Passive Air Seal Clearance Control for Gas Turbine Engines
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Solution Overview
Problem
Gas turbine engines face inefficiencies due to air leakage through small gaps between rotating and stationary components, which are difficult to maintain due to thermal and mechanical deformations, leading to suboptimal clearance heights and reduced engine efficiency.
Innovation Solution
A passive clearance control system comprising a sealing member and a land with a geometric configuration that maintains a constant clearance height by accommodating thermal and mechanical expansions, using a ramp or wedge design that adjusts to maintain optimal alignment and reduce air leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fixed clearance height is used for all operating conditions, then device complexity is reduced, but manufacturing precision and operational reliability deteriorate due to inability to maintain optimal clearance under thermal and mechanical deformations
Solution Approach 1:
The patent applies parameter changes by incorporating a variable clearance mechanism that adjusts the gap between rotating and stationary components based on operating conditions. The clearance height is changed as a function of rotor speed or temperature, allowing the system to maintain optimal clearance across different operating modes without requiring complex active control systems. This resolves the contradiction by enabling precision clearance control through passive parameter variation rather than active control.
Solution Approach 2:
The patent implements dynamics by transitioning from a fixed clearance design to a dynamic clearance system that automatically adapts to changing operating conditions. The clearance height varies with rotor speed or thermal expansion, allowing the sealing components to maintain optimal alignment throughout the operational range. This dynamic approach improves precision while avoiding the complexity of active control systems.
2Loss of energy
If tight tolerances are maintained for sealing gaps, then air leakage is reduced improving efficiency, but reliability deteriorates due to difficulty maintaining alignment under thermal expansion and mechanical deformations
Solution Approach 1:
The patent applies dynamics by implementing a clearance control mechanism that allows the gap between sealing surfaces to vary with operating conditions. As the rotor spins or thermal expansion occurs, the clearance height adjusts automatically to maintain optimal sealing. This dynamic adaptation ensures consistent sealing performance and reduces air leakage across the entire operational range, resolving the contradiction between tight tolerances and reliability under deformation.
Solution Approach 2:
The patent changes the clearance parameter as a function of operating conditions such as rotor speed or temperature. By varying the clearance height dynamically, the system maintains effective sealing without requiring consistently tight tolerances that would be difficult to maintain under thermal and mechanical stress. This parameter variation improves both energy efficiency and sealing reliability.
3Manufacturing precision
If active clearance control systems are used to maintain optimal clearance, then manufacturing precision and operational reliability improve, but device complexity increases and control accuracy becomes difficult to achieve
Solution Approach 1:
The patent applies self-service by designing a passive clearance control system that automatically adjusts clearance height in response to operating conditions without requiring external control systems. The mechanism uses the engine's own operational parameters (such as rotor speed or thermal expansion) to drive the clearance adjustment, eliminating the need for complex sensors, actuators, and control algorithms. This self-regulating approach achieves precision clearance control while minimizing system complexity.
Solution Approach 2:
The patent replaces complex active mechanical control systems with a simpler passive mechanical mechanism. Instead of using motors, sensors, and control electronics to adjust clearance, the invention employs a mechanical linkage or geometric design that automatically adjusts clearance based on operating conditions. This substitution reduces device complexity while maintaining precision clearance control.
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 a consistent clearance height across various operational modes, enhancing the mechanical and thermal efficiency of gas turbine engines by minimizing air leakage and accommodating thermal and mechanical growths of engine components.
Implementation Method 1
the engine casings grow in diameter due to thermal expansion. Additionally, the turbine shafts grow in length due to thermal growth resulting from the high temperatures reached during operation of the engine
Implementation Method 2
it is difficult to maintain the tight tolerances required with these sealing arrangements due to deformations that the engine undergoes during various stages of operation
Data Source
AI summary
A seal for restricting leakage of a fluid through a gap disposed between rotating and stationary components concentrically aligned within a gas turbine engine comprises a sealing member and a land. The sealing member is positioned on either the rotating or stationary component of the gas turbine engine and closes a gap between the rotating member and the stationary member. The land is positioned opposite the sealing member on either the rotating or stationary component of the gas turbine engine such that a clearance height is provided between the sealing member and the land. In one embodiment, the land is geometrically shaped according to expected changes in the gap and relative axial position of the sealing member and land during operation of the gas turbine engine. The sealing member and the land are positioned with respect to each other so that the clearance height is maintained approximately constant during operation of the gas turbine engine.