Effect of di-n-butyl ether blending with soybean-biodiesel on spray and atomization characteristics in a common-rail fuel injection system

In this work, the spray and atomization characteristics of soybean biodiesel, di-n-butyl ether (DBE)/biodiesel blends and 0# diesel were investigated by using a high pressure common-rail injection system. The macroscopic spray characteristics such as the spray tip penetration (STP), the cone angle and the spray projected area were obtained from the spray images captured through high speed schlieren photography. The results show that as DBE is blended into biodiesel, the STP is decreased and the spray cone angle, projected area are increased and when the DBE volume fraction in the DBE/biodiesel blends reaches 30%, the STP, the spray cone angle and the projected area are comparable to that of diesel. For all the tested fuels, the microscopic spray characteristics such as the Sauter Mean Diameter (SMD) and statistical size distributions were measured by particle/droplet image analysis (PDIA) technique. The droplets number density distribution shows that for all the tested fuels, the region near the central of spray has the largest droplets number density and it decreases sharply as the position shifts from the center to the edge of the spray. As DBE is blended into biodiesel, smaller SMD is observed, which indicates that DBE addition can promote the atomization of biodiesel.