Study on the Lubrication Performances of Crankshaft Main Bearings in a 16V Marine Diesel Engine

摘要

As the key components of internal combustion engine(ICE), the crankshaft main bearings are used to support the crankshaft and connecting rod mechanism whose rotary motion realizes the energy conversion from heat energy to mechanical power in cylinder. The lubrication performances and wear life of crankshaft main bearings directly affect ICE working efficiency and reliability. Therefore, it is very important to study the lubrication performances of crankshaft main bearings. In this paper, a 16V marine diesel engine was studied. Based on the AVL-Designer software platform, a dynamic model of crankshaft and connecting rod mechanism and a hydrodynamic lubrication model of crankshaft main bearing were built. The numerical analyses were carried out on the lubrication performances of crankshaft main bearings under different speed conditions. The results were obtained, such as the external load, the maximum oil film pressure, the minimum oil film thickness, the relative eccentricity, the friction power loss of each crankshaft main bearing. The results showed that the maximum external load acting on the fifth crankshaft main bearing was the largest and the lubrication condition of the fifth crankshaft main bearing was the worst under different calculated speed conditions. Under rated speed condition, the maximum external load acting on the fifth crankshaft main bearing was the largest and was 31.17% larger than the average maximum external load of all nine crankshaft main bearings. As a result, the minimum oil film thickness of the fifth crankshaft main bearing was the thinnest, which was only 1.18μm and was 54.71% lower than the average minimum oil film thickness of all nine crankshaft main bearings. The minimum oil film thickness ratio was only 1.25. The minimum oil film thickness was much more thin in the circumferential direction from 170° to 230°, where the surfaces contact frequently occurred and the abrasion was unavoidable. The analytical results coincide considerably with the actual abrasion phenomenon in the fifth crankshaft main bearing.