Gas Turbine Diffuser Case Support Structure Thermal Stress Management
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Solution Overview
Problem
Gas turbine engines face thermal stress concentrations due to rapid temperature changes in the diffuser case and support structure during transient operations, which can lead to structural issues and inefficiencies in thermal management.
Innovation Solution
A diffuser case support structure is designed with a fairing made of a high-temperature resistant material and a diffuser frame made of a stronger material, featuring a monolithic component configuration, seals to maintain thermal isolation, and a sliding joint to allow radial movement, reducing thermal gradients and stress concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the inner diffuser case structure is made stiff to support the shaft bearing, then the structural strength is improved, but the thermal stress concentrations are exacerbated due to rigid thermal gradients
Solution Approach 1:
The support structure is divided into multiple struts that are spaced apart rather than forming a continuous rigid structure. This segmentation allows individual struts to flex independently under thermal stress, reducing stress concentrations while maintaining overall structural strength for bearing support.
Solution Approach 2:
The struts are designed with varying cross-sectional properties along their length, with thicker sections at ends for strength and thinner middle sections for flexibility. This parameter variation allows the structure to maintain strength where needed while accommodating thermal expansion and reducing stress concentrations in other areas.
2Device complexity
If the diffuser case and support structure are made as a single integrated component, then the manufacturing complexity is reduced, but the thermal gradient stresses increase due to differential thermal expansion
Solution Approach 1:
The diffuser case and support structure are separated into distinct components rather than being integrated. This allows each component to be made from materials optimized for its specific thermal and mechanical requirements, reducing differential thermal expansion stresses while maintaining manufacturing efficiency through modular assembly.
Solution Approach 2:
Different materials are used for the diffuser case and support structure components to match their functional requirements. The support structure uses materials with thermal expansion properties matched to the diffuser case, reducing thermal gradient stresses, while each component is independently manufactured from optimal materials.
3Temperature
If the fairing is made from high-temperature resistant material, then the thermal resistance is improved, but the weight of the component increases
Solution Approach 1:
The fairing is constructed with varying material properties in different regions, using high-temperature resistant materials only where thermal exposure is greatest, while using lighter materials in cooler regions. This local differentiation maintains thermal resistance where needed while minimizing overall weight.
Solution Approach 2:
The fairing uses composite material construction combining high-temperature resistant materials with lighter structural materials. This allows the fairing to withstand thermal conditions in critical areas while reducing overall weight through strategic material selection and placement.
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 solution effectively minimizes thermal stress concentrations and maintains structural integrity by reducing thermal gradients between the diffuser case and fairing, allowing for efficient thermal expansion and contraction while supporting the engine's operational transients.
Implementation Method 1
the bushing provides a load path between the fastener and the diffuser frame to allow radial movement of the fairing with respect to diffuser frame
Implementation Method 2
a first seal configured to maintain a seal between the outer diffuser case and the fairing
Data Source
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AI summary
The present invention relates to a pre-combustor diffuser case support structure (60) for a gas turbine engine (10) including a fairing (48) , the fairing defining a plurality of passages (52) circumferentially spaced apart and forming at least a portion of a fluid path between a compressor and a combustor of the gas turbine engine and a diffuser frame (58), which includes a plurality of struts (62). Each of the plurality of struts is disposed between a pair of adjacent passages of the plurality of passages. The diffuser frame is configured to couple an inner diffuser case (54) to an outer diffuser case (56). A sliding joint (72) is formed between the fairing and the diffuser frame, the sliding joint comprising a fastener (74) extending generally axially through an aperture (78) disposed in the fairing. The sliding joint allows the fairing to thermally expand and contract radially.