| In recent years,the new type of aircraft has higher performance and stability requirements for the engine,which brings great challenge to the development of new engine.Tip clearance is an important parameter affecting the safety and stability of engine performance,and the research on its measurement technology is important for the development of new engine.Therefore,in order to improve the engine performance and stability,and promote the further development of aerospace industry,it is of great significance to study and improve tip clearance measurement technology.A new method for measuring tip clearance based on AC discharge plasma is presented,the method allows non-contact measurement without affecting the original structure of the engine.The discharge probe used in the measurement system is small,which is easy to install,and can work normally in the harsh environment of the engine.In order to verify the applicability of this method,the following research work has been carried out in this article.Firstly,the basic concept of gas discharge plasma and the motion process of charged particles in the gas discharge process are introduced in the article.By three kinds of classical gas discharge theory,the linear relationship equation between the gas breakdown voltage and the discharge gap is deduced under the standard atmospheric pressure,which verifies the feasibility of the proposed tip clearance measuring method based on the AC discharge plasma,and provides a theoretical basis for the establishment of measurement system.Secondly,the development of numerical simulation of gas discharge and three common numerical simulation methods are introduced,and a more mature fluid dynamic model is established by the software Comsol Multiphysics.The simulation results show that there is a linear relationship between breakdown voltage and discharge gap,which indicates the correctness of the theoretical analysis of the measuring system and the reliability of the proposed method.The influence of different pressure,temperature and power frequency on the system model is studied by simulation.The simulation results show that with the increase of air pressure,the breakdown voltage increases.the higher the temperature,the lower the breakdown voltage.the higher the frequency of the power supply and the lower the breakdown voltage.The influence of different parameters on numerical simulation results is studied by simulation,which provides an important reference value for the establishment of experimental platform of measurement system.Then,an experimental platform based on AC discharge plasma tip clearance measurement system is built,and the influence of different probe materials,the structure of the probe and the change of temperature and humidity under atmospheric pressure on the measurement results of the system is studied.The results show that the discharge probe of tungsten copper material has the dual characteristics of high temperature resistance and easy breakdown,which is more suitable as a discharge probe material,and the breakdown voltage of the tip structure is lower,however the electric field between the probe tip and the blade is very uneven,which leads to the high breakdown voltage fluctuation and effects the accuracy of the measurement results.The influence of temperature and humidity changes on tip clearance measurement under atmospheric pressure is negligible.Finally,the calibration of the relationship between the tip clearance and the breakdown voltage,the measurement of the tip clearance and the error analysis of the measurement results are carried out on the experimental platform of the tip clearance measuring system.The results present that there is a high degree of coincidence between the measured value and the actual value.The error of the measurement results is within ±0.05 mm,and the error of most of the measured values is below ±0.02 mm.From this we can find that the initial design of the measurement system has high measurement accuracy and strong applicability. |
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