Effects of mineral and biodiesel fuel compositions on spray evolution and mixture distribution

Experimental investigations on the fuel spray from a multi-jet common rail injection system both under non-evaporative and evaporative conditions have been carried out. Mineral diesel fuel, 1st and 2nd generation biofuels have been used. Non-evaporative system consisted of a high-pressure optically accessible cylindrical vessel while a single cylinder optically accessible diesel engine represented evaporative conditions. Soybean Methyl Ester (SME100), Rapeseed Methyl Ester (RME100), Gas To Liquid (GTL100) and their blends 50% in volume with reference fuel (SME 50, RME 50, GTL 50) have been tested in both systems. Engine operating conditions characteristics of Euro5 diesel engine have been analysed. Images of the spray evolution have been detected by high resolution CCD cameras, and synchronized with the fuel injection. The spray tip penetration, the contour plot and the liquid spatial distribution of the jets have been measured in order to determine the spatial and temporal distribution of the biofuels and to analyze the influence of different biodiesel fuels on the air-fuel mixture preparation. Images recorded in the non evaporating system show a negligible variation of the tip penetration for the different fuels. Nevertheless, a comparison of the tip penetration measured by means of the experimental data and Hiroyasu theoretical correlation has been made and showing very good agreements in both the systems. Finally, a different spatial distribution of the liquid fuel has been noted analyzing the luminous intensity spatial distribution along the jet axis with respect to the fuel and the investigation system.