Combustion and Emissions of a Diesel Engine Fueled with Diesel-Biodiesel-Ethanol Blends and Supplemented with Intake CO2 Charge Dilution

Abstract

This study investigated the influence of a four-cylinder naturally aspirated direct-injection diesel engine fueled with diesel-biodiesel-ethanol blended (DBE) fuels tested at a steady state speed of 1800 rev/min under different engine loads, ethanol volume and intake carbon dioxide (CO 2) dilution ratios on engine performance, combustion characteristics, regulated gaseous emissions, and soot agglomerates. Overall, the experimental results indicate that DBE blends can in general improve brake thermal efficiency (BTE) and reduce nitrogen oxides (NO x), carbon monoxide (CO), CO 2 , volatile organic fractions, particulate mass (PM), and particulate number (PN) concentrations, while brake-specific fuel consumption (BSFC) and hydrocarbon (HC) might increase slightly. Compared with ultra-low-sulfur diesel, DBE blends can maintain a good tradeoff relationship among PM-PN-NO x. Compared with biodiesel, the blended fuels perform better in suppressing brake-specific particle number emissions (BSPN), leading to a reduction of ultrafine and nanoparticle numbers. The combined effect of DBE blends with intake CO 2 dilution has marginal effects on BSFC and BTE, significantly reducing NO x emission while slightly increasing particulate emissions. On particulate characteristics, DBE blends produce soots with curved, tortuous, and disorganized nanostructures with low soot burnout temperature and strong oxidation rate favoring PM-PN reduction.