Gas Turbine Rotor Bow Mitigation via Flywheel Energy Storage

Solution Overview

Problem

Gas turbine engines experience thermal bowing due to asymmetric heat distribution after shutdown, leading to undesirable vibrations and potential damage, as existing methods to reduce thermal gradients are insufficient for timely engine restarts.

Innovation Solution

A method involving a clutch mechanism coupling the rotor assembly to a mechanical energy storage device, such as a spring or fluid system, to store and release energy for controlled rotation of the rotor assembly, mitigating thermal bowing by redistributing thermal gradients.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the rotor assembly is allowed to rest after shutdown to naturally reduce thermal gradient through free convection, then thermal bowing is reduced, but engine restart is delayed

Engineering Contradiction:

Improvethermal bow reductionVSAvoidengine restart delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system performs preliminary action by storing mechanical energy in the flywheel during engine operation, before shutdown occurs. This pre-stored energy is then released after shutdown to actively rotate the rotor assembly and reduce thermal gradients, eliminating the need to wait for natural convection while preventing thermal bowing.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention replaces the passive thermal convection system with an active mechanical rotation system. Instead of relying on natural heat transfer mechanisms, the stored mechanical energy from the flywheel directly rotates the rotor assembly to redistribute thermal gradients, achieving faster thermal bow reduction.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Productivity

If the rotor assembly operates with thermal bowing, then engine can restart immediately, but vibrations increase and damage occurs to surrounding components

Engineering Contradiction:

Improveengine restart speedVSAvoidvibrations and component damage

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The system performs preliminary action by storing mechanical energy in the flywheel during engine operation, before shutdown occurs. This pre-stored energy is then released after shutdown to actively rotate the rotor assembly and reduce thermal gradients, eliminating the need to wait for natural convection while preventing thermal bowing.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention replaces the passive thermal convection system with an active mechanical rotation system. Instead of relying on natural heat transfer mechanisms, the stored mechanical energy from the flywheel directly rotates the rotor assembly to redistribute thermal gradients, achieving faster thermal bow reduction.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

This approach effectively reduces or eliminates thermal bowing by rotating the rotor assembly to reposition warmer and cooler sections, thereby minimizing thermal differences and preventing damage to the engine components.

Implementation Method 1

storing mechanical energy at the mechanical energy storage device via rotation of the rotor assembly at or below the speed limit

Methodology Applied

Scientific EffectMechanical energy storage: Mechanical Accumulator

Implementation Method 2

compressing or tensioning a spring mechanically coupled to the rotor assembly, to rotate the rotor assembly

Methodology Applied

Scientific EffectElastic energy storage: Spring

Implementation Method 3

pressurizing a fluid within a pneumatic or hydraulic system, in which changes in pressure of the fluid rotates the rotor assembly

Methodology Applied

Scientific EffectHydraulic energy storage: Hydraulic Accumulator

Implementation Method 4

coupling a rotor assembly to a mechanical energy storage device via a clutch mechanism when the rotor assembly is at or below a speed limit

Methodology Applied

Scientific EffectFriction coupling: Friction

Data Source

PatentUS10760498B2System and method for removing rotor bow in a gas turbine engine using mechanical energy storage device

Publication Date: 2020.09.01 GENERAL ELECTRIC CO

AI summary

The present disclosure is directed to a gas turbine engine structure and method for reducing or mitigating bowed rotor. The method includes coupling a rotor assembly to a mechanical energy storage device via a clutch mechanism when the rotor assembly is at or below a speed limit below an idle speed condition; storing mechanical energy at the mechanical energy storage device via rotation of the rotor assembly at or below the speed limit; releasing mechanical energy from the mechanical energy storage device to rotate the rotor assembly following shutdown of the gas turbine engine; and rotating the rotor assembly via the mechanical energy from the mechanical energy storage device.