Flexible Strut Mounting for Gas Turbine Exhaust Thermal Stress

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Solution Overview

Problem

Turbine exhaust cases face significant stress due to thermal mismatch between inner and outer shrouds and airfoils, which current technologies have not adequately addressed, leading to non-negligible stress levels.

Innovation Solution

The implementation of a turbine exhaust case design featuring radially outer and inner annular shrouds with circumferentially spaced axially projecting fingers and flexible strut mounting structures that allow for radial deflection to accommodate thermal expansion of struts, reducing stress through enhanced thermal relief.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If struts are rigidly mounted between inner and outer shrouds, then structural strength is improved, but thermal stress increases due to thermal expansion mismatch

Engineering Contradiction:

Improvestructural strengthVSAvoidthermal stress

Core Design Contradiction:

StrengthVSStress or pressure

Solution Approach 1:

The mounting structure changes from rigid to flexible, allowing the struts to accommodate thermal expansion through elastic deformation of the flexible fingers rather than transmitting thermal stress rigidly through the structure

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs flexible fingers made of elastomeric material that can radially deflect to accommodate thermal growth of struts, providing a flexible mounting solution that reduces thermal stress while maintaining structural integrity

Inventive Principle:

Principle #30Flexible shells and thin films

2Stability of the object's composition

If struts are rigidly fixed to shrouds, then structural stability is improved, but adaptability to thermal growth deteriorates

Engineering Contradiction:

Improvestructural stabilityVSAvoidadaptability to thermal growth

Core Design Contradiction:

Stability of the object's compositionVSAdaptability or versatility

Solution Approach 1:

The mounting structure transitions from a static rigid connection to a dynamic flexible connection that can adapt its configuration in response to thermal conditions, allowing the flexible fingers to deflect radially as struts thermally expand

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The flexible fingers made of elastomeric material provide the necessary adaptability to accommodate thermal growth while maintaining structural stability through their elastic properties

Inventive Principle:

Principle #30Flexible shells and thin films

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 design effectively mitigates thermal stress by allowing for flexible mounting of struts, maintaining structural integrity while accommodating thermal growth, thereby reducing stress levels and improving engine performance.

Implementation Method 1

the axially projecting fingers being radially deflectable into said radial gap in response to a thermal growth of said struts

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS8944753B2Strut mounting arrangement for gas turbine exhaust case

Publication Date: 2015.02.03 PRATT & WHITNEY CANADA CORP

AI summary

A turbine exhaust case comprises inner and outer annular shrouds defining therebetween an annular hot gaspath. A circumferential array of exhaust struts extends across the gaspath. The exhaust struts are mounted at one radial end thereof on a flexible strut mounting structure. The flexible strut mounting structure is radially deflectable relative to the outer and inner shrouds to accommodate thermal expansion of the exhaust struts during engine operation.