Effects of Oil Groove Locations on the Performance of the Big End Bearing of a Medium Speed Diesel Engine

Elastohydrodynamic lubrication (EHL) analysis has proved to be an effective predictive tool in understanding the behaviour of dynamically loaded journal bearings in internal combustion engines. The allowance of the bearing surface compliance in the analysis gives rise to more realistic predictions of bearing performance. Recently, the use of such a predictive tool was extended to the lubrication of the connecting rod bearing of a medium speed diesel engine, results of which are reported in this paper. Efforts were concentrated on the understanding of the bearing oil feed groove upon bearing behaviour. The starting and finishing locations of the oil groove were varied over a wide range. It was found that the overall minimum oil film thickness was significantly reduced when the oil groove started before 45° bearing angle. The same was true if the finishing location of the groove was beyond the location of 300° bearing angle. In the oil groove region, the minimum oil film thickness occurs at the edges of the groove. Predictions correlated very well with wear patterns observed on the actual con-rod bearing after service.