A tribo-dynamic model of coupled journal-thrust water-lubricated bearings under propeller disturbance

Abstract

The main purpose of this study is to develop a tribo-dynamic numerical model for coupled journal-thrust water-lubricated bearings (also referred as coupled bearings) used in rim driven thruster under propeller disturbance, in which the four degree of freedom (4-DOF) dynamic model of the propeller rotor is bridged with the transient mixed friction model of the coupled bearing. A validating experiment for the coupled water-lubricated bearing is performed to support the correctness of the developed tribo-dynamic model. In the model, the disturbing forces and moment caused by the propeller are calculated by the quasi-steady method. Based on the numerical study, the transient coupling effects between the dynamic characteristic of the propeller rotor and the mixed friction of the coupled bearing are revealed. Furthermore, parametric studies are carried out to identify the effects of the structural and working condition parameters on the tribo-dynamic responses of the coupled bearing. Numerical results indicate that disturbing moment leads to the increase in the transient contact force of the coupled bearing, and the coupling hydrodynamic pressure at the common boundary significantly affects the tribo-dynamic behaviors of the coupled bearing. Parametric studies demonstrate that there exists the optimal radial clearance and tilting angle to minimize the transient contact force of the coupled bearing during operation. In addition, numerical studies reveal that the propeller rotor mass is an important parameter affecting the tribo-dynamic responses of the thrust bearing.