Blade Outer Air Seal with Reverse Retention Hook
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Solution Overview
Problem
Gas turbine engines face challenges in reducing airflow leakage around rotating blades, which affects efficiency and stability, particularly due to the limitations of conventional blade outer air seals (BOAS) in maintaining effective sealing and reducing aerodynamic losses.
Innovation Solution
The implementation of a reverse retention hook and axial/radial retention features in the BOAS, combined with an abradable plasma-sprayed seal, which is axially constrained and radially retained, to enhance sealing between the blade tips and the engine casing, thereby reducing airflow leakage and improving aerodynamic stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional blade outer air seals are used, then the structure is simple, but airflow leakage around rotating blades increases
Solution Approach 1:
The BOAS is divided into multiple segments that can be assembled together to form a complete seal around the rotating blades. Each segment contains retention features that work independently to maintain sealing effectiveness while allowing modular installation and replacement
Solution Approach 2:
The retention hooks and retention features are pre-configured on the BOAS segments during manufacturing. These features are designed to engage with corresponding structures on the casing and blades before operation begins, ensuring proper positioning and sealing contact are established in advance
2Loss of energy
If the BOAS is positioned in close proximity to the blade tip to improve sealing, then airflow leakage reduces, but the risk of blade contact and erosion increases
Solution Approach 1:
The abradable seal material properties are specifically engineered to allow controlled wear. The material parameters are selected so that the seal can be positioned close to the blade tip for effective sealing, while the blade surface remains harder and more durable, creating a controlled wear pattern that protects the expensive blade
Solution Approach 2:
The potential harmful effect of blade contact with the seal is converted into a beneficial wear mechanism. The abradable seal material is designed to wear away controllably when contacted by the blade, maintaining sealing effectiveness over time while protecting the blade from damage
3Stability of the object's composition
If the BOAS structure is made more complex with additional retention features, then positioning stability improves, but manufacturing difficulty increases
Solution Approach 1:
Multiple retention functions are combined into integrated features on the BOAS segments. The retention hooks and retention features are designed to work together as a unified system, reducing the number of separate components needed while maintaining positioning stability
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
The enhanced BOAS design effectively reduces airflow leakage, improves engine stability, and increases stall margins by maintaining a secure position within the engine, leading to increased operational efficiency and performance.
Implementation Method 1
an abradable plasma-sprayed seal
Data Source
Figure 1
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AI summary
A blade outer air seal (BOAS) for a gas turbine engine according to an exemplary aspect of the present disclosure includes, among other things, a seal body having a radially inner face and a radially outer face that axially extend between a leading edge portion and a trailing edge portion. The BOAS includes a trough disposed on the radially inner face and an abradable seal received within the trough. The trough is open to expose a leading edge of the abradable seal to a core flow path of the gas turbine engine.