Research On The Dynamic Behavior Of A Rotor System Supported By Rolling Bearing With Squeeze Film Damper

Squeeze-film dampers(SFD)are commonly used to provide additional damping to the rotor-bearing system in order to reduce the system vibration mostly caused by the nonlinear motion and improve the system stability,which are widely applied in aero-engines,gas turbines and other industrial equipment.In this dissertation,the SFD is used to the rotor system supported by rolling bearings.The nine-degree-of-freedom mathematical model of the coupling rotor system with SFDs is established,and dynamic behavioral responses of the rotor system in normal and fault operation conditions are analyzed.The results show that key parameters such as the centralizing spring stiffness and radial clearance of the SFD and the surface damage of the rolling bearing directly affect the occurrence and duration of the nonlinear dynamic behavior of the system.The conclusions of this paper have important theoretical and engineering significance for realizing system vibration reduction and reducing the impact of faulty components on system operation.The main contents of this paper are as follows:(1)Considering the coupling effect between the rolling bearing and the nonlinear oil film force of the SFD,the transient dynamics model of single disc rotor system coupled with SFD without fault is established.The nonlinear oil film force model of the SFD adopts the Reynolds circumferential boundary condition.The contact force model of the rolling bearing considers the influence of inertial force and analyzes the contact force between the inner and outer rings of the bearing separately.The results show that the Reynolds boundary condition can accurately express the actual motion of the bearing shell compared to the traditional coordinated concentric circle assumption when studying the transient response of rotor system coupled with SFD.Besides,the four-degree-of-freedom bearing model is closer to the actual condition of the rolling bearing operated in the coupled system.(2)Considering the coupling effect between the surface damage of the rolling bearing and the nonlinear oil film force of the SFD,the transient dynamics model of single disc rotor system coupled with SFD under fault is established.The failure feature of the outer ring of the rolling bearing is considered and the related fault model is established in order to determine the crack path of the outer ring and obtain a rough surface curve.The results show that the establishment of a fault outer ring model of bearing has a practical significance for analyzing the influence of fault bearing on the vibration stability of coupling system.(3)The fourth-order Runge-Kutta method is used to solve nonlinear dynamic differential equations of the rotor system of with or without faults.In this paper,bifurcation diagram,Poincare map and orbit diagram are applied in studying the effects of rotor speed,structural parameters of SFD including centralizing spring stiffness and radial clearance on the nonlinear dynamic response of the rotor system.The results show that:(1)Regardless of the rotor operation,the application of SFD can improve the vibration stability of the coupling system.Especially when the rotor system runs at high speed,the SFD can effectively suppress the nonlinear vibration of the system.(2)The application range of centralizing spring stiffness of SFD at low speed is larger than that at high speed.When bearing failure occurs,the suppression effect of SFD on the nonlinear dynamic response of rotor system is weakened.(3)At low speed,the radial clearance of SFD in a certain range can reduce the bifurcation behavior of the system,but the effect is not obvious.As summation,this thesis provides theoretical basis for modeling and dynamic characteristics analysis of rotor system's nonlinear vibration,especially for dynamic characteristics analysis of rotor system considering bearing surface damage.