细水雾灭火系统作用下特大断面公路隧道火灾特性数值模拟研究

细水雾灭火系统在公路隧道中的应用引发了较多关注,但是针对特大断面公路隧道的研究仍然不足。以2种大断面及4种特大断面公路隧道为研究对象,选取额定流量35 L/min、额定压力10 MPa的高压细水雾喷头,选择4种喷头布置形式,考虑火源功率、位置、遮挡物等影响因素,以隧道顶棚达到耐火极限的临界温度和相邻车辆被引燃的临界热辐射强度为判据,利用FDS模拟软件分析得到适用于隧道的细水雾喷头布置方案。结果表明对于特大断面隧道,细水雾单排顶喷布置不能有效抑制30 MW的大货车火灾,应采用增加顶喷或侧喷喷头的布置形式,从而保护隧道结构安全,防止相邻车辆被引燃。

Numerical simulation of fire characteristics in highway tunnel with super large section under water mist extinguishing system

In recent years, the application of water mist system in highway tunnels has attracted more attention due to its fire control and cooling effect, but most studies have focused on conventional road tunnels. As the planning and construction speed of tunnel with large section increases, the influence of water mist system on its application deserves further study and consideration, but there are little researches on this aspect. The aim of ths work is to numerically study the fire characteristics of super large section highway tunnel under the effect of water mist extinguishing system. Two kinds of large section tunnels and four types of super large section tunnels were selected as the subjects of this paper. A high-pressure water mist nozzle with the rated flow of 35 L/min and the rated pressure of 10 MPa was selected, and four types of water mist nozzle layout were considered, including influencing factors of fire heat release rate, fire location, and obstruction blocking. The critical temperature of the tunnel ceiling reaching fire resistance limit and the critical thermal radiation intensity required for ignition of adjacent vehicles were selected as the criterion. By simulation and analysis with Fire dynamics simulation software (FDS), the layout scheme of water mist nozzle suitable for tunnel with super large section was obtained. The results showed that the single-row top spray arrangement scheme of water mist for super large section road tunnels cannot effectively suppress the 30MW truck fire. The arrangement scheme of the top or side spray nozzle should be used to protect the tunnel structure and prevent vehicle ignition.