不同阻塞条件下的隧道火灾全尺寸试验研究

为了研究阻塞条件下的隧道火灾危险性,选取某隧道网络中的某一支路作为火灾试验区,采用轴流风机通风,额定通风量为27 m3/s,以甲醇池火为火源,火源功率分别为0.25、0.50和1.00 MW。通过改变火源功率和隧道内风门的开闭模式开展全尺寸试验,分析火源横截面和隧道中心线竖直截面风速、隧道纵向拱顶温升、隧道中心面纵向温升等参数,研究了不同阻塞条件下的隧道火灾烟气扩散规律,获得了抑制隧道火灾危险性的风门控制模式。研究结果表明:①在隧道通风网络中,对称风流通过风门后,隧道截面距风门22 m处风速在整流作用下逐渐趋于均匀;②建立了考虑隧道阻塞比的隧道风量衰减模型,该模型可根据隧道阻塞比的变化预测隧道阻塞作用下的风量损失,同时可以计算沿程阻力损失的风量;③在自然通风条件下,当火源功率大于0.50 MW时,火灾烟气在火羽流作用下迅速向隧道拱顶浮动,通过对流换热使得拱顶温度急剧升高,对于隧道结构的稳定性具有巨大的破坏作用;可采用调节风门的方式控制通过起火区域的风量,从而优化隧道火灾危险控制模式,局部风速大小对火灾危险性影响不大;当起火区域风量不足时,人眼高度处的1.8 m高温度升幅较大,不利于人员逃生与救援;④阻塞条件下隧道断面不对称进风流易造成风流结构紊乱,使得隧道火灾烟气温度分布不稳定,危险性较大。

Experimental study on safety full-scale of tunnel fire disaster under different blocking conditions

In order to study the fire risk of tunnel under blocking conditions,a branch of tunnel network was chosen as the experimental field.The axial flow fan was used for ventilation,and the rated ventilation rate was 27 m3/s.Taking methanol pool fire as fire source,the heat release rate of fire source is 0.25,0.50 and 1.00 MW respectively.The full-scale experiment was carried out by changing the heat re?lease rate of fire source and the opening and closing mode of air door.The smoke diffusion law of tunnel fire under different blocking condi?tions was studied by analyzing the parameters of air speed profile of fire source cross section,air speed profile of vertical section in tunnel centerline,excess ceiling temperature along tunnel and excess temperature profile of vertical section in tunnel centerline.The air door con?trol mode is obtained to suppress the fire risk of tunnel.The results show that:①in tunnel ventilation network,the air speed gradually tends to be uniform on tunnel section(22 m away from the airdoor)by rectification after the symmetrical air flow passing through the air door.②The air flow attenuation model of tunnel considering blocking ratio is proposed.The model can predict the air loss under the action of tunnel obstruction according to the change of tunnel blocking ratio,and can calculate the air volume loss along the road resistance loss.③Under the condition of natural ventilation,when the heat release rate of fire source is greater than 0.50 MW,the fire smoke will rise to the ceiling of tunnel rapidly driven by the fire plume,and the ceiling temperature will rise sharply through heat convection,which will have a great damage to the stability of tunnel structure.The air volume through the fire area can be controlled by adjusting the air door,thus optimizing tunnel fire risk control mode.The local wind speed has little influence on the fire risk.When the air volume in the fire area is insufficient,the temperature rise at the eye height is large,which is not conducive to personnel escape and rescue.④Under the blocking condition,the asymmetric inlet air flow of tunnel section easily causes the air flow structure disorder,which makes the temperature distribution of tunnel fire smoke unstable and dangerous.