CMC Intersegment Seal Structure for Hot-Gas Leakage Control
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Solution Overview
Problem
Existing gas turbine engine blade outer air seal assemblies face challenges in preventing fluid leakage due to gaps between adjacent components, particularly in high-temperature environments where traditional metallic seals are temperature-limited and prone to thermal growth, leading to increased exposure of intersegment seals to hot gases.
Innovation Solution
A ceramic matrix composite intersegment seal assembly is designed with a base portion and two seal portions connected by a rib, forming an H-shape, where the first seal portion is generally rectangular and the second seal portion is radially extending, providing enhanced sealing and retention capabilities, and is formed using a fibrous woven structure with silicon carbide fibers and matrix, allowing for densification and machining for precise fitment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If traditional metallic seals are used in blade outer air seal assemblies, then the seals can provide initial sealing capability, but they are temperature-limited and prone to thermal growth which increases exposure of intersegment seals to hot gases
Solution Approach 1:
The patent applies composite materials by transitioning from traditional metallic seals to ceramic matrix composite (CMC) seals. The CMC material combines ceramic particles within a matrix structure, providing both high-temperature resistance and dimensional stability. This composite approach allows the seal to withstand temperatures where metallic seals would fail while maintaining consistent dimensions to prevent thermal growth and ensure reliable sealing at the interface between blade and shroud.
2Temperature
If ceramic matrix composite intersegment seal is used, then high-temperature resistance and thermal stability are improved, but manufacturing complexity increases due to densification and machining requirements
Solution Approach 1:
The patent applies segmentation by dividing the intersegment seal into distinct functional zones: a first seal portion for primary sealing contact, a second seal portion for secondary retention, and a rib connecting them. This segmentation allows each portion to be optimized for its specific function and enables modular manufacturing approaches, reducing overall manufacturing complexity while maintaining high-temperature performance.
Solution Approach 2:
The patent applies local quality by providing different structural characteristics to different portions of the seal. The first seal portion has specific dimensional tolerances for primary sealing, while the second seal portion has different geometry for retention. The rib provides structural support with yet another set of properties. This localized optimization allows precise fitment where needed while simplifying manufacturing in other areas.
3Reliability
If featherseals are provided between adjacent blade outer air seals to prevent fluid leakage, then sealing capability is improved, but the gaps between adjacent components still expose intersegment seals to hot gases
Solution Approach 1:
The patent applies merging by combining multiple sealing functions into a single integrated intersegment seal structure. The first seal portion provides primary sealing to prevent fluid leakage, while the second seal portion provides secondary retention. The rib connects these portions and provides structural support. This merged structure eliminates the need for separate featherseals and reduces gaps between components, thereby minimizing hot gas exposure while maintaining enhanced sealing capability.
Data Source
AI summary
A blade outer air seal assembly includes a blade outer air seal segment that has a base portion that extends from a first axial side to a second axial side and from a first circumferential side to a second circumferential side. An intersegment seal is arranged adjacent the first circumferential side. The intersegment seal has a first seal portion and a second seal portion connected by a rib.