Effect of rotor misalignment on stability of journal bearings with finite width

Abstract

The present work studies the dynamic response of fluid film bearing of finite length which is subjected to rotor misalignment. Vibration analysis of the rotor is used to obtain the limits of stability at different operating conditions. The lubricant flow in the bearing is considered laminar, incompressible and isoviscous. For a given small excitation of the bearing shaft, a time dependent Reynolds equation is introduced to investigate the dynamic response of the fluid film bearing. At a misalignment direction angle and misalignment degree, nonlinear perturbation dynamic equations are introduced and solved to determine the critical stability limit of motion for different values of eccentricity ratio. Vibration data is collected to obtain the transition from stable to unstable operating conditions (stability map). It is concluded here that increasing the value of misalignment degree yields to an increase in the value of critical bearing stability limit for a given value of misalignment direction angle. The critical stability number increases as the misalignment direction angle decreases and/or the steady state eccentricity ratio increases.

Keywords

• Journal bearings
• Sliding element bearings
• Dynamic behavior of bearings
• Stability analysis
• Hydrodynamic lubrication
• Misalignment of journal bearings