Ceramic Matrix Composite Turbine Flowpath Mounting
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Solution Overview
Problem
Gas turbine engine turbine flowpath components made of low-ductility materials like ceramic matrix composites face challenges with inconsistent frictional forces in mechanical clamped joints and thermal expansion mismatch with metallic hardware, requiring a lightweight, high-temperature-resistant, and predictable mounting configuration.
Innovation Solution
A turbine flowpath structure made from ceramic matrix composite material that serves as both a shroud and transition duct, utilizing an annular centering spring and radial pins to maintain position and prevent movement, eliminating the need for air cooling and reducing thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional mechanical clamped joints are used with CMC materials, then the structure can be assembled, but the frictional forces become inconsistent leading to unreliable mounting
Solution Approach 1:
The patent replaces conventional mechanical clamped joints that rely on friction with a mechanical interlocking system using keys and keyways. This substitution eliminates the inconsistency of frictional forces by using positive mechanical engagement, where the key physically locks the CMC component to the metallic structure, providing reliable and predictable mounting without depending on friction coefficients.
Solution Approach 2:
The patent introduces keys as intermediary elements between the CMC component and the metallic structure. These keys act as mediators that transfer and distribute loads through defined mechanical interfaces rather than relying on direct frictional contact. The keyways provide controlled engagement paths, making the mounting system more predictable and reliable.
2Temperature
If CMC materials are used to replace metallic shroud structures, then high-temperature capability is improved, but thermal expansion mismatch with metallic hardware causes mounting problems
Solution Approach 1:
The patent explicitly accounts for thermal expansion mismatch by designing the mounting system to accommodate differential expansion between CMC and metallic materials. The structure includes expansion joints and flexible connections that allow the CMC components to expand and contract at different rates from the metallic hardware without causing stress or damage, thereby maintaining mounting stability across temperature cycles.
Solution Approach 2:
The patent uses composite material principles by combining CMC components with metallic structures in a hybrid assembly. The design recognizes the complementary properties of each material - using CMC for high-temperature exposure zones and metals for structural support - and creates appropriate interfaces that leverage the strengths of both materials while managing their incompatibilities through careful joint design.
3Ease of manufacture
If metallic shroud structures are used, then ease of manufacture and mounting is improved, but weight and air cooling requirements increase
Solution Approach 1:
The patent changes the material parameter from metallic to CMC, which fundamentally alters the weight-to-strength ratio and thermal properties. Although CMC components may require more careful manufacturing processes, the overall system benefits from reduced weight and eliminated cooling requirements. The manufacturing approach is adapted to work with CMC characteristics, such as using joining techniques suitable for ceramic materials rather than traditional metal fabrication methods.
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 provides a lightweight, high-temperature-resistant turbine flowpath structure that operates without air cooling, minimizing specific fuel consumption and ensuring reliable mounting, while accommodating thermal expansion differences between materials.
Implementation Method 1
an annular centering spring disposed between the stationary structure and the flowpath member, the centering spring urging the flowpath member towards a centered position within the stationary structure
Implementation Method 2
radial pins fixed to the centering spring and extending into corresponding slots formed in the back surface of the flowpath member, so as to prevent relative lateral movement and relative rotation of the flowpath member and the centering spring
Data Source
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AI summary
A turbine flowpath apparatus is provided for a gas turbine engine having a centerline axis. The apparatus includes: an annular flowpath member (56) of low-ductility material, the flowpath member (56) having a flowpath surface and an opposed back surface, and having a cross-sectional shape comprising a generally cylindrical forward section (62) and an aft section (64) that extends aft and radially outward at a non-perpendicular, non-parallel angle to the centerline axis; an annular stationary structure (78) surrounding the flowpath member (56); and an annular centering spring (70) disposed between the stationary structure (78) and the flowpath member (56), the centering spring (70) urging the flowpath member (56) towards a centered position within the stationary structure (78).