Research On Turbine Blade Tip Clearance Test And Numerical Analysis

Turbine blade tip clearance is of great importance to the efficiency and security of aeroengine. The studies on some key technologies about numerical analysis andtesting of turbine blade tip radial clearance are carried out in this dissertation.Firstly the numerical simulation of the tip clearance is conducted by taking a low-pressure turbine engine as research object. The influences of centrifugal load and temperature load are considered, as well as the mathematical model of its starting process. A simulation method of the engine turbine blade tip radial clearance is put forward, which is applicable to all periods of starting process. The simulation results show that during starting process, the radial deformation of the casing and the blade is mainly affected by the temperature load,and the radial deformation of the roulette mainly depends on the centrifugal load. The comparison between the numerical analysis results and the engine manual data show apparent coincidence, which validates the correctness of the results of numerical analysis.Secondly the basic principles of eddy current sensor are studied. On the basis of the principle of eddy current and the theory of finite element modeling, 3D finite element model of eddy current is established. By comparing eddy current distributions of probe sensors with different shapes, the coil of probe sensor for tip clearance measurement is designed. According to the characteristics of the turbine blade tip radial clearance and the existing sensor measurement circuit, a new principle diagram of measurement circuit is designed.Finally an eddy current sensor is made on the basis of the designed measurement circuit and sensor probe. The experimental researches on both static and dynamic characteristics of the sensor are conducted. Least square linear fitting for the static calibration data is used, whose result shows that the designed sensor has better linearity between 2 ~ 11 mm. By using all the fitting methods, the result of gauss curve fitting coincides with the original data best. In order to conduct the experiment of dynamic measurement, a phonic wheel with variable gear teeth in height is designed to simulate the change of tip clearance. Circular calibration of sensor is carried out by using single gear teeth. The tip clearances are measured in situations of various rotational speeds. The comparison between measured data and calibration data indicates that the designed sensor is capable to the measurement of blade tip radial clearance.