Simulating Friction Power Losses in Automotive Journal Bearings

Journal bearings are used in a large number of critical positions in automotive internal combustion engines (ICE) and contribute a major contribution to the total friction power losses in these engines. Due to the worldwide effort to reduce CO2 emissions, automotive manufacturers investigate the remaining potential for friction reduction also in the journal bearings, which leads to severe operating conditions due to the lower viscosity lubricants. At the same time modern ICEs utilize higher combustion pressures for increased thermodynamical efficiency, which imposes further stress on the journal bearings. These reasons motivate in addition the accurate and reliable simulation of the operating conditions and friction power losses in journal bearings.Within this work, the lubrication of journal bearings is investigated in detail starting from an extensive thermo-elastohydrodynamic (TEHD) simulation, which yields important insights into the thermodynamical behavior of journal bearings. From these results a powerful isothermal elastohydrodynamic (EHD) simulation model using a simple approach to calculate equivalent temperature is derived. The capabilities of the presented simulation methods are compared to extensive experimental measurements performed on a journal bearings test-rig, which show excellent agreement.