The effect of a pine oil/diesel blend on the particulate emission characteristics of a diesel engine under a pre-injection strategy with EGR

Abstract

Pine oil is a clean alternative fuel with a high oxygen content that can effectively improve engine combustion and emissions. To further evaluate the potential of pine oil for emission reduction, the effect of pine oil/diesel blend fuels on the particulate emission characteristics of a diesel engine under a pre-injection strategy with exhaust gas recirculation (EGR) was analyzed. Fuels including D100 (pure diesel), P20 (pine oil blending volume ratio is 20%) and P40 (pine oil blending volume ratio is 40%) were tested. The results showed that, with the blending of pine oil, the curve of particle size distribution (PSD) changed from triple peak to bimodal, and the geometric mean diameter (GMD), the particle number concentration (PNC) and the particle mass concentration (PMC) were reduced. As the pre-injection timing (PIT) advanced, the number and mass concentration of total particles and the GMD decreased for all tested fuels, while those of ultra-fine and sub-23 nm particles increased slightly. Large particles in the accumulation mode were affected more by the PIT. As the pre-injection ratio (PIR) increased, the total PNC and PMC increased for all fuels, as well as the GMD of particles. However, the proportion of sub-23 nm particles in total particles was reduced by 50% and 75% respectively for P20 and P40 fuels. The particle emissions emitted from blends are more sensitive to the PIR than to PIT. The shapes of PSD curves under different PITs and PIRs were approximately the same but the peak values of PSD changed. For D100 and P20 fuels, advancing PIT could effectively weaken the trade-off between PNC and NOx. Compared to the PNC of D100 under the single injection strategy, that of P40 was reduced by 77.48% at a PIT of −50° CA ATDC and a PIR of 5%. Advancing the PIT and decreasing the PIR represented a better injection strategy to achieve a lower PNC. It was demonstrated that particle emissions from the diesel engine could be significantly improved by blending pine oil and optimizing the pre-injection strategy.