Regimes during single water droplet impacting on hot ethanol surface

In order to deepen the knowledge of the mechanisms of liquid pool fire suppression with water mist/spray, a series of preliminary experiments were carried out for a water droplet impacting upon target liquid surface. Ethanol was chosen as the target liquid and heated to simulate the temperature conditions as it burned. The water droplet used in the experiments was about 2.0 mm with impact Weber number altering from 30 to 695. The results show that three typical impact regimes including crater-jet, penetration and surface bubble are observed. The pool temperature and Weber number have important influences on the impact behaviors and characteristic parameters including the crown height, and the energy conversion rate during the crater evolution and jet evolution. The maximum crown height depends on Weber number but is weakly dependent on the pool temperature. The ratio of the sum of crater potential energy and surface energy to initial impact energy is linearly related to the dimensionless pool temperature. Likewise, for the cases of crater-jet, as the Weber number and pool temperature increase, the conversion rate of crater potential energy and surface energy to jet potential energy and surface energy increases linearly.