Study On The Interaction Between Diesel Pool Fire And The Coupling System Of Ventilation And Water Mist

Fire is one of the most serious disasters which human beings face, causing tremendous harm to the human society and the natural environment, tunnel fire is particularly noteworthy. The research and application of fire prevention technology have been promoted by the increasingly severe fire situation. As the Vienna convention and the Montreal protocol are signed, the halon suppression agent which has been widely used is prohibited to use, therefore finding the ideal substitutes is becoming a problem to be solved. Due to the characteristics of environmentally friendly, extinguishing quickly, widely applied and so on, water mist is considered to be the ideal substitute of halon suppression agent, achieving great attention of national researchers. However, its mechanisms of fire suppression are not yet clear, especially in ventilation environment or other complex environments, which prevents its widespread application. Therefore, exploring the mechanisms of fire suppression by water mist is an important part to promote the water mist fire suppression system to the practical stage.This thesis revolves the interaction between diesel pool fire and the coupling system of ventilation and water mist, build up a6m×1.5m×2m small-scale tunnel experiment platform firstly. Then through the measurement and analysis of the temperature, thermal flux, wind speed and concentration of O2and CO monitored at measuring points, the process of fire suppression by the coupling effect of ventilation and water mist is divided into three stages, namely strengthening stage, controlling stage and extinguishing stage. The dominant mechanisms of different fire suppression stages are analyzed. At the same time, the main factors which impacted the coupling effect of ventilation and water mist are explored as well. The results reveal that from the perspective of fire suppression mechanism, strengthening stage is mainly characterized by flame cooling and attenuation of radiant thermal flux, controlling stage is mainly characterized by surface cooling and attenuation of radiant thermal flux and extinguishing stage is mainly characterized by surface cooling and dynamic effect. From the point of controlling effect of the coupling system, the coupling effect of vertical ventilation mode with water mist is better than longitudinal ventilation mode. When the working pressure of water mist is up to10MPa, the increase of work pressure is very limited for fire suppression effect of the coupling system. The installation of water mist nozzle spacing should be less than or equal to the offset caused by the ambient wind speed.Based on the results of tunnel experimental platform and scale analysis of the fire suppression process under the coupling effect of ventilation and water mist, a large scale tunnel model is established, afterwards a numerical simulation is conducted by the fire dynamics simulation software FDS within the tunnel model. Through the comparison of experimental and simulation results, the reliability of the scale relation as well as the applicability of experiment results applied to large scale space are explored. The results show that the law of fire suppression process and temperature field development of numerical simulation is basically consistent with the experiments, the effect of predictions coincide with the real situation, therefore scale simulation can be used to predict the process of fire suppression under similar conditions.