Influence of chemical and physical properties of n-heptane and RME on combustion process in a compression ignition engine

Images of premixed combustion in the visible wavelength range were taken in a CR Euro 5 optically accessible compression ignition engine. The effect of fuel properties on combustion process was evaluated using commercial diesel fuel, as reference, rapeseed methyl ester (RME) and a paraffinic fuel, such as n-Heptane. The choice of monocomponent fuel, free of aromatic, allowed to analyze the contribution to soot formation with respect to European diesel fuel. The first soot occurs at same location for the analyzed fuels but at different time. Evaluation of the soot volumetric fraction was made during combustion for all the fuels. n-Heptane was the fuel which gave the lowest soot production in occardance with its better physical and chemical characteristics. The total amount of soot formed during the combustion of RME resulted to be intermediate between n-Heptane and diesel fuel.