Reduced-scale Experimental Research on Fires in Tunnels with Natural Ventilation

AbstractThe 1/15 reduced-scale experiments were conducted using the Froude number conservation to investigate smoke diffusion characteristics in tunnel fires with natural ventilation. The effects of some factors such as: heat release rate, shaft distance, shaft size, train blockage and smoke curtain were studied. A porous bed propane burner, placed on the tunnel floor, was used to simulate the fire source. A series of K- type thermocouples were used to measure tunnel ceiling smoke temperatures. A hotwire anemometer was used to measure smoke volume rate and smoke temperature in the ventilation shaft. The experimental results indicated that all factors, except for the smoke curtain, have no major effect on the dimensionless ceiling temperatures in the fire section of the tunnel. Moreover, the fire size and train blockage do not have a significant effect on the dimensionless ceiling temperatures in the non-fire section of the tunnel. Nevertheless, the dimensionless ceiling temperatures in the non-fire section of the tunnel decreased with the decrease of the shaft distance and the increase of the shaft size. When the smoke curtain is used in the tunnel, the dimensionless ceiling temperatures in the fire channel are higher than in the case when the smoke curtain is not used. Moreover, there is no smoke in the evacuation channel. The fire size and train blockage do not have a considerable effect on the dimensionless temperatures and smoke volume rates in the shaft. Nonetheless, the dimensionless smoke temperatures in the shaft decrease with the increase in the shaft distance or the shaft size. Moreover, dimensionless smoke flow rates through the shaft increase with the decrease in the shaft distance or the increase in the shaft size