Gasoline spray characteristics using a high pressure common rail diesel injection system by the method of laser induced exciplex fluorescence

Abstract

The liquid and vapor phases of gasoline sprays were investigated using a common rail diesel injection system in a constant volume vessel by laser induced exciplex fluorescence (LIEF) and compared with diesel sprays. The effects of injection pressure and ambient pressure on gasoline sprays were measured under evaporating conditions. The results reveal that: the liquid phase penetration has a little change as the fuel is injected, while the vapor phase penetration increases constantly with obvious branch-like structures generated at the downstream vapor phase. The spray volume and mass of entrained gas both increase roughly linearly versus the mass of injected fuel. Compared with diesel sprays in similar conditions, gasoline sprays display a significantly shorter liquid penetration, while a smaller difference between the vapor penetration lengths of gasoline and diesel sprays is observed. The maximum equivalence ratio of gasoline sprays is still more than 2 at selected conditions. As the ambient pressure increases, the penetration lengths of liquid and vapor phases both reduce, and the mean equivalence ratio also decreases with a drop of spray volume. Conversely, the mass of entrained gas rises continually. With the increase of injection pressure, the liquid phase penetration length maintains almost no change. However, the vapor penetration length shows a declined trend during the injection pressure rise at iso-injected fuel mass condition. The spray volume and mass of entrained gas give a slight reduction when the injection pressure enhances. Oppositely, the mean equivalence ratio presents an increased tendency with similar mass of injected fuel.