A Study of Boilover in Liquid Pool Fires Supported on Water Part I: Effects of a Water Sublayer on Pool Fires

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Abstract
Under certain circumstances, the water on which a burning pool of liquid fuel is supported may begin to boil. The water vapor that is released and escapes through the fuel surface tends to atomize the oil, which results in an emulsive-droplet flame above the fuel surface. This phenomenon, called boilover, has been observed for large scale pool fires, but the mechanism causing it to occur has not been fully investigated yet. This paper describes fundamental aspects of the effect of a boiling water sublayer on the behavior of pool fires. A burner system in which the burning surface of the fuel can be fed into the flame so that the fuel/water interface with respect to the edge of the container remains fixed was used. Ten different single-component and six different multicomponent fuels were tested. Conventional flow visualization techniques were applied to study the liquid motion, and results for an ethylbcnzene pool in a 4.8cm diameter pan are presented. Data obtained include temperatures and mass loss history of the liquid fuel and water, flame height, and irradiance from the flame. Results show that when the water sublayer starts to boil, the temperature gradient across the fuel layer vanishes, the temperature level of the fuel decreases, and the burning rate of the fuel decreases. Contrary, the large pool fires show an opposite result that when the boilover occurs, the burning rate of the fuel increases. Thus it was suggested that for the small pool fires, additional external radiant heat is required to simulate quantitatively the boilover phenomenon for the large pool fires.