Abstract: The use of exhaust gas recirculation (EGR) is an effective way of achieving low temperature combustion (LTC) in diesel engines thereby enabling lower levels of the in-cylinder oxides of nitrogen (NOx) to be produced. In addition the fuel injection strategy used and the control of boost pressure are key aspects in attaining low NOx and soot emissions simultaneously. In the work reported in this paper, experiments were performed on an advanced testing engine platform which allows EGR, fuel injection timing and boost pressure to be precisely controlled and the influence of each parameter on the emissions to be studied independently. The results indicate that within the investigated LTC ranges, the ratio of EGR plays the most effective role in NOx reduction; the injection pressure and boost have a more modest effect on NOx emissions in general. Nevertheless, the increased injection pressure lowers the soot emission across the EGR sweep and the augmented boost reduces the soot significantly from a high soot level. It was also observed that with the high levels of the EGR, both the carbon monoxide and unburned hydrocarbon emissions increase. The effect is attributed to the reduced oxygen concentration and the lowered flame temperature.    

Key words: diesel engines, exhaust gas recirculation (EGR), boost pressure control, injection strategy, low temperature combustion (LTC), NOx and soot emission