Device and method for gas turbine unlocking

1. A method for unlocking a rotor in an aeroderivative gas turbine following shut-down of the aeroderivative gas turbine, the method comprising:

providing an air intake plenum of the aeroderivative gas turbine,

providing a compressor of the aeroderivative gas turbine, the compressor comprising a compressor air intake,

providing a combustor of the aeroderivative gas turbine,

providing a high pressure turbine of the aeroderivative gas turbine,

providing a power turbine of the aeroderivative gas turbine, and

providing a forced air-stream generator,

wherein the air intake plenum is in fluid communication with a combustion-air flow path of the aeroderivative gas turbine, the compressor air intake, and the forced air-stream generator;

providing a shutter arrangement, arranged and controlled to selectively open and close the combustion-air flow path, wherein the shutter arrangement is provided in the combustion-air flow path through which air enters the air intake plenum;

providing a silencer arrangement, wherein the silencer arrangement comprises a plurality of parallel arranged silencer panels, the silencer arrangement defining a plurality of air passageways such that a respective air passageway is defined between respective pairs of adjacent parallel arranged silencer panels, each air passageway having an air outlet aperture, and a respective shutter provided by the shutter arrangement is movably arranged at each air outlet aperture to selectively open and close the respective air passageway; and

cooling the rotor, when the rotor is locked following shut down of the aeroderivative gas turbine, by closing the shutters of the shutter arrangement and generating an overpressure in the air intake plenum using the forced air-stream generator, the overpressure being sufficient to force pressurized air through the locked rotor of the aeroderivative gas turbine.

2. The method according to claim 1 , wherein the overpressure ranges between 0.05 and 0.3 Bar above ambient pressure.

3. The method according to claim 1 , wherein the overpressure ranges between 0.1 and 0.15 Bar above ambient pressure.

4. An aeroderivative gas turbine comprising:

an air intake plenum;

a compressor comprising a compressor air intake in fluid communication with the air intake plenum;

a combustor;

a high pressure turbine;

a power turbine;

a forced air-stream generator arranged in fluid communication with the air intake plenum; and

a silencer arrangement;

wherein a shutter arrangement is provided in a combustion-air flow path through which air enters the air intake plenum, the shutter arrangement arranged and controlled to selectively open and close the combustion-air flow path to pressurize the air intake plenum by the forced air-stream generator, up to a pressure sufficient to force pressurized air through the aeroderivative gas turbine; and

wherein the silencer arrangement comprises a plurality of parallel arranged silencer panels, the silencer arrangement defining a plurality of air passageways such that a respective air passageway is defined between respective pairs of adjacent parallel arranged silencer panels, each air passageway having an air outlet aperture, and a respective shutter provided by the shutter arrangement is movably arranged at each air outlet aperture to selectively open and close the respective air passageway.

5. The aeroderivative gas turbine according to claim 4 , wherein the shutter arrangement is disposed downstream of the silencer arrangement with respect to an air stream in the combustion-air flow path.

6. The aeroderivative gas turbine according to claim 4 , wherein the shutters are pivoting shutters arranged to reciprocatingly pivot around respective axes to selectively open and close the air passageways.

7. The aeroderivative gas turbine according to claim 4 , wherein the shutters are simultaneously controlled by an opening and closing actuator.

8. The aeroderivative gas turbine according to claim 6 , wherein each pivoting shutter is arranged to pivot around a respective pivoting shaft extending parallel to a respective parallel arranged silencer panel and downstream from a trailing edge of the respective parallel arranged silencer panel.

9. The aeroderivative gas turbine according to claim 8 , wherein a respective inclined plate is arranged parallel to each pivoting shaft and extends in an air flow direction downstream of each respective parallel arranged silencer panel, each inclined plate and a respective pivoting shutter converging to one another in the air flow direction and being arranged to form a trailing profile extending downstream of the respective parallel arranged silencer panel.

10. The aeroderivative gas turbine according to claim 4 , wherein each parallel arranged silencer panel has planar surfaces, opposing planar surfaces of each pair of adjacent parallel arranged silencer panels defining the respective air passageways having a substantially rectangular cross section with a first dimension parallel to the planar surfaces and a second dimension orthogonal to the planar surfaces, the first dimension being larger than the second dimension.

11. The aeroderivative gas turbine according to claim 10 , wherein the first dimension is at least ten times the second dimension.

12. The aeroderivative gas turbine according to claim 6 , further comprising a beam arranged downstream of each parallel arranged silencer panel with respect to air flow in the combustion-air flow path, and wherein each pivoting shutter is pivoted downstream from the beam.

13. The aeroderivative gas turbine according to claim 9 , wherein each inclined plate is supported by a respective beam and extends parallel thereto.

14. The aeroderivative gas turbine according to claim 4 , wherein each air outlet aperture is at least partly surrounded by a sealing gasket co-acting with the respective shutter.

15. The aeroderivative gas turbine according to claim 14 , wherein each air outlet aperture is entirely surrounded by the sealing gasket.

16. The aeroderivative gas turbine according to claim 14 , wherein the sealing gasket has a self-sealing shape, such that a sealing action of the sealing gasket is increased by air pressure in the air intake plenum.

17. The aeroderivative gas turbine according to claim 14 , wherein the sealing gasket comprises a gasket body and a sealing lip projecting from the gasket body, the sealing lip co-acting with the respective shutter when the respective shutter is in a closed position, wherein pressure in the air intake plenum presses the sealing lip against the respective shutter.

18. The aeroderivative gas turbine according to claim 14 , wherein each air outlet aperture is at least partly surrounded by a gasket retention profile, the sealing gasket being anchored in the gasket retention profile.

19. The aeroderivative gas turbine according to claim 14 , wherein an end stop is provided for each air outlet aperture, the end stop defining a closing position of the respective shutter.

20. The aeroderivative gas turbine according to claim 4 , wherein the forced air-stream generator and the compressor air intake are arranged facing each other in the air intake plenum.

21. The aeroderivative gas turbine according to claim 20 , wherein the forced air-stream generator is arranged inside a gas turbine compartment below a ventilation air entrance.

22. The aeroderivative gas turbine according to claim 4 , wherein the forced air-stream generator is configured to prevent air flow through the forced air-stream generator when the forced air-stream generator is inoperative.

23. The aeroderivative gas turbine according to claim 22 , wherein the forced air-stream generator comprises a positive displacement compressor.

24. The aeroderivative gas turbine according to claim 23 , wherein the forced air-stream generator comprises a rotary compressor.