SUPPRESSION OFFIRE AND GAS EXPLOSION BY WATER MIST

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Water mist is environmentally acceptable as compared with Holon, and is attractive as an alternative fire suppressant. In the present study, we investigated experimentally and analytically the effect of water mist on the diffusion flame which appears in fires and the premixed flame which induces the gas explosion, on the basis of combustion science. The extinguishment of the diffusion flame is mainly affected by the ratio of mist mass fraction and mist diameter, which is defined as surface area parameter, and the evaporation Damkohler number. On the other hand, the burning velocity of premixed flame decreases with the water mist addition mainly due to the thermal effect which includes the latent heat of evaporation and heat capacity of water vapor. However, the chemical effect on the burning velocity cannot be neglected. Reduction of the burning velocity is mainly affected by the increase of mole fraction of added water mist. These results could be applied to the design of the water mist fire extinguishment system.