Transient lubrication model for inclined hydrodynamic bearing considering gyroscopic effect

The dynamic behaviors of hydrodynamic journal bearings can be influenced by several coupling factors, including cavitation, elastic deformation, surface asperity, and even electromagnetic fields in systems. In this study, we establish a transient lubrication model to investigate the dynamic lubrication process of journal bearings, fully considering these physical phenomena in the application of micropumps. Rotor trajectory measurements are conducted to validate the proposed model, which results in an error margin of less than 9.6%. Furthermore, the tribodynamic responses of hydrodynamic journal bearings are analyzed theoretically under various operational conditions, such as start-up, shock loading, and speed variation. The variation in the flow field from the mixed-lubrication regime to the hydrodynamic lubrication regime is investigated and qualified during the start-up stage. The analytical model enables the prediction of the transient lubrication performance under various load conditions, such as sharp shock, helping verify the design effectiveness of the journal bearing. Additionally, the dynamic relationships between the motion parameters and forces are demonstrated and compared. Our findings indicate that the gyroscopic torque can suppress the deflection of the rotor and that the hydrodynamic force can inhibit the rotor’s radial displacement, thus maintaining the rotor’s dynamic stability. The methods proposed in this work are instructive for the theoretical modeling and optimization of inclined journal bearings.