纵向通风下隧道长度对临界风速的影响分析

临界风速可有效控制烟气蔓延,是隧道防灾通风重要参数。为分析隧道长度对临界风速的影响,采用量纲分析法构建临界风速与隧道长度关系公式,并分别在5 MW和30 MW火源热释放速率下,对不同长度隧道的火灾进行数值模拟以量化研究隧道长度对临界风速的影响。结果表明,隧道长度对临界风速具有影响,且不同火源释放速率时影响也有所不同:无量纲火源热释放速率小于0.15时,临界风速随隧道长度增大呈现1/41次方增长关系;无量纲火源热释放速率高于0.15时,临界风速随隧道长度增大呈现1/25次方增长关系。进而建立了考虑隧道长度的无量纲临界风速计算公式。

Analysis on Influence of Tunnel Length on Critical Ventilation Velocity under Longitudinal Ventilation

Critical ventilation velocity can effectively control the spread of smoke, which is the key parameters of tunnel fire research and disaster prevention design. The relationship between critical ventilation velocity and tunnel length is constructed by dimension analysis. In order to quantify the effect of tunnel length on critical ventilation velocity, numerical simulation of tunnel fires with different lengths is carried out under two kinds of heat release rates (HRR) of 5 MW and 30 MW. The results show that the tunnel length has an impact on the critical ventilation velocity, and the impact of different HRR is different. When the dimensionless HRR is low (Q^*<0.15), the critical ventilation velocity in the dimensionless state increases with the tunnel length of 1/41 power growth. However, when the dimensionless HRR is high (Q^*>0.15), it increases with the tunnel length of 1/25 power growth. And the dimensionless critical ventilation velocity calculation formula considering the length of the tunnel is proposed.