Study on four degree of freedom operation characteristics of the water-lubricated bearing for energy recovery turbocharger

This paper studies the four degree of freedom (FDF) motion characteristics of water-lubricated bearings in energy recovery turbochargers. In response to the load imbalance at both ends of the water-lubricated bearing-rotor system, a numerical theoretical model is proposed that combines the Reynolds-averaged equation and kinetic equation to solve the FDF characteristics. The model is solved to examine the effects of load phase difference, radial clearance, and length–diameter ratio on the FDF motion of the water-lubricated bearing-rotor system, including locus, hydrodynamic force, and tilting torque. The results indicate that a greater load phase difference between the two ends of the shaft correlates with an increase in both the inclination angle of the shaft and the trajectory amplitude at its ends. With the radial clearance increasing, the hydrodynamic force and tilting moment generated by the water film will reduce, while the working area and trajectory amplitude will expand, but the eccentricity is relatively small. Increasing the length–diameter ratio will enhance the load-bearing capacity and tilt moment and increase the tilt angle and trajectory amplitude of the shaft.