Gas Turbine Blade Outer Air Seal Thermal Control
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Solution Overview
Problem
The varying thermal environment in gas turbine engines causes radial tip clearance changes due to thermal expansion and centrifugal loading, leading to increased core air leakage and negative effects on engine performance, efficiency, and component life, especially when power is reduced.
Innovation Solution
A blade tip clearance control system with radially adjustable Blade Outer Air Seals (BOAS) and a full hoop thermal control ring, where the BOAS carrier segments are pivotally mounted and axially retained, allowing for precise control of radial tip clearance through thermal expansion management, and a heat shield is used to slow down transient responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the radial tip clearance is designed to prevent blade tip rubbing under high power operations, then reliability is improved, but core air leakage increases when engine power is reduced, worsening engine performance and efficiency
Solution Approach 1:
The blade tip clearance control system dynamically adjusts the radial position of the blade outer air seals relative to the blade tips. The carrier segments are radially movable along the turbine rotor, allowing the system to adapt the tip clearance to varying engine operating conditions - maintaining small clearance at high power to prevent rubbing while achieving optimal clearance at reduced power to minimize air leakage and maximize efficiency
Solution Approach 2:
The system changes the physical parameter of tip clearance by controlling the thermal expansion of the thermal control ring. By managing the temperature of the ring (which has different thermal expansion properties than the rotor), the system can precisely control the radial position of the air seals, thereby adjusting the tip clearance parameter in response to changing engine power levels
2Adaptability or versatility
If thermal expansion is allowed to occur naturally under varying thermal environments, then adaptability is improved, but radial tip clearance varies uncontrollably, worsening leakage and performance
Solution Approach 1:
The system deliberately utilizes thermal expansion by incorporating a thermal control ring made of material with specific thermal expansion properties. This ring is positioned to control the radial location of the blade outer air seals. By controlling the temperature of this ring, the system can precisely manage the tip clearance, converting the natural phenomenon of thermal expansion into a controllable mechanism for performance optimization
Solution Approach 2:
The system incorporates feedback through temperature sensing and active cooling mechanisms. Temperature sensors monitor the thermal state of the thermal control ring, and cooling passages provide active thermal management. This feedback loop allows the system to maintain precise control over the radial position of air seals and the tip clearance, ensuring optimal performance across varying thermal environments
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 system effectively maintains optimal radial tip clearance, reducing core air leakage and enhancing engine performance, efficiency, and component life by passively controlling thermal expansion and minimizing centrifugal growth, thus improving fuel burn and operational reliability.
Implementation Method 1
the radial tip clearance varies. The radial tip clearance may be influenced by mechanical loading (e.g., radial expansion of the blades and/or their supporting disks due to speed-dependent centrifugal loading) and thermal expansion
Implementation Method 2
a heat shield is used to slow down transient responses
Implementation Method 3
radial expansion of the blades and/or their supporting disks due to speed-dependent centrifugal loading
Data Source
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AI summary
A clearance control system for a gas turbine engine is provided. The system includes an inner axial wall that extends between a forward wall and an aft wall. The system also includes an outer axial wall that extends parallel to the inner axial wall to pivotally receive a full hoop thermal control ring.