Study on oil film stiffness and damping characteristics of grinding mill’s sliding shoe bearings under low-speed heavy-load conditions

Abstract

To investigate the dynamic stability of large grinding mills’ sliding shoe bearings operating under low-speed, heavy-load conditions, the kinetic model for the hybrid dynamic-static lubrication of multi-oil-chamber sliding shoe bearings was established in the current research. The influence of rotational speed, design clearance, width-to-diameter ratio, and deflection angle of hollow shaft on oil film characteristics was systematically simulated and analyzed. Using a full-scale 4-meter-diameter sliding shoe bearing test platform, the pressure distribution and film thickness of the oil film during mill operation were measured via multi-point array measurements. The validation results indicate that the maximum relative error between model predictions and experimental values is 7.07%, confirming the correctness of the numerical model. Simulation results indicate that within the rotational speed range of 5–15 r/min, oil film stiffness is primarily governed by the hydrostatic throttling mechanism, exhibiting significant ‘speed insensitivity’. Meanwhile, the damping characteristics are controlled by the squeeze film effect, surging to 1.15 × 10 8  N·s/mm at the extremely low speed of 5 r/min. The nonlinear effects of structural parameters and disturbance factors are elucidated. It was found that optimizing the width-to-diameter ratio from 0.21 to 0.25 could reduce the maximum oil film pressure by 26.7% and achieve a 14.1% damping gain. Notably, when the deflection angle of the hollow shaft exceeds 0.004°, causing a localized pressure surge and induces a ‘stiffness nonlinearity surge’.