Research On Blade Tip Clearance And Blade Tip-timing Measurement Based On Microwave Sense

Blade is the core component of the large-sized rotating machines,the operating parameters of blade such as the blade vibration and tip clearance affect the normal operation and working efficiency of the whole system.The tip clearance between the tip and the casing is closely related to the fuel efficiency,thrust and service life of the engine.The real-time measurement of the blade clearance is of great significance to the blade design,flow field analysis and active clearance control.As a non-contact real-time measurement method,the tip-timing method is widely used in the on-line measurement of blade vibration parameters.However,the existing fiber,capacitor,eddy current and other types of tip clearance and tip-timing sensor are insufficient in the high temperature,pollutants and high rotating speed,which cannot meet the measurement requirement of the aircraft engine and other high temperature harsh environment.To solve this problem,in this paper,the method of measuring the tip clearance and the tip-timing based on microwave sensor is studied,and on this basis,the microwave tip clearance sensor and the tip clearance and the tip-timing measurement system were developed.A novel method which measures the tip clearance and tip timing parameters at the same time based on microwave sensor is developed,using the phase information of microwave reflection signal to solve the tip clearance,and the strength information to solve the time of arrival of the blades.This project builds the models of microstrip antenna structure and the coupling with end face reflection,analyzes the effect of the material parameters changes on the performance of microwave sensor under limited structure and high temperature environment and realizes its optimal design;the orthogonal demodulation,arctangent algorithm and the transmission path phase compensation are used to realize the accurate measurement of phase difference;to overcome the shortcomings of the low quality of the demodulated phase signal and eliminate the effect of the reflection signal by the sensor end face,a measurement method is proposed to realize the high precision measurement of the time of arrival of blade tip,which uses the orthogonal demodulation to obtain the strength information of reflection signal and uses both edges of the signal to calculate the time of arrival;the carrier frequency adaptive adjustment method is introduced to track the minimum standing wave point of the antenna,thus improving the resistance of the sensor parameters to temperature drift?According to the requirement of the sensor characteristics and the characteristics of small microwave antennas,the resonant cavity sensor structure are designed and their performance is simulated and analyzed,and the feasibility of using the resonant frequency to measure the tip clearance is analyzed.The influence of sensor structure size parameters on bandwidth and impedance is analyzed.The field strength of near field distribution of the sensor and the influence of the structure size on the sensor characteristic are simulated.The influence of temperature change on the performance of resonant cavity sensor and micro-strip antenna sensor is analyzed.And a micro-strip antenna tip clearance sensor was designed and fabricated.The blade tip clearance and the tip-timing measurement system based on microwave sensor are designed and the principle prototype is made.The structure and circuit design of the measuring system are introduced.The phase is calculated by the sampling of the IF signal.The timing signal is generated by the analog circuit.Using the end reflection to obtain the phase reference of the transmission path,the frequency of minium standing wave is tracked to stable sensor signal-to-noise ratio.The circuit amplitude and phase imbalance is corrected through the calibration source.Finally,the feasibility of the microwave tip clearance and the tip timing measurement method and the measurement system are verified by experiments.The calibration of the microwave tip clearance sensor was carried out,and the dynamic measurement of the tip clearance was carried out by using the prototype of the measuring system.The experiment of the tip-timing measurement was carried out and compared with the measurement result of the fiber bundle tip-timing measurement system.