Flowing Combustion Characteristics Of Flammable Liquid On Sand And Gravel Base In Open Environment And Heat Transfer Analysis In Stable Stage

Flammable liquids are easy to volatilize and burn in the daily environment,and they are easily ignited after leakage.Although they rarely cause explosions after a fire,they will evolve into flowing fires,which accelerate the spread of fires and increase the difficulty of fire rescue.Through preliminary experiments,it was found that the sand containment effect will slow down the spread of flowing fire and reduce the burning area.At present,there is no general containment method for large area flowing fires,and the containment effect lacks specific theoretical basis and experimental data.To provide a theoretical basis for fire prediction,risk assessment,smoke exhaust and leakage containment of flammable liquids,it is necessary to study the leakage,spread,combustion dynamics of flowing fire under the action of sand and gravel containment in an open environment,and the coupling of heat transfer and combustion.In the unidirectional liquid flow fire experiment,the unignited spread experiment and ignited combustion experiment on sand and gravel substrate were carried out to study the spread and combustion kinetics characteristics of n-heptane and alcohol fuel under different sand and gravel particle sizes.The spread distance,flame front and burning rate were analyzed,and the effect of heat transfer on the burning intensity of flowing fire was explored.The results show that since the adsorption capacity of sand and gravel decreases with the increase of the particle size of sand and gravel,the spreading distance and speed of the unignited fuel in the spreading stage increase with the increase of the particle size of sand and gravel,and are smaller than those of the unignited fuel sand condition.With the increase of the particle size of sand and gravel,in the stable combustion stage,the stable flame front distance of the ignition fuel first increases and then decreases,and the stable combustion rate first decreases and then increases.The heat transfer analysis shows that when the particle size of sand and gravel increases from 0.25 mm to 4mm,the decrease of heat conduction feedback is the main reason for the decrease of burning rate;and when the particle size of sand and stone is further increased to 8mm,the heat radiation feedback An increase in,leads to an increase in the burning rate.Finally,it is concluded that the adsorption capacity of sand and gravel is the main factor affecting the spreading stage,and the thermal feedback is the main factor affecting the stable combustion stage.0.25 mm fine sand is more suitable for blocking and extinguishing flowing fire.In the radial flow fire experiment,the flow fire spread and combustion experiment of alcohol fuel on sand and non-sand substrate were carried out.The spread radius and steady burning rate were analyzed,and the effect of heat loss on the burning intensity of flowing fire was further explored in the heat transfer analysis.The results show that the spreading radius and velocity of both unignited and ignited fuels increase with the leakage rate during the spreading stage.In the stable combustion stage,the burning radius of the flow fire of the sand-stone base is smaller than that of the sand-free base,and the burning rate is higher than that of the sand-free base.The heat transfer analysis shows that the flow heat feedback of the sand-stone base is greater than that of the sand-free base,which is 2.59-3.62 times that of the latter.The increase of the heat feedback leads to the increase of the burning rate,of which the heat conduction feedback accounts for 83.14%-90.16% of the heat feedback,is the main thermal feedback.