# US 10,309,316 B2 · Bowed rotor start mitigation in a gas turbine engine

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- Number: US 10,309,316 B2
- Document ID: US10309316B2
- Status: Granted
- Kind: B2
- Application number: 15/042,368
- Filed: 2016-02-12
- Published: 2017-08-17
- Granted: 2019-06-04
- Earliest claimed: 2016-02-12
- Assignees: United Technologies Corporation
- Applicants: United Technologies Corporation
- Inventors: John P. Virtue, Jr.; Amy R. Grace; Parakrama Herath
- Web page: https://patentgrep.com/patent/US10309316B2

## CPC

- F02C 7/268: Starting drives for the rotor {, acting directly on the rotor of the gas turbine to be started}
- B64D 31/06: actuated automatically
- B64F 5/0045
- F05D 2270/303: Temperature
- F05D 2270/334: Vibration measurements
- F02C: GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS (construction of turbines F01D; jet-propulsion plants F02K; construction of compressors or fans F04; generating combustion products of high pressure or high velocity F23R; using gas turbines in compression refrigeration plants F25B11/00)
- B64D: EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
- B64F: GROUND OR AIRCRAFT-CARRIER-DECK INSTALLATIONS SPECIALLY ADAPTED FOR USE IN CONNECTION WITH AIRCRAFT; DESIGNING, MANUFACTURING, ASSEMBLING, CLEANING, MAINTAINING OR REPAIRING AIRCRAFT, NOT OTHERWISE PROVIDED FOR; HANDLING, TRANSPORTING, TESTING OR INSPECTING AIRCRAFT COMPONENTS, NOT OTHERWISE PROVIDED FOR
- F05D: INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS

## Abstract

A bowed rotor start mitigation system for a gas turbine engine is provided. The bowed rotor start mitigation system includes a controller operable to receive a vibration input indicative of an actual vibration level of the gas turbine engine and a speed input indicative of a rotor speed of the gas turbine engine. The controller generates a bowed rotor start mitigation request based on comparing the actual vibration level to a modeled vibration level at the rotor speed.

## Claims

### Claim 1

A bowed rotor start mitigation system for a gas turbine engine, the bowed rotor start mitigation system comprising:
a controller operable to receive a vibration input indicative of an actual vibration level of the gas turbine engine and a speed input indicative of a rotor speed of the gas turbine engine, the controller generating a bowed rotor start mitigation request based on comparing the actual vibration level to a modeled vibration level at the rotor speed;
a motoring controller operable to determine whether to reduce a motoring time determined by a risk model based on a result of comparing the actual vibration level to the modelled vibration level at the rotor speed, wherein the risk model maps core temperature model data with time data and ambient temperature data to establish the motoring time as an estimated period of motoring to mitigate a bowed rotor of the gas turbine engine; and
a digital storage unit operable to store time and temperature data for the risk model, wherein the digital storage unit is operable to continue monitoring of temperature data while the gas turbine engine is shut down and the bowed rotor start mitigation system is operable to compare monitored temperature data with modelled temperature data to validate one or more temperature models of the gas turbine engine.

### Claim 2 (depends on 1)

The bowed rotor start mitigation system as in claim 1, wherein comparing the actual vibration level to the modeled vibration level at the rotor speed is triggered to be performed at a rotor speed threshold that is below a resonance speed of the gas turbine engine.

### Claim 3 (depends on 1)

The bowed rotor start mitigation system as in claim 1, wherein the controller is operable to perform the comparing of the actual vibration level to the modeled vibration level during a dry motoring mode of the gas turbine engine below a resonance speed of the rotor.

### Claim 4 (depends on 3)

The bowed rotor start mitigation system as in claim 3, wherein the controller drives motoring of the gas turbine engine to a bowed rotor mode determination speed that is less than a dry motoring mode speed to perform the comparing of the actual vibration level to the modeled vibration level at a range of rotor speeds up to the bowed rotor mode determination speed prior to reaching the dry motoring mode speed.

