Abstract
KEYWORDS: Soot in oil, Diesel Engines, EGR, Lubricant Oil, CFD
ABSTRACT
The mechanisms of soot transfer to the lubricating oil in light-duty diesel engines with high pressure EGR systems have been investigated. The rate of accumulation of soot-in-oil determined by the thermogravimetric analysis of oil-change samples from 15 engines was approximately 1%wt per 15,000km. Sixteen engine conditions covering a range of brake loads, speed and EGR rates were investigated using the CFD code Kiva-3V. The influence of EGR on In-cycle production of soot and the reintroduction of some of this to the combustion chamber with EGR as Re-cycled soot contributions is investigated. Examining the relative importance of near –surface transport of soot by thermophoresis to the liner and from blow-by gases to surfaces in the ring pack shows the former to be the dominant mechanism of soot transfer. EGR increases the rate of deposition of soot on the liner by both increasing net production of soot and, through re-cycling, the concentration of soot near the wall. At EGR levels greater than 20% the contribution of the re-cycled soot becomes the major source for soot-in-oil.