Study on heat generation and dissipation characteristics of connecting rod small-end bearing in diesel engine

Abstract

Based on thermal-elastohydrodynamic lubrication and micro-convex peak contact theory, the calculation model of thermal-elastic fluid for connecting rod small-end bearing was established. The lubrication and friction characteristics of the small-end bearing were analyzed. The heat generation and dissipation mechanism and heat distribution rule of small-end bearing were obtained. The effect of cylinder pressure, rotation speed and roughness of small-end bearing surface on heat generation and heat transfer was discussed. The results show that the connecting rod small-end bearing is mostly in the state of mixed lubrication during the movement, and the heat is generated mainly through the friction on the bearing surface; the bearing mainly dissipates heat by means of heat conduction through small-end and piston pin. Piston pin and bushing accounted for 99.8% of heat dissipation, while the heat dissipation through lubricating oil out of bearing is relatively small. Cylinder pressure, rotation speed and roughness have great influence on the heat generation of the bearing. The increase of cylinder pressure will cause the total friction power loss of bearing increases. With the increase of rotation speed, the total friction power loss always increases after reduces. The increase of roughness also increases the friction power loss of bearing. The change of total friction power loss of the bearing mainly ranges from crankshaft angle 270°CA to 630°CA. Cylinder pressure, rotation speed and roughness have little influence on heat distribution rule of bearing. The increase of cylinder pressure and rotation speed is beneficial to the heat dissipation of lubricating oil, while the increase of roughness is not conducive to the heat dissipation of lubricating oil.