In order to research the influence of different gas parameters and ambient pressures on the characteristics of air-assisted spray

spray characteristics especially the macroscopic morphology change of spray were studied under various injection durations

injection pressures and ambient pressures in a constant volume vessel by high-speed photography. And the spray characteristic parameters such as spray penetration distance and the projected area of spray were qualitatively analyzed. The results show that air-assisted spray penetration distance develops in two stages and the projected area of spray increases linearly under different test conditions. Increasing injection pressure and decreasing ambient pressure are both beneficial to increasing the spray penetration distance and the projected area of spray

while air duration has little influence on them. The spray morphology in different air pressures and air durations are almost the same

with only slight difference. Spray morphology is greatly affected by the ambient pressure

in thick “spindle” shape under low ambient pressure

and in “anchor hook” and “cone” shape under high ambient pressure. With the increase of ambient pressure

the projected area of thin spray region begins to shrink and gradually disappears under high ambient pressure

and the spray is mainly concentrated in the core area.