Nonlinear Dynamic Behavior Of Turbocharger Rotor-Bearing Systems

With the progress of society,turbochargers have been widely used in automobiles,ships and internal combustion engines.The key component of a turbocharger is a rotor system consisting of a turbine,an impeller,and a bearing.The reliability of the device is closely related to the rotor system.The reason why there are strong nonlinear dynamic characteristics in the rotor system is mainly because there are more nonlinear forces in the system,such as rubbing force,oil film force,eccentric force and so on.In a rotor system,weak changes in certain parameters tend to change the form of motion of the system.Therefore,a reasonable choice of parameters can ensure the smooth operation of the rotor.In this paper,the bearing rotor system of a turbocharger is used as a research object.The effects of frictional force and nonlinear oil film force on the dynamic characteristics of the system are studied.First of all,in order to study the impact of rubbing force on the system,according to the theory of rotor dynamics,it is simplified to a rigid-supported double-disc rotor system model,and the differential equations of motion are established based on full consideration of the rotor gravity and eccentric forces.Perform dimensionless processing.Secondly,in the study of the interaction between the film force and frictional friction force,the turbocharger is simplified to a double disk bearing rotor system model supported by a sliding bearing;Finally,the two models were qualitatively analyzed and quantitatively analyzed.For the two-disk rotor system model,the nonlinear behavior of the system caused by local rubbing is studied.The fourth-order Runge-Kutta method with variable steps is used to solve the system equations numerically.Nonlinear analysis methods such as time history diagram,phase diagram,axial trajectory map and Poincare cross-section map were used to analyze the bifurcation evolution of the response of the turbocharger bearing rotor system with parameters during rubbing.For the double-disk bearing rotor system model,under the coupling of frictional force and nonlinear oil film force,the cycle,quasi-periodic,double-period bifurcation,double period bifurcation and chaos of the turbocharger rotor system are analyzed.For nonlinear dynamic behavior,the effects of rotor system parameters: frequency ratio,friction coefficient,eccentricity,stiffness coefficient,and damping coefficient on the periodic and chaotic motion of the rotor system are discussed.Through the above dynamic analysis of the rotor system,it provides some theoretical references for turbocharger design.