Optimization study on the lubrication performance of water-lubricated stern bearings with journal bending deformation based on axial end openings of power function curves

Abstract

To improve the lubrication performance of water-lubricated stern bearings under journal bending deformation, this study proposes a new axial opening structure based on a power-function profile. The design enlarges the bearing diameter near the rear axial end of the journal and introduces a curved opening that improves pressure distribution within the fluid film, thereby increasing the minimum film thickness. A shaft deflection equation under combined fluid film pressure and propeller load is derived using the displacement superposition method. Based on this, a lubrication model incorporating the proposed geometry is developed and numerically verified. The influence of key geometric parameters on bearing performance is analyzed. Results show that the optimized axial opening significantly increases the minimum film thickness and reduces the peak film pressure. In the studied case, the minimum film thickness improved from 8.91 μm to 49.91 μm. The proposed method offers a practical approach to enhance bearing reliability under deformation conditions through structural optimization.