SOF Component of Lubricant Oil on Diesel PM in a High Boosted and Cooled EGR Engine

The engine in the research is a single cylinder DI diesel using the emission reduction techniques such as high boost, high injection pressure and broad range and high quantity of exhaust gas recirculation (EGR). The study especially focuses on the reduction of particulate matter (PM) under the engine operating conditions. In the experiment the authors measured engine performance, exhaust gases and mass of PM by low sulfur fuel such as 3 ppm and low sulfur lubricant oil such as 0.26%. Then the PM components were divided into soluble organic fraction (SOF) and insoluble organic fraction (ISOF) and they were measured at each engine condition. The mass of SOF was measured from the fuel fraction and lubricant oil fraction by gas chromatography. Also each mass of soot fraction and sulfate fraction was measured as components of ISOF. The experiment was conducted at BMEP = 2.0 MPa as full load condition of the engine and changing EGR rate from 0% to 40 %. In the case without catalyst, the soot fraction has a tendency of increase with increasing EGR rate, especially over 30% of EGR rate due to in-cylinder oxygen concentration decreasing. In the case of low soot concentration at 30% or lower EGR rate condition, the large quantity of fraction in PM is due to lubricant oil. The fraction due to unburned fuel is small quantity and the sulfate fraction is also small quantity of total PM fractions in comparison with the previous regulation. The experiment also conducted with oxidation catalyst. Exhaust gas emissions and fractions in PM were measured before and after oxidation catalyst. SOF has the tendency of decrease by oxidation catalyst and especially SOF of lubricant oil origin is reduced greatly. On the contrary soot and sulfate are hardly changed by oxidation catalyst.