机械通风条件下细水雾抑制酒精火的试验研究

Experimental study on alcohol pool fire suppression with water mist under different mechanical ventilation conditions

通过全尺寸模拟试验研究了细水雾和机械通风共同作用下小室酒精池火的特性以及机械通风风量和风速等对细水雾抑制酒精池火的影响。试验中通过改变变频器频率来调节机械通风的风量和风速,获取不同机械通风条件下细水雾抑制酒精火的温度、热辐射强度、总热流强度以及O2和CO体积分数等特性参数,并分析讨论了机械通风对细水雾抑制酒精池火的影响。结果表明:随着机械通风量的增加,烟气平均升温速率和平均降温速率线性下降,细水雾施加后对火场对流传热的抑制作用更加明显;同时,机械通风使得火场O2体积分数更接近环境大气值,细水雾施加之后CO的生成量明显降低;机械通风不影响细水雾控火效果,并有助于和细水雾灭火系统共同保障火场安全。

Based on a series of full-scale simulated experiments, the characteristics of alcohol pool fire under applications of water mist and mechanical ventilation systems were studied, and the effects of mechanical ventilation exhaust rate on water mist systems in alcohol pool fire suppression were analyzed. The experiments were carried out in a confined room with a smoke exhaust fan installed on one side to provide mechanical ventilations. The experiments were conducted under six different ventilation conditions with 90 s pre-burning time. The wind flux and speed were adjusted through changing the transducer frequency to provide different ventilation exhaust rates, and the wind speed was measured by anemograph. Smoke temperature was measured by using 1-mm-diameter K type thermocouples, and the radiation intensity and heat flux intensity were collected by heat-flow meter. Oxygen and carbon monoxide concentrations of alcohol pool fire environment under applications of both of water mist and mechanical ventilation systems were measured by using a gas analyzer throughout the experimental process. The experimental results showed that water mist systems could suppress alcohol pool fire effectively, but could not extinguish it quickly. Smoke temperature, radiation intensity and heat flux intensity decreased quickly while water mist was applied. With the increase of mechanical smoke exhausting rate, the average smoke temperature decreased gradually, and both average heating rate and cooling rate of smoke temperature decreased linearly. In addition, the total heat flux intensity reduced quickly with large mechanical smoke exhausting rate, and it could be seen that the convection heat transfer intensity was decreased by water mist systems under these conditions. Meanwhile, with the increase of mechanical ventilation rate, the oxygen concentration decreasing rate reduced before water mist applied, while carbon monoxide concentration changed little. Nevertheless, the oxygen concentration increased quickly and the carbon monoxide generation decreased obviously after the application of water mist. It was shown that the mechanical ventilation systems could reduce smoke temperature and convection heat transfer intensity while at the same time increasing the oxygen concentration and decreasing carbon monoxide production. Under the working condition described in this article, the mechanical ventilation did not influence the performance of water mist systems in alcohol pool fire suppression. More than that, it could work together with water mist systems and promote fire safety corporately.