Experimental And Mechanism Study On Liquid Fire Suppression Of Lightweight Porous Materials

All modernized lifestyles rely on energy as a support,and fossil fuels dominate the energy sector.The rapid development of the petrochemical industry has brought about many safety hazards,with liquid fires being the most dangerous.A novel approach has been proposed to study the use of lightweight porous inorganic solid materials to suppress combustion by covering the liquid surface of liquid fires.Lightweight inorganic porous solid materials were prepared using waste glass as a base material.Based on experimental research and existing theoretical analysis of the mechanism of combustion suppression by porous media covering the fuel liquid surface,simulation software was used to investigate the effectiveness of porous media in suppressing liquid fires.First,waste glass,red mud,and silica ash were used as matrix materials.Foaming agent,foam stabilizer,and fluxing agent were added in proportion to form a powdered mixture.The mixture was then processed through sampling,preheating,sintering foaming,and annealing to obtain the lightweight porous inorganic solid materials used in the experiments.These materials have extremely low thermal conductivity,low specific heat capacity at constant pressure,and are non-combustible.Four different sizes of cubes（labeled A11 to A44,with the first digit representing increasing size and the second digit represents increasing coverage thickness）and cylinders（labeled B11 to B44）were made from the materials.A total of 24 experimental conditions were set,labeled as A11 to A14,A22,A24,A34,A44 and B11 to B44,with different thicknesses of 0.5cm,1.0cm,1.5cm,and 2.0cm,respectively.The control group A0 had no coverage on the liquid surface.Normal heptane was used as the liquid fuel,and quartz glass was used to simulate the tank material.The experimental apparatus was used to conduct 600 seconds experiments to obtain data on flame size,temperature at 3cm,6cm,9cm,12cm,and 15cm above the liquid surface,fuel mass consumption,smoke temperature,oxygen volume fraction in the smoke,exhaust velocity,and liquid fuel bottom temperature.The parameters defined include the maximum reduction in flame height（β）,the percentage decrease in temperature at different positions above the liquid surface（η）,the maximum reduction in fuel mass consumption(χ_loss),the ratio of experimental conditions to the control group in terms of heat release rate(χ_loss),and the lower（a_b）and upper（a_u）limits of the percentage decrease in liquid fuel bottom temperature.All these parameters represent the experimental conditions where the suppression of liquid combustion is most effective and the porous particles are covered to a thickness of 2.0cm.These results provide evidence from multiple perspectives that lightweight porous particles have a good effect in suppressing liquid combustion.Liquid fuel combustion is mostly the combustion of vapor after evaporation.By analyzing the mechanisms of fuel evaporation and evaporative combustion,the evaporation and combustion of liquid fuel covered by porous media can be divided into three sub-processes:heat transfer from the porous media surface to the fuel,heating and evaporation of the fuel through the pores of the porous media,and combustion of the vapor releasing heat.Mechanism analysis of these sub-processes led to the development of a mathematical model for the suppression of liquid combustion by porous media.A simulation model with the same dimensions as the experiments was constructed using multi-physics simulation software.Three simulation conditions were set:natural cooling and evaporation of the liquid fuel surface（S1）,direct heating and evaporation of the liquid fuel surface（S2）,and heating and evaporation of the liquid fuel covered by porous media（S3）.According to related studies,the thermal flux at the liquid fuel surface is 10%of the heat release rate of the fire source.The simulated thermal flux was set to 10%of the experimental data,gradually increasing to around 40 k W/m² during the stable stage.The simulation was conducted for 600 seconds,and the temperature field and evaporated amount of the liquid fuel were obtained.The evaporated amounts for S1,S2,and S3 were 7.779g,14.429g,and 5.238g,respectively.This study experimentally verified the effectiveness of porous media in suppressing liquid fires,defined parameters to quantify the suppression effect,and developed a mathematical model for the suppression of liquid fires by porous media based on experiments and theory.The simulation using multi-physics software confirmed the effectiveness of porous media in suppressing liquid combustion.