Impact of platform edge doors on ventilation requirements of underground transit systems
Air change at underground transit stations is highly depend on the piston effect created as a result of train arrival and departure. The generated air movement supplies underground station with the required air changes during normal operation. During emergency, Tunnel Ventilation System (TVS) operates in exhaust mode to create tenable environment for evacuation from the station. Installation of platform edge doors (PEDs) could substantially change air movement (during normal mode) and smoke flow migration patterns (during emergency mode) within the tunnel and station resulting in additional ventilation requirements.
In this paper, ventilation requirements of underground transit stations with and without platform edge doors have been discussed. Station fire scenarios have been considered at the presence of fully enclosed platform edge doors. Smoke extraction and variations of smoke flow patterns have been investigated using two different ventilation configurations: a) standard TVS which is comprised of a series of ventilation fans at both ends of platform to exhaust smoke. b) Over Track Exhaust (OTE) system with an exhaust duct above each track. Functionality of both systems have been investigated using 3D Computational Fluid Dynamics (CFD). Outcomes show that presence of PEDs improve overall tenability within the station when a proper ventilation system is in place to localize smoke extraction by providing a strong upward flow to properly delay smoke propagation into the platform level.