重载铁路隧道可燃物极大丰富条件下火灾温度场数值模拟

针对重载铁路隧道内重载列车运载大量可燃物贯穿整条隧道的情况,建立了500m双线重载铁路隧道模型,利用大涡模拟技术,采用数值模拟的方法探讨了可燃物极大丰富条件下重载铁路隧道内,不同初始火源功率、起火位置下可燃物(红松木)火灾蔓延规律,进而分析了重载列车起火后隧道内火灾沿纵向、横向的温度分布特点、变化规律及后果影响。结果表明:重载铁路隧道内重载列车一旦发生火灾,不同起火位置对火灾向周围的蔓延速度有着明显的影响,而当火灾发生大面积蔓延时,由于隧道内通风量受限,将最终形成两侧隧道口附近燃烧剧烈,而中部较长区域燃烧受到显著抑制的特点。这也导致了隧道内拱顶附近处的最高温度位置由初始火源正上方,沿纵向逐渐向隧道洞口移动,并最终稳定在两侧隧道口附近,同时隧道中部温度也发生大幅度降低,这种温度分布特征对隧道衬砌结构损伤及破坏将产生重要影响。

Numerical simulation of fire temperature field for Heavy-haul railway tunnel with extremely abundant fuel

Heavy haul trains often carry large amounts of combustible materials through a whole railway tunnel, which probably brings about an extreme fire to the tunnel. In this paper a model of 500m double-track heavy haul railway tunnel is established, and the large eddy simulation technology is used to investigate the fire propagation of red pine in the tunnel, under different initial fire power and fire source positions in extremely abundant fuel conditions. The attributes of longitudinal and cross-sectional temperature distribution with their influences are analyzed respectively. The results indicate that for a fire of the heavy haul train in the tunnel, different initial fire source positions affect the fire spread speed significantly. When the wide propagation of fire breaks out, due to the limited tunnel ventilation, it will finally lead to relatively severe burning near both side portals of the tunnel, while the combustion in a considerably long central region will be relatively weak. This causes that the highest temperature region near the tunnel vault moves longitudinally from right above of initial fire position to the tunnel portals gradually, and finally stabilizes near both side portals of the tunnel. Meanwhile, the temperature in the tunnel central region will decline dramatically. The above characteristics of temperature distribution in the tunnel could have important effects on tunnel lining structure damage and failure.