flowpath;

a plurality of variable vanes disposed within the compressor section; and

a bellcrank assembly operatively coupled to the plurality of variable vanes, articulation of the bellcrank assembly causing rotation of the plurality of variable vanes, the bellcrank assembly comprising:

a first bellcrank segment having a first bellcrank arm for receiving an input rotation from an actuation mechanism, the first bellcrank segment defining a first bellcrank barrel;

a second bellcrank segment having a second bellcrank arm for outputting rotation to the plurality of variable vanes, the second bellcrank segment defining a second bellcrank barrel;

a bolt extending through the first and second bellcrank barrels to couple the first and second bellcrank segments to each other within the axial direction;

a torsion spring having an end including a keyed geometry, the end engaged with one of the first and second bellcrank segments, the torsion spring extending from the first bell crank segment to the second bellcrank segment, wherein the torsion spring has a spring coefficient sufficient to maintain a rigid connection between the first and second bellcrank segments during a normal operating condition of the compressor, the torsion spring allowing relative rotation of the first bellcrank segment and the second bellcrank segment during a surge condition.

8. The gas turbine engine of claim 7 , further comprising a torque frame defining an aperture, the bolt and the spring extending through the aperture, wherein the torque frame is a single plate or multiple stacked plates.

9. The gas turbine engine of claim 8 , wherein the torque frame wall is located proximate a longitudinal midpoint of the bellcrank assembly.

10. The gas turbine engine of claim 8 , further comprising a shear bushing disposed within the aperture defined by the torque frame wall.

11. The gas turbine engine of claim 7 , wherein the keyed geometry comprises at least one protrusion received within a recess defined by at least one of the first and second bellcrank segments.

12. The gas turbine engine of claim 7 , wherein the first and second bellcrank barrels extend along a longitudinal axis of the bellcrank assembly.

13. A method of surge protection for a variable vane assembly in a gas turbine engine comprising:

maintaining a rigid connection between a first bellcrank segment and a second bellcrank segment during a normal operating condition of the compressor using a torsion spring, the first and second bellcrank segments being mechanically coupled to each other through the torsion spring;

allowing relative rotation of the first bellcrank segment and the second bellcrank segment to each other during a surge condition; and

absorbing mechanical energy with the torsion spring engaged with at least one of the first and second bellcrank segments during relative rotation of the first bellcrank segment and the second bellcrank segment during a surge event.

14. The method of claim 13 , wherein the first and second bellcrank segments is maintained within the axial direction with a bolt extending through a first bellcrank barrel and a second bellcrank barrel defined respectively by the first bellcrank segment and the second bellcrank segment.

15. The method of claim 13 , further comprising preloading at least one of the first and second bellcrank segments with a preload torque applied by a keyed geometry of the torsion spring and at least one of the first and second bellcrank segments.

16. The method of claim 13 , further comprising defining a mounting location of the first and second bellcrank segments with a torque frame wall.

17. The method of claim 16 , wherein the torque frame wall is a single plate or multiple stacked plates.

18. The method of claim 16 , further comprising defining a rotational path with a shear bushing disposed in an aperture of the torque frame wall.