Active Clearance Control for Gas Turbine Engine

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Solution Overview

Problem

Gas turbine engines face challenges in maintaining optimal radial tip clearance due to thermal expansion and contraction, which affects engine performance across varying operational conditions.

Innovation Solution

An active clearance control system with a puller engaging air seal segments, supported by a full-hoop thermal control ring, allows for selective extension and retraction of air seal segments using an actuator-driven rod, maintaining consistent clearance without rigidly mounting the puller to the air seal segments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the radial tip clearance is designed to prevent blade tip rubbing under high power operations, then reliability is improved, but the clearance increases under reduced power conditions, reducing engine performance

Engineering Contradiction:

Improveblade tip rubbing preventionVSAvoidengine performance

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The air seal segments are designed to be movable rather than fixed, allowing them to dynamically adjust their radial position in response to changing thermal conditions and blade tip positions, thereby maintaining optimal clearance across different power conditions

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the radial position parameter of the air seal segments by applying thermal gradients through cooling air flow, causing the segments to contract or expand and thereby adjust the tip clearance to optimal values for different operating conditions

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If a rigid puller mounting is used to extend and retract air seal segments, then control precision is improved, but interference with cooling schemes increases

Engineering Contradiction:

Improveclearance control precisionVSAvoidcooling scheme interference

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The puller is designed with a flexible plate structure that can deflect and deform to accommodate the cooling air passages and thermal expansion of the air seal segment, allowing precise control without rigid constraints that would interfere with cooling flow paths

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The flexible plate acts as an intermediary between the rod actuator and the air seal segment, transmitting the control force while accommodating thermal deformation and preserving cooling air flow paths that would be blocked by a rigid direct connection

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

This system effectively maintains consistent radial tip clearance, supporting engine performance by accommodating thermal expansion and contraction, while minimizing interference with cooling schemes and reducing radial tolerance stacks.

Implementation Method 1

the thermal environment in the engine varies and may cause thermal expansion and contraction such that the radial tip clearance varies

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

the thermal environment in the engine varies and may cause thermal expansion and contraction such that the radial tip clearance varies

Methodology Applied

Scientific EffectThermal contraction: Thermal Contraction

Data Source

PatentUS10316684B2Rapid response clearance control system for gas turbine engine

Publication Date: 2019.06.11 RTX CORP

AI summary

An active clearance control system for a gas turbine engine includes an air seal segment and a puller engageable with the air seal segment.