Extinguishment of a Laminar Jet Diffusion Flame Using a Soap Bubble Filled with Nitrogen Gas

Inert gases, such as nitrogen, argon and carbon dioxide, are able to extinguish a fire more cleanly than water and dry chemical extinguishing agents.However, to extinguish the fire completely, a large amount of inert gas is needed to be released at the vicinity of the fire or into a confined space containing the fire.If a capsule is filled with an extinguishing inert gas, and ruptures due to contact with the flame zone, the high concentration extinguishing gas can be directly supplied to the fire.By using this capsule, it may be possible to increase the effectiveness and decrease the amount of the extinguishing inert gas needed in firefighting.In the present study, in order to clarify the fundamental characteristics of flame extinguishment by an inert gas capsule, extinguishment experiments of a methane-air laminar jet diffusion flame by a soap bubble capsule filled with nitrogen gas have been performed.Visualization of flow released from the bursting bubble has also been carried out by using laser tomography and schlieren techniques.Results show that, when the soap bubble bursts, two different kinds of nitrogen gas flow are formed.The first flow is generated by the pressure difference between the inside and outside of the soap bubble.The second flow is generated by the soap liquid film dynamics.Combined, these two flows of nitrogen gas extinguish the laminar jet flame.The first flow extinguishes the flame base locally, and the second flow leads to blow out of the whole flame.