Behavior of non-spread diffusion flames of combustible liquid soaked in porous beds

Experimental studies were conducted to investigate the behavior of non-spread diffusion flames of liquid fuel soaked in porous sand beds of different depths. Sand bed depths from 50 to 80 mm and sand size of 1.55 mm were chosen as the porous beds. Pure methanol was used as the liquid fuel. The effects of sand bed depth on flame temperature profile, position and thickness of the vapor/liquid coexisting region, vapor region moving speed, combustion duration time, fuel consumption, and amount of fuel residues in the porous beds were studied in the experiments. Theoretical analysis was conducted to account for the experimental results. The capillary effect and heat conduction are the controlling mechanisms of the processes. The capillary pressure decreases with increasing bed depth due to the effects of gravity. Thus, only when the fuel soaked in the ground is shallow enough, combustion can be applied for effective soil decontamination. The presented heat transfer model can quantitatively predict the interface position of the combustion of the liquid fuel in the porous bed and explain the appearing maximum value in the fuel consumption rate curves in the early stage of the combustion. These results confirmed that heat conduction is the dominant mode of heat transfer in the beginning stage of combustion