Turbine Blade Seal Decoupling Thermal Stress
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Solution Overview
Problem
Existing turbine blades face reduced working life due to large forces generated by differential deformations between airfoil and platform caused by high temperatures, as existing connection methods place joints close to the hot gases path, exacerbating thermal stress.
Innovation Solution
A turbine blade design featuring a mechanically decoupled seal closer to the hot gases path to minimize force transmission between airfoil and platform, combined with a permanent joining in areas away from the hot gases path, using materials like metallic felt or foam for compliance and oxidation resistance, and brazing for durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the connection between airfoil and platform is realized in zones close to the hot gases path, then the structural integrity is improved, but the working life is reduced due to large differential deformation forces
Solution Approach 1:
The blade is divided into functionally distinct zones: a sealing zone near the hot gases path with mechanically decoupled seal elements, and a joining zone away from the hot gases path with permanent mechanical connection. This segmentation allows the seal to handle thermal expansion independently while the permanent join provides structural strength in a low-stress region.
Solution Approach 2:
Mechanically decoupled seal elements (such as C-rings or elastomeric seals) are introduced as intermediary components between the airfoil and platform. These seals accommodate differential thermal expansion and contraction without transmitting large forces to the permanent joining, thereby protecting the structural connection from thermal stress.
2Force
If a mechanically decoupled seal is used closer to the hot gases path, then the force transmission between airfoil and platform is minimized, but the structural integrity may be compromised
Solution Approach 1:
The connection system is segmented into two functional parts: a mechanically decoupled seal for force isolation near the hot gases path, and a permanent mechanical joining for structural integrity in a low-stress zone away from the hot gases path. This segmentation allows each component to optimize its specific function without compromising the other.
Solution Approach 2:
Different connection qualities are applied at different locations: mechanically decoupled sealing elements are placed where thermal stress is high (near hot gases path) to minimize force transmission, while permanent rigid joining is placed where thermal stress is low (away from hot gases path) to provide structural support. Each location receives the appropriate connection type for its thermal and mechanical environment.
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 the impact of differential deformations on blade life by minimizing force transmission between airfoil and platform, while maintaining structural integrity and preventing hot gas ingress through efficient sealing, thus extending the blades' operational lifespan.
Implementation Method 1
The seal is a mechanically decoupled seal... having a compliant behaviour so as to minimise forces transmitted from the airfoil to the platform and vice versa
Implementation Method 2
The seal is preferably oxidation resistant and has high temperature properties
Data Source
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AI summary
The blade (1) of a turbine comprises an airfoil (2) and a platform (3) manufactured in two separated pieces joined together. The blade (1) comprises a seal (4) interposed between the airfoil (2) and platform (3) in a position closer to a hot gases path (5) than a joining (6). The seal (4) is a mechanically decoupled seal.