Application of bioethanol to advanced CI engines; dual fuel and RCCI combustion modes - a review

This review will be concentrated on the application of bioethanol to advanced CI engines. Among the several advanced CI engines, dual fuel combustion and RCCI engine are selected to discuss. In the dual fuel combustion with ethanol and diesel, fumigation and dual injection are only discussed. Most studies have shown that the main challenge in using bioethanol in DF mode is the considerable increase of HC and CO emissions, particularly at low load operating conditions. In DF combustion, it is clear from experimental and computational works than the PRR is significantly reduced by introducing the split injection, resulting in the decrease of knock intensity. In addition, diesel post injection or double injection as same as split injection was suggested to reduce HC and CO emissions. DF combustion with ethanol and diesel can be operated from low to high loads (0.2-1.95 MPa IMEP), particularly up to 2.2 MPa IMEP with E85, with very low NOx and soot emissions. The researches on the DF combustion adopted wet ethanol PFI and biodiesel produced from the inedible vegetable oils DI are required in the future. In RCCI combustion, double injection fueling strategy is the most commonly adopted for the diesel injection. It is composed of the early pilot at 60 CAD bTDC to raise the reactivity in the squish region and the second main injection at around 25-30 CAD bTDC to ignite the cylinder charge. The premixed ratios for RCCI with single injection and double injection were studied up to 80%, and 90%, respectively.