Jet Water Atomization And Research On Fire Mechanism

According to "The Montreal Protocol on Substances that Deplete the Ozone Layer" , Halons used widely for fire-extinguishing are inhibited gradually. It is very urgent to find safe extinguishing reagents to replace Halons for world. Now, FM-200, Carbon dioxide, Intergen, Aerosol and SDE are main substitutes used in our country. This thesis indicates that water mist is a very ideal extinguishing reagent through analysis of economy and performances.Now, many investigations on the suppression systems fire-extinguishing by the water mist are conducted in many developed countries and they have got some achievements. Now the Chinese government has paid the more attention to water mist fire suppression systems and the investigation prospect of water mist fire suppression systems technology. This thesis paper detailedly introduces the definition, origin, fire mechanism and application of water mist fire suppression systems. Adopt CFD research technique, and contrapose water mist extinguishing system simulation and comparison with Fluent software, make a dispersed network phase model, educe optimal water mist extinguishment diameter and jet velocity.Design of a water mist fire suppression systems can not depend on the general principle entirely because of the complexity of extinguishing mechanisms of water mist fire suppression. In laboratory scale experiments it is found that there are two different fires extinguishing process owing to variety of parameter of water mist. Then we get the critical value which is necessary for water mist fire suppression by flame cooling.The future of the rock gas is soft, floating and dark. In the process of water mist fire suppression the phenomenon of fire expansion may be found initially. Theoretic study showed that evaporation of the droplet in surface of fuel play a crucial role in the fire expansion. In experiments of varied conditions, it is found that volatility of fuel and characteristics of water mist determine the degree of fire intensification. It is found that add water in the model will make fuel surface temperature and fire heat release rate descend. And with increase of water quantity, fire intensification will be weakened, extinguishing time also be shorten.From the combustion specialty of spray fire, interaction of water mist and methane flame was studied by theoretic analysis and simulation. Mechanisms of methane flame suppression by water mist were analyzed in this paper. It is found that the major extinguishment Mechanisms in methane flame suppression by water mist include flame cooling, oxygen depletion and radiation attenuation. Simulation results showed that the mist entraimnent in base of methane flame might be the crucial faction in fire suppression. It was also found that large average diameter of methane flame will shorten extinguishing time of spray fire.