Ceramic Matrix Composite Blade Outer Air Seal
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Solution Overview
Problem
Existing gas turbine engines face challenges in maximizing the percentage of combustion products passing over turbine blades due to leakage issues around the blade outer air seal, particularly when using ceramic matrix composite materials, which can be exacerbated by the use of cobalt-based alloys or steels for bristle seals.
Innovation Solution
A sealing surface member is positioned between the aft end of the axial seal and the forward hook of the blade outer air seal, providing a sealing surface that complements the curved portion of the forward hook, and is made of ceramic matrix composite materials or cobalt-based alloys, with additional features like radially inwardly extending ledges and tabs to enhance sealing and prevent rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a blade outer air seal is positioned radially outward of the turbine blade to maximize combustion products passing over blades, then the percentage of combustion products directed across turbine blades is improved, but leakage radially outwardly around the blade outer air seal occurs
Solution Approach 1:
The sealing system is divided into multiple segments: an axial seal positioned forward of the forward hook, a sealing surface member positioned intermediate the axial seal and forward hook, and the blade outer air seal with forward and aft hooks. This segmentation allows each component to address specific leakage paths, with the axial seal handling forward leakage and the sealing surface member addressing the gap between the axial seal and forward hook, thereby reducing overall radial leakage while maintaining high combustion product utilization.
2Reliability
If ceramic matrix composite materials are used for the blade outer air seal to improve performance, then the seal effectiveness is improved, but the sealing surface compatibility with cobalt-based alloy bristle seals deteriorates
Solution Approach 1:
The sealing surface member acts as an intermediary component between the axial seal and the forward hook of the blade outer air seal. It provides a sealing surface that is compatible with cobalt-based alloy bristle seals while being positioned against the ceramic matrix composite blade outer air seal. This intermediary sealing surface member resolves the material incompatibility issue by providing an intermediate interface that works effectively with both ceramic and cobalt-based alloy materials.
3Reliability
If seals are added to the blade outer air seal to prevent radial leakage, then leakage prevention is improved, but the device complexity increases
Solution Approach 1:
The axial seal and the blade outer air seal are merged into an integrated sealing system where the axial seal is supported on the vane support and extends aftward, while the blade outer air seal with forward and aft hooks is supported on static structure. The sealing surface member bridges these two seals, creating a unified sealing arrangement that prevents radial leakage without requiring entirely separate, complex sealing mechanisms. This merging approach achieves effective leakage prevention while maintaining reasonable system complexity.
Data Source
AI summary
A gas turbine engine includes a turbine section having a turbine rotor and at least one blade extending outwardly of the turbine rotor. The turbine rotor rotates about an axis of rotation. A blade outer air seal is positioned radially outward of the at least one blade. The blade outer air seal has an axially forward hook and an axially aft hook supported to static structure. An axial seal is attached to static structure forward of the forward hook, and has a sealing portion extending in an aft direction. A sealing surface member is positioned intermediate an aft end of the axial seal and a forward end of the forward hook to provide a sealing surface for sealing between the seal and the blade outer air seal.