Research on lubrication performance and dimensional tolerance of engine main shaft journal bearings based on oil film formation ability

Purpose This study proposes a dual-threshold tolerance optimization method for bearing dimensions based on the oil film formation capability, aiming to address the lubrication failure issue of sliding bearings caused by improper clearance design. Design/methodology/approach In this study, by adopting the finite element method based on the Reynolds equation and taking into account the influence of contact pressure during the operation of journal bearings, the lubrication characteristics of engine main shaft journal bearings under the working conditions of different loads and rotational speeds are systematically analyzed, and the tolerance zone range is optimized based on this analysis. Findings Excessively small clearance leads to a sharp increase in fluid shear resistance and an abnormal rise in torque; huge clearance weakens the hydrodynamic effect, promotes the transition of the lubrication state to mixed lubrication, causes a significant increase in contact pressure and intensifies the wear risk. Based on this, a dual-threshold tolerance optimization method is proposed: the convergence point of torque variation with clearance is taken as the lower tolerance limit, and the final zero point of contact pressure is taken as the upper tolerance limit. Originality/value The tolerance design method and determined tolerance range proposed in this study provide a theoretical basis and practical guidelines for optimizing the design of journal bearings and improving their lubrication reliability and service life. This method can be popularized and applied to the bearing tolerance design of other heavy-load, high-speed key equipment.