Abstract
To study the fuel atomization problem when raw vegetable oil is used as an alternative fuel of compression-ignition internal combustion engine, this paper investigated the differences in spray characteristics between raw sunflower oil and regular diesel under different experimental conditions using the Schlieren method. The focus of this study is the effects of fuel temperature and injection pressure on the spray penetration distance, the spray cone angle, and the air entrainment of fuels injected into the constant volume vessel. The results show that both the spray penetration distance and the spray cone angle of the sunflower oil increase with increasing the fuel injection pressure and fuel temperature, which are similar to those of regular diesel.