Water droplet impacting on burning or unburned liquid pool

A series of experiments was conducted on single water droplet impacting onto pool liquid with or without burning surface. Three typical liquid fuels were used: heptane, butanol and ethanol, which were separately burned in a square glass pool with various side lengths (50 mm, 75 mm, 100 mm, 125 mm and 150 mm), respectively. The water droplet diameter was around 2.2 mm and the falling height was fixed at 80 cm. The impact processes were recorded using a high-speed digital camera at 2000 frames per second. The results show that the impact behaviors are obviously different between the cases of unburned and burning liquid pools. Although pool size has no evident effect on impacting behaviors compared to liquid fuel type both for unburned and burning pools, it influences the crater evolution for burning pool. In addition, the maximum crater width and depth are independent of pool size for unburned pool, while it decreases with the increase of pool size for burning pool. The impacted liquid properties including density, surface tension and viscosity have a significant effect on crater evolution. The crater evolution time is longer in unburned pool than that in burning pool, and the crater evolution time in ethanol pool is larger than those in the other two pools.