Numerical Simulation on Accident Ventilation Modes in Subway Tunnel Fire

Abstract

Different ventilation modes and smoke exhaust methods will influence the smoke spread and toxicity distribution during fires in subway tunnels and also threaten the passengers' safe emergency evacuation. In order to supply the support needed the for passengers’ safe emergency evacuation, the flow rules of smoke exhaust during different fire ventilation modes are studied based on the practice of Tianjin Metro. According to the hypothesis of burning mid carriage stops in the middle of the tunnel, based on the Probability Density Function (PDF) combustion model, the k   turbulence model and the P-1 radiation model, the simulation models of the toxic smoke flowing status at different ventilation modes are set up with FLUENT software. In accordance with the theory of smoke “Effect of Boundary Layer Attachment,” the simulation models are proved to be reliable. Studies revealed that the smoke spread scope, the temperature and the smoke toxicity distribution in subway tunnels are varied in different ventilation modes. The simulation results show that the ventilation mode, with the aisle doors opened in the non-accident tunnels postponing pressure, could be used in the subway tunnel with 10MW fire intensity. With this ventilation mode, not only the toxic smoke can be followed and controlled efficiently, but also the passengers’ evacuation time can also be increased. The research may give an important reference for the efficient ventilation mode choices, as well as for the passengers’ evacuation project during a subway tunnel fire.