The Scale Effect And Effectiveness Evaluation Of Water Mist Indoor Fire Suppression

Water mist, as a new fire extinguishing agent replacement of Halon, has the advantages of no pollution, no effect on the human body, low water consumption and wide range of application. But there is also disadvantage, such as low fire extinguishing efficiency. This paper is committed to study the fire extinguishing efficiency of water mist containing additive and at different spatial scales, in order to discover methods to improve the efficiency of water mist fire extinguishing agent.For indoor solid fire of Class A, the paper designed and built a small-scale spatial and ISO9705experiment. By comparing the parameters like ambient temperature, heat flux and gas content (02, CO and CO2) at different spatial scales and power of fire sources, the paper took qualitative and quantitative analysis on indoor fire suppression performance of water mist.The experimental results showed:In small-scale space, pure water mist and water mist with additives had very good inhibiting effect on high flame temperature and heat flux produced by wood crib fire, but low flame temperature and heat flux (under550mm) increased significantly. Water mist with additives had better inhibiting effect. The time of water mist with additives making room temperature50%reduced was shorter. And the indoor oxygen content can be restored faster than pure water mist without producing poisonous gases CO. In the ISO9705experiment, with the increase of the fire source power in center, the growth rate of temperature in South location was higer than the North location and the heat flux growed exponentially. After appling the water mist, the time of making room temperature and heat flux50%reduced was decreased with curve. With the increase of the fire source power in corner, the growth rate of temperature in North location was higer than the South location and the heat flux growed with the function of first degree. After appling the water mist, the time of making room temperature and heat flux50%reduced was increased with line, but the extent was small. With the increase of the fire source power, the rate of oxygen consumption indoor was faster and the oxygen concent indoor was lower. After appling the water mist, the oxygen content indoor recover to21%in100s. When the fire source power in0.15MW and0.25MW, wood crib would happen incomplete combustion reaction and generate CO, but the content was at low level, about0.1%. However, when the fire source power in0.5MW and1.0MW, the CO content would continued to increase and reach0.6%. Due to the surrounding space, CO generated by the corner fire was more than the center fire.The utilization of water mist is concerned with the volume of limited space and fire source power. The ratio of the fire source power and the volume of limited space reaches a number, the extinguishing time will appear a phenomenon of a sharp rise. Therefore, the project design should pay attention to the particular water mist system in the position of a turning point in a given limited space and reasonably determine the configuration of water mist.