Blade Outer Air Seal with Angled Hook Assembly
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Solution Overview
Problem
The assembly of blade outer air seals in gas turbine engines is challenging due to the need for effective mounting of their assemblies, particularly ensuring that the bulk of combustion products pass over turbine blades, which requires reliable and efficient attachment mechanisms.
Innovation Solution
The use of blade outer air seals with forward and aft hooks supported on an attachment block, where the hooks extend at angles between 20 and 70 degrees relative to the web, and are formed from a laminate structure with inner reinforcement members and outer overwraps, along with wedge seals across circumferential gaps, facilitates secure and efficient assembly by allowing sliding onto attachment hooks and case hooks on a static casing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If blade outer air seals are mounted radially outwardly of the turbine blades, then combustion products can effectively pass over the blades, but the assembly and mounting become challenging
Solution Approach 1:
The blade outer air seal assembly is divided into multiple segments including a central web, forward hook, aft hook, and multiple laminate layers. Each segment can be independently manufactured and positioned, allowing the assembly to be constructed piece-by-piece and mounted section by section, thereby simplifying the overall assembly process while maintaining the functional integrity of the complete structure
Solution Approach 2:
The hooks are pre-formed as integral parts of the air seal assembly during manufacturing, with the forward and aft hooks extending at predetermined angles (20-70 degrees) from the web. This preliminary formation of attachment features eliminates the need for separate attachment component installation, reducing assembly complexity while ensuring proper geometric relationships are maintained
2Reliability
If hooks extend at angles between 20 and 70 degrees relative to the web, then secure attachment is achieved, but manufacturing complexity increases
Solution Approach 1:
The air seal assembly is constructed as a composite structure with multiple laminate layers (including CMC laminates) that are wrapped around and bonded to form the hooks and web. This composite construction allows the hooks to be formed as integral parts of the laminated structure, achieving the required angular geometry (20-70 degrees) through the layering and wrapping process rather than separate machining operations
Solution Approach 2:
The hook angle parameter is optimized to fall within the range of 20-70 degrees relative to the web, representing a specific parameter change that balances attachment security with manufacturability. This angular range provides sufficient mechanical advantage for secure mounting while remaining achievable through standard laminate wrapping and forming techniques
3Strength
If laminate structure with inner reinforcement and outer overwrap is used, then structural integrity is enhanced, but manufacturing process complexity increases
Solution Approach 1:
The laminate structure employs different material properties and configurations at different locations: inner reinforcement laminates provide core structural support and dimensional stability, while outer overwrap laminates provide environmental protection and surface integrity. This local differentiation of laminate functions optimizes structural performance throughout the assembly without requiring uniform complexity throughout the entire structure
Solution Approach 2:
The laminate structure is organized in nested layers with the inner reinforcement member positioned centrally, surrounded by intermediate laminate layers, and encased by the outer overwrap. This nested arrangement allows each layer to contribute specific structural functions while being integrated into the complete assembly, achieving high structural integrity through systematic layering rather than monolithic construction
Data Source
AI summary
A gas turbine engine includes a compressor section and a turbine section. The turbine section includes at least one rotor and at least one blade extending radially outwardly from the rotor to a radially outer tip. A blade outer air seal assembly is positioned radially outwardly of the radially outer tip of the blade. The blade outer air seal has forward and aft hooks, and the forward and aft hooks are supported on forward and aft seal hooks of an attachment block. The blade outer air seal forward and aft hooks extend at angles relative to an upper surface of a web that is between 20 and 70 degrees. A method is also disclosed.