CMC Intersegment Seal Structure for Turbine Outer Air Seal Gaps

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Solution Overview

Problem

Existing blade outer air seals in gas turbine engines face challenges in preventing fluid leakage and maintaining durability at high temperatures, particularly when using ceramic matrix composite materials, due to larger gaps between segments and thermal growth issues.

Innovation Solution

A blade outer air seal assembly featuring an intersegment seal formed from ceramic matrix composite material with an H-shaped design, including a first and second seal portion and an axially extending rib, providing primary and secondary sealing surfaces and retention, which is manufactured through a process of laminating fibers and densification to enhance structural integrity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If featherseals are provided between adjacent components to prevent fluid leakage, then sealing capability is improved, but the thermal growth mismatch between CMC and metallic components causes larger gaps that expose intersegment seals to high-temperature gases, leading to structural failure or erosion over time

Engineering Contradiction:

Improvesealing capabilityVSAvoidexposure to high-temperature gases

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The intersegment seal is formed from ceramic matrix composite (CMC) material, matching the thermal expansion characteristics of the CMC blade outer air seal segments. This composite material approach eliminates the thermal growth mismatch problem that occurs with metallic seals, preventing excessive gaps while maintaining sealing capability and protecting against high-temperature gas exposure.

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If a simple seal structure is used, then manufacturing ease is improved, but the seal lacks sufficient retention capability in case of structural failure or erosion

Engineering Contradiction:

Improveseal structure simplicityVSAvoidretention capability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The intersegment seal is divided into multiple functional portions: a first seal portion for primary sealing, a second seal portion for secondary retention, and a rib connecting them. This segmentation provides both manufacturing simplicity through modular construction and enhanced reliability through redundant retention mechanisms, ensuring the seal remains secured even if one portion fails.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The second seal portion acts as a pre-positioned backup retention mechanism. If the first seal portion experiences structural failure or erosion, the second seal portion is already in place to provide secondary retention, preventing catastrophic failure and allowing for gradual degradation rather than sudden loss of sealing function.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentEP3719263B1Blade outer air seal assembly with intersegment seal

Publication Date: 2026.04.29 RTX CORP

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AI summary

A blade outer air seal assembly (104) includes a blade outer air seal segment (105) that has a base portion (124) that extends from a first axial side (A1) to a second axial side (A2) and from a first circumferential side (C1) to a second circumferential side (C2). An intersegment seal (160) is arranged adjacent the first circumferential side. The intersegment seal has a first seal portion (164) and a second seal portion (166) connected by a rib (168).