Preliminary Experimental Investigation on the Backdraft Phenomenon of Fire in Tunnel with Liquid Fuel

摘要

Sealing tactics are widely used for fighting tunnel fires involving liquid fuels, where the main principle is to reduce the oxygen supply in the tunnel to suffocate the fire. However, the unbumt fuel can vaporize to combustible vapor when the entrances are sealed and the concentration of combustible vapor is usually high. Once the entrances are unsealed, fresh air can be drawn in and the backdraft phenomenon may occur leading to serious consequences for the security of firefighters. A 1 /9 scale model of a tunnel fire with liquid fuel is established to simulate the sealing and unsealing process. The temperature variation after unsealing in case of different fuel areas is considered to explore the factors influencing the backdraft phenomenon in tunnel fires. Results show that the occurrence of backdraft in the tunnel is mainly affected by the temperature distribution and the amount of fuel gas in the tunnel before unsealing. When the concentration of combustible vapor is above its lower explosion limit and the maximum temperature in the tunnel is higher than a threshold temperature as the entrances are unsealed, backdraft may occur. The threshold temperature value is found to be about 300 °C under the experimental conditions of this paper.