Abstract Plug-holing of the smoke layer is an unfavorable phenomenon for the smoke extraction efficiency in the naturally ventilated tunnel with vertical shaft. In this work, theoretical analysis and large eddy simulation (LES) are carried out to investigate how to prevent the occurrence of the plug-holing phenomenon and improve smoke extraction efficiency. The results show that the occurrence of plug-holing is influenced by the height, cross-sectional area and total pressure loss coefficient of the vertical shaft, as well as the thickness of the smoke layer. A modified dimensionless number Fr* is proposed to represent the proportion of smoke in the exhausted mass flow. Fr* varies as the −1/4 power of the cross-sectional area of the shaft, −1/2 power of the height of the shaft, and increases linearly with the thickness of the smoke layer. The critical value of Fr* for predicting whether the plug-holing phenomenon occurs is determined to be 0.34 by combining the results of the previous small-scale experiment. In addition, a smoke reservoir is designed under the shaft to increase the thickness of the smoke layer, which is proven to be effective in preventing the occurrence of the plug-holing phenomenon and improving the smoke extraction efficiency of the vertical shaft. The findings of this paper contribute to the understandings of smoke extraction for naturally ventilated tunnel with vertical shaft, and the results are also useful to the fire protection engineering in tunnels.

中文翻译：

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立井自然通风隧道排烟效率及储烟器排烟效率数值研究

摘要 竖井自然通风隧道烟气层堵塞是影响排烟效率的一个不利现象。在这项工作中，通过理论分析和大涡模拟（LES）来研究如何防止堵塞孔现象的发生和提高排烟效率。结果表明，堵孔的发生受竖井高度、截面积、总压损系数以及烟层厚度的影响。提出了一个修正的无量纲数 Fr* 来表示排气质量流中烟雾的比例。Fr* 随竖井截面积的-1/4 次方、竖井高度的-1/2 次方变化，并随烟层厚度线性增加。结合之前的小规模实验结果，确定预测是否出现堵孔现象的临界值Fr*为0.34。此外，在竖井下方设计了储烟器，增加了烟层的厚度，被证明可以有效防止堵孔现象的发生，提高竖井的排烟效率。本文的研究结果有助于理解竖井自然通风隧道排烟问题，对隧道消防工程也有一定的借鉴意义。竖井下方设计了储烟器，增加了烟层的厚度，被证明可以有效防止堵孔现象的发生，提高竖井的排烟效率。本文的研究结果有助于理解竖井自然通风隧道排烟问题，对隧道消防工程也有一定的借鉴意义。竖井下方设计了储烟器，增加了烟层的厚度，被证明可以有效防止堵孔现象的发生，提高竖井的排烟效率。本文的研究结果有助于理解竖井自然通风隧道排烟问题，对隧道消防工程也有一定的借鉴意义。