Numerical and experimental investigation on thermohydrodynamic performance of turbocharger rotor-bearing system

For high-speed rotor-bearing systems, mechanical performance is strongly coupled with thermal behavior. In this paper, experiments and numerical simulations are conducted to investigate the thermohydrodynamic (THD) performance of a turbocharger rotor-bearings system. The temperature of the lubrication system and the vibration of the rotor were predicted by numerical simulation and have been validated by experiment. Four subsynchronous frequencies were excited by inner and outer films. Three of them showed conical bending and one cylindrical. The results suggest that solid parts play a significant role in THD analysis, because the temperature fields of solid parts affect the oil film clearances by thermal expansion. The rotor transfers considerable heat from the turbine to the inner film, and then a great quantity of heat will continuously be transferred from the inner film to the outer film by rings. Moreover, three-dimensional transient thermal fields of oil films are proved essential for high-speed oil film bearings, for the temperature and viscosity distributions along the film thickness cannot be negligible. Since the undeveloped thermal boundary layers exist in the oil film, it may cause errors if simplified into a two-dimensional model with thickness-averaged temperature fields.