Research On The Dynamics Of Rotor-Cylindrical Bearing System And Rotor-Elloptical Bearing System

For a turbo-generator sets rotor-bearing system, there is an important problem of the the rotordynamic characteristics influence by bearings, especially on the oil-film force of sliding-bearing which may cause oil-film whirl and whip instability of the system, it has great impact on accident prevention and safety operation. Hence, it crys for further research on non-linear dynamic characteristics and instable mechanism of rotor-bearing system and mastering influence the discipline between system characteristic parameter and dynamic stability. Because the Cylindrical sliding-bearing and elloptical sliding-bearing are two common bearings using in turbo-generator sets, it is necessary to compare and analysis the system characteristic influenced by these two kind of bearings.Firstly, the oil force models of cylindrical sliding-bearing and elloptical sliding-bearing are deducted in this dissertation. The model of the practical rotor-bearing system is established by FEM (Finite Element Method) and the rule of bearing stiffiness and damping coefficient changing with the increment speed of bearing is found.Secondly, the natural frequency, the normal mode shapes and the stability of the rotor-bearing system are investigated by Newmark direct numerical integration method. The process and characteristics of oil whirl and whip in rotor system are successfully simulated. The rule of the amplitude of rotor-bearing system with the changing of the eccentricity of rotor, the clearance of the bearing, the slenderness ratio, oil viscosity and ovality are presented using numerical results. The dynamic characteristic of rotot-bearing system sported by cylindrical sliding-bearing and rotot-bearing system sported by elloptical sliding-bearing are compared and analysed.Lastly, experiments are carried out to study the phenomenon of oil whip and oil whirl under the supporting of cylindrical sliding-bearing and elloptical sliding-bearing. The result illustrate the system oil-film instability discipline, get the conclusion through compare and anslysis of the two parts follows: one is the different system stable influence of the two different bearings, and the other is experiment and numerical simulation.The analysis results of this dissertation provides theory basis for nonlinear design of turbine sets.