Investigation into particle emission characteristics of partially premixed combustion fueled with high n-butanol-diesel ratio blends

Based on a 4-cylinder turbocharged intercooler diesel engine fueled with n-butanol/diesel blends, this paper investigated the effect of various parameters on emissions under the early-injection partially premixed combustion (PPC) strategy and pre-injection PPC strategy. The potential for realizing PPC with different fuel reactivity and oxygen content was evaluated. The experimental results indicated that the peak value of heat release rate (HRR) increased and the heat release duration shortened after mixing the n-butanol under the same injection timing. The start of combustion (SOC) was advanced and the proportion of premixed combustion decreased as the growth of pre-injection ratio. The heat release process was delayed when the n-butanol ratio was increased. As the growth of n-butanol ratio, the peak value of the accumulation mode particles reduced and that of the nucleation mode particles increased sharply. The geometric mean diameter (GMD) of the particles was significantly reduced when the pre-injection timing was changed from −25 to −35° CA ATDC. As the growth of the pre-injection ratio, the GMD of the particulates had a tendency to decrease. Under the same pre-injection conditions, the total number and mass concentration of the particulates both reduced obviously with the increase of n-butanol ratio.