双流体细水雾对木垛火的灭火特性研究

Study on wood crib fire suppresion characteristics of twin-fluid water mist

使用气泡雾化喷头和氮气、空气及二氧化碳3种雾化气体对木垛火进行双流体细水雾灭火试验,研究了双流体细水雾与木垛火的相互作用特点及细水雾和雾化气体的协同灭火机理。结果表明,水流率足够的条件下,双流体细水雾可以快速抑制木垛火,但完全扑灭木垛内部的火焰需要较长时间;喷头施加的水流率越大,灭火时间越短;雾化气体起到了辅助灭火的作用,且雾化气体本身的灭火能力越强,对应的双流体细水雾的灭火时间越短。

In order to study the mechanisms and effectiveness of wood crib fire extinction by twin-fluid water mist, a series of experiments were conducted in a 3 m ×3 m× 3 m confined space under varying conditions. In the course of experiments, water mist nozzle is effer- vescent atomizer and atomization media is nitrogen, air and carbon dioxide respectively. At first, the relation between water flow rate and gas flow rate was measured and the water mist characteristics of the effervescent atomizer were determined as well. The results of the tests show that the water flow rate of the effervescent atomizer is decreased by an increase of gas flow rate at certain operation pressure. The vol- ume mean diameter and axial mean velocity of the twin-fluid water mist are strongly influenced by the water flow rate and operation pres- sure. The volume mean diameter is increased while the axi^il mean velocity is reduced by the increase of water flow rate or the decrease of operation pressure. In the fire suppression experiments, some K- type thermocouples were used to measure the flame temperature above and inside the wood crib and a gas analyzer was used to measure the concentrations of oxygen, carbon monoxide and carbon dioxide. The resuks of the fire suppression experiments show that twin-fluid water mist can supl^ress wood crib fire in a short time, but it is difficult to extinguish the flame inside the wood crib. When increasing the water flow rate, the wood crib fire can be extinguished more easily. The re- suits of the fire suppression experiments also indicate that both water mist and atomization gas affect the fire suppression process. The mo- mentum of atomization gas causes the water mist arrive at the surface of the wood more easily. In addition, the characteristics of the atom- ization gas influence the extinguishing efficiency of twin-fluid water mist. When the atomization gas is carbon dioxide, the extinguishing efficiency of twin-fluid water mist is the best while the fire will be dif- ficultly extinguished when the atomization gas is air.