Research On Fire Smoke Characteristic Parameters Change Under The Action Of Water Mist In Long And Narrow Space

For the special size characteristics of narrow space,its length and width ratio is large,the smoke spread vertically and quickly accumulate in the space after the fire,temperature rise,large concentration lead to great difficulties to supply oxygen.Because of the particularity of the particularity of difficult to be found after the fire in narrow space results in evacuation can not be carried out in a timely manner and more difficult to evacuate.High pressure water mist using water as material,on one side it avoids the destruction of the ozone layer by the Halon fire extinguishing agent or increasing greenhouse effect in terms of environmental protection..The cooling effect of water mist on fire is remarkable,and it absorbs smoke particles.Therefore,in this paper,the experimental and numerical simulation methods are used to analyze the characteristic parameters of the smoke in narrow space under the action of the high pressure water mist.The fire smoke temperature variation law near and far from fire source under the action of high pressure water mist is analyzed.The experimental results show that the process of fire smoke temperature variation law near and far from fire source is that it decreases rapidly and then decreases slowly.The reasons for the decrease of the fire smoke temperature of near and far from fire source are not completely consistent.Near fire source it is because of the suppression and cooling effect of the high pressure water mist on the plume.In addition to the above mentioned,it also because of water mist blocking part of the smoke spread which makes that far fire smoke is unable to replenish energy by convection and heat radiation.The variation law of the fire smoke temperature drop rate,which is near and far from fire source under the condition of high pressure water mist,was studied.From the experimental results,it is found that the temperature drop rate near and far from the fire source decreases with the decrease of the smoke layer height,which is V3.0m>V2.5m>V2.0m,but the bottom fire smoke temperature drop rate(V1.5m)is slightly higher under some condition.The variation law of the top smoke temperature along the longitudinal space is obtained under the action of the high pressure water mist.The experimental results show that the smoke temperature in the top layer is exponentially decaying along the longitudinal direction under the action of water mist.Attenuation curve fitting formula is T = l0 + l1 exp(-x/l2).At the early stage of the spray,the amplitude of attenuation is obvious,and the latter is relatively low.The variation of O2 and CO concentration under high pressure water mist was obtained.It can be seen from the experimental data that the concentration of O2 in the flue gas shows a rapid rise and slow recovery.The change of CO concentration showed a slow rise,then the CO concentration began to decline rapidly,and finally the CO concentration began to slow down.Based on the experimental parameters,the change of smoke temperature and CO concentration with time was analyzed by FDS.The results are compared with the experimental results.It is found that the numerical results are in well agreement with the experimental results,which can be used to show the smoke parameters of long and narrow space fire under the action of water mist.