Ceramic Blade Tip Crown for CMC Airfoil Rub Protection
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Solution Overview
Problem
Gas turbine blades experience degradation due to interaction with blade tracks or other structures during operation, leading to exposure of ceramic matrix composite materials to the environment, which can damage them.
Innovation Solution
A turbine blade design featuring a protective crown made of monolithic ceramic materials positioned radially outward to engage with the blade track, shielding the ceramic matrix composite airfoil from rub and environmental exposure, with a crown retainer securing the protective crown in place to prevent radial motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the turbine blade uses ceramic matrix composite materials for the airfoil, then the blade can operate at higher temperatures and improve efficiency, but the blade becomes susceptible to environmental degradation and damage from blade track interaction
Solution Approach 1:
A protective crown made of monolithic ceramic material is introduced as an intermediary component between the blade track and the CMC airfoil. This crown absorbs the environmental exposure and mechanical interaction with the blade track, shielding the CMC materials from degradation while allowing the blade to operate at high temperatures
Solution Approach 2:
The blade employs a composite structure combining CMC materials for the airfoil with a monolithic ceramic protective crown. This composite approach leverages the high-temperature capabilities of CMC while adding the environmental resistance and mechanical protection of monolithic ceramic, resolving the contradiction between temperature performance and reliability
2Reliability
If the protective crown is positioned radially outward to engage the blade track, then the CMC airfoil is protected from rub and environmental exposure, but the blade structure becomes more complex
Solution Approach 1:
The protective crown is integrated with the airfoil structure through a crown retainer system that combines multiple retention features into a unified assembly. The retainer includes a flange received in a channel and secured with fasteners, merging the protective function with the structural attachment system to minimize additional complexity
Solution Approach 2:
The blade tip structure is segmented into distinct functional components: the CMC airfoil, the protective crown, and the crown retainer. This segmentation allows each component to be optimized for its specific function while maintaining overall protection, with the retainer acting as a separate retention mechanism that can be independently designed and installed
3Reliability
If the protective crown is secured with a crown retainer including flange and channel, then the protective crown remains stable during operation, but the manufacturing process becomes more complex
Solution Approach 1:
The flange-receiving channel is pre-formed in the airfoil structure during manufacturing, and the flange is pre-attached to the protective crown. This preliminary preparation of retention features allows for stable assembly during operation while simplifying the overall manufacturing process by enabling pre-fabrication of retention components
Data Source
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AI summary
Turbine blades for use in gas turbine engines are disclosed herein. Each blade includes an airfoil and a protective crown. The airfoil includes ceramic matrix composite materials. The protective crown includes ceramic-containing materials and is mounted to a radially-outer end portion of the airfoil.