Calculation And Simulation Of The Hybrid Bearings Nonlinear Centre Trajectory

The journal centre motion trajectory reflects the working condition of the bearing. Based on the research of the journal centre motion trajectory, we can determine the bearing rotation accuracy and minimum oil film thickness, we can judge the stability of rotor and the rationality of the bearing design parameters. By using Hybrid Bearing Active Control Technology, journal centre doing predetermined elliptical motion can be achieved, and we can also achieve the machining of Non-circular complex parts. So we take the four oil cavity Hybrid bearings with the oil grooves as the research object; calculated the oil film pressure distribution and non-linear journal centre motion trajectory of Capillary restrictor under the certain conditions; and researched the influence of the rotor speed, oil pressure, bearing radius clearance for non-linear journal centre motion trajectory, the author also calculated the variation of non-linear journal centre motion trajectory under dynamic loading,and simulated the vibration experiment of the journal centre motion trajectoryFirstly, the Hybrid Bearing mathematical model is established. Using the finite difference method, calculate the hybrid bearing of capillary throttling oil film pressure distribution by the Reynolds equation and flow equilibrium equations. The equation of motion of the rotor-bearing system is established, which is based on the nonlinear oil film force, journal inertial force and dynamic load. The nonlinear journal centre motion trajectory is calculated by using the Euler method. In order to compare the nonlinear model with the linear model, we established the linear model; calculated the stiffness and damping coefficients using finite difference method and calculated the linear journal centre motion trajectory which is eddy’s moving near the equilibrium position for small displacement by using the oil film force linearization method.Secondly, nonlinear journal centre motion trajectory is calculated under different speed, different oil pressure and different bearing radius clearance. We also analyzed their influence on journal centre equilibrium position, and calculated the critical speed of the bearing system.Thirdly, we researched change rule of nonlinear journal centre trajectory, nonlinear journal centre trajectory displacement, the maximum film pressure and minimum film thickness under step load, rectangular pulse load, sinusoidal pulse load over time. Step load makes the journal centre converge to a new equilibrium position. Because of the short time of rectangular pulse and the sinusoidal pulse to the journal, the journal centre motion trajectory will still converge to the original equilibrium position with the load disappearing.Finally, taking the Hybrid bearing system as the research object, system dynamics process and the resonance phenomenon are studied under sinusoidal excitation force. We simulated the system’s amplitude-frequency characteristics and obtained amplitude-versus-frequency curve and the resonance frequencies using MATLAB under virtual sinusoidal force.