Capacitive Wear Indicator for Gas Turbine Blade Clearance
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Solution Overview
Problem
Existing methods for detecting blade tip clearance in gas turbine engines are inadequate for accurately measuring clearance at multiple locations and times during engine operation, particularly under varying conditions such as ground idle, flight idle, max cruise, and max power, which affects performance and efficiency.
Innovation Solution
A method and apparatus using wear indicators with capacitors encapsulated in potting materials like alumina or boron nitride, attached to blade outer air seals, measure clearance by detecting changes in capacitance as blade tips rub against them, allowing for multiple measurements during an engine run and providing data on operational performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional blade clearance detection methods are used, then measurement capability is limited, but measurement precision and ability to detect at multiple locations and times is insufficient
Solution Approach 1:
The blade clearance detection system is segmented into multiple wear indicators positioned at different locations around the engine, with each indicator containing its own capacitor. This allows independent measurement at multiple locations simultaneously, resolving the limitation of traditional single-point measurement methods.
Solution Approach 2:
The patent replaces traditional mechanical contact-based clearance measurement methods with a capacitive sensing system. The capacitor measures clearance through electrical field interaction with the blade tip, eliminating mechanical contact and enabling non-contact, multi-point, and continuous measurement capabilities.
2Measurement precision
If wear indicators with capacitors are used, then measurement capability improves, but device complexity increases
Solution Approach 1:
The wear indicator integrates multiple functions into a single component: the capacitor plates are formed as integral parts of the indicator structure, with insulating material providing both electrical isolation and mechanical support. This merging reduces the number of separate components and simplifies the overall device despite the advanced measurement capability.
Solution Approach 2:
The wear indicator serves multiple functions simultaneously: it provides clearance measurement through the capacitor, structural support through the insulating material, and wear detection through the indicator portion that contacts or nears the blade tip. This multi-functionality reduces the need for separate components for each function.
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
This solution enables precise detection of blade tip clearance at multiple locations and times, improving engine performance and identifying potential over-rub conditions, thus enhancing manufacturing processes and operational efficiency.
Implementation Method 1
A capacitor is formed having a first plate, a second plate, and a dielectric between the first plate and the second plate
Data Source
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AI summary
A wear indicator (100) for detecting blade clearance in a gas turbine engine includes a capacitor (102) connected to a first conductor and a second conductor. The capacitor (102) includes a multiple of layers (104) arranged transverse to a rub direction, each layer (104) separated by an insulator (106) and including a first plate (108), a second plate (110), and a dielectric (112) between the first plate (108) and the second plate (110). A method of detecting blade clearance in a gas turbine engine (20), includes determining a change in capacitance between the first and second capacitance and determining an amount of material removed from the wear indicator (100) by the blade (84) corresponding to the change in capacitance.