Blade Outer Air Seal Intersegment Seal Thermal Stress Reduction
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Solution Overview
Problem
Existing blade outer air seal assemblies in gas turbine engines face challenges in ensuring efficient sealing and minimizing thermal stress due to the mismatch in temperature gradients between the hot gas path and the colder attachment regions of the seal segments.
Innovation Solution
The implementation of an intersegment seal with a circumferentially extending portion and radially extending tabs that form a T-shaped cross-section, secured by a clip, which creates cavities that allow gas path air to be pumped into the gaps between seal segments, reducing thermal stress by heating the attachment regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional sealing structures are used, then sealing function is provided, but thermal stress increases due to temperature gradient mismatch between hot gas path and colder attachment regions
Solution Approach 1:
The patent introduces an intersegment seal as an intermediary component between adjacent seal segments. This seal includes a circumferentially extending portion that contacts the gas path and radially extending tabs that extend into recesses formed in the seal segments. The intersegment seal acts as a mediator that allows controlled thermal expansion and reduces stress concentration at the interfaces between segments, thereby reducing thermal stress while maintaining sealing effectiveness.
Solution Approach 2:
The air seal assembly is divided into multiple discrete seal segments arranged circumferentially around the gas path, rather than using a single continuous seal. Each segment can independently respond to thermal gradients, reducing overall thermal stress. The segmentation allows for expansion joints and flexible connections that accommodate differential thermal expansion between the hot gas path region and the colder attachment regions.
2Reliability
If seal segments are joined tightly to ensure sealing, then sealing effectiveness improves, but thermal stress increases due to constrained thermal expansion
Solution Approach 1:
The connection between seal segments and the support structure is designed to be dynamically adjustable rather than rigidly fixed. The segments can expand and contract radially in response to thermal conditions while maintaining circumferential sealing contact. This dynamic capability allows the sealing function to be maintained while accommodating thermal expansion, thereby reducing thermal stress.
Solution Approach 2:
Different regions of the seal assembly have different mechanical properties tailored to their specific functions. The circumferentially extending portion of the intersegment seal has properties optimized for sealing contact, while the radially extending tabs and recesses are designed with properties that accommodate thermal expansion. This local differentiation of mechanical properties allows tight sealing in critical areas while providing flexibility in regions subject to thermal stress.
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 design reduces thermal stress on the blade outer air seal segments by utilizing gas path air to heat the hook attachment regions, minimizing the thermal gradient and improving the thermal performance of the seal assembly.
Implementation Method 1
utilizing gas path air to heat the hook attachment regions
Implementation Method 2
gas path air to be pumped into the gaps between seal segments
Data Source
AI summary
A blade outer air seal assembly includes a support structure. A blade outer air seal has a plurality of segments that extend circumferentially about an axis and mounted in the support structure. At least two of the segments have a first wall circumferentially spaced from a second wall. A base portion extends from the first wall to the second wall. A recess is arranged in at least one of the first wall and the second wall. An intersegment seal is arranged between the at least two segments. The intersegment seal has a circumferentially extending portion and a radially extending tab. The radially extending tab extends into the recess to define at least two cavities within the recess.