公路隧道内纵向通风对火灾参数影响的试验研究

Experimental study of the influence of the longitudinal ventilation on the fire parameters in highway tunnels

公路隧道发生火灾时易造成严重后果,纵向通风作为火场排烟降温的常用措施会改变燃烧的火源功率及相关火灾参数,影响公路隧道通风排烟的设计。利用按照弗洛德相似性原理自行设计建造的公路隧道火灾烟气输运特性研究试验台,研究了不同纵向通风风速下燃料火源功率、火焰形状和烟气层高度、距火源2 m人眼高度处一氧化碳体积分数、隧道横截面竖向温度及隧道纵向人眼高度处温度的变化规律。结果表明,所研究的火灾参数与纵向通风之间呈现非线性变化关系,火源功率在纵向通风作用下出现"双驼峰"现象,随风速增大,火源功率、火焰主体长度与亮度的变化规律相似,平均燃烧速度与一氧化碳体积分数、温度变化规律一致。

The paper is to be engaged in an experimental study of the influence of the longitudinal ventilation on the fire disaster risk probabilities in the highway tunnel. One of the likely causes to result in such fires is the inefficiency of the longitudinal ventilation for extraction and cooling of the fire and smoke,for the longitudinal ventilation may change the fire size of the combustion with the other factors aggravating the fire and smoke. Therefore,in this paper,we have to take into careful account the various factors of the fire size,the flame shape,the height of the smoke spreading layer,and the carbon monoxide concentration rate in the human eye level 2 m away from the fire source,the vertical temperature of the cross section of the tunnel,and the temperature distribution at the human eye level with the longitudinal ventilation at different velocities. To clarify all the influential factors,we have done experiments to test the rig of the highway tunnel fire smoke moving features according to the Froude Principle. What is more,the size of the cross-sectional area of the jet fan has to be reduced according to the Froude Principle to be more practical and applicable. For this purpose,we have adopted the so-called method of＂seven-point integrated average velocity＂to test the velocity of the fan. The results that we have gained from the experiment demonstrate that：（ 1） The fire size tends to reveal a＂double-hump＂style of longitudinal ventilation,while the fire size,flame brightness and length tends to reflect the same changing regularity,which represents a non—linear relation with the longitudinal ventilation velocity. The height of the smoke layer would keep increasing linearly with the increase of longitudinal ventilation velocity until the test rig is full of smoke. And,then,the carbon monoxide concentration and the temperature distribution may gradually get to stabilized at the peak value.（ 2） There can be found a similar changing tendency among the fire size of the fuel,the average burning rate,the carbon monoxide concentration,the temperature and the flame shape along with the change of the longitudinal ventilation,which can reach its peak value at about 0. 78 m/s. According to the Froude Principle,the velocity should be 2 m/s correspondingly in the actual highway tunnel.