Influence of methanol-biodiesel blends on the particulate emissions of a direct injection diesel engine

In this study, Euro V diesel fuel, biodiesel, and methanol-biodiesel blends were tested in a 4-cylinder direct-injection diesel engine to investigate the combustion characteristics and particulate emissions of the diesel engine under five engine loads at the maximum torque engine speed of 1800 rpm. Compared with Euro V diesel fuel, biodiesel gives lower and earlier heat release rate. For the blended fuels, the peak heat release rate becomes higher and retarded. With regard to particulate mass concentration, biodiesel generates less than Euro V diesel fuel, while the blended fuels result in significant reduction especially at high engine loads. Compare with Euro V diesel fuel, the total particle number concentration of using biodiesel is always higher while the geometric mean diameter (GMD) of the particles is lower. With the blended fuel, the total number concentration and GMD decrease in comparison with pure biodiesel. Further analysis shows that the difference between the total number concentration of biodiesel and Euro V diesel fuel is in particles smaller than 50 nm rather than in the larger particles. The use of methanol-biodiesel blends, compared with biodiesel, could reduce the number concentration of all sizes. A comparison between the particulate mass emission and total particulate number concentration with the mass of fuel burned in the diffusion mode show that they are strongly related to each other, even for the blended fuel.