Numerical Simulation of a Fire Accident in a Longitudinally Ventilated Railway Tunnel and Tenability Analysis

The present study examines the prevailing conditions in a railway tunnel after a train fire accident and the ability of the ventilation system to create the proper conditions for a safe passenger evacuation. The examined scenario included an event of a 20-MW diesel pool fire on a suburban train, immobilized in the middle of a 1.5-Km long, linear shaped rectangular tunnel ventilated by a longitudinal jet fan system, and the people's movement during the evacuation was effectuated along walking platforms. More specifically, three scenarios with different fan activation times and different evacuation processes were examined. A Large Eddy simulation model (LES) was used for the simulation of the air flow in the railway tunnel. The evaluation of the ventilation system criteria considered the achievement of the air critical velocity inside the railway tunnel, and for the people's safe evacuation, the Fractional Effective Dose (FED) value was examined. It was found that the most important action in a tunnel fire is the time, after the start of a fire, the ventilation system is activated.