Study on Flame Expansion Phenomenon in Pool Fire Extinguished by Water Mist

The theoretical and experimental studies on the phenomenon of flame expansion in pool fire extinguishment with water mist are presented in the paper. Firstly, the theoretical analysis on fire expansion phenomenon is made. It's found that, both the interaction of water mist with flame and hot fuel lead to the flame expansion phenomenon in liquid pool fire extinguishment with water mist. The impacting on fuel vapor by water mist jet flow, which corresponding to the interaction of water mist and flame, and the azeotropic effects, which corresponding to the interaction of water mist and hot fuel, are these two kinds of root causes for fire expansion phenomenon. And the theoretical analysis also indicates that the flame characteristics, the interaction of water mist and pool fire, the momentum of water mist are the key factors to leading to an expanded fire. Then, three groups of experiments are set to study the above factors. The experimental results show that the impacting effects of the water mist jet flow to fuel vapor and the azeotropic effects of the mixtures of water and hot fuel are the main causes for fire expanding. And the flame characteristics, the momentum of water mist are important to the size of expanded fire. The existence of a certain amount of fuel vapor in the fuel vapor rich core of pool fire and the impacting of water mist with adequately large momentum are the prerequisites for fire expansion. It's also found in the experiments that the fire expansion start from the bottom of the pool fire and not much related to the far-end of the flame. The experimental results indicate that the theoretical analysis are fit the fire expansion phenomenon well.