Study On Atomization Mechanism Of Double-flow Centrifugal Atomizer And Fire-fighting Law Of Water Mist

With the improvement of human environmental awareness,halon and other fire extinguishing agents are gradually replaced.Water mist is considered the main alternative because of its clean,environmentally friendly,rapid fire fighting,low water consumption,low-cost,and formed a huge research network of water mist fire extinguishing.In the study of water mist,it is found that the centrifugal atomizer spray of the single-tube and double-flow water mist system is the solid spray,and the fire rate is faster than not dissolved carbon dioxide water mist fire extinguishing system.single-tube and double-flow water mist system is that carbon dioxide is dissolved in water and precipitated in the centrifugal atomizer as the pressure is reduced.The flow mechanism and spray characteristics of two-phase（gas and liquid）flow in centrifugal atomizer were investigated and the six double-swirling atomizers were designed in this paper.The internal and external flows of the centrifugal nozzles were respectively investigated in the single phase and two-phase flow inlet through high speed camera.Based on the experiment,the three-dimensional simulation model of the inter flow in the centrifugal atomizer was proposed and was simulated by the software Fluent.The internal flow density and external velocity characteristics were obtained.The results was that a stable cylindrical air core inside the atomizer was formed if the inlet flow is pure water,and the spray is a hollow fog cone.If the inlet is flows was gas and liquid mixture,there is a conical gas-liquid mixing zone inside the atomizer,and the spray is a solid fog cone.The numerical results are agree with the experimental results.Pure water mist fire extinguishing only rely on physical effects,making the development of water mist fire extinguishing system is constrained.On the basis of existing development technologies,how to further improve the fire extinguishing effectiveness of the water mist and reduce the losses caused by the fire has become a concern of the water mist researchers at this stage.At present,a more widely method is to add additives to the water mist to improve the fire-extinguishing efficiency through physical and chemical effects.In this paper,we mainly used the method of controlling variables and selected three kinds of fuel,such as ethanol,diesel oil and gasoline,to explore the fire extinguishing mechanism under the different conditions with 1%KCl,1%FeCl₂,1%SDBS and 1%Na₂C₂O₄.The results showed that the water mist containing 1%KCl and 1%FeCl₂ additive in confined spaces mainly relied on chemical action,interrupting the reaction of the combustion chain,thereby restrain the flame and accelerated the flame extinguishment.The dominated fire-extinguishing mechanism of water mist with 1%SDBS additive is the cooling and isolation of the fuel surface.While Na₂C₂O₄ is not suitable for extinguishing system additives.