CMC BOAS Feather Seal Assembly for Thermal Expansion Mismatch
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Solution Overview
Problem
Existing blade outer air seal assemblies in gas turbine engines face challenges in ensuring effective sealing across turbine blades due to thermal expansion and mismatched growth rates between ceramic matrix composite and metallic components, leading to potential leakage and reduced efficiency.
Innovation Solution
A blade outer air seal assembly with radially extending slots and a feather seal that accommodates thermal expansion by rotating within these slots, maintaining sealing effectiveness despite changes in the gap between seal segments, and utilizing ceramic matrix composite or metallic materials for enhanced durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If blade outer air seals are made of ceramic matrix composite fiber layers, then high temperature durability is improved, but thermal expansion mismatch with metallic components causes sealing failure
Solution Approach 1:
The air seal assembly is divided into multiple seal segments arranged circumferentially, with feather seals positioned at the interfaces between segments. This segmentation allows each component to accommodate thermal expansion independently while maintaining overall sealing integrity at high temperatures.
Solution Approach 2:
The feather seal acts as an intermediary element between the ceramic matrix composite seal segments and metallic components. It accommodates thermal expansion mismatches by rotating within radially extending slots, preventing direct stress transmission that would cause sealing failure.
2Stability of the object's composition
If seal segments are rigidly connected, then structural stability is improved, but thermal expansion causes gap formation and leakage
Solution Approach 1:
The feather seal is designed to rotate dynamically within radially extending slots rather than being rigidly fixed. This dynamic capability allows the seal to adapt to thermal expansion and contraction of seal segments, maintaining continuous contact and preventing gap formation that would lead to leakage.
3Device complexity
If feather seal thickness is reduced to fit narrow slots, then device complexity is reduced, but sealing effectiveness deteriorates
Solution Approach 1:
The ratio of slot width to feather seal thickness is optimized to between 1.5 and 2.5, representing a specific parameter change that balances structural constraints with sealing performance. This parameter optimization ensures adequate sealing effectiveness while maintaining manufacturability and avoiding excessive device complexity.
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 effectively maintains sealing integrity across varying temperatures and thermal expansions, reducing leakage and enhancing the operational efficiency of gas turbine engines by using a feather seal that rotates within radially extending slots, accommodating thermal growth mismatches and ensuring robust mateface sealing.
Implementation Method 1
accommodates thermal expansion by rotating within these slots, maintaining sealing effectiveness despite changes in the gap between seal segments
Data Source
AI summary
A blade outer air seal assembly includes a support structure and a blade outer air seal having a plurality of segments extending circumferentially about an axis and mounted to the support structure. At least two segments have a base portion extending from a first circumferential side to a second circumferential side, a first protrusion extending from the first circumferential side and having a first slot, and a second protrusion extending from the second circumferential side and having a second slot. A feather seal is arranged in the first slot and the second slot between the at least two segments such that the feather seal is pivotable between first and second positions in response to relative movement between the first and second protrusions.