Turbo Machine Rotor Bow Mitigation via Intermittent Turning

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Solution Overview

Problem

Turbo machine rotor bow occurs due to uneven cooling after shutdown, leading to blade and surface damage, and existing mitigation methods either require long wait periods or add weight and complexity to the engine.

Innovation Solution

A method involving intermittent rotation of the rotor over specific periods with alternating frequencies and durations to manage thermal gradients, using a motive force less than a threshold torque to minimize wear and deterioration, and a controller to execute these operations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the rotor is continuously rotated after shutdown to mitigate rotor bow, then rotor bow is reduced, but wear and deterioration of the gear system increases due to high contact pressure without active lubrication

Engineering Contradiction:

Improverotor bow mitigationVSAvoidgear system wear

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies periodic action by implementing intermittent rotation cycles where the rotor is rotated for a first period of time and then discontinued for a second period of time. This periodic operation allows the rotor to be turned sufficiently to mitigate bow while providing rest periods that reduce cumulative wear on the gear system components.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent applies dynamics by making the rotation operation variable rather than continuous. The system dynamically adjusts between rotating and non-rotating states, and between different rotation speeds (first and second speeds), optimizing the balance between rotor bow mitigation and gear system wear reduction based on operational conditions.

Inventive Principle:

Principle #15Dynamics

2Temperature

If the rotor is rotated at high speed to mitigate rotor bow, then cooling effectiveness improves, but wear on the gear system increases due to high contact pressure

Engineering Contradiction:

Improverotor cooling effectivenessVSAvoidgear system wear

Core Design Contradiction:

TemperatureVSObject-affected harmful factors

Solution Approach 1:

The patent applies dynamics by implementing variable rotation speeds during the mitigation process. The rotor is rotated at a first speed during active rotation periods and at a second speed during discontinuation periods, allowing optimization of cooling effectiveness while reducing wear during high-speed operation through intermittent lower-speed phases.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent applies periodic action by alternating between different rotation speeds in defined cycles. The rotor operates at a first speed for a first period of time to provide effective cooling, then transitions to a second speed for a second period of time to reduce wear, creating a periodic speed variation pattern.

Inventive Principle:

Principle #19Periodic action

3Reliability

If complex systems are added to mitigate rotor bow, then rotor bow is reduced, but device complexity and weight increase

Engineering Contradiction:

Improverotor bow mitigationVSAvoidsystem complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies self-service by utilizing the existing turning gear system already present in the turbo machine for dual purposes: both for normal startup/shutdown operations and for rotor bow mitigation. This eliminates the need for separate dedicated mitigation systems, reducing overall device complexity while maintaining effectiveness.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent applies universality by enabling the turning gear system to perform multiple functions: standard operational turning during startup and shutdown, and specialized rotor bow mitigation through controlled intermittent rotation patterns. This multi-functionality avoids adding dedicated equipment for bow mitigation.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 mitigates rotor bow by reducing thermal gradients and wear on the gear system, minimizing high contact pressure and extending the lifespan of engine components without the need for complex systems or prolonged shutdowns.

Implementation Method 1

uneven cooling of the rotor shaft results in the top of the shaft being longer than the bottom, thereby creating a condition called bowed rotor

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

The uneven cooling of the rotor shaft results in the top of the shaft being longer than the bottom

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS11525370B2Method and system for mitigating rotor bow in a turbo machine

Publication Date: 2022.12.13 GENERAL ELECTRIC CO

AI summary

An aspect of the present disclosure is directed to a method for mitigating rotor bow in a turbo machine. The method includes rotating a rotor over a first period of time; discontinuing rotation of the rotor for a second period of time; and iterating, over an overall period of time, rotation of the rotor over the first period of time and discontinuing rotation of the rotor for the second period of time.