Experiment Reserch And Numeric Simulation On Effervescent Atomization Of Water Mist Fire Extinguisher System

With the limitation and the gradual elimination of halons, water mist fire suppression system has been one of the important study topic on fire technique. Effervescent atomization is a method of producing water mist through twin flow, which has many advantages in terms of smaller drop size and lower injection pressure. Furthermore, the amount of atomizing gas required is considerably less than that of other twin-fluid atomization techniques. Based on the mechanism of effervescent atomization, a new system of water mist used effervescent atomizer was designed. That developed a new method of producing water mist, and accumulated a lot of necessary experimental data.An effervescent atomizer to produce water mist was designed firstly in this work, and an experimental device was constructed. Characteristic of flux was measured and recorded. The relationship of pressures and discharge coefficient was fitted. And the flow field of water mist was studed through numerical simulation.The Influence of the spray nozzle's size on flux characteristics and pressure was analysised experimentally. Gas and liquid inlet diameter have little influence on flux, with the increasing of gas and liquid inlet diameter the mass flow rate of gas decrease. Outlet diameter have much influence on mass flow rate, mass flow rate of gas flux increase with the increasing of outlet diameter. Mixing chamber diameter have much influence on mass flow rate of liquid and gas, mass flow rate of gas flux increased with the increase of mixing chamber diameter.Through numerical simulation of the flow field of water mist, we found that: the maximum average velocity is near the axis, velocity changes remarkably in radical direction from -20 to 20mm. Average velocity increases firstly and then decreased in axial direction. When the water mist is injected, the temperature of fire field decreases in all direction, the smaller the drops, the stronger the suppression.The results show that effervescent atomization system was feasible in water mist. It is economic and good performance in fire suppression. It is suitable for fire suppression in the future.