Effects of various split injection strategies on combustion and emissions characteristics in a single-cylinder diesel engine

The purpose of this study is to investigate combustion and exhaust emissions characteristics by applying various split-injection strategies in order to determine the optimal injection that improves fuel efficiency and reduces exhaust emissions, compared with single-injection combustion. The split-injection strategies, such as the change of injection pressure, injection timing, and injection interval, were applied to single-cylinder diesel engine. From the analysis of the experimental results, it was revealed that, when the injection pressure was increased without changing the injection timing in split injection, indicated mean effective pressure (IMEP) and brake mean effective pressure (BMEP) decreased and brake specific fuel consumption (BSFC) deteriorated, owing to the increase of dwell duration. The increase of injection interval induced deterioration of BSFC and caused an increase in NOx and HC emissions with significant reduction in CO and soot emissions. On the other hand, the retardation of injection timing with a fixed injection interval caused an improvement of the BSFC, and a decrease in NOx, CO, and HC emissions. However, soot emission increased. According to the analysis, a short injection interval and injection timing around top dead center (TDC), with not too high injection pressure, improve the BSFC and emission characteristics in split-injection diesel combustion.