Engine Clearance Control for Transient Blade Tip Rub Prevention

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing aircraft engine clearance control systems fail to adequately anticipate and mitigate blade tip rubs due to excessively tight clearance gaps, particularly during transient operations like climbs or evasive maneuvers.

Innovation Solution

The implementation of a clearance control system that independently controls fan pitch and fan speed to minimize transient turbine or compressor clearance impacts, while maintaining thrust response, by adjusting the rate of change of fan speed and using fan pitch to control thrust.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If active clearance control is used to minimize operating clearances, then fuel efficiency and thrust are improved, but blade tip rubs occur during transient operations due to clearance lag

Engineering Contradiction:

Improvefuel efficiencyVSAvoidblade tip clearance stability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The system anticipates transient conditions by monitoring engine operating parameters and pre-adjusts clearance gaps before blade tip rubs can occur. The controller detects upcoming transient operations and proactively modifies clearance control to prevent the harmful effect rather than reacting after the problem arises.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The clearance control system dynamically adjusts clearance gaps in real-time based on detected transient conditions. Instead of static clearance settings, the system continuously modifies clearance control parameters responsive to changing engine operating conditions, allowing the clearance to adapt during transient operations.

Inventive Principle:

Principle #15Dynamics

2Manufacturing precision

If conventional clearance control systems are used, then steady-state clearance is optimized, but they fail to anticipate and mitigate blade tip rubs during transient operations

Engineering Contradiction:

Improveclearance gap precisionVSAvoidresponse to transient conditions

Core Design Contradiction:

Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

The system continuously monitors engine operating parameters and uses this feedback to detect transient conditions. The controller adjusts clearance control based on real-time feedback from sensor data, creating a closed-loop control system that adapts to changing conditions rather than relying on predetermined schedules.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

By detecting transient conditions through monitored parameters, the system takes preliminary action to adjust clearance gaps before blade tip rubs occur. This anticipatory adjustment maintains precision while adapting to transient operations.

Inventive Principle:

Principle #10Preliminary action

3Speed

If rotor speed is increased rapidly during climbs or maneuvers, then thrust response is improved, but blade tip length increases more rapidly than shroud expansion causing rubs

Engineering Contradiction:

Improverotor speed responseVSAvoidblade tip rub

Core Design Contradiction:

SpeedVSObject-affected harmful factors

Solution Approach 1:

The system applies preliminary anti-action by detecting the onset of transient conditions and pre-adjusting clearance gaps to counteract the harmful effect of blade tip growth. This compensatory action occurs before the rub condition develops, offsetting the mechanical growth mismatch between blades and shroud.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The clearance control system dynamically responds to rapid rotor speed changes by continuously adjusting clearance gaps. This dynamic adjustment allows the system to maintain safe clearances even during rapid acceleration maneuvers while preserving thrust response.

Inventive Principle:

Principle #15Dynamics

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 the risk of blade tip rubs during transient operations by dynamically adjusting clearance gaps, thereby improving engine efficiency, reducing fuel burn, and extending turbine life.

Implementation Method 1

Active clearance control, in at least some conventional systems, attempts to cause the shroud or stator to expand or contract by changing the thermal environment of the hardware.

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS12313012B2System and method for reducing a clearance gap in an engine

Publication Date: 2025.05.27 GENERAL ELECTRIC CO

AI summary

A method for reducing a clearance gap between a plurality of rotor blades and a shroud assembly of an engine includes determining, with a flight control system, that an airplane is in a first flight condition. The method also includes adjusting the clearance gap to a first clearance gap distance associated with the first flight condition. Further, the method includes receiving, with the flight control system, a demand for a second flight condition. During the second flight condition, the method includes adjusting at least two independently controllable parameters, the at least two independently controllable parameters comprising, at least, a first parameter for optimizing the clearance gap and a second parameter for satisfying a thrust demand of the engine, the first parameter having a first impact on the clearance gap, the second parameter having a second impact on the clearance gap, the first impact being greater than the second impact.