Comparison of the effect of biodiesel-diesel and ethanol-diesel on the particulate emissions of a direct injection diesel engine

Experiments were conducted on a 4-cylinder direct-injection diesel engine using ultralow sulfur diesel blended with biodiesel or ethanol to investigate the particulate emissions of the engine under five engine loads at the maximum torque engine speed of 1800 rpm. Four biodiesel blended fuels and four ethanol blended fuels with oxygen concentrations of 2%, 4%, 6%, and 8%were used.With the increase of oxygen content in the blended fuels, the brake specific fuel consumption becomes higher and the brake thermal efficiency improves slightly. The smoke opacity, the particulate mass concentration and the brake specific particulate emissions all decrease, and the reductions are more obvious for the ethanol blended fuels, while the proportion of soluble organic fraction (SOF) in the particle increases with the biodiesel blended fuels having slightly higher proportion of SOF than the ethanol blended fuels. In addition, the total number concentration of particles smaller than 750 nm in diameter decreases gradually for the ethanol blended fuels but increases significantly for the biodiesel blended fuels. The biodiesel blended fuels also increase the number concentrations of particles smaller than 50 nm and particles smaller than 100 nm while the ethanol-blended fuels reduce these particles.