Key Parameters And Smoke Control Effects Of Air Curtain Smoke Exhaust System In Tunnel

As the tunnel itself is a long and narrow structure with limited entrances and exits,it is easy to produce toxic and harmful high-temperature gas and it is not easy to exhaust when a tunnel fire occurs.Meanwhile,it is difficult to escape and rescue.This issue has always been concerned and studied.Push-pull air curtain has been gradually applied to the field of fire protection due to its characteristics such as smoke blocking,exhausting,heat insulation,and no impact on personnel escape.In this paper,push-pull air curtain is also used to control the spread of tunnel fire smoke and is committed to optimization the parameters of the air curtain,so as to achieve high efficient and energy saving of tunnel smoke exhaust,and prevent person from being injured by high-temperature toxic smoke during escape and rescue.In this paper,a tunnel is taken as the research object,and the smoke discharge effect of the push-pull air curtain in tunnel fire is studied by combining small-scale experiment and numerical simulation.The specific content is as follows:In the small-scale experiment,7 experimental conditions were designed by adjusting the opening size of the air curtain and the air volume of blowing and suction.The results show that the smoke exhaust effect of the push-pull air curtain is better than that of the single suction air curtain.When the amount of air blowing and suction is certain,reducing the length of the air curtain is beneficial to enhance the isolation ability of the blowing and suction flow.When the opening size of the air curtain is certain,the larger the air volume,the better the smoke control effect,but it should not be too large,because the improvement of smoke control effect is limited and energy is wasted.By comparing the results of numerical simulation with the small-scale experiment under the same working condition,it is found that the consistency is high,which shows that it is feasible to use numerical simulation method to analyze the smoke exhaust effect of the push-pull air curtain.FDS software was used to carry out numerical simulation and analyze the influence of air curtain spacing,width,and blowing and suction speed on smoke exhaust effect when the HRR was 5-30 MW in the two cross-section tunnels.The results show that:(1)when the distance between air curtains is 80 m,the smoke exhaust effect is better and the economy is higher.(2)The wider the air curtain is,the higher the smoke control efficiency is.In a 7.5m×4.8m section tunnel,when the blowing and suction speeds are 10m/s and 14m/s respectively,and the widths of the blowing and suction curtains are 0.8m and 1.6m,respectively.The smoke control efficiency can reach more than 95%;In a 15m×4.8m section tunnel,only by increasing the width of the air curtain,the improvement of the smoke control efficiency is limited.(3)When the width of the blowing and suction curtains are 0.6m and 1.2m respectively,increasing the blowing and suction speed can increase the "rigidity" of the air curtain and reduce the escape of smoke.When the blowing and suction speeds are 16m/s and 23m/s respectively,the smoke control effect of air curtain is better,but when the HRR of the ignition source is 30 MW,the smoke control efficiency still has room to improve.(4)When the smoke exhaust volume of the smoke exhaust system is certain,the smoke control effect of the air curtain and ordinary smoke is compared.The results show that the air curtain has better smoke blocking and cooling effects,and the area behind the air curtain is more conducive to evacuation.