Gas Turbine Blade Outer Air Seal Clearance Control
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Solution Overview
Problem
Conventional active clearance control systems in gas turbine engines are not well-suited for rapid throttle operations, as they fail to rapidly respond to thermal and mechanical growth, leading to increased tip clearance and potential tip rubbing during high throttle conditions, which reduces efficiency and increases fuel consumption.
Innovation Solution
A clearance control assembly that includes a static outer shroud seal, an actuator, a load-applying member, and a lever system, which allows for rapid adjustment of the seal's position to minimize clearance between the rotor tip and the seal, using a seal carrier and hooks for mounting, enabling rapid response to thermal and mechanical changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional active clearance control systems are used, then clearance control during cruising portions is achieved, but rapid response to thermal and mechanical growth during rapid throttle operations is not achieved
Solution Approach 1:
The blade outer air seal is made dynamically adjustable through a clearance control assembly that includes an actuator, load-applying member, and lever system. This allows the seal position to change rapidly in response to varying thermal and mechanical conditions, particularly during rapid throttle operations, transforming a static clearance control system into a dynamic one that can adapt to changing operating conditions.
Solution Approach 2:
The clearance control system is segmented into distinct functional components: the blade outer air seal, seal carrier, actuator, load-applying member, and lever system. This segmentation allows each component to be optimized for its specific function and enables independent control of different aspects of clearance management, improving overall system responsiveness and reliability.
2Loss of energy
If tip clearance is minimized to improve efficiency, then fuel consumption is reduced, but potential for tip rubbing during rapid throttle operations increases
Solution Approach 1:
The clearance control assembly implements a feedback mechanism where the position of the blade outer air seal is continuously adjusted based on real-time operating conditions. The actuator receives signals about thermal and mechanical growth and modifies the seal position accordingly, creating a closed-loop control system that maintains optimal clearance while preventing tip rubbing during rapid throttle operations.
Solution Approach 2:
The system takes preliminary action by positioning the blade outer air seal in advance to account for anticipated thermal and mechanical growth during rapid throttle operations. By proactively adjusting clearance before tip rubbing can occur, the system prevents harmful contact while maintaining efficient operation.
3Ease of operation
If thermal expansion is used to control clearance, then clearance adjustment is achieved, but response time is slow and not suitable for rapid throttle operations
Solution Approach 1:
The clearance control assembly introduces mechanical intermediaries (actuator, load-applying member, lever system) that mediate between the thermal expansion of components and the actual clearance adjustment. These intermediaries amplify and accelerate the clearance adjustment process, converting slow thermal expansion into rapid mechanical position changes that can respond to rapid throttle operations.
Solution Approach 2:
The system replaces reliance on pure thermal expansion with a mechanically-driven adjustment system. The actuator and associated mechanical components directly control the position of the blade outer air seal, substituting the slow thermal expansion mechanism with a faster mechanical actuation system that can respond immediately to changing operating conditions.
Data Source
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AI summary
A clearance control assembly (70) for providing clearance control between a blade outer air seal (86) and an airfoil tip (88) of a gas turbine engine includes an outer case (78), a first blade outer air seal carrier (96), a blade outer air seal (86), an actuator (89), a load-applying member (92), and a lever (94). The first blade outer air seal carrier (96) is positioned radially inward of the outer case (78). The blade outer air seal (86) is positioned radially inward of and mounted to the blade outer air seal carrier (96). The load-applying member (92) is positioned to be acted upon by the actuator (89) during operation of the actuator (89). The lever (94) is connected to the outer case (78) and is operably in contact with the load-applying member (92) and the first blade outer air seal carrier (96).