| Air curtain,widely used in stairwells,mine tunnels,subway stations,has great application prospects for not only effectively preventing smoke from spreading to safe areas,but also not hindering the personnel safety evacuation.The crossing passage work as an evacuation channel weighs highly when fire emergency occurs.Generally,using the fans at both ends of the tunnel in the absent of fire to supply air to maintain positive pressure in the crossing passage is not economic,reasonable nor applicable.As the main factor that threatens life safety in tunnel fires,it needs to propose a safe and effective smoke prevention measure in order to ensure the safe evacuation in the crossing passage.In this paper,the air curtain smoke prevention technology is applied to the subway tunnel in a crossing passage.In terms of using theoretical analysis methods,the factors affecting the smoke protection efficiency of the air curtain can be summarized as: jet velocity,jet angel and the width of the outlet.Based on the Froude criterion,a small-scale experimental rig was built at a scale ratio of 1:15,which verified the rationality and reliability of the FDS numerical simulation results.According to the small-scale experiment and theory of air curtain,influences on air curtain affecting by these factors are discussed.The characters of smoke distribution in cross passage are analyzed based on different fire scenarios and it proves that it is essential to prevent smoke from cross passage way.Three factors(jet velocity,jet angle,and width of the outlet)were analyzed using orthogonal analysis methods to determine the primary and secondary relationships affecting smoke prevention effectiveness and the best factor combination levels.The primary relationship of affecting smoke prevention effectiveness in turn of air jet velocity,width of the outlet and jet angel.The best combination of these three factors are: air jet velocity=9m/s,air jet angel α=30°and the width of the outlet=0.4m.To ensure the safe evacuation of personnel in the access channel,air curtain parameters are guaranteed at least: air jet velocity≥7m/s,air jet angel α=30°and the width of the outlet≥0.3m.Besides,relationship which between the best jet velocity and the heat release rate has been proved that jet velocity and heat release rate are in linear relation while the jet angel and width of the outlet remain unchanged. |
