| Aero-engine is known as "The pearl in the crown of modern industry",which is a comprehensive embodiment of national defense force.As one of the few countries in the world that can research and develope aero-engines independently.Due to its high working speed,large power,complex structure and light weight and heavy load,turbofan engines are easily affected by various loads,leading to prominent vibration problems.According to the research,vibration problem accounts for 70 percent of aero-engine failure.Therefore,it is of great significance to study the rotor dynamic characteristics of aero-engine.This paper,the commonly used rotor dynamics calculation methods of aero-engine are compared and analyzed.SAMCEF is selected to carry out dynamic calculation and experimental test on the simplified rotor-support-casing system.On this basis,to AЛ-31Ф turbofan engine simulation,both inside and outside double rotor structure to carry out the research on dynamic response sensitivity calculation,and dispersion.This paper studies from the following aspects:First of all,in this paper,a variety of commonly used finite element methods for rotor dynamics are introduced,and a typical drum-rotor system is taken as an example to verify the similarity between the results of finite element method with few degrees of freedom by MATLAB and commercial software ANSYS and SAMCEF.The error of critical speed and unbalance response is about 5%.The accuracy of the Matlab finite element method with fewer degrees of freedom is determined,which can be used to do the simulate calculation for the following complicated cases which cannot be conducted by commercial software.Secondly,the low-pressure rotor-support-casing system was taken as the research object.Finite element method and professional Rotor analysis software samcef and experimental method were used to get Rotor dynamic characteristics.The maximum error between the first and second critical speeds and mode shapes of the rotor system obtained by the two methods is 5%.The unbalance response characteristics of the rotor system obtained by the two methods are very close to each other.The reliability of the finite element method is also verified.Than,according to the Russian AЛ-31Ф turbofan engine,a simplified two-rotor-support system is established by using the dynamic similarity criterion.Critical speed and unbalanced response of double-rotor system are calculated and analyzed by finite element analysis software.The results show that the unbalanced response caused by the high-pressure rotor is greater than that caused by the low-pressure rotor.In the end,The concepts of unbalance response sensitivity and dispersion are proposed for a two-rotor support system.According to the response results of the same size imbalance occurring at different locations,the sensitivity of the high-pressure compressor disk is higher than that at other locations,and the sensitivity of high pressure compressor fulcrum is higher than that of other measurement points.Based on the idea of Monte Carlo random sampling,the dispersion of the unbalanced response is analyzed.The unbalanced quantity was distributed to each disk according to a certain weight ratio to simulate several actual unbalanced working conditions,the average amplitude of the low-pressure and high-pressure compressor fulcrum are 20μm,μm and μm respectively.The research results provide reference for the selection of dynamic calculation methods,structural design,dynamic balance and vibration control of complex rotor systems for aero engines. |