### Claim 5 (depends on 3)

The bowed rotor start mitigation system as in claim 3, wherein the controller periodically performs the comparing of the actual vibration level to the modeled vibration level in the dry motoring mode to determine whether bowed rotor mitigation has completed prior to reaching an engine starting time.

### Claim 6 (depends on 1)

The bowed rotor start mitigation system as in claim 1, wherein metrics of attempted bowed rotor mitigation are recorded based on determining that the attempted bowed rotor mitigation was unsuccessful or incomplete.

### Claim 7

A gas turbine engine system comprising:
a motoring system operable to drive rotation of the gas turbine engine;
a vibration monitoring system operable to monitor actual vibration of the gas turbine engine;
an electronic engine control operable to receive a vibration input indicative of an actual vibration level from the vibration monitoring system and a speed input indicative of a rotor speed of the gas turbine engine, the electronic engine control generating a bowed rotor start mitigation request that drives the motoring system to perform bowed rotor mitigation based on comparing the actual vibration level to a modeled vibration level at the rotor speed; and
a motoring controller operable to determine whether to reduce a motoring time determined by a risk model based on a result of comparing the actual vibration level to the modelled vibration level at the rotor speed, wherein the risk model establishes the motoring time based on temperature data as an estimated period of motoring to mitigate a bowed rotor of the gas turbine engine.

### Claim 8 (depends on 7)

The gas turbine engine as in claim 7, wherein the actual vibration level is sampled below twenty-five percent of a resonance speed of the rotor to predict whether vibration amplitude of the rotor will be unacceptable for transiting the resonance speed.

### Claim 9 (depends on 7)

The gas turbine engine as in claim 7, wherein a maintenance request is triggered based on the actual vibration level exceeding a maintenance action threshold after completing an attempt of bowed rotor mitigation.

### Claim 10

A method of bowed rotor start mitigation for a gas turbine engine, the method comprising:
receiving a vibration input indicative of an actual vibration level of the gas turbine engine;
receiving a speed input indicative of a rotor speed of the gas turbine engine;
generating, by a controller, a bowed rotor start mitigation request based on comparing the actual vibration level to a modeled vibration level at the rotor speed;
determining whether to reduce a motoring time determined by a risk model based on a result of comparing the actual vibration level to the modelled vibration level at the rotor speed, wherein the risk model maps core temperature model data with time data and ambient temperature data to establish the motoring time as an estimated period of motoring to mitigate a bowed rotor of the gas turbine engine;
continuing monitoring of temperature data while the gas turbine engine is shutdown; and
comparing monitored temperature data with modelled temperature data to validate one or more temperature models of the gas turbine engine.

### Claim 11 (depends on 10)

The method as in claim 10, further comprising:
triggering the comparing of the actual vibration level to the modeled vibration level at a rotor speed threshold that is below a resonance speed of the gas turbine engine.

### Claim 12 (depends on 10)

The method as in claim 10, wherein the comparing of the actual vibration level to the modeled vibration level is performed during a dry motoring mode of the gas turbine engine below a resonance speed of the rotor.

### Claim 13 (depends on 12)

The method as in claim 12, further comprising:
driving motoring of the gas turbine engine to a bowed rotor mode determination speed that is less than a dry motoring mode speed to perform the comparing of the actual vibration level to the modeled vibration level at a range of rotor speeds up to the bowed rotor mode determination speed prior to reaching the dry motoring mode speed.

### Claim 14 (depends on 12)

The method as in claim 12, further comprising:
periodically performing the comparing of the actual vibration level to the modeled vibration level in the dry motoring mode to determine whether bowed rotor mitigation has completed prior to reaching an engine starting time.

### Claim 15 (depends on 10)

The method as in claim 10, further comprising:
recording metrics of attempted bowed rotor mitigation based on determining that the attempted bowed rotor mitigation was unsuccessful or incomplete.

### Claim 16 (depends on 10)

The method as in claim 10, further comprising:
triggering a maintenance request based on determining that the actual vibration level exceeds a maintenance action threshold after completing an attempt of bowed rotor mitigation.