Multi Body Dynamics Analysis Of Sliding Bearing And Gear Rotor System

Sliding bearing-gear rotor system is vital in many fields, such as the agricultural machinery industry, power industry, shipbuilding industry, vehicles, mining equipment, etc.The stiffness and damping characteristic of Sliding bearing is variable along the radial direction and the axial cross section length. The dynamic characteristic of the sliding bearing has a great influence on the dynamic characteristics of gear rotor system, the service life and the reliability. The dynamic characteristic including the sliding bearing joint of the gear rotor system is hotspot and nodus, it is necessary to study farther.In order to simulate the dynamic characteristic of the sliding bearing-gear-rotor system more effectively and realistic, on the basis of the theory of fluid dynamics, finite element and multi body dynamics, specific to the fluid dynamic, equivalent stiffness, damping of sliding bearing and the dynamic analysis of the sliding bearing-gear-rotor system,this paper has studied these aspect and achieved corresponding results as follow:(1) The analysis of fluid dynamic is the keypoint of the calculation of equivalent stiffness and damping parameters of sliding bearing. Based on the fluid mechanics theory, considering the bearing oil film turbulence, using fluid finite element analysis software, the model of sliding bearing with different boundary conditions was established. Contrast the different calculation methods of bearing oil film force, the most effective was chosen and obtains the characteristic of the bearing oil film and the law of the pressure of oil film influenced by inlet oil pressure, rotational speed and the gap ratio. The change of oil film pressure values becomes smoother with the high speed. The speed of the sliding bearing too low or too high makes the oil film phenomena. The broken area of oil film is closely to the rotate speed, inlet oil pressure and eccentricity ratio.(2) Based on the perturbation theory, combined with the dynamic mesh technique and the theory of two-phase flow, the equivalent stiffness and damping bearing was calculated by using the method of dividing the shaft into many sections. This paper has built the simulate model of multi section and multi conditions, the distribution law of radial equivalent stiffness and damping under different speed and different axial position were obtained, This will lay the foundation for the further research of the dynamic characteristics of sliding bearing-gear-rotor system. The result shows that the direct stiffness Kxx increases with the speed increased first decreases and then increases, direct stiffness Kyy with the speed increased first increases and then decreased; the cross stiffness Kxy and Kyx increases with the increase of rotational speed; the direct damping of Cxx and Cyy increased with the speed increase and then decrease; cross damping Cxy along with the increasing rotational speed increased toward the negative direction and then change positively; cross damping Cyx increased with the speed and then decreased after the increase in the negative direction.(3) Based on the multibody dynamics theory, considering the equivalent sliding bearing stiffness damping of the radial and axial joint under the multi section and multi condition, the dynamic simulation model of sliding bearing-gear-rotor system has been built by ADAMS.The dynamic characteristic of system under different condition was calculated. This paper has compared the calculation angular velocity value with its theoretical value, verified the validity of the calculation model and analysis results, compared and analysed the different of the system dynamic characteristic with the sliding bearing or not.