The Numerical Experimentation And Analysis Of Dynamic Balance For High Speed Rotors

At present, the Micro-turbine engines have broad prospects of development and applications in many fields. The micro-turbine engine, with the features of small size, light weight and high-speed, is a kind of power equipment with high-energy density and high power-weight ratio.The certain kind of micro-turbine rotor researched is typical flexible rotor which works beyond of its second critical speed.However, there are many differences between it and generic flexible rotor since its working speed is 120000rpm.The micro-scale characteristic request high precision in processing and assemblage, also excellent vibration trait. Then it will be assured that turbine engine can work safely, stably and exactly.Hence it's necessary to process high speed dynamic balance for this kind of high-speed rotor.It is difficult to prepare the motor drive, bearings, signal acquisition and balancing quality evaluation for its high working speed.As it is difficult to establish the high speed dynamic balance bedstand,it is necessary to use finite element technology for virtual test simulation.This is helpfull for comprehension of turbine rotor dynamics and research of balancing technology with specific implementation plans.Based on the finite element software MSC.Marc, the finite element physical modeling of bearing-rotor systerm was established including the three-dimensional structure modeling, bearing modeling by the springs with stiffness and damping characteristics, material modeling with suitable characteristics. First the static natural vibration frequency and mode of this flexible rotor is calculated and then the rotor dynamic characteristics was inspected, including the characteristics of stress and strain, contact and the dynamic inherent vibration characteristics. The frequency of vibration under the dynamic state is dynamic frequency. According to calculations it is founded that the dynamic frequency is very obvious.It then concluded that when the working speed exceed 200 Hz, it is not be able to ignore the dynamic frequency factor.Through the specific analysis of the rotor's structure, the possible maximum unbalanced distribution of the whole structural components of rotor was estimated from its unbalanced factors.So 14 different kinds of unbalanced conditions ware summed up.According to its first and second mode,4 balanced surfaces and 6 virbration measuring points are selected and arranged.The influence coefficient method was used to dynamic balance calculation.The emulation of unbalanced conditions calculation and dynamic balance calculation concluded that this dynamic balance scheme can meet certain balanced requirements.Finally,with the feasibility analysis that low-speed test verify high-speed dynamic balance test,the practical low-speed bedstand was designed for real dynamic balance test to deduce the high-speed test and verify the numerical dynamic balance.