A study of oil consumption on a diesel engine with independently lubricated turbocharger

摘要

The present work aims at deepening the phenomenon of oil consumption, paying particular attention to the study of oil consumption contribution deriving from turbocharger. In order to evaluate the quantity of oil that leaks from turbocharger oil seals, it was necessary to design a turbocharger lubricating oil system that is totally independent from the main lubricating circuit. The oil consumption from both turbocharger and engine was measured with gravimetric method. A Mercedes OM364LA medium-duty diesel engine was run at maximum power output for more than 300 hours. Different lubricating oils were alternated in order to evaluate the influence of some lubricating oil parameters on oil consumption, while a reference oil was tested at different times to estimate the oil consumption trend during life for both engine and turbocharger. In particular three oil parameters were considered: SAE grade (5W-30 vs 10W-40), basestock nature (mineral versus synthetic) and viscosity index improver nature (Olefin versus styrene-isoprene copolymers). The results of the experiment pointed out a turbocharger contribution to the total oil consumption ranged between 20% in the initial part of the experiment and 5% in the final part. The percent decrease over the entire test duration was due to a reduction of turbocharger absolute contribution, probably related to an improving performance of oil seals after running-in, and to a large increase of total engine oil consumption because of an arising bore- polishing of cylinder liners. A significant influence of basestock nature on turbocharger oil consumption emerged: a 25% reduction of turbocharger contribution occurred when synthetic basestocks were used. The reason for this seems to be the lower volatility of synthetic basestocks compared to the mineral ones. No significant influence of viscosity emerged.