Abstract:The objective of this study was to investigate the macroscopic spray characteristics of different 0%-100% blends of biodiesel derived from drainage oil and diesel (BD0, BD20, BD50, BD80, BD100), such as spray tip penetration, average tip velocity at penetration, spray angle, average spray angle, spray evolution process, spray area and spray volume under different injection pressures (60, 70, 80, 90, 100 MPa) and ambient pressures (0.1, 0.3, 0.5, 0.7, 0.9 MPa) using a common rail system equipped with a constant volume chamber. The characteristic data was extracted from spray images grabbed by a high speed visualization system. The results showed that the ambient pressure and injection pressure had significant effects on the spray characteristics. As the ambient pressure increased, the spray angle increased, while the spray tip penetration and the peak of average tip velocity decreased. As the injection pressure increased, the spray tip penetration, spray angle, spray area and spray volume increased. The increasing blend ratio of biodiesel brought about a shorter spray tip penetration and a smaller spray angle compared with those of diesel. This is due to the comparatively higher viscosity and surface tension of biodiesel, which enhanced the friction effect between fuel and the injector nozzle surface and inhibited the breakup of the liquid jet.

The spray characteristics of diesohol fuel have a direct effect on the thermal efficiency and combustion emissions performance of diesel engines. In this research, we investigated the spray characteristics of diesohol fuel under different fuel injection pressures (Pinj) in a high‐pressure common‐rail injection system and at various spray ambient pressures (Pamb) in a constant‐volume pressure vessel by using high‐speed photography technology. The research results support the concept of adding a certain percentage of ethanol to diesel, creating diesohol fuel, which can reduce the environmental impacts of vehicle emissions. Experiments on the spray characteristics were performed and the results suggested that the addition of ethanol has no significant effect on the spray tip penetration, spray cone angle, and spray tip speed. However, atomization conditions such as injection pressure and ambient pressure have a significant impact on the spray characteristics of the blended fuel.