Study On The Effect Of Air Curtain And Mechanical Smoke Extraction On Smoke Diffusion And Evacuation In Tunnel Fire

With the rapid development of China's transportation industry,the number and scale of various traffic tunnels are increasingly expanding.This poses a higher challenge to the fire and smoke design of tunnels.In recent years,as a new type of smoke prevention technology,the smoke-protected air curtain has attracted the attention of researchers,but there are only few studies on the application of air curtains in tunnel fires.This paper proposes that the combination of air curtain and mechanical smoke exhaust should be applied to tunnel fires to control the spread of smoke in tunnel fires.Based on the fire dynamics simulation software FDS,the following issues were studied:(1)Simulate and compare the natural ventilation and the combined effect of the air curtain and the mechanical exhaust.The comparison results show that:compared with the natural ventilation,the combination of air curtain and mechanical exhaust can effectively control the flue gas.In the tobacco control area,it is feasible to prove that this type of smoke control method is applied in tunnels.(2)Under different fire source power scenarios,the smoke diffusion characteristics with a smoke vent spacing from 20?110 m and the corresponding air curtain spacing from 40?220 m were simulated.The optimal design of the air curtain and smoke vent's spacing was discussed by analyzing the smoke temperature,carbon monoxide concentration and visibility at different positions from the tunnel fire source.The results show that the smoke temperature,carbon monoxide concentration and visibility index are more conducive to the escape in all the studied conditions when the smoke vent spacing is 60 m and the air curtain spacing is 120 m.(3)Under different fire source power scenarios,the smoke diffusion characteristics with air curtain injection angle from 5?30°,air curtain thickness from 0.4?1 m and air curtain injection velocity from 5-30 m/s were simulated.The optimal design values of air curtain injection angle,air curtain thickness,and air curtain jet velocity was discussed by analyzing the smoke temperature,carbon monoxide concentration and visibility at different positions from the tunnel fire source.The results show that the optimal air curtain injection velocity is 5?10m/s and the optimal air curtain thickness is 0.4m under the heat release rate of 10?50MW fire source.The optimal air curtain injection angle is 20°under the heat release rate of 10?20MW.(4)Pathfinder simulation software was used to simulate the best design conditions for smoke control.The simulation results show that under the optimal parameter design,the air curtain and the mechanical smoke exhausting method can effectively prevent the smoke from spreading and provide a safe evacuation environment for the personnel.(5)Different combinations of air curtain injection velocity and smoke exhaust volume was simulated,and the efficiency of air curtain under various working conditions was calculated.The obtained fitting relationship between the air curtain injection velocity,smoke exhaust volume and the the efficiency of air curtain is as follows:?=-2.17211V0.42962 Q0.57979 +1.2803...