Flame expansion behavior induced by a water droplet impacting on burning and stratified oil-water pool

The dynamic process of a water droplet impacting stratified oil-water and the phenomena of instantaneous flame expansion were recorded using a high-speed digital camera. The flame expansion scales (flame height and flame volume) were calculated under various conditions. Moreover, the effects of the water droplet diameter and impact height on the flame expansion scales and flame expansion duration were quantitatively analyzed. For a water droplet impacting the burning oil pool, the flame expansion is mainly caused by the steam explosion. But for the water droplet impacting the stratified oil-water, many small daughter oil droplets splash to increase the contact area between the fuel and air, which is probably the main reason for the instantaneous expansion of the flame. The flame expansion duration, height, and volume increase with the water droplet diameter and the impact height. The frequency of flame pulsation decreases gradually with the increase of the impact height. For the burning diesel oil pool, the flame volume expands about 50-135 times, while for the burning diesel layer on the water surface, the flame volume expands only 6 to 16 times.