Experimental study of flame spread behavior and heat transfer mechanism over n-butanol fuel in trays of different widths

Abstract

As the initial stage of liquid fuel leakage fire, flame spread process determines the development of fire and the severity of energy damage, which is a matter of great concern. Flame spread experiments were conducted in trays with the length of 130 cm and different widths, i.e., 15, 30, 60 and 90 cm. The fuel thicknesses were 0.2, 0.5, 1.0 and 1.5 cm. Results show that in the 15 cm wide tray, the flame height gradually becomes stable, flame spread behavior meets the assumption that radiation is neglectable. However, in trays wider than 15 cm, the assumption no longer applies. The flame height keeps increasing, and the heating effect of radiation weakens the convection between hot fuel and cold unburnt fuel. In the 90 cm trays, the flame front overlaps with the subsurface flow front. A heat transfer equilibrium model is further established, and it is found that the ratio of flame radiation to total heat input (Qrad/Qin) increases with tray width for 1.5 cm thick fuel, Qrad/Qin are 4.4%, 23.2%, 39.0% and 41.1% in 15, 30, 60 and 90 cm wide trays. Besides, for 90 cm wide trays, Qrad/Qin generally shows a decreasing trend with the increase of fuel thickness.