Effect of pre-injection strategy on the reduction of exhaust emissions from n-pentanol/biodiesel engine

N-pentanol can be used as an additive component of biodiesel to achieve NOx and soot emission reductions while improving the low-temperature fluidity of biodiesel. This paper investigates the mechanism of pre-injection strategies (pre-main injection interval and pre-injection ratio) on the emission characteristics of n-pentanol/ biodiesel engines. It extends the study to investigate the effect pattern of pre-injection strategies on formaldehyde emissions. The results show that the emission characteristics of the n-pentanol/biodiesel engine can be effectively improved by using a pre-injection strategy compared to a single injection. With the pre-main injection interval increase, the in-cylinder combustion stability was improved, and the generation of NOx and soot was effectively suppressed. Compared to a single injection, a pre-main injection interval of 15 degrees CA resulted in a 15.38 % decrease in CA50 and an 18.32 % increase in IMEP. Meanwhile, the increase of the pre-main spray interval broke the trade-off relationship between NOx and soot, and when the main pre-spray interval was increased from 15 degrees CA to 30 degrees CA, Soot and NOx generation were reduced by 27.46% and 21.30%, respectively. As the proportion of pre-injection increases, the center of gravity of combustion is shifted forward, the combustion exotherm is more concentrated, and the soot emission is significantly reduced. When the percentage of pre-spray was increased from 0 % to 20 %, CA50 decreased by 19.23 %, IMEP increased by 1.32 %, and soot generation decreased by 61.02 %. When the proportion of pre-spray was increased from 15 % to 20 %, CH2O emissions were reduced by 14.81 %.