Analysis on Modeling Rotor System with Sidling Bearing and Ring Seal by Using FEM

Abstract

An Ultrahigh-pressure multi-stage centrifugal pump works in high speed, with a long shaft and featured in complex structure. To improve the safety and reliability of operations demanded in a high level, the Ultrahigh-pressure multi-stage centrifugal pump develops in the direction of large equipment and integration of pump and electromotor. Except that the hydraulics, structure and control of electric must fulfill the design requirements, the research on vibration characteristic and stability of the shafting areatter is also important. Those characteristics are of great impacts on quality, life and reliability of Ultrahigh-pressure multi-stage centrifugal pumps. Therefore, it is very important to do dynamic analysis for the rotor shafts of ultrahigh-pressure centrifugal pumps. In this paper, the problems of modeling steady rotor system with sliding bearings and ring seal by using Finite Element Method are discussed. Discussion is conducted on the film force of sliding bearings and the method of its application in modeling, as well as the method of simulating film stiffness. Radial stiffness and damping of the film are the important factors of dynamic characteristics of the rotor systems, however the circumferential stiffness and damping are both small and generally not considered. In this dynamics model, the assumption of a rotor system in static equilibrium position plus small disturbance of the film is used to calculate the incremental film force, and the dynamic characteristic of film. Aiming for Rotor- Bearing System for 3800kW EHV, multistage centrifugal pumps are built. In the simulation analysis, modal shapes and critical speeds of the rotor are calculated, and the stability of the rotor system is analyzed. The results show that the method is reliable and useful for the design of the structures and parameters of EHV multi-stage centrifugal pumps.