Tribo-dynamic modeling of main shaft journal bearings in wind turbines for improved startup and reduced friction wear

As wind turbine capacities increase, sliding bearings have been increasingly adopted for their cost-effectiveness and reliability. However, unsteady rotational speeds and complex main shaft motions under transient wind conditions often lead to inadequate lubrication and edge wear, thereby increasing the risk of bearing failure. Existing simulation models fail to simultaneously capture the multi-degree-of-freedom (DOF) dynamics of the main shaft, the tribological characteristics at the bearing interfaces, and the interactive effects among multiple bearings, thereby limiting a comprehensive understanding of the friction and wear mechanisms. To address this, a coupled tribo-dynamic framework for multi-bearing main shaft systems is developed, which fully accounts for the 6-DOF dynamics of the main shaft and the mixed elastohydrodynamic lubrication behavior of segmented bearing pads. Numerical results show that stochastic wind loads induce slow shaft rotation and significant tilting, which aggravate lubrication degradation. Increasing oil supply pressure improves lubrication performance and shaft acceleration, while appropriate pad-edge modifications mitigate localized contact, thereby reducing friction and wear. The proposed approach provides a systematic tool for evaluating friction- and wear-related risks and offers design guidelines to enhance the reliability of large-scale wind turbine bearings.