Gas Turbine Diffuser Case Thermal Stress Management
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Solution Overview
Problem
Gas turbine engines face excessive thermal stress concentrations due to rapid temperature changes in the diffuser case structure during transient operations, which can lead to structural issues from the thermal gradients between hotter and colder components.
Innovation Solution
A diffuser case assembly design featuring a fairing made of high-temperature resistant materials and a physically independent diffuser frame, with hollow struts forming channels for fluid flow and sliding joints to accommodate thermal expansion, minimizing 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 rapid temperature changes
Solution Approach 1:
The diffuser case is divided into multiple segments including an outer diffuser case, an inner diffuser case, and a fairing. These segments can expand and contract independently to accommodate thermal gradients, reducing thermal stress concentrations while maintaining structural strength through the support of shaft bearings.
Solution Approach 2:
The diffuser case assembly uses composite material construction with the outer diffuser case, inner diffuser case, and fairing made from materials suitable for withstanding thermal environments. This allows different parts to have different thermal properties, managing thermal stress while maintaining overall structural integrity.
2Stability of the object's composition
If the diffuser case structure is made rigid to maintain structural integrity, then the structural stability is improved, but the ability to accommodate thermal expansion is reduced
Solution Approach 1:
The diffuser case assembly incorporates dynamic elements that allow for thermal expansion and contraction. The segmented structure with the outer diffuser case, inner diffuser case, and fairing can move relative to each other, accommodating thermal changes while maintaining structural stability through proper support and connection design.
3Temperature
If the fairing is made of high-temperature resistant materials, then the thermal resistance is improved, but the thermal gradient between the fairing and diffuser case increases
Solution Approach 1:
The fairing acts as an intermediary component between the hot core gases and the diffuser case. It is designed to withstand high temperatures while managing heat transfer to the diffuser case, using its structure and material properties to control the thermal gradient and protect the underlying structure.
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 design reduces thermal stress concentrations by maintaining a consistent temperature difference between the fairing and the diffuser case assembly, enhancing structural integrity and reducing the risk of damage during operational transients.
Implementation Method 1
the sliding joint is configured to move radially in response to at least one of thermal expansion and contraction of the fairing in a radial direction
Implementation Method 2
the channel is configured to conduct a flow of fluid between a compartment radially outside the inner diffuser case to a compartment radially inside the inner diffuser case
Data Source
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AI summary
A diffuser case assembly for a gas turbine engine includes a fairing (48) disposed circumferentially about a longitudinal axis (24). The fairing (48) defines a plurality of passages (52) circumferentially spaced apart and forming at least a portion of a fluid path (C) between a compressor (40) and a combustor (44) of the gas turbine engine. A diffuser frame (58) includes a plurality of struts (62). Each of the plurality of struts (62) is disposed between a pair of adjacent passages of the plurality of passages (52). The diffuser frame (58) is configured to couple an inner diffuser case (54) to an outer diffuser case (56).