Experimental Study on Effect of Infiltration Depth on Burning Characteristic and Fuel Residual Feature of Inert Porous Media Bed Soaked by Combustible Liquid

A series of fire tests were performed to study the effect of infiltration depth on the burning behavior and fuel residue of porous media bed soaked by liquid fuel. Ethanol was used as liquid fuel and quartz sand was used to naturally stack to form the porous media bed with different infiltration depths within the range of 60–180 mm. Burning rate, internal temperature of porous media bed, flame height, movement speed of fuel vapor zone, and fuel residue percentage was measured and analyzed. Results show that within current test scope, fuel mass loss rate in quasi stable period is negatively correlated with infiltration depth, and the relationship between mass loss rate and infiltration depth can be well characterized by power function. Quasi stable flame height also decreases gradually with the increase of infiltration depth. With the range of 78.5–79.2°C, the temperature growth retardation occurred inside sand bed, and sand bed was hence assessed as a distinct three-zone feature. The movement speed of vapor zone decreases linearly with the increase of infiltration depth, and the maximum measured value is about 0.041 mm/s. Axial temperature distribution of flame and plume can be well characterized based on McCaffery's plume relationship, but the length of continuous flame and intermittent flame zone is shortened to some extent. Within current test range, fuel residue percentage increases with the increase of infiltration depth and particle size, and maximum fuel residual percentage is at 5.29% in the case with 180 mm infiltration depth, which is obviously smaller than previous scholars’ results. In addition to the depth of infiltration, the boiling point and viscosity of liquid fuel and the effective thermal conductivity of sand bed are also important influencing factors.