Study on Characteristics of Multi-Point Support Bearings for Marine Ultra-Long Shafting Under Different Operating Conditions

Strong nonlinear coupling exists between shafting dynamics and bearing lubrication performance in ultra-long multi-support propulsion shafting systems of large ships. This coupling may lead to bearing load redistribution and local oil-film instability. Taking the propulsion shafting system of an actual ship as the research object, this study develops a coupled shafting–bearing quasi-static model. The model considers hull deformation and inertial loads induced by ship motion. A BP neural network is used to represent the nonlinear support characteristics of the bearings and improve the efficiency of multi-condition calculations. The results show that hull deformation and ship-motion accelerations change the bending state of the shafting and the relative position of the journals within the bearings. These changes significantly affect bearing loads, oil-film pressure, minimum oil-film thickness, and journal eccentricity. As the sea state becomes more severe, local bearing load concentration and oil-film deterioration become more pronounced. Some performance parameters may exceed their allowable limits. Bearings at different positions also exhibit different sensitivities to operating conditions and distinct potential failure modes. The proposed method provides a theoretical basis and engineering reference for bearing arrangement, shaft alignment, and safety assessment of ultra-long propulsion shafting systems under complex sea conditions.