Abstract:

To effectively prevent and control soil environmental fires caused by liquid fuel leaks, and to advance post-disaster environmental decontamination efforts, and to investigate the influence of particle gradation on flame spread behavior in liquid-fuel-soaked porous media, combustion experiments were conducted on 0# diesel-soaked loess beds with different particle gradations. Structural parameters, internal temperature distributions, burning rates, and flame spread rates were measured and analyzed to explore the influence mechanism of particle gradation on the combustion process of the soaked bed. It was found that particle gradation significantly affects flame spread behavior by altering the porosity, dry bulk density, particle contact conditions, and pore connectivity of the loess bed. With increasing particle diameter, the pore scale increases and the dominant heat transfer mechanism gradually shifts from solid-phase conduction to convective heat transfer, leading to enhanced heat transfer and higher internal temperatures. The average burning rate is closely related to the pore structure of the loess bed. The combustion rate of the matrix particle size d_b=0.116 mm series operating conditions shows an overall decreasing trend with the increase of particle size d_a added. Whereas for the d_b=1.800 mm and d_b=4.375 mm series, it first increased and then decreased due to the combined effects of heat transfer enhancement and fuel transport variation. In addition, the flame spread rate first decreases and then increases with increasing particle diameter, exhibiting a critical particle size. A fire spread rate prediction model based on effective particle diameter was established and shows good performance under small particle-size conditions.

Key words: liquid fuel, soaked, loess bed, particle gradation, fire spread, burning rate