Experimental and Theoretical Study for Tunnel Fires with Natural Ventilation

Natural ventilation mode is a ventilation strategy to control fire-induced hot smoke and provide safe and secure egress routes in subway tunnels. The study was carried out in a 1/15 reduced-scale tunnel using Froude modeling technique to investigate the fire-induced smoke temperature distribution and smoke exhaust through vertical shafts located at the ceiling of the scaled tunnel. A porous bed burner placed on the tunnel floor was used to simulate the fire source and propane was used as the fuel. The temperature distributions under the tunnel ceiling were measured using a series of K-type thermocouples to analyze smoke temperature distribution characteristics. The smoke temperature and velocity in the ventilation shafts were also monitored using hot wire anemometers. The effect of fire size, shaft distance, shaft geometry, train blockage on ceiling temperature distributions and smoke exhaust from shafts were studied. Based on the one-dimensional theory, the ceiling temperature decay characteristics were studied. Finally, empirical equations for predicting ceiling temperature distributions and smoke exhaust in tunnel fires with a natural ventilation mode were derived.