Gas Turbine Shroud Compliant Layer Stress Distribution

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Solution Overview

Problem

Gas turbine engine turbine shrouds experience localized stress due to differing thermal expansion rates of components, leading to potential damage and breakage of ceramic blade track segments.

Innovation Solution

A turbine shroud design incorporating a metallic carrier, ceramic blade track segment, and a load-distribution system comprising a compliant member and rigid load pads, which compresses to distribute loads and prevent further movement, thereby reducing localized stress and maintaining contact across a range of temperatures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If rigid mounting is used between metallic carrier and ceramic blade track segment, then structural stability is improved, but localized stress concentration occurs due to different thermal expansion rates

Engineering Contradiction:

Improvestructural stabilityVSAvoidlocalized stress

Core Design Contradiction:

Stability of the object's compositionVSStress or pressure

Solution Approach 1:

A compliant member is introduced as an intermediary element between the metallic carrier and ceramic blade track segment. This compliant member has different mechanical properties than either the metal or ceramic, allowing it to accommodate differential thermal expansion while distributing loads evenly across the interface, thereby preventing stress concentration that would occur with rigid mounting.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The compliant member's mechanical parameters (such as elasticity modulus, thickness, and material composition) are specifically designed to change or adapt under thermal loading conditions. By selecting materials and dimensions that allow controlled deformation, the system accommodates thermal expansion differences between the metallic carrier and ceramic blade track segment without creating localized stress concentrations.

Inventive Principle:

Principle #35Parameter changes

2Stress or pressure

If compliant member is made thinner to allow more compression, then load distribution is improved, but structural strength is reduced

Engineering Contradiction:

Improveload distributionVSAvoidstructural strength

Core Design Contradiction:

Stress or pressureVSStrength

Solution Approach 1:

The compliant member is constructed from composite materials that combine the benefits of flexibility and strength. By using composite structures, the member can be made thinner to allow greater compression and improve load distribution while maintaining sufficient structural strength to withstand operational loads without excessive deformation or failure.

Inventive Principle:

Principle #40Composite materials

3Ease of operation

If rigid load pads are added to the compliant member, then movement control is improved, but device complexity increases

Engineering Contradiction:

Improvemovement controlVSAvoiddevice complexity

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The compliant member is segmented by incorporating multiple rigid load pads at specific locations. These discrete pads provide controlled contact points that guide and limit the movement of the ceramic blade track segment relative to the metallic carrier. The segmentation approach allows movement control to be achieved through strategically placed simple elements rather than a complex overall structure.

Inventive Principle:

Principle #1Segmentation

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

The load-distribution system effectively reduces localized stress on ceramic blade track segments, maintaining multiple defined contact sites and preventing damage, while allowing for controlled radial expansion and contraction, thus enhancing the durability and efficiency of the turbine shroud.

Implementation Method 1

The compliant member may have an uncompressed thickness and may be configured to compress to distribute loads transmitted between the first mating surface of the carrier and the second mating surface of the blade track segment during use of the turbine shroud

Methodology Applied

Scientific EffectCompression: Compression

Implementation Method 2

The compliant member may be engaged with the first and second mating surfaces. The compliant member may have an uncompressed thickness and may be configured to compress to distribute loads

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 3

Such shrouds sometimes include components having different rates of thermal expansion which may cause the components to experience areas of localized stress during heating and cooling of the shroud

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS10294809B2Gas turbine engine with compliant layer for turbine shroud mounts

Publication Date: 2019.05.21 ROLLS ROYCE NORTH AMERICAN TECHNOLOGIES INC

AI summary

A turbine shroud for use in a gas turbine engine includes a carrier, a blade track segment, and a load-distribution system. The carrier is arranged around a central axis of the turbine shroud. The blade track segment is configured to be supported by the carrier. The load-distribution system is positioned between the carrier and the blade track segment to distribute loads transmitted between the carrier and the blade track segment.