Experimental Studies On Fire Enhancement During The Interaction Of Water Mist And Pool Fire

During the interaction of water mist and some kind of pool fires, the phenomenon of fire enhancement would occur, which means the flame dimension would become larger and the burning becomes heaver, suddenly. This is a quite complex process in which a serial of interaction behaviors happen between the water mist and the pool fire, and also between the water mist and the fuel. So far, most of researches in this literature in the world have only focused on the estimating of the possible reasons of the fire enhancement phenomenon, but there is a lack of research on the real reasons and the dimensions of fire enhancement.In this thesis, the fire enhancement phenomenon has been experimentally studied based on an experimental setup considering the interactions between water mist and pool fire. The experiment can be divided into two parts based on the different locations of the water mist sprinklers according to the properties of the pool fire. During the first part, the sprinkler was located at the intermittent flame area where the water mist can be directly spread into the plume area and the interaction between water mist and buoyant fire plume can be ignored; During the second part, the sprinkler was located at the buoyant fire plume area, where the interaction between water mist and the buoyant fire plume become very important. These two kinds of interactions between water mist and buoyant fire plume have been investigated in two parts'experiment, respectively. The basic parameters of fire burning including the shape of flame, the temperature of the flame area, the temperature of the fuel and the radiation heat flux. By analyzing the experimental data, we have studied some characteristics of fire burning with different kinds of fuels and different pressures of the water mist system including the flame shape, the temperature distribution and the fire radiation at the moment of fire enhancement.Through the analysis of the experiment, we found that the fire enhancement phenomenon was closely related to the physical and chemical properties of the fuel. Fuels soluble in water, such as the alcohol, can not trigger the fire enhancement phenomenon after the implementation of water mist, while fuels dissoluble in water, such as gasoline and diesel oil, can lead to an opposite result. When the sprinkler was in the intermittent flame area, under the condition of the experiment, both the gasoline and the diesel oil have triggered the fire enhancement phenomenon obviously. And as the pressure of water mist system increased, the maximum value of flame radiation heat flux decreases, the radiation strengthening rate decreased, at the same time, the time that the radiation strengthening lasted became shorter. When the sprinkler was in the buoyant plume area, whether the fire enhancement phenomenon occurred largely depended on whether the water mist can pass through the buoyant fire plume. In the experiment, the fire enhancement phenomenon was implicit when t the water mist can't pass through the buoyant fire plume, otherwise, clear fire enhancement phenomenon could be seen.