Towards a comprehensive understanding of mode transition between biodiesel-biobutanol dual-fuel ICCI low temperature combustion and conventional CI combustion - Part ΙΙ: A system optimization at low load

Abstract

This paper investigated the mode transition between ICCI low temperature combustion and conventional CI combustion with the parameters of energy ratio, intake temperature and engine load, and the control strategies were system analyzed to improve the smoothness during the mode transition process. Results shown that the direct mode switching from ICCI combustion to CI combustion (ICCI–CI) was suitable at low engine load, but the fluctuation of IMEP was higher when direct mode transition from ICCI to CI (ICCI–CI). Retarded the biodiesel injection timing to −38 oCA ATDC in the first transitional cycle could reduce the combustion instability. Biodiesel and butanol fuel compensation in the first cycle when the combustion mode switched to ICCI also could reduce the fluctuation of IMEP, and the corresponding fuel adjustment of biodiesel and butanol were relatively small, in which the increased fuel of biodiesel and butanol were 4.5%–11.1% and 2.6%–5.3%, respectively. The fluctuation of IMEP was higher when biodiesel compensation using two transitional cycles, that was not suitable for the smoothness of CI–ICCI mode switching process. However, the butanol compensation using two transitional cycles could enhance the combustion stability and reduce the fluctuation of IMEP during the CI–ICCI mode switching.