特大断面公路隧道线型感温火灾探测系统适用性研究

随着我国公路交通量日益增多,大断面、特大断面公路隧道不断涌现,可靠、有效的隧道火灾探测越来越重要。选取了6种典型的隧道断面,综合考虑探测器类型、纵向风速、火源功率、火源位置等因素,运用火灾动力学模拟软件FDS分析了系列火灾场景下温度、烟气分布、探测器报警时间、报警位置偏移量等特性。研究结果表明: 隧道断面尺寸、纵向风速越大,感温探测器报警时间越长。通过对顶棚烟气温度的分析,发现特大断面隧道中线型感温探测系统采用差温报警较定温报警更有效。在使用差温报警时,纵向通风会使报警位置发生偏移,报警位置偏移量d与隧道纵向风速v、火源到隧道顶棚距离Hd满足线性关系式:d=6.404v+0.923Hd-6.762。随着隧道断面尺寸的增大,需要敷设更多的感温光纤以在规定时间(60 s)内探测到火灾。对于高度H≥12 m的隧道,即使增设多条感温光纤,也无法在60 s内有效报警,需补充设置基于火焰和烟气特征的非接触式火灾探测器。

Applicability of linear heat fire detection system in super-large section highway tunnels

With increasing highway traffic and the emergence of large-section and super-large section highway tunnels in China, reliable and effective tunnel fire detection is becoming increasingly important. In this study, six tunnel cross-sections are selected for fire dynamics simulations by FDS, for which the detector type, longitudinal velocity, fire location, and fire power are varied, and the temperature, smoke, alarm time, and alarm position offset are analyzed. The results show that the alarm time will gradually become longer with the larger section and higher velocity. The differential temperature alarm is more suitable for the tunnel''s linear heat fire detection system than the fixed temperature alarm. When using differential temperature alarm, the longitudinal ventilation will cause alarm position offset, and the offset depends on the longitudinal velocity and section hydraulic height. As the tunnel section size increases, more fibers are needed to detect the fire in time. For tunnels higher than 12 m, non-contact fire detectors based on flame and smoke characteristics should be used, given the longer alarm time of the linear heat detector.