Profile Design for Misaligned Journal Bearings Subjected to Transient Mixed Lubrication

Misalignment between the shaft and the bearing of a journal bearing set may be inevitable and can negatively impact journal bearing performance metrics in many industrial applications. This work proposes a convex profile design of the journal surface to help counteract the negative effects caused by such a misalignment. A transient mass-conserving hydrodynamic Reynolds equation model with the Patir-Cheng flow factors and the Greenwood-Tripp pressure-gap relationship is developed to conduct the design and analysis. The results reveal that under transient impulse loading, a properly designed journal profile can help enhance the minimum film thickness, reduce mean and peak bearing frictions, and increase bearing durability by reducing the asperity-related wear load. The mechanism for the minimum film thickness improvement due to the profile design is traced to the more even distribution of the hydrodynamic pressure toward the axial center of the bearing. The reason for the reductions of the friction and wear load is identified to be the decreased asperity contact by changing the lubrication regime from mixed lubrication to nearly hydrodynamic lubrication. Parametric studies and a case study are reported to highlight the key points of the profile design and recommendations for profile height selection are made according to misalignment parameters.