A study of the tribo-dynamic behavior of worn water-lubricated bearings during the start-up process

Abstract Water-lubricated bearings (WLBs) have gained extensive application as support bearings in marine propulsion systems owing to their environmental compatibility and elimination of oil leakage risks. However, prolonged operation of WLBs inevitably leads to wear of the friction interface, consequently altering the bush profile. Given that the transient characteristics of WLBs are highly sensitive to variations in bush profile, such wear-induced modifications inevitably induce significant changes in the transient trio-dynamic behaviors of WLBs, particularly during the start-up phase. This study investigates the impact of wear parameters on the dynamic characteristics of bearings by developing a mathematical model for the transient startup of worn WLBs. A comparison of the calculated data with the relevant experimental data confirms the validity of the model. Simulation results reveal that increased wear depth facilitates more rapid attainment of maximum hydrodynamic force in WLBs. However, when wear depth exceeds the optimal value (corresponding to a dimensionless wear depth of 0.1 in this study), the achievable maximum hydrodynamic force is significantly reduced. Specifically, the maximum hydrodynamic pressure decreased from 2.3 MPa to 1.375 MPa, representing a 40% reduction. Furthermore, both positive and negative wear deviation angles were found to adversely affect bearing startup performance. Optimal start-up characteristics were observed at a wear deviation angle of 0°. These findings provide valuable theoretical insights for the structural design and performance optimization of water-lubricated bearings in marine applications.