CMC Turbine Ring Assembly Fastening
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Solution Overview
Problem
Turbine ring assemblies made of ceramic matrix composite (CMC) materials face mechanical stress issues due to metal attachment portions expanding under hot conditions, which can weaken the CMC sectors and cause vibrations.
Innovation Solution
A turbine ring assembly design that secures each CMC ring sector using a fastener bolt and a fastener plate, with pegs and annular spacers to control position and prevent radial movement, allowing for deformation under temperature and pressure variations without relying on metal interfaces, and featuring rectilinear bearing surfaces for improved sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal attachment portions are used to secure CMC ring sectors, then the ring sectors can be held in position, but the metal portions expand under hot conditions causing mechanical stresses that weaken the CMC sectors
Solution Approach 1:
The patent changes the material parameter of the attachment portions from metal to CMC material, which has different thermal expansion characteristics. This allows the attachment portions to expand less under hot conditions, reducing mechanical stresses on the CMC ring sectors while maintaining their holding position function.
Solution Approach 2:
The patent uses homogeneous CMC material for both the ring sectors and the attachment portions. This ensures uniform thermal expansion behavior across all components, preventing differential expansion stresses that would otherwise weaken the CMC ring sectors when connected to metal parts.
2Ease of manufacture
If metal attachment portions are used to secure ring sectors, then the assembly can be constructed, but vibrations occur due to expansion under hot conditions
Solution Approach 1:
The patent changes the thermal expansion parameter of the attachment portions by using CMC material instead of metal. This reduces the differential expansion between components under hot conditions, eliminating the source of vibrations while maintaining ease of assembly construction.
3Productivity
If CMC ring sectors are used instead of metal, then cooling requirements are reduced and performance increases, but mechanical stresses increase due to thermal expansion differences with metal interface parts
Solution Approach 1:
The patent changes the material composition parameter of the attachment portions to match the CMC ring sectors. This eliminates thermal expansion mismatches at the interface, reducing mechanical stresses on the CMC sectors while maintaining the high performance benefits of CMC materials.
Solution Approach 2:
The patent creates a homogeneous CMC-based assembly where both ring sectors and attachment portions are made of CMC material. This ensures consistent thermal and mechanical properties throughout the assembly, preventing stress concentrations at metal-CMC interfaces while maintaining engine performance.
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 effectively reduces mechanical stresses on CMC sectors, prevents vibrations, and maintains sealing integrity across temperature changes, enhancing the performance and reliability of turbine engines by minimizing the need for metal interfaces and reducing cooling requirements.
Implementation Method 1
enabling the ring sector, and by extension the ring, to deform under the effects of temperature rises and pressure variations
Implementation Method 2
there is less need to be accurate when providing radial holding since straightening effects will be limited and there will be less additional stresses when hot
Data Source
AI summary
A turbine ring assembly includes both a plurality of CMC ring sectors forming a turbine ring and a ring support structure, each ring sector having a portion forming an annular base that presents an outside face in the radial direction of the turbine ring, with first and second attachment tabs projecting therefrom in the radial direction, each attachment tab presenting an end that is free, each ring sector having third and fourth attachment tabs, each extending in the axial direction of the turbine ring between the free end of the first attachment tab and the free end of the second attachment tab. Each ring sector is fastened to the ring support structure by a bolt having a bolt head bearing against the ring support structure and a thread co-operating with tapping formed in a plate, the plate co-operating with the third and fourth attachment tabs.