Gas Turbine Rotor Rotation Control for Thermal Bow Mitigation

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Solution Overview

Problem

Gas turbine engines experience thermal bowing due to asymmetric heat distribution during shutdown, leading to rotor eccentricity and potential damage from vibrations and blade-casing contact.

Innovation Solution

A control system with a second power source, such as a rechargeable battery, is used to rotate the rotor at low speeds following engine shutdown to mitigate thermal bowing, utilizing a torque source and controller to manage power distribution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the rotor assembly is allowed to rest until thermal gradient naturally decreases, then thermal bowing is eliminated, but engine restart time is delayed

Engineering Contradiction:

Improvethermal bow mitigationVSAvoidengine restart time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system performs preliminary action by automatically rotating the rotor assembly immediately after shutdown using stored energy (battery/capacitor) before thermal bowing fully develops. This preliminary rotation begins thermal equalization before the natural cooling process would complete, thereby mitigating thermal bow while enabling quicker restart compared to passive resting.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system maintains continuous useful action by keeping the rotor assembly rotating at controlled speeds during the shutdown period. Instead of allowing complete停止, the rotor continues to rotate slowly, continuously distributing heat and preventing thermal gradient formation, thus eliminating thermal bow without requiring extended downtime.

Inventive Principle:

Principle #20Continuity of useful action

2Reliability

If the rotor assembly rotates at high speeds during shutdown, then thermal gradient is reduced quickly, but excessive vibrations and centrifugal forces are generated

Engineering Contradiction:

Improvethermal gradient reductionVSAvoidvibrations and centrifugal forces

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The system applies dynamics by varying the rotation speed of the rotor assembly during shutdown. The controller dynamically adjusts speed to optimal levels that provide sufficient thermal equalization while minimizing harmful vibrations and centrifugal forces. Speed is not fixed but adapted to the thermal state and operational requirements.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes physical parameters by controlling rotation speed within specific ranges (e.g., 0-10 RPM or 0-100 RPM) rather than maintaining constant high speed. This parameter change allows the system to achieve thermal gradient reduction at lower, safer speeds, balancing thermal management with vibration and force control.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If a mechanical starter system is used to rotate the rotor during shutdown, then thermal bowing is mitigated, but mechanical complexity and wear are increased

Engineering Contradiction:

Improvethermal bow mitigationVSAvoidmechanical starter system

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The system replaces the traditional mechanical starter system with an electrical or electromagnetic rotation mechanism. During shutdown, electrical energy from a battery or capacitor drives an electromagnetic motor to rotate the rotor assembly, eliminating the need for complex mechanical linkages, flyweights, and mechanical contact components, thereby reducing mechanical complexity and wear.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The system introduces an intermediary energy storage device (battery or capacitor) that mediates between the shutdown event and the rotor rotation requirement. This intermediary provides the necessary energy to drive the electromagnetic motor during the shutdown period, enabling thermal bow mitigation without requiring direct mechanical coupling or complex starter mechanisms.

Inventive Principle:

Principle #24Intermediary (Mediator)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Prevents rotor thermal bow by rotating the engine at low speeds, reducing vibrations and preventing damage to casings and blades, and can be easily integrated into existing engines without mechanical modifications.

Implementation Method 1

the second power source comprises a rechargeable battery, and the torque source comprises an engine alternator

Methodology Applied

Scientific EffectElectromagnetic conversion: Electromagnetic Induction

Data Source

PatentUS12480423B2System and method for mitigating bowed rotor in a gas turbine engine

Publication Date: 2025.11.25 GENERAL ELECTRIC CO

AI summary

A turbomachine for a vehicle is provided. The turbomachine includes a first rotatable component; a first power source operatively coupled with the first rotatable component; a second power source selectively coupled with the first rotatable component; and a controller having one or more processors and one or more memory devices, the one or more memory devices storing instructions that when executed by the one or more processors cause the one or more processors to perform operations, in performing the operations, the one or more processors are configured to: receive an input indicating an engine shutdown of the turbomachine; and in response to the engine shutdown, cause the second power source to provide power to and rotate the first rotatable component.