Investigation of bioethanol low-carbon fuel for diesel engines under idling conditions: Combustion, engine performance and emissions

In this study, the low idle operation is defined as the engine running at the lowest engine speed with a few slight loads. Idling is necessary for most vehicles, especially for buses and trucks that frequently travel long distances, as drivers often rest inside the vehicle. However, under idling conditions, weak air flow and low air-fuel ratio result in poor air to fuel mixture, ultimately causing incomplete combustion and the production of more harmful exhaust emissions. Bioethanol, as a low-carbon fuel, has great potential for application in diesel engines due to its unique properties. In this research, the influences of different diesel-bioethanol blends (BE0, BE5, BE10, BE15) on combustion and emissions of a diesel engine were investigated under idle conditions. The main results show that there was no phase separation phenomenon even up to 15% bioethanol was directly blended with diesel by volume. And adding bioethanol to diesel had no significant impact on combustion pressure peak, but it postponed the start of combustion (SOC). Surprisingly, the nitrogen oxide (NO_x) and smoke were simultaneously decreased by over 52% and 78% with the intervention of bioethanol, respectively.