Temperature distribution characteristics of linear fires in utility tunnels under the influence of sealing ratios and vertical positions of the fire source

This study delves into two key factors affecting fire development process and longitudinal ceiling temperature attenuation characteristics in a utility tunnel: the sealing ratios and the vertical positions of the linear fire source. The evolution process of linear fire is typically divided into five stages. In the stable combustion stage, the flame height at the end of the liner fire source is observed to be higher than that at the center. During the rapid loss stage of mass, the mass loss rate peaks and then stabilizes for a period of time, the maximum peak growth rate is 1.35 (the fire source is located at position 02), the duration shortens as the distance between the liner fire source and the ceiling decreases and the sealing ratio increases. When the sealing ratio is 100 %, the maximum temperature growth rate is 2.25 with the change of fire source position. The ceiling temperature in the upper part of the linear fire zone is lower in the center and higher on both sides, however, the distribution is asymmetric. A mathematical model of longitudinal ceiling temperature attenuation is established. The results may provide guidance for the control of linear fires in long-narrow confined spaces.