Floating Clearance Control Ring for Gas Turbine Tip Clearance
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Solution Overview
Problem
Traditional clearance control systems in gas turbine engines are large, heavy, and slow to respond, providing limited improvement in tip clearance and increasing engine efficiency demands, as they are affected by differential thermal expansion of various engine components.
Innovation Solution
A clearance control system featuring a clearance control ring with a floating mount that is not directly tied to the engine case, using a conduit to deliver compressor air at different temperatures to adjust the position of the outer air seal, allowing it to move radially in response to temperature changes, thereby maintaining optimal clearance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional clearance control systems use valves and manifolds to direct fan air to engine case locations, then tip clearance is improved, but the system becomes large, heavy, and expensive with slow response
Solution Approach 1:
The patent extracts the essential function of tip clearance control from the complex traditional system (valves and manifolds) and implements it through a simplified structure consisting of a carrier element with a movable outer air seal. This extraction removes unnecessary complexity while retaining the core functionality of controlling tip clearance through thermal expansion/contraction of the carrier element.
Solution Approach 2:
The carrier element acts as an intermediary component between the engine case and the outer air seal. It mediates the thermal expansion and contraction effects to control tip clearance, replacing the need for complex valve and manifold systems. The carrier element's ability to expand and contract with temperature changes provides a direct and responsive control mechanism.
2Manufacturing precision
If traditional clearance control systems use valves and manifolds to direct fan air, then cooling air thermally shrinks the engine case, but the response is slow and clearance improvement is limited
Solution Approach 1:
The patent applies local quality by concentrating the thermal control function in the carrier element rather than relying on bulk engine case cooling. The carrier element is specifically designed to respond to thermal changes and control the outer air seal position, providing localized and rapid tip clearance adjustment without requiring slow propagation of cooling air through the entire engine case.
3Adaptability or versatility
If blades, BOAS, and supporting structure are made of different materials, then they respond differently to temperature changes, but this causes blade rubbing or increased clearance
Solution Approach 1:
The patent utilizes parameter changes by designing the carrier element with specific thermal expansion characteristics that compensate for the differential thermal responses of blades, BOAS, and supporting structures. By controlling the carrier element's material properties and geometry, the system maintains optimal tip clearance across varying temperature conditions despite the different materials used in various components.
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 achieves faster thermal response and tighter high-pressure turbine clearances, improving thrust specific fuel consumption (TSFC) and reducing system weight and complexity compared to traditional systems.
Implementation Method 1
Since the blades, the BOAS, and the structure that support the BOAS are different sizes and/or are formed of different materials, they respond to temperature changes in different manners. As these structures expand at different rates in response to temperature changes, the tip clearance may be reduced and the blade may rub on the BOAS
Implementation Method 2
The cooling air thermally shrinks the engine case at these locations to improve tip clearance and thus fuel burn
Data Source
Figure 1
Figure 2A~3
Figure 4A~5
AI summary
A clearance control system for a gas turbine engine (20) comprises at least one case support (72) associated with an engine case (70) defining an engine center axis (A). A clearance control ring (66) is positioned adjacent the at least one case support (72) to form an internal cavity (68) between the engine case (70) and the clearance control ring (66). The clearance control ring (66) includes a first mount feature (74). An outer air seal (64) has a second mount feature (76) cooperating with the first mount feature (74) such that the clearance control ring (66) can move independently of the engine case (70) in response to changes in temperature. An injection source (70) inject flow into the internal cavity to control a temperature of the clearance control ring (66) to allow the outer air seal (64) to move in a desired direction to maintain a desired clearance between the outer air seal (64) and an engine component (62).