Effects of palm oil biodiesel addition on exhaust emissions and particle physicochemical characteristics of a common-rail diesel engine

Abstract

In this study, the effects of varying diesel/biodiesel blending ratios on exhaust emissions and particle physicochemical characteristics were conducted on a four-cylinder high-pressure common-rail diesel engine. The experiment involved the application of reference diesel (B0) and several diesel/biodiesel blends (B20, B50, B70 and B100) as the alternative fuels for diesel engine. The results indicated that the addition of biodiesel resulted in a significant reduction of HC, CO and soot emissions except for NOx, the generation of soot precursors such as polycyclic aromatic hydrocarbons (PAHs), ethylene and acetylene were inhibited, and the unregulated emissions of formaldehyde and acetaldehyde increased slightly, while they still were <45 ppm. At rated load, the soot and PAHs emissions of B70 fuel decreased by 28% and 24%, respectively. With the increase of biodiesel blending ratio, the molar and mass ratios of O/C, aliphatic hydrocarbon functional groups (CH) and oxygen-containing functional groups (-OH and -C=O), as well as the degree of disorder (sp3/sp2) on soot surface increased. Furthermore, the initial oxidation temperature and burnout temperature of B20, B50 and B70 soot samples were lower than those of B0 soot samples, and their apparent activation energy decreased by 4.67%, 9.76% and 17.09%, respectively.