Characteristic Study On Alcohol Fire Suppression By Ultra-fine Water Mist In Confined Space

In recent years, given the advantages of environmental protection and high efficiency, advanced water mist fire extinguishing technology has become the main alternative technology to halon fire extinguishing agents. It also becomes the hotspot in fire science territory. Along with the development of ultrasonic atomization and Jet fog technology, the second generation of water mist fire extinguishing technology---ultra-fine water mist has appeared. The size of the droplets is less than 50μm, and the property is just like the gaseous extinguishing agent. The ultra-fine water mist can flow easily and bypass obstacles to reduce the power of the fire source. A high concentration of droplets can suspend for a long period of time in the space, reduce the oxygen concentration in the combustion region, and accelerate cooling of flames and smoke. At the same time, ultra-fine water mist has good heat-absorbing properties. Its large surface area can speed up the cooling of smoke and absorb the thermal radiation of flames.The experimental platform for the ultra-fine water mist restaining liquid fire systerm was built. Alcohol was selected as the investigated subject. The experiments between alcohol and ultra-fine water mist with or without additives were carried out separately.Through changing pre-ignition time, mist flux and discharging time, the experiment of using ultra-fine water mist to restrain alcohol fire was carried out. The variation trend of smoke layer temperature and the heat release rate of alcohol fire under different experimental conditions were found. At the same time, the photoes of the flame was taken by high speed camera, and then the Matlab image process was used to study the collected fire flame profile. The experimental result showed that heat absorbing and oxygen separating function played an important part in the restraining process. Then, the flame combustion rate and tensile rate was studied before and after dischaging ultra-fine water mist and the law for the restraining process was analyzed.Through changing the concentration of NaCl in the ultra-fine water mist, the experiments of using additive ultra-fine water mist to restrain alcohol fire under different conditions were carried out. The experiment results showed that the more the concentration of NaCl, the better to extinguish the alcohol fire. This is mainly because the droplet can penetrate the flame region easier, reach the falme root.