In order to investigate the combined burning characteristics of soaked porous media sand bed under different combustible liquid layer heights, a series of burning tests with different sand sizes and liquid layer heights were conducted. The characteristic parameters, fuel (ethanol) mass loss rate, flame height, internal temperature of porous media (quartz sand) and plume temperature were measured, and the effect mechanism of liquid layer height was analyzed and studied. The results show that the existence of combustible liquid layer has a certain effect on burning characteristics of quartz sand infiltration layer. When there is a liquid layer above the sand layer (h=20—60 mm), the mass loss rate of quartz sand infiltration layer increases obviously, which can be attributed to the preheating effect of liquid layer burning. The flame height increases firstly and then stabilizes with the increase of liquid layer height, which shows the similar trend with mass loss rate. The temperature growth retardation occurs inside sand bed within 78.7—79.0℃ (which is close to fuel boiling point), so the vapor zone movement speed inside sand bed can be evaluated. As the height of the liquid layer increases and the particle size of the quartz sand decreases, the velocity of the vapor zone in the sand layer gradually increases. In addition, based on previous scholar's plume relationship and current experimental data, an empirical formula is obtained to describe axial temperature of flame and plume for combustible liquid-soaked inert porous media sand bed.

Keywords： porous media ; liquid layer height ; combustion ; phase change ; heat transfer ; flame appearance