考虑轴承热弹变形的增压器转子临界转速分析

Analysis and Research on Critical Speed of Turbocharger Rotor Considering Thermoelastic Deformation of Floating Ring

针对不同入口油温下浮环轴承因受热变形而改变涡轮增压器转子系统振动特性的问题,提出从浮环轴承的热弹性变形角度研究高速涡轮增压器转子系统的临界转速变化规律。首先,实验测量3种典型入口油温下浮环轴承处的温度,基于热固耦合分析得到浮环轴承热弹性变形后轴承的内外间隙值,发现随着入口油温从20℃增加到70℃和120℃,内油膜间隙分别增大13%和31%,外油膜间隙分别减小7%和15%;其次,研究浮环轴承间隙与油膜动力特性系数间的关系,发现内油膜刚度和外油膜刚度都随着入口油温增加而减小;然后,基于有限元法构建了涡轮增压器转子系统动力学模型,采用瞬态升速分析得到转子系统临界转速,其与实验测试结果的误差仅为1.5%,表明仿真模型参数选取合理;最后,分析了3种入口油温下因浮环轴承发生热弹性变形而引发涡轮增压器转子系统临界转速变化的规律,发现随着入口油温升高,转子系统临界转速下降。该结论对高速涡轮增压器结构设计和故障诊断具有一定参考价值。

The floating ring bearing changes the vibration characteristics of the turbocharger rotor system due to thermal deformation at different inlet oil temperatures.This paper aims to study the critical speed change law of the high-speed turbocharger rotor system from the perspective of the thermal elastic deformation of the floating ring bearing.First,the temperature of the floating ring bearing at three typical inlet oil temperatures is experi⁃mentally measured.Based on the thermo-solid coupling analysis,the clearance value of the floating ring bearing after thermoelastic deformation is obtained.It is found that as the inlet oil temperature increases from 20℃to 70℃and 120℃,the inner oil film clearance increases by 13%and 31%,and the outer oil film clearance decreas⁃es by 7%and 15%,respectively.Secondly,the relationship between the floating ring bearing clearance and the dynamic characteristic coefficient of the oil film is studied,illustrating that the stiffness of both inner oil film and outer oil film decrease with the increase of the inlet oil temperature.Then,a dynamic model of the turbocharger rotor system is constructed based on the finite element method,and the transient acceleration analysis is used to obtain the critical speed of the rotor system.Calculated error compared with the experimental test is only 1.5%,indicating that the simulation model parameters are selected reasonably.Finally,the influence of the thermal elastic deformation of the floating ring bearing on the critical speed of the turbocharger rotor system is analyzed under three different inlet oil temperatures,and it is found that with the increased inlet oil temperature,the criti⁃cal speed of the rotor system decreases.This conclusion has certain reference value for the structural design and fault diagnosis of high-speed turbochargers.