CMC Turbine Ring Assembly With Radial Pins for Stable Positioning
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The use of ceramic matrix composite (CMC) materials in aeronautical turbine rings faces challenges due to their different mechanical behavior compared to metallic materials, leading to radial movement and performance issues when integrated with existing interference-fitted assemblies, which are not suitable for CMCs and result in thermal distortion and reduced temperature limits.
Innovation Solution
An assembly for a turbomachine turbine that includes radial retaining pins screwed into a support casing, with anti-rotation means to prevent loosening and adjustable positioning to address residual radial play, ensuring the CMC ring sectors are securely retained without radial movement, using axial pins and split pins for rotational locking and interference fitting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If axial pins are used to retain CMC ring sectors, then the assembly is simpler and CMC compatibility is improved, but radial play remains causing radial movement and performance degradation
Solution Approach 1:
The retention system is divided into two independent functional components: axial pins for basic positioning and radial retaining pins for radial stability. This segmentation allows each component to perform its specific function optimally without compromising the other, resolving the contradiction between assembly simplicity and radial position stability.
Solution Approach 2:
Radial retaining pins act as intermediary elements between the support casing and CMC ring sectors. These pins specifically address the radial play issue that axial pins cannot resolve, serving as a mediator that eliminates radial movement while maintaining the overall assembly structure.
2Strength
If interference-fitted assembly is used for metallic rings, then retention strength is improved, but CMC material compatibility deteriorates due to thermal expansion differences
Solution Approach 1:
The retention system transitions from a static interference-fit design to a dynamic adjustable system. Radial retaining pins can be positioned and adjusted to accommodate the thermal expansion characteristics of CMC materials, allowing the assembly to adapt to temperature changes while maintaining retention strength.
Solution Approach 2:
The retention mechanism changes from fixed interference-fit parameters to adjustable pin-based parameters. This allows the retention system to accommodate varying thermal expansion parameters of CMC materials without compromising strength, as the pin positions can be optimized for different thermal conditions.
3Temperature
If CMC ring sectors are used, then cooling ventilation needs are reduced and temperature limits are improved, but radial movement occurs due to different mechanical behavior
Solution Approach 1:
The retention function is segmented into axial positioning (prevented by axial pins) and radial stabilization (prevented by radial retaining pins). This segmentation allows CMC ring sectors to operate at high temperatures while each pin type addresses specific movement modes, ensuring radial position stability despite thermal effects.
Solution Approach 2:
Radial retaining pins serve as intermediary elements that specifically counteract radial movement tendencies of CMC materials at high temperatures. These pins mediate between the thermal expansion characteristics of CMC and the structural requirements for radial stability, allowing temperature resistance without compromising position stability.
Data Source
AI summary
An assembly for a turbomachine turbine includes at least one ring sector made of CMC material and a support casing including an upstream flange and a downstream flange between which each ring sector is disposed, each ring sector including a base that has a radially external face from which radially extend two lugs, the lugs of each ring sector being retained between the two flanges of the support casing by axial pins each engaged in one of the flanges of the ring support casing and in the lug of the ring sector facing said flange, the assembly further including, for each ring sector, at least one radial retaining pin screwed into the support casing and coming to radially bear against a lug of the at least one ring sector to retain it in position, and anti-rotation system for rotationally locking the radial retaining pin.