Time-varying dynamic characteristic analysis of journal–thrust coupled bearings based on the transient lubrication considering thermal-pressure coupled effect

This work studied the time-varying dynamic coefficients of journal–thrust coupled (JTC) bearing within a diesel engine crankshaft system. A transient thermoelastohydrodynamic coupled lubrication model of JTC bearings was established by considering pressure, flow, and heat continuity conditions at journal–thrust interface. On this basis, the dynamic coefficients of three degrees of freedom were further calculated. A transient lubrication experiment was conducted on a test rig to validate the established model. Parametric analysis was conducted to explore the transient lubrication performance and the dynamic coefficient of JTC bearing under different input parameters. Moreover, for cases when the crankshaft undergoes large axial movement, the influence of the JTC bearing dynamic coefficients on the natural characteristics of crankshaft were further analyzed to provide an analysis method for crankshaft vibration characteristics.