Classification of different regimes of ethanol pool fires*

The characteristics of ethanol pool fires subject to ambient swirl were explored in this laboratory setup. Twenty vertically oriented thin acrylic vanes, 91.5 cm tall by 15.25 cm wide, were placed 49 cm from the center of an ethanol pool fire, which had diameters ranging from 1.9 cm to 7.6 cm. The vanes were all oriented at the same fixed angles from the radial direction for various different angles ranging from 0 degrees to 85 degrees, thereby imparting verious levels of circulation to the air entrained by the pool fire. It was found that different levels of swirl and values of the pool diameter, or associated Grashof number, resulted in different configurations of the flame. Configurations included a global puffing instability, a helical instability that generates a tall fire whirl, and a blue whirl that is associated with vortex breakdown and the edge flames becoming detached from the surface of the ethanol pool. The transition between these different regimes was recorded for varying ethanol pool diameters.