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Diesel fuel injection system is the most important part of the direct-injection diesel engine and, in recent years, it has become one of the critical technologies for emission control with the help of electronically controlled fuel injection. Common rail injection system has great flexibility in injection timing, pressure and multi-injections. Many studies and applications have reported the advantages of using common rail system to meet the strict emission regulation and to improve engine performance for diesel engines. The main objective of this study is to investigate the effect of pilot-, post- and multiple-fuel injection strategies on engine performance and emissions. The study was carried out on a single cylinder optical direct injection diesel engine equipped with a high pressure common rail fuel injection system. Spray and combustion evolutions were visualized through a high speed charge-coupled device (CCD) camera.

This paper has investigated the effects of High Pressure Loop (HPL) and Low Pressure Loop (LPL) Exhaust Gas Recirculation (EGR) gas mixture on combustion and emissions characteristics in a light-duty automotive diesel engine. This mixed supply strategy of dual-loop EGR is expected to be efficient for the reduction of NOxand smoke without the loss of turbocharger power. The results from the combined HPL and LPL EGR system were compared with those from only HPL EGR and only LPL EGR system respectively. Characteristics including temperature and mass flow rates of intake charge, air excess ratio, O₂ concentration in intake charge, difference in pressure between intake and exhaust, pumping loss, fuel consumption, CO, HC, NOx emissions, and smoke opacity were compared and analyzed at two operating conditions. Fuel consumption, NOx emission, and smoke were reduced with dual EGR mixture.