Study on the influence of the longitudinal position of fire source and tunnel width on the maximum ceiling gas temperature

Abstract

Tunnel fires can result in significant damage to both personnel and property due to the high temperature generated. In this research, a set of numerical simulations were carried out to investigate the smoke flow characteristics in a tunnel with a variable placement of the fire source along the longitudinal centerline. The results showed that due to the influence of the width and the location of the fire source, when the fire source is closer to the upstream portal, most of the air supplied for combustion will come from the upstream, and the downstream cold air will be subjected to more intense smoke entrainment, resulting in different supplementary wind speeds on both sides and an inclined flame. Meanwhile, as the fire source moves from the upstream opening towards the center of the tunnel, the flame changes from inclined to vertical, and the air supplied for combustion shifts mostly from the upstream portal to evenly from both sides. The maximum ceiling gas temperature gradually increases to a maximum value in a non-linear pattern. The empirical equations were suggested for estimating the maximum ceiling gas temperature at various longitudinal positions within the tunnel.