Turbine Shroud Assembly Retaining Elements
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Solution Overview
Problem
Turbine ring assemblies in aeronautical gas turbine engines face challenges in maintaining ceramic matrix composite (CMC) ring sectors in position due to differential expansions and mechanical stresses, especially when subjected to heat, which affects engine performance and requires efficient cooling and stress management.
Innovation Solution
The use of annular flanges with inclined portions and locking elements with specific thermal expansion coefficients to compensate for expansion differences and reduce mechanical stresses, ensuring secure holding of CMC ring sectors both cold and hot without generating excessive stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If CMC ring sectors are used to reduce cooling requirements, then engine performance is improved, but differential expansion between metal supporting structure and CMC ring sectors causes positioning issues and mechanical stress
Solution Approach 1:
The patent changes the geometric parameters of the retaining elements by providing inclined portions on their housings that can rotate about a radial axis. This allows the retaining elements to adapt their orientation in response to thermal expansion differences between the metal supporting structure and CMC ring sectors, maintaining secure positioning while accommodating differential expansion movements.
Solution Approach 2:
The retaining elements are designed with rotational capability about a radial axis, transforming them from static components to dynamic ones. This dynamic feature allows the inclined portions to automatically adjust their angle relative to the ring sectors during thermal cycling, ensuring continuous secure retention despite temperature-induced dimensional changes.
2Reliability
If retaining elements are used to secure ring sectors, then positioning is improved, but mechanical stress on ring sectors increases under thermal loading
Solution Approach 1:
The retaining elements incorporate rotational freedom about a radial axis, allowing them to dynamically adjust their orientation in response to thermal expansion. This dynamic adaptation reduces mechanical stress on the ring sectors by accommodating dimensional changes rather than rigidly constraining them, while still maintaining secure retention.
Solution Approach 2:
The design explicitly accounts for thermal expansion differences between materials by allowing the retaining elements to rotate and adjust their position. The inclined portions are configured to accommodate the expansion of the metal supporting structure relative to the CMC ring sectors, reducing thermal stress while maintaining retention.
3Stress or pressure
If clearance is provided between retaining elements and ring sector openings when cold, then stress is reduced, but retention effectiveness decreases when hot
Solution Approach 1:
The retaining elements are designed to rotate about a radial axis in response to thermal expansion. When cold, clearance reduces stress; when hot, the rotational movement allows the inclined portions to engage more fully with the ring sectors, dynamically transitioning from a low-stress state to a high-retention state based on temperature conditions.
Solution Approach 2:
The geometric parameters of the retaining elements, specifically their angular orientation, are allowed to change with temperature through rotational movement. This parameter change enables the system to optimize both stress reduction when cold and retention effectiveness when hot, rather than being constrained by a fixed geometry.
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
This solution effectively maintains the position of CMC ring sectors during operation, reducing mechanical stresses and optimizing engine performance by compensating for thermal expansion, thus enhancing the reliability and efficiency of turbine ring assemblies.
Implementation Method 1
When hot, the holding force is taken over by the expansion of the retaining elements, an expansion that does not cause significant stress on the ring sectors because of the presence of clearance when cold between the retaining elements and the openings located on the ring sector tabs.
Implementation Method 2
The implementation of such inclined portions at the level of the annular flanges of the ring support structure helps to compensate for the differences in expansion between the annular flanges and the lugs of the ring sectors and therefore to reduce the mechanical stresses to which the ring sectors are subjected during operation.
Data Source
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AI summary
A turbine ring assembly includes ring sectors forming a turbine ring, and a ring support structure having two annular flanges, each ring sector having a portion forming an annular base with an inner face defining the inside face of the turbine ring and an outer face from which there project at least two tabs, the tabs being retained between the two annular flanges. Each tab of the ring sectors includes a projecting portion on its face situated facing one of the two annular flanges, this projecting portion co-operating with a housing present in the annular flange. Each tab of the ring sectors includes an opening in which there is received a portion of a retention element secured to the annular flange situated facing the tab. The retention element is made of a material having a thermal expansion coefficient that is greater than that of the material of the ring sectors.