Bending vibration of an automotive turbocharger under the influence of rotor imbalance

As one of the most common faults, rotor imbalance in a turbocharger will give rise to the bending vibration, which may cause damages to and even destroy the bearings and impellers. Therefore, it is necessary to detect rotor imbalance as early as possible. The present paper develops a mathematical model for investigating the rotor dynamic characteristics of a commercial automotive turbocharger supported on floating ring bearings. In order to reveal the behaviours of oil film instabilities the model takes into account nonlinear hydrodynamic oil film forces instead of linearization. A twodimensional elastic collision model is introduced to deal with the rub-impact process between such solid parts as journal, floating ring and the bearing. In addition, the change of clearances in floating ring bearing due to temperature increases are also estimated by ignoring the variation of lubricating oil viscosity. Following model development, a numerical simulation is implemented to study the bending vibration of the turbocharger and floating ring bearing under the influence of rotor imbalance. This study paves a foundation for the monitoring of turbochargers.