鼠笼局部断裂的刚度特性及其转子动力学特性分析

STIFFNESS OF SQUIRREL-CAGE WITH LOCAL CRACK AND DYNAMIC CHARACTERISTIC OF A RIGID ROTOR SYSTEM SUPPORTED BY CRACKED SQUIRREL-CAGE

本文针对带有局部断裂的鼠笼刚度特性以及其支承的转子系统动力学特性开展研究.首先基于力学分析推导了鼠笼局部断裂刚度理论计算公式.其次,基于带有局部断裂的鼠笼有限元模型进行其刚度计算,并采用最小二乘法对有限元刚度计算结果进行分析,提出了鼠笼局部断裂后的拟合经验刚度公式,通过对比分析得出局部断裂对鼠笼刚度特性的影响.最后,建立带有鼠笼局部断裂的两支点弹性支承转子系统的动力学模型,并仿真获得了带有鼠笼局部断裂转子系统的固有特性和振动响应的变化规律.结果表明:鼠笼局部断裂导致其刚度下降以及支承刚度不对称,引起转子系统临界转速下降,且水平、垂直振动有差异,轴心轨迹呈椭圆形.

The stiffness of a squirrel-cage with local crack was analyzed,and the dynamic characteristics of a rigid rotor system supported by the cracked squirrel-cage were studied.Firstly,the analytical stiffness of the cracked squirrel-cage was deduced by static analysis.And then the stiffness was predicted by employing the finite element method(FEM)for the cracked squirrel-cage with different cracked positions and different number of cages.According to the FEM results,a stiffness formula of the cracked squirrel-cage was obtained by use of the least squares fitting.To find out the effects of the cracked squirrel-cage on natural frequencies and dynamic characteristics,the theoretical model of the rigid rotor system supported by cracked squirrel-cages was established and simulated.The results show that,when the local crack appears on the squirrel cage,the stiffness of the support decreases,which leads to a decrement in the critical speed.Additionally,the cracked squirrel-cage also can cause a difference between the radial and horizontal stiffness,and thus results in elliptical orbit of shaft center.