Heat Transfer and Spread Characteristics of Continuous Ethanol Spill Fires on Sand Substrates

Spill fire is common in industry, with the characteristics of large burning area and difficult to extinguish. To study its mechanism more deeply, a series of experiments of ethanol spill fire were carried out on sand substrate. The flame spread distance was measured, and the heat feedback and burning rate were analyzed. The experimental results showed that 0.25 mm sand made the proportion of heat conduction feedback in the quasi-steady stage reach about 70% of all thermal heat feedback, and the steady burning rate also reached the maximum value. With the increase of sand size, the proportion of heat conduction feedback decreased, the heat convection feedback gradually dominated, and ultimately the steady burning rate decreased first and then increased. This showed that sand affected the heat transfer in the quasi-steady stage of spill fire by changing the heat transfer process and the proportion of three modes of heat transfer, thus changed the steady burning rate. Furthermore, the influence of sand on the spread of ethanol in terms of mass transfer was also analyzed. For the initial spread stage, the obstructive effect of sand on the fuel spread was quantified based on Darcy's law. It was found that the obstructive capacity of sand on fuel spread had a quadratic relationship with its specific surface area.