为对近火源区长度进行研究,以城市公路隧道为研究对象,采用理论分析与数值模型相结合的方法,探究了大火源功率、有效顶棚高度和火源横向位置对近火源区长度的影响,对36个工况的数值模拟和温度场变化规律的研究与分析.结果表明:火焰未撞击顶棚时,火源功率对近火源区长度几乎没有影响;当火焰持续撞击顶棚并形成水平扩展火焰时,近火源区长度受火源功率和有效顶棚高度影响较大,其无量纲形式与无量纲火源功率的2/3次方呈线性关系;随着火源与侧壁距离的减小,近火源区长度呈自然指数增加趋势;火源贴壁时,近火源区长度是火源位于隧道中部时的1.866倍;提出了近火源区长度预测模型,基本揭示了烟气由过渡阶段转入一维蔓延阶段起始位置的变化规律,能够为定量研究各阶段烟气流动特性提供参考依据.%To study the length of area near the fire source , taking the urban highway tunnel as the research object , the influ-ence of large fire source heat release rate ( HRR) , the effective ceiling height and the horizontal position of fire source on the length of area near the fire source were studied by using the numerical simulation method , and the numerical simulation of 36 working conditions and the variation laws of temperature field were studied and analyzed .The results showed that the fire source HRR had no influence on the length of area near the fire source when the flame did not impact the ceiling , while the fire source HRR and the effective ceiling height significantly influenced the length of area near the fire source when the flame continuously impacted the ceiling and formed the horizontally extending flame , and there was a linear relationship between the dimensionless form of the length of area near the fire source and the 2/3 power of dimensionless fire source HRR .The length of area near the fire source increased as a natural exponential function with the decrease of the distance between fire source and side wall .When the fire source attached to the wall , the length of area near the fire source was 1.866 times as long as that when the fire source located in the middle of the tunnel .A prediction model of the length of area near the fire source was put forward , which basically revealed the variation laws about the initial position of smoke converting from the transition stage to the one -dimensional spreading stage , and it can provide the reference basis for the quantitative research on the smoke flow characteristics at different stages .
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