Effects of Aromatic Components in Fuel on Flame Temperature and Soot Formation in Intermittent Spray Combustion

The effects of aromatic components in fuel on ignition and combustion of intermittent spray were examined experimentally. Four types of fuel with different aromatic components, and with similar cetane number and calorific value were used in this study. Fuels were injected into the high-temperature and high-pressure vessel with the injection pressures of 100 MPa and 60 MPa using an electronically controlled fuel injection system developed by the authors. Injection rate shaping applied to the experiments was rectangular, which is a typical injection rate shaping of a common rail type injection system. Images of spray flames were captured using an ICCD camera under ambient conditions corresponding to a turbo-charged diesel engine, 6.1 MPa and 1030 K. A two-color pyrometry technique was applied to the images of spray flame to quantify two-dimensional distributions of flame temperature and soot in flame.

Through systematic experiments, it was explored that the aromatic components have little effects on ignition delay and combustion period. However, the aromatic components have significant effects on flame temperature and soot formation. The flame temperature and the amount of soot in flame become higher as the aromatic components in fuel increase. The injection pressure has a great effect on spray combustion, i.e., shorter combustion period and rapid soot oxidization with high injection pressure. However the effects of aromatic components on combustion were not changed qualitatively by the increased injection pressure.