Investigating the Effect of Opening Aspect Ratio and Combustion Source Conditions on Behavior of Backdraft Phenomenon by Large Eddy Simulation

Backdraft is a special phenomenon of fire that occurs in a closed environment with limited ventilation and it can increase temperature, pressure and intensify fire. In this paper, with the method of Large Eddy Simulation and using Fire Dynamics Simulator, the behavior of the backdraft phenomenon in a closed enclosure is investigated. Changing the aspect ratio of opening, fuel injection from the combustion source and displacement of the combustion source are the three basic parameters whose effect on the dynamic and thermodynamic behavior of the backdraft to extinguish or delay it was investigated. The results indicate that if the fuel participates in reaction with a lower concentration, backdraft can occur at low pressures. By reducing the aspect ratio of opening, the time of occurrence of the backdraft phenomenon was delayed and was able to reduce the peak dynamic pressure resulting from this phenomenon by nearly 4 Pascals; However, due to the presence of semi-combustible materials, the possibility of a second backdraft occurred. Also, by displacement the combustion source and bringing it closer to the opening, it was observed that the backdraft phenomenon occurred on a smaller scale and it is possible to extinguish it completely.