Numerical study on the influence of subway platform air curtains on smoke diffusion

To control longitudinal smoke spread and increase the time available for evacuation at subway platforms, this paper proposes a system for separating smoke on subway platforms using a combination of external air supply platform air curtains, stair (or escalator) air curtains, and a mechanical smoke exhaust system. In this paper, CFD simulations are conducted using Fire Dynamics Simulator (FDS) to investigate the impact of various air curtain speeds at a 20 degrees angle on smoke dispersion. The results show that: (1) The system is effective and reasonable, which can effectively prevent longitudinal smoke diffusion in the platform. (2) For the 2.5 MW firepower, when the air curtain speed is between 3 m/s and 5 m/s, the protected area is not affected by smoke. The supplementary cold air from the air curtains mixed and dispersed the heat, leading to a decrease in the temperature of the suspended ceiling above the fire source by approximately one-third, to below 200 degrees C. (3) For the 5.0 MW firepower, when the air curtain speed is 4 m/s, the protected area is not affected by smoke. The enhanced impact of the air curtain on fire source combustion surpasses the cooling effect of supplementary air.