Abstract The previous researchs of the critical velocity are mainly for single-point tunnel and limited for branched tunnel. The critical velocity together with the driving force for preventing smoke backflow in branched tunnel cannot be precisely predicted by former correlations. Experiments are conducted in this work to investigate the fire-induced smoke movement in branched tunnel under the cases of critical ventilation velocity condition. The pressure change in branched tunnel is analyzed on the basis of one dimensional theory, and the fire source and bifurcation angle was taken into account. Results show that the bifurcation angle has a significant influence on the critical velocity and the driving force for preventing smoke backlayering due to the local resistance. The pressure difference due to the plume blockage created by the fire are expressed on the basis of experimental data. Based on the theoretical analysis of pressure change, new relatively correlations considering the bifurcation angle and heat release rate are proposed to predict the critical velocity together with the required pressure rise for preventing smoke backflow in branched tunnel. The predicted critical velocity by proposed model are found to comply well with the experimental data.

中文翻译：

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支管火灾中防止烟气回流的临界速度和驱动力建模与试验研究

摘要 以往对临界速度的研究主要针对单点隧道，对分支隧道的研究有限。以前的相关性无法准确预测临界速度以及防止分支隧道中烟气回流的驱动力。本文通过实验研究了临界通风速度条件下分支隧道内火灾引起的烟气运动。基于一维理论分析了支管内压力变化，并考虑了火源和分叉角。结果表明，分叉角对临界速度和防止由于局部阻力引起的烟气背层的驱动力有显着影响。由火灾造成的羽流堵塞引起的压力差是根据实验数据表示的。在对压力变化的理论分析的基础上，提出了考虑分叉角和放热率的新的相对相关性，以预测临界速度以及防止支管烟气回流所需的压力升高。发现由提出的模型预测的临界速度与实验数据很好地符合。