Research On Coaxiality Measurement Method Based On Vector Projection For Multi-stage Rotor

Coaxiality measurement method of multi-stage rotor is an important technology for high precision assembly measurement and position error adjustment in the combined rotor assembly for aero-engine high-pressure compressor with some advantages of fast measurement,high precision measurement,assembly guidance,low cost and so on.It is widely used in precision coaxiality measurement and multistage rotor assembly for aero-engine and other scientific researches.The assembly quality is decided by the coaxiality measurement precision for the multi-stage rotor,and then affect the vibration strength when the engine works at high speed.The multistage rotor of aero-engine is assembled by the rabbet,resulting in the coaxiality measurement section is covered and can not be measured by traditional method.Therefore,the problem of the coaxiality measurement is the main obstacle of improving the assembly quality for multi-stage rotor of aero-engine.The research of the paper is aimed at the problems of the coaxiality can not be measured directly and low adjustment accuracy in the multi-stage rotor assembly for aero-engine.The geometrical model is researched and used to analyze the vector projection characteristic of location and orientation errors for single-stage rotor in the multi-stage rotor assembly.The cumulative distribution function of eccentricity vector for each stage rotor is obtained to measure the coaxiality of multi-stage rotor.The circular profile measurement model and filter technology are also proposed to improve the measurement accuracy of eccentricity vector for single-stage rotor to increase the precision of the multi-stage rotor assembly.The main researches of the dissertation are described as follows:Firstly,the coaxiality measurement method based on the vector projection theory is proposed to solve the problem that the coaxiality cannot be measured directly and the low precision assembly for multi-stage rotor of engine.The assembly model is proposed based on the principle and process of multi-stage rotor assembly for aeroengine.The spatial distribution of the eccentricity vector accumulation can be obtained by analyzing the propagation of location and orientation errors in the multistage rotor assembly,and then establish the relationship between the location and orientation errors of each stage rotor and the coaxiality of multi-stage rotor.The coaxiality measurement and assembly adjustment methods are derived by using the objective function with the assembly phase difference as the variable.It can be seen from the experiment that the coaxiality of multi-stage rotor can be obtained and optimal by controlling the phase of single-stage rotor.Secondly,the circular profile measurement model with four bias errors is established to solve the problem that the concentricity measurement with low accuracy for single-stage rotor of aero-engine,which takes eccentricity,probe offset,radius of tip head of probe,and tilt error into account.The relationship between four bias errors and radius of component can be obtained by analyzing the influence of each bias error on the components with different radii for circular profile measurement.Besides,the error separation method based on the circular profile measurement model is proposed.It can be seen from the experiment that,when the eccentricity is 25μm,compared to the results by using the Limacon model,the concentricity measurement accuracy is improved 0.6μm by using the proposed model for the component radius of 11.1mm.Thirdly,the filter with non-uniform sample angle is designed to solve the problem that filtering with low precision for single-stage rotor of aero-engine,which based on the proposed circular profile measurement model with four bias errors.The distribution with real sample angle is obtained by analyzing the sample angle deviation caused by the four bias errors.The Gauss filter with non-uniform sample angle is designed from the analysis of mean line filter technology.It can be seen from the experiment that,compared to the results by using the Gauss filter with uniform sample angle,the eccentric angle measurement accuracy is improved 5.2° by using the proposed Gauss filter for the component radius of 10.5mm.The morphological filter with non-uniform sample angle is designed from the analysis of envelope filter technology.It can be seen from the experiment that,compared to the results by using the morphological filter with uniform sample angle,the eccentric angle measurement accuracy is improved 5.8° by using the proposed morphological filter for the component radius of 10.5mm.Lastly,the unit experiments of circular profile measurement and filter for singlestage rotor are set up under the situation of four bias errors at different levels.Besides,the unit experiment of coaxiality measurement and assembly adjustment is set up for multi-stage rotor.At the same time,the comprehensive experiment of coaxiality measurement and assembly adjustment is set up for multi-stage rotor to verify the proposed methods.It can be seen from the experiment that,compared to the results by using the direct assembly method that the bias errors without eliminating,as the level of the bias errors increases,the coaxiality accuracy is improved 69% by using the proposed methods for multi-stage rotor.The uncertainty evaluation report is obtained and the results show that the coaxiality and coaxiality of the expanded uncertainty are 37μm and 4μm(k=2),respectively,which is measured at the height range of 600mm.