Analysis of Vibration of a Rotor-Bearing System Caused by Radial Clearance, Number of Balls and Rotor Speed

This article aims to study the effects of changes in internal radial clearance, number of balls and rotor speed on the vibration responses of a balanced rotor-bearing system. This rotor-bearing system is modeled and simulated using FEA software ‘COMSOL Multiphysics’. The rotor-bearing system consists of a rotor shaft and rigid disk, which are supported by two SKF 6205 bearings. Three levels of each factor are considered, i.e., three radial clearances: 1, 27 and 53 μm, three ball numbers: 6, 9 and 12 and three rotor speeds: 2800, 6500 and 10200 rpm. The mean displacement (MEANZ) and RMS velocity (RMSVZ) of the inner race center (IRC) in vertical direction (Z-direction) are used as output vibration responses. Full factorial design (FFD) and analysis of variance (ANOVA) are used for design of experiments and their analysis, respectively. Regression equations are prepared, and various plots are plotted using Design Expert software. The results show that MEANZ increases considerably with increase in radial clearance; however, it decreases slightly with increase in number of balls. But, MEANZ is not affected by the change in rotor speed. Also, the RMSVZ increases significantly with increase in radial clearance, increases slightly with rotor speed, and decreases with increase in the ball numbers. This study will enable vibration diagnostic experts to grasp the impact of three factors that lead to vibrations in the rotor-bearing system.