An experimental investigation on blockage effect of metro train on the smoke back-layering in subway tunnel fires

Abstract

This paper investigates the influence of metro train on the smoke back-layering in the subway tunnel fires. Due to the reduction of cross-sectional area of subway tunnel, the ventilation velocity will increase when the ventilated air flows across the metro train. Both the inertia force of ventilated air and the heat loss of back-flowed smoke gas will be enhanced by the ventilation with higher velocity. Then the smoke back-layering will be different from that in the subway tunnel without metro train. A series of small-scale experiments were conducted to study the smoke back-layering in the tunnel with metro train inside and the results showed that the smoke back-layering length was greatly influenced by the metro train. Compared to that in the tunnel without metro train, the back-layering length in the current study was much reduced due to the enhanced inertia force and heat loss. Based on the smoke gas temperature distribution and fire dynamics theory, a new physical model including the factor of metro train length was developed to predict the length of smoke back-layering in the tunnel.