Abstract Effect of blockage on critical ventilation velocity in longitudinally ventilated tunnel fires was investigated based on small-scale experiments and numerical simulations. Blockages were located right upstream of the fire or 3.5 m upstream of the fire. At each location, blockages have five blockage ratios and two orientations. Experimental data shows that the factors as blockage ratio, blockage-fire distance and blockage orientation could have coupling effect on the critical ventilation velocity. For blockage right upstream of the fire, the critical ventilation velocity decreases with the increasing blockage ratio when blockages are horizontally positioned, while there is first decrease and then increase in the critical ventilation velocity for blockage vertically positioned. A correlation was proposed to predict the critical ventilation velocity for blockages right upstream of the fire and horizontally positioned. For blockage 3.5 m upstream of the fire, the change in the critical ventilation velocity is very slight with the increasing blockage ratio for blockages vertically positioned, however, when blockages are horizontally positioned, there is an increase in the critical ventilation velocity for large blockage ratios. The change in the critical ventilation velocity with increasing blockage ratio is more obvious for blockages right upstream of the fire than that for blockages 3.5 m upstream of the fire. Numerical simulations were also conducted in the tunnel without fire. The altered tunnel flow field due to the obstruction of blockage was observed and its effect on the critical ventilation velocity was addressed. Comparison of the critical ventilation velocity between the experimental data and the results from previous studies showed that the critical ventilation velocity changed differently with the existence of blockage. The reason for this difference might be that the relative position between the blockage and the fire, and the fuel type could have coupling effect on the critical ventilation velocity.

中文翻译：

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纵向通风隧道火灾中堵塞对临界通风速度的影响

摘要 基于小规模试验和数值模拟，研究了堵塞对纵向通风隧道火灾临界通风速度的影响。堵塞物位于火灾上游或火灾上游 3.5 m 处。在每个位置，阻塞有五个阻塞率和两个方向。实验数据表明，堵塞比、堵塞火距和堵塞方向等因素对临界通风速度有耦合作用。对于火源正上游的堵塞物，当堵塞物水平放置时，临界通风速度随着堵塞率的增加而降低，而垂直放置时，临界通风速度先减小后增加。提出了一种相关性来预测火灾上游和水平位置堵塞的临界通风速度。对于火源上游 3.5 m 处的堵塞物，垂直放置的堵塞物随着堵塞率的增加，临界通风速度的变化非常小，而当堵塞物水平放置时，大堵塞比的临界通风速度增加. 与火源上游 3.5 m 的阻塞相比，火源上游阻塞物的临界通风速度随阻塞率的增加变化更为明显。在没有火灾的隧道中也进行了数值模拟。观察到由于堵塞造成的隧道流场改变，并解决了其对临界通风速度的影响。实验数据与前人研究结果的临界通风速度的比较表明，临界通风速度随着堵塞的存在而变化。造成这种差异的原因可能是堵塞物与火灾的相对位置、燃料类型对临界通风速度有耦合作用。