Transient tribo-dynamic model for journal bearings during start-up considering 3D thermal characteristic

Abstract The study presents a transient tribo-dynamic model for journal bearings to reveal the mutual effect between the mixed thermoelastohydrodynamic (mixed-TEHD) performance and the journal dynamic behavior during start-up. In the developed model, the bearing shell, oil film, and journal are considered as a heat conduction coupling system, whose transient 3D thermal characteristic is determined by a general transfer equation. The established model is verified by comparing the numerical predictions, including the transient temperature distribution, maximum temperature, axis orbit and contact time, with the published results. The evolution of the mixed-TEHD performance during start-up is presented. And the impacts of the acceleration time, radius clearance and bearing shell thickness on the transient mixed-TEHD performance are evaluated. The simulation results indicate that the dynamic contact load during start-up may be underestimated when the thermal characteristic is absent. The simulation results also indicate that a maximum temperature can be observed before the hydrodynamic pressure is fully formed. Furthermore, the present study demonstrates that although a short acceleration time can reduce the asperity contact pressure, it leads to a relatively large temperature rise. The present study also demonstrates that a smaller radial clearance and a thinner bearing shell tend to generate a larger maximum temperature and thermal expansion, which leads to the increase in the risk of the thermally induced failure during start-up.