Gas Turbine BOAS Spring Clip for Stress-Reduced Seal Installation
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Solution Overview
Problem
Ceramic matrix composite blade outer air seals in gas turbine engines face challenges with high thermal gradients, delamination risk, and complex manufacturing and installation processes, requiring an efficient and stress-reducing solution for the outer air seal to blade tip interface.
Innovation Solution
A spring clip system that allows for individual installation and removal of blade outer air seals, featuring a clip with a biasing element and a hook that engages with a control ring, providing radial preloading and anti-rotation, while minimizing radial features to reduce thermal gradient stresses and simplify manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ceramic matrix composite blade outer air seals are used, then sealing effectiveness is improved, but thermal gradient stresses and delamination risk increase
Solution Approach 1:
The blade outer air seal is divided into multiple axial segments that can be individually installed and removed. Each segment has a reduced radial footprint compared to traditional full-annulus seals, which minimizes the contact area with the blade tip and reduces thermal gradient stresses while maintaining effective sealing through the segmented configuration
Solution Approach 2:
The air seal segments are positioned at specific axial locations where sealing is most critical, rather than providing uniform sealing across the entire blade height. This localized approach concentrates sealing effectiveness where needed while minimizing the overall thermal exposure and stress on the ceramic matrix composite material
2Reliability
If traditional attachment methods are used, then connection to control ring is achieved, but manufacturing and installation complexity increases
Solution Approach 1:
The attachment system combines multiple functions into integrated components: the spring clip provides both mechanical retention of the air seal segments to the control ring and simultaneous preload application. The biasing element merges the retention and preloading functions into a single mechanism, simplifying both manufacturing and installation compared to separate attachment and preloading systems
Solution Approach 2:
The spring-loaded attachment system automatically maintains preload on the air seal segments through the biasing element, providing self-adjusting retention without requiring external adjustment mechanisms. The system self-regulates the connection force between the air seal and control ring, reducing installation complexity and ensuring reliable attachment
3Reliability
If radial features are added for attachment, then connection capability is improved, but thermal gradient stresses increase
Solution Approach 1:
Instead of using traditional radial features that extend through the air seal structure, the invention uses axial segmentation with minimal radial protrusions. The segments attach to the control ring through axial positioning and spring-loaded retention, eliminating the need for large radial features that would create thermal barriers and increase gradient stresses
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
Enables efficient, stress-reduced, and simplified installation and removal of blade outer air seals, reducing delamination risks and bearing loads, while maintaining effective sealing and thermal management.
Implementation Method 1
a spring clip comprising a clip base, a biasing element and a retention feature
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A clip (52) for an air seal assembly, comprising a clip base (54) having a control ring interface (55); a biasing element (56) coupled to the clip base opposite the control ring interface (55); wherein the clip (52) is insertable into a clip receiver (50) and configured to engage a notch (78) of a blade outer air seal (36) and configured to detachably couple with a clip mounting flange (58).