Effect of close post-injection on particle size distribution in diesel engine

In this study, the effects of close post-injection strategies on particle size distributions and number concentrations in diesel engine are analyzed experimentally. The particle formation/oxidation conditions with different injection strategies were elucidated based on combustion analysis. One focus is the effects of post-injection fuel mass and interval on the total particle emissions. Two representative low and medium engine loads are chosen to perform the experiments. It was found that the optimal strategy for reducing particle emission is lower post-injection fuel mass with larger interval. Post-injection can only reduce particle emission effectively in higher load condition, while in lower load, post-injection only reduces nucleation particles notably. Combustion analysis showed that the post-injection lowered the incylinder temperature in the early stage and raised temperature in the later stage, therefore it reduced particle emission by promoting particle oxidation. NOx is also reduced as post-injection is adopted due to the lowered peak temperature. © 2016, Science Press. All right reserved.