Thermomechanical Analysis and Lubrication Failure Mechanisms in High-Power Diesel Engine Main Bearings

The lubrication condition of the crankshaft main bearing is a critical factor in determining the operational stability and reliability of diesel engines. This study addresses the issues of bearing overheating and adhesion failure observed during the development and testing phase of a high-power density V6 diesel engine. Based on theories of flexible multibody dynamics and mixed lubrication, a numerical simulation model for main bearing lubrication was established. The model innovatively integrates the flexible deformation characteristics of the crankshaft, crankcase, and connecting rods, while incorporating the cavitation effect of the lubricant film to comprehensively simulate bearing lubrication behavior under actual engineering conditions. The simulation results indicate that significant stress concentration occurs at the fillet transition between the crank arm and the main journal of the first main bearing due to abrupt geometric changes. Additionally, as this bearing is located at the flywheel end of the crankshaft, it is subjected to greater inertial forces and alternating loads compared to the other bearings. The combined influence of these factors leads to a sharp increase in asperity contact pressure at the first main bearing, resulting in a dramatic rise in localized thermal load and ultimately causing severe ablation failure. This study not only reveals the underlying mechanism of main bearing failure but also provides important theoretical support for the design of high-reliability bearings.