Study On Nonlinear Dynamics Of The Low-Pressure Rotor-Bearing System Of 200MW Turbine Set

For a large-scale high-speed rotor-bearing system, the oil-film force of sliding-bearing may cause oil-film instability of the system, which has great impact on accident prevention and safety operation. The practical rotor-bearing system is of high dimension and strong nonlinearity, so it is difficult to analyze it directly. Considering the local nonlinearity of the rotor-bearing system, a systematic dimension reduction method is applied in this paper for low-pressure rotor-bearing of the 200MW turbine set system. The model of the rotor-bearing system is established by FEM(Finite Element Method). The fixed-interface component mode synthesis procedure is applied to significantly reduce the dimension of the system. After reduction, the effective numerical method is adopted to explore the response and stability information of the system, and the state of motion and type of the bifurcation are analyzed by Floquet theory.First, the nonlinear dynamical model of the low-pressure rotor-bearing of the 200MW turbine set system is established by FEM, by the fixed-interface component mode synthesis procedure, the nonlinear dynamical model of the low-pressure rotor-bearing of the 200MW turbine set system is presented. The number of degrees of freedom is reduced sharply from 112 to 8, and the Runge-Kutta method is applied to solve the equation of motion. By the numerical calculation , the stability information of the nonlinear dynamical of low-pressure rotor-bearing system supported by column bearing is simulated separately during the speed ascending and descending process. The threshold speed and the typical characteristics of the oil whip of the system are simulated under the nonlinear model of oil film force, and the state of motion and type of the bifurcation are analyzed by Floquet multiplicators which is computed by the shooting method .Secondly, the the nonlinear dynamical model of the low-pressure rotor-bearing system by column bearing with reduced dimensions is presented. The numerical results show the rule of the amplitude with the eccentricity of rotor , the length-to-diameter ratio, oil viscosity and the clearance-to-radius ratio of the bearing under the definite speed . Based on the front journal of the generator, the...