Abstract
Fuel injection parameters such as fuel injection pressure (FIP) and start of main injection (SoMI) timings significantly affect the performance and emission characteristics of a common rail direct injection (CRDI) diesel engine. In this study, a state-of-the-art single cylinder research engine was used to investigate the effects of fuel injection parameters on combustion, performance, emission characteristics, and particulates and their morphology. The experiments were carried out at three FIPs (400, 700, and 1000 bar) and four SoMI timings (4 deg, 6 deg, 8 deg, and 10 deg bTDC) for biodiesel blends [B20 (20% v/v biodiesel and 80% v/v diesel) and B40 (40% v/v biodiesel and 60% v/v diesel)] compared to baseline mineral diesel. The experiments were performed at a constant engine speed (1500 rpm), without pilot injection and exhaust gas recirculation (EGR). The experimental results showed that FIP and SoMI timings affected the in-cylinder pressure and the heat release rate (HRR), significantly. At higher FIPs, the biodiesel blends resulted in slightly higher rate of pressure rise (RoPR) and combustion noise compared to baseline mineral diesel. All the test fuels showed relatively shorter combustion duration at higher FIPs and advanced SoMI timings. The biodiesel blends showed slightly higher NOx and smoke opacity compared to baseline mineral diesel. Lower particulate number concentration at higher FIPs was observed for all the test fuels. However, biodiesel blends showed emission of relatively higher number of particulates compared to baseline mineral diesel. Significantly lower trace metals in the particulates emitted from biodiesel blend fueled engine was an important finding of this study. The particulate morphology showed relatively smaller number of primary particles in particulate clusters from biodiesel exhaust, which resulted in relatively lower toxicity, rendering biodiesel to be more environmentally benign.
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