Gas Turbine Bowed Rotor Mitigation via Vibration Monitoring

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Solution Overview

Problem

Gas turbine engines face challenges in restarting due to the 'bowed rotor' condition caused by thermal expansion, which leads to undesirable vibration and potential damage during engine startup.

Innovation Solution

A bowed rotor start mitigation system that includes a controller to compare actual vibration levels with modeled levels, triggering dry motoring and adjusting starter valve positions to mitigate the risk of a bowed rotor condition by limiting rotor speed and extending motoring time to homogenize temperatures, thereby preventing high amplitude oscillations and rubs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the engine is restarted immediately after shutdown, then productivity is improved, but the risk of bowed rotor condition increases due to thermal expansion

Engineering Contradiction:

Improveengine restart speedVSAvoidrotor condition

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The system performs preliminary detection of thermal conditions and rotor bow status before allowing engine restart. Temperature sensors monitor the engine core temperature and calculate thermal differentials across the rotor to determine if the rotor is bowed before startup is permitted, preventing restart until conditions are safe

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system continuously monitors temperature data from multiple sensors during engine operation and shutdown, calculating the rotor bow status in real-time. This feedback is used to dynamically control the restart authorization, allowing restart only when thermal conditions indicate the rotor is not bowed

Inventive Principle:

Principle #23Feedback

2Loss of energy

If thermal expansion is allowed to occur naturally, then energy loss is reduced, but component deflection and bowed rotor condition result

Engineering Contradiction:

Improvethermal energy retentionVSAvoidrotor geometry

Core Design Contradiction:

Loss of energyVSShape

Solution Approach 1:

The system replaces direct mechanical measurement of rotor bow with a computational approach using temperature sensors and thermal models. The electronic control unit calculates rotor thermal differentials and determines bow status based on temperature data, avoiding the need for complex mechanical measurement systems

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The system changes the physical state monitoring approach by measuring temperature parameters rather than direct mechanical displacement. Temperature sensors monitor thermal conditions and the control unit translates these thermal parameters into rotor bow status determination, enabling indirect detection of geometric changes

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If vibration monitoring is implemented, then detection precision is improved, but device complexity increases

Engineering Contradiction:

Improvevibration detection accuracyVSAvoidmonitoring system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The system uses existing temperature sensors designed for other purposes (monitoring engine thermal conditions) to also detect rotor bow status. The same temperature data used for general engine control and thermal management is additionally processed to determine rotor geometric conditions, making the sensor system multi-functional without adding dedicated measurement devices

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

Effectively prevents the bowed rotor condition by reducing vibration and extending component life, allowing safe engine startup by monitoring and adjusting the dry motoring process based on vibration data and thermal models.

Implementation Method 1

a vibration monitoring system operable to monitor actual vibration of the gas turbine engine

Methodology Applied

Scientific EffectVibration: Vibration

Implementation Method 2

the engine is hot and due to heat rise, the upper portions of the engine will be hotter than lower portions of the engine. When this occurs thermal expansion may cause deflection of components of the engine

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS10443505B2Bowed rotor start mitigation in a gas turbine engine

Publication Date: 2019.10.15 RTX CORP

AI summary

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.