Interlocking Ring Structures for CMC BOAS Retention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Metallic and cantilevered support hooks for ceramic matrix composite (CMC) blade outer air seals (BOAS) in gas turbine engines experience excessive deflection when mated to CMC structures, leading to corner stresses and potential delamination due to the mismatch in material properties.
Innovation Solution
A BOAS retention assembly utilizing interlocking ring structures with shiplap flanges that provide load-sharing between identical and interchangeable retention rings, preventing rotation and reducing deflection by securing the CMC BOAS to an engine casing structure through a pair of interlocking retention rings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metallic or cantilevered support hooks are used to secure CMC BOAS, then the BOAS can be coupled to the engine casing, but excessive deflection occurs due to material property mismatch
Solution Approach 1:
The retention assembly is divided into multiple identical retention rings that are circumferentially spaced around the BOAS. Each ring independently supports the BOAS, distributing the load and reducing deflection through multiple contact points rather than relying on a single support hook.
Solution Approach 2:
Multiple retention rings work together in unison to provide combined support for the BOAS. The rings are positioned at different circumferential locations and collectively prevent deflection by distributing the supporting function across multiple identical structures.
2Reliability
If support hooks are used to secure CMC BOAS, then the BOAS can be retained, but corner stresses increase leading to potential delamination
Solution Approach 1:
The retention function is segmented across multiple retention rings positioned at different circumferential locations around the BOAS. This distributes the retention forces across multiple contact zones, preventing stress concentration at any single corner or location of the BOAS.
Solution Approach 2:
Each retention ring provides localized support at specific circumferential positions around the BOAS. The multiple rings create distributed local support zones that collectively prevent stress concentration and delamination by avoiding single-point loading.
3Device complexity
If a single retention ring is used, then the structure is simpler, but rotation of the BOAS cannot be prevented
Solution Approach 1:
Multiple identical retention rings are combined circumferentially around the BOAS to provide both retention and rotational stability. The rings work together as a unified system where each ring contributes to preventing rotation, with the combined effect of all rings providing comprehensive anti-rotation support.
Solution Approach 2:
The solution moves from a single-ring concept to a multi-ring concept distributed in the circumferential dimension. By adding rings at different circumferential positions, the system gains rotational stability without significantly increasing radial or axial complexity.
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A blade outer air seal retention assembly (160) may comprise a forward retention ring (162a) and an aft retention ring (162b) coupled to the forward retention ring (162a). The forward retention ring (162a) may comprise a first shiplap flange (180a) extending aft from the forward retention ring (162a). The aft retention ring (162b) may comprise a second shiplap flange (180b) extending forward from the aft retention ring (162b).