Effect of Bioethanol on Combustion and Exhaust Emissions in a Diesel-Bioethanol Dual-Fuel Combustion Engine

The purpose of this study is to investigate the effect of the bioethanol port injection ratio and the in-cylinder diesel injection timing on combustion and exhaust emissions characteristics using a dual-fuel combustion strategy. Dual-fuel combustion was applied to a single-cylinder diesel engine with a displacement volume of 373.3 cm(3). In a diesel-bioethanol dual-fuel combustion system, there is no need for additives to solve any phase separation between diesel and bioethanol. The combustion and emissions characteristics were investigated through the study of the indicated mean effective pressure (IMEP), ignition delay, heat release rate, indicated specific nitrogen oxides (ISNOx), indicated specific soot (ISsoot), indicated hydrocarbon (ISHC), and indicated carbon monoxide (ISCO). It revealed that IMEP increased with increases to the bioethanol port injection ratio, and the effect of bioethanol on IMEP can be clearly observed in early injection timing. The rate of combustion pressure rise decreased with an increase of port injection ratio. The ignition delay increased with an increase of the bioethanol port injection ratio and with the advance of the in-cylinder injection timing. ISNOx and ISsoot emissions can be simultaneously reduced by a diesel-bioethanol dual-fuel combustion strategy because of the high latent heat and oxygen content of bioethanol. The ISHC and ISCO emissions in the dual-fuel combustion (DFC) generally increased with the port injection ratio. However, when the in-cylinder injection fuel flowed into the squish region, the ISCO emission decreased with an increase of port injection ratio due to the oxygen effect of bioethanol. (C) 2015 American Society of Civil Engineers.