椭圆轴承-转子系统的稳定性与分岔

Stability and bifurcation of elliptic bearing-rotor systems

针对200 MW汽轮发电机组轴系,建立了椭圆轴承-转子系统的动力学模型和椭圆轴承油膜力非线性模型.利用固定界面模态综合法将608个自由度的非线性动力学系统降至30个自由度,然后采用Rouge-Kutta法对降维后的模型进行数值求解,得到随转速变化的频响曲线、分岔图和三维谱图,并据此分析系统的稳定性.利用转速变化的频响曲线,分析了偏心距、润滑剂黏度系数和轴承长径比等参数对系统动力特性的影响.数值结果表明:椭圆轴承-转子系统的稳定性区域要大于圆轴承?转子系统的稳定性区域.

The nonlinear dynamic behavior of elliptic bearing-rotor system was investigated by working on 200 MW steam turbine as an example. The finite element method was employed to establish a dynamical model of the system and a nonlinear model derived from the variational principle was adopted to describe the oil force of elliptic bearings. Then, the nonlinear dynamic system with 608-degree-of-freedom was reduced to a 30-degree-of-freeodm model in terms of the fixed interface mode synthesis method. The Rouge-Kutta method was employed to solve the reduced model numerically, and the frequency-response curve, the bifurcation diagram, and the three dimensional spectral plot obtained were used to analyze the stability of the rotor-bearing system. The effects, on the dynamic behavior of the system, of the eccentricity, the oil viscosity and the length-to-diameter ratio of bearing were discussed in terms of the frequency-response curve. The numerical results show that the stability range of the elliptic bearing-rotor model is larger than that of the circular bearing-rotor system.