| In recent years,with the increasing complexity of parking space,the fire risk coefficient of underground parking garage is increasing.The fire in underground parking garage occurs frequently all over the country,which threatens the safety of public life and property and hinders the orderly development of society.As a new fire-fighting means of economic and environmental protection,the application of water mist fire-fighting technology in underground parking garage has become a research hotspot of relevant experts.Therefore,the application of water mist fire-fighting system in underground parking garage fire is of great significance for the prevention and control of underground parking garage fire.The fog field characteristics of fine water mist nozzles with flow coefficients K of 1.0,1.7 and 2.0 were studied experimentally using a high-pressure pump set fine water mist fire suppression system.Experimental results show that the flow coefficient K of the spray nozzle remains unchanged when the pressure at the nozzle inlet is increased,and that the spray volume increases exponentially when the K value is increased from 1.0 to 2.0.At a minimum working pressure of 10 MPa,the area of concentration of droplet size increased from 70 to 110 microns with the K value,and D0.99 corresponded to the largest increase in droplet size.On the basis of the study of the fog field characteristics of the fine water mist nozzle,a reduced size underground parking garage fire test platform was built,the experiment selected the flow coefficients K 1.0 and 1.7 fine water mist nozzle,set up two experimental working conditions and conducted a large number of fire experiments.Experimental results show that: two working conditions of fine water mist can effectively reduce the temperature of the fire field,successfully put out the fire;two working conditions of the fire extinguishing time is 250 s,200s,when K = 1.7,the fine water mist extinguishing time is shorter,the fire extinguishing efficiency is also higher.A 1:1 FDS mathematical model is established based on the real fire experiment platform.The simulation results show that the experimental measurement values are in good agreement with the simulation results,which verifies the reliability of the numerical model calculation.Taking the underground parking garage of a kindergarten as the research object,a full-scale numerical model was established by using the fire dynamics simulation software FDS.The installation height,spray pressure and spray cone angle of the sprinkler were changed in the simulation,and the fire extinguishing characteristics and extinguishing effects of water mist in underground parking garage under different working conditions were studied.The simulation results show that:(1)The fire extinguishing effect of the water mist is related to the installation height of the nozzle.Under 3.0m and 3.5m working conditions,the fire-extinguishing time is short and the fire-extinguishing efficiency is high,but the smoke removal effect is better under 3.0m working condition.Therefore,it is suggested that the installation height of 3.0m should be selected for the water mist nozzle;(2)The fire extinguishing effect is not linearly related to the spray intensity.The critical spray pressure of the water mist fire extinguishing system is 15 MPa.Under this pressure,the effect of the water mist is better than that of the water mist.After the water mist is applied,the height of the smoke layer is basically above the safe height.Therefore,it is suggested that the spray pressure should be 15MPa;(3)The atomization effect of water mist is closely related to the atomization cone angle.The suppression effect of water mist with different atomization cone angle is different.The temperature of the fire site decreases rapidly under 110 ° and 150 ° conditions,and the fire extinguishing effect is better than other conditions.110 ° condition has obvious effect on agglomeration and sedimentation of smoke particles,and the effect of smoke removal is more stable.Therefore,110 ° is recommended for the atomization cone angle of water mist. |
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