Numerical simulation on double fire source tunnel

A tunnel double fire source FDS numerical model was built in order to provide reference for the risk assessment and evacuation. The double fire source simulation in tunnel at different fire widths and fire spacings was carried out. The distribution law of ceiling longitudinal temperature, temperature in the fire field at the center of the fire source, flow field and heat radiation intensity near the fire field were studied. The results show that in a double fire source tunnel, heat and smoke will accumulate in the fire site due to the mutual influence of the fire sources. As the width of the fire source increases, heat release rate per unit area of the fire source decreases, the maximum temperature in the tunnel decreases rapidly and the temperature at the opening of the tunnel remains basically unchanged, so the longitudinal temperature attenuation factor at the far end gradually decreases. The temperature between the double fire sources near the ground shows a "concave" distribution, the temperature in the most of the intervals remains basically stable and the stable temperature shows an upward trend with the increase of the fire source width. The maximum flow velocity of smoke in the tunnel appears inside the fire plume, which is less affected by the fire source spacing and greatly affected by the fire source width. With the increase of the fire source width, the maximum flow velocity in the tunnel decreases, the buoyancy effect weakens, the thickness of the smoke layer increases and the smoke deposition process becomes more obvious. The radiation intensity near the ground between double fire sources is greatly affected by the distance between the fire sources and it is less affected by the width. As the distance between fire sources increases, the radiation intensity drops rapidly, but it still causes great harm to rescuers. © 2022 Central South University of Technology. All rights reserved.