城市公路隧道近火源区质量卷吸速率研究

Research on smoke entrainment rate of urban highway tunnel near the fire source area

质量卷吸速率是火灾烟气防控时不可忽视的关键因素.以全尺寸的城市公路隧道为研究对象,采用量纲分析和数值模拟的方法,探究了火源功率、有效顶棚高度、火源横向位置、隧道宽度对烟气质量卷吸速率的影响.通过对前人所提出的卷吸模型适用性分析和20组模拟工况下卷吸速率变化规律的研究,结果表明:对于具有不同卷吸机理的大、小火源功率的隧道火灾,前人提出的Ⅱ、Ⅲ阶段的卷吸模型具有一定局限性;采用集气罩法测定了火源近场区质量卷吸速率,并用离散化方法对阶段Ⅱ、Ⅲ截面质量流率进行计算,提高了结果的准确性;基于量纲分析的方法构建了火源功率、隧道宽度、火源位置、有效顶棚高度等重要因素间的无量纲烟气卷吸模型,结合数值模拟并对数据拟合得到了Ⅱ、Ⅲ阶段烟气质量卷吸速率的定量关系式.

The mass entrainment rate is a key factor that can not be ignored when preventing and controlling flue gas.The full-scale urban highway tunnel was taken as the research object,and dimensionless analysis and numerical simulation methods were used to investigate the influence of fire power,effective ceiling height,fire source lateral position and tunnel width on the mass entrainment rate of flue gas.Through the analysis of the suitability of the rolling suction model proposed by previous researchers and the variation of the entrainment rate under the 20 simulation conditions,the results show that for the large and small power sources with different entrainment mechanisms,the entrainment models proposed by predecessors at the stage II and III have certain limitations.The mass entrainment rate in the near-field area of the fire source was measured by the hood method.And the mass flow rate of the stage II and III sections was calculated by the discretization method with the accuracy of the results being improved.Based on the dimensional analysis method,the dimensionless smoke entrainment model was constructed,which is associated with the key factors,such as the fire power,the tunnel width,the fire source position,and the effective ceiling height.And the quantitative relation formulas of gas mass entrainment rate in stage II and III were obtained by numerical simulation and data fitting.