Active multi-effector control of high pressure turbine clearances

1. A method of operating a gas turbine engine, comprising:

commanding an acceleration of the gas turbine engine;

accelerating a high pressure turbine rotor as a result of the command; and

moving a variable pitch high pressure compressor vane toward an open position after accelerating the high pressure turbine rotor, thereby reducing an acceleration rate of the high pressure turbine rotor thereby reducing a change in a clearance gap between the high pressure turbine rotor and a blade outer airseal.

2. The method of claim 1 , further comprising:

directing a portion of a turbofan bypass stream to an outer circumference of a turbine case to control a thermal growth of a turbine case in which the blade outer airseal is located.

3. The method of claim 1 , further comprising:

increasing a rotational speed of a low pressure turbine in response to the slowing of the acceleration rate of the high pressure turbine rotor; and

modulating a fuel flow to a combustor of the gas turbine engine to reduce an acceleration rate of the low pressure turbine.

4. The method of claim 3 , wherein modulating the fuel flow is reducing a rate of the fuel flow.

5. The method of claim 1 , wherein the reducing the acceleration rate of the high pressure turbine rotor prevents a rub condition between the blade outer airseal and the high pressure turbine rotor during the acceleration of the gas turbine engine.

6. A gas turbine engine, comprising:

a turbine section including:

a high pressure turbine rotor having a plurality of rotor blades;

a blade outer airseal disposed radially outboard of the turbine rotor and defining a radial clearance gap between the plurality of rotor blades and the blade outer airseal;

a compressor section including:

a high pressure compressor rotor operably connected to the high pressure turbine rotor via an outer shaft;

a high pressure compressor stator including a plurality of variable pitch stator vanes;

an actuation system operably connected to the plurality of variable pitch stator vanes configured to move the variable pitch stator vanes between a closed position and an open position; and

an engine control system configured to:

command an acceleration of the gas turbine engine;

cause acceleration of the high pressure turbine rotor based on the command; and

move a variable pitch high pressure compressor vane of the plurality of variable pitch stator vanes toward an open position after the acceleration of the high pressure turbine rotor, thereby slowing an acceleration rate of the high pressure turbine rotor thereby reducing a change in the clearance gap between the high pressure turbine rotor and a blade outer airseal.

7. The gas turbine engine of claim 6 , further comprising:

a low pressure turbine disposed downstream of the high pressure turbine rotor; and

a combustor disposed upstream of the high pressure turbine;

wherein the engine control system is additionally configured to modulate a fuel flow to the combustor in response to the slowing of the acceleration rate of the high pressure turbine rotor, thereby reducing an acceleration rate of the low pressure turbine.

8. The gas turbine engine of claim 7 , wherein modulating the fuel flow is reducing a rate of the fuel flow.

9. The gas turbine engine of claim 7 , wherein the low pressure turbine is secured to an inner shaft separate from the outer shaft.

10. The gas turbine engine of claim 6 , wherein the blade outer airseal is disposed in a high pressure turbine case.

11. The gas turbine engine of claim 6 , wherein the reducing the acceleration rate of a high pressure turbine rotor prevents a rub condition between the blade outer airseal and the high pressure turbine rotor during the acceleration of the gas turbine engine.

12. The gas turbine engine of claim 6 , wherein each of the plurality of variable pitch stator vanes is rotatable about a respective vane axis to move between the open position and the closed position.

13. An active clearance control system of a gas turbine engine, comprises an engine control system configured to:

command an acceleration of the gas turbine engine;

cause acceleration of a high pressure turbine rotor based on the command; and

move a variable pitch high pressure compressor vane toward an open position after the acceleration of the high pressure turbine rotor, thereby slowing an acceleration rate of the high pressure turbine rotor thereby reducing a change in a clearance gap between the high pressure turbine rotor and a blade outer airseal disposed radially outboard of the high pressure turbine rotor.

14. The active clearance control system of claim 13 , wherein the engine control system is additionally configured to modulate a fuel flow to a combustor of the gas turbine engine in response to the slowing of the acceleration rate of the high pressure turbine rotor, thereby reducing an acceleration rate of a low pressure turbine of the gas turbine engine.

15. The active clearance control system of claim 14 , wherein modulating the fuel flow is reducing a rate of the fuel flow.

16. The active clearance control system of claim 13 , wherein the reducing the acceleration rate of a high pressure turbine rotor prevents a rub condition between the blade outer airseal and the high pressure turbine rotor during the acceleration of the gas turbine engine.

17. The active clearance control system of claim 14 , wherein each of the plurality of variable pitch stator vanes is rotatable about a respective vane axis to move between the open position and the closed position.