Rotor bow management

Patent metadata

Field	Value
Publication number	US-10927757-B2
Application number	US-201816203664-A
Country	US
Kind code	B2
Filing date	Nov 29, 2018
Priority date	Dec 15, 2017
Publication date	Feb 23, 2021
Grant date	Feb 23, 2021

Abstract

A method of reducing rotor bow in a high pressure rotor of a gas turbine engine that has in axial flow a low pressure rotor and a high pressure rotor. The method involves storing bleed air from the gas turbine engine when the engine is running to provide stored pneumatic energy; and using that stored pneumatic energy after the engine has been shut-down to rotate the high pressure rotor at a speed and for a duration that reduces rotor bow. A gas turbine engine wherein rotor bow in the high pressure rotor after engine shut-down has been reduced by carrying out the aforesaid method is also disclosed.

First claim

I claim:

1. A method of reducing rotor bow in a high pressure rotor of a gas turbine engine that has in axial flow a low pressure rotor and a high pressure rotor, the method comprising the steps of:
storing bleed air from the gas turbine engine when the engine is running to provide stored pneumatic energy, wherein the stored pneumatic energy is provided by a pneumatic energy storage system that comprises an air tank, a pneumatic motor, an accessory gear box and a microcontroller; and
using the stored pneumatic energy after the engine has been shut-down to rotate the high pressure rotor at a speed and for a duration that reduces rotor bow,
wherein the pneumatic energy storage system is powered by a rechargeable battery that is recharged by a permanent magnet alternator that is driven by the accessory gear box.

2. A method according to claim 1 , wherein the gas turbine engine comprises in axial flow a low pressure compressor, and a high pressure compressor, and wherein the bleed air is provided by the high pressure compressor.

3. A method according to claim 2 , wherein the gas turbine engine comprises in axial flow an intermediate pressure compressor.

4. A method according to claim 1 , wherein the stored pneumatic energy is in the form of compressed air.

5. A method according to claim 1 , wherein the high pressure rotor is rotated at a speed from 0.1 rpm to 20 rpm for 1 minute to 10 hours.

6. A method according to claim 5 , wherein the high pressure rotor is rotated continuously for that duration.

7. A method according to claim 5 , wherein the high pressure rotor is rotated discontinuously for that duration.

8. A method according to claim 7 , wherein the high pressure rotor is rotated by approximately 180° per rotation.

9. A method according to claim 1 , wherein the high pressure rotor is rotated at a speed from 0.5 rpm to 15 rpm for 5 minutes to 8 hours.

10. A method according to claim 9 , wherein the high pressure rotor is rotated continuously for that duration.

11. A method according to claim 9 , wherein the high pressure rotor is rotated discontinuously for that duration.

12. A method according to claim 11 , wherein the high pressure rotor is rotated by approximately 180° per rotation.

13. A pneumatic system for controlling rotor bow, the system comprising:
an air tank configured to receive compressor bleed air from a compressor of a gas turbine engine when the engine is running, the air tank further configured to provide stored pneumatic energy, wherein the gas turbine engine has, in axial flow, a low pressure rotor and a high pressure rotor;
a valve configured to control the flow of the compressor bleed air into the air tank;
an accessory gearbox configured to rotate the low pressure rotor and the high pressure rotor;
a pneumatic motor or an air turbine starter configured to rotate the high pressure rotor with the stored pneumatic energy after the engine is shut down for a duration that reduces rotor bow;
a permanent magnet alternator driven by the accessory gearbox;
a re-chargeable battery configured to be re-charged by the permanent magnet alternator, wherein the re-chargeable batter is configured to power the pneumatic system.

Assignees

• Rolls Royce Plc

Inventors

• Stevenson Andrew

Classifications

• F02C7/277

  the starter being a {separate} turbine · CPC title

• F01D25/36

  using electric motors · CPC title

• F02C6/16

  for storing compressed air · CPC title

• F05D2270/65

  Pneumatic actuators · CPC title

• F01D25/34 Primary

  Turning or inching gear · CPC title