| Tiny clearance measurement is one of the crucial technical bottlenecks in clearance controlling between the aero-engine's rotor blades and the casing, and in orientation of air bearing or magnetic bearing. These clearances may heavily affect the reliability and performance of the aero-engine.According to the analysis of several clearance measurement methods and the characteristics of the clearances among the aero-engine components, this paper conducts application researches on eddy current method and capacitance method. Firstly, a kind of clearance measurement application system based on eddy current method has been designed to measure the air bearing's eccentricity, which has a precision of micron and fulfilled the requirement. Secondly, by comparing and analyzing several measure circuits of capacitive displacement sensor, the clearance measurement application system based on the latest programmable capacitance-digital converter AD7746 is proposed. In order to avoid parasitic capacitance's influence on measuring results and enhance its anti-jamming ability, equal potential driven technology is used in capacitance sensor's transmission wires. Wide measurement range and high precision can be achieved by configuring compensation registers of AD7746. This system has been tested many times on the own-designed experiment platform, which shows that expected targets have been achieved with nice linearity, good repeatability and high precision. This system is hoped to be used in practical measurement for tip clearance in aero-engine.In the aspect of digital signal processing, wavelet analysis technology has been studied in this paper. By wavelet analysis of the clearance signals achieved in the previous eddy current method clearance measurement system, noise reduction and singularity point detection are realized effectively, as a result, the system's measurement precision is improved with certain fault detection ability. |
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