Soot emission of a CI engine fueled with various PRF/oxygenate blends

Due to the increasingly stringent regulation of particulate matter (PM) emission, research of soot emission characteristics of diesel engines has been a hot topic for years. One of the methods to suppress soot formation is the use of oxygenated fuels. Numerous previous studies have reported that the reduction of PM emissions depends both on the overall oxygen percentage of the fuel and on the molecular structure of blended oxygenates. The effect of molecular structure has sometimes been attributed to differences in auto-ignition quality. This paper reports on tests of soot emission on a modified in-line 6-cylinder DAF HD Diesel engine with several selected oxygenates mixed with PRFs (i.e. different mixtures of n-heptane and iso-octane). In order to isolate the effect of molecular structure, the blend compositions are chosen such, that both the overall oxygen fraction and the auto-ignition quality of all blends are the same. Still, significant differences in soot propensity are observed.