This paper systematically introduces a new tunnel fire ventilation theory focusing on fire size. The model was established by simplifying and analyzing basic thermal fluid dynamic equation sets instead of referencing similar criterion to Froude to reveal the logical relationship among the heat release rate of the, fire source, tunnel ventilation velocity and tunnel height. According to this new theory, the critical speed of tunnel ventilation is a logarithmic function of the fire size, which explains why the critical speed is independent of the heat release rate for a large tunnel fire. Using this new concept of fire size, the criteria for a tunnel fire classification system based on quantifications are given and the physical characteristics of various fires are described mathematically. Compared with existing experimental data, the new theory successfully predicts the critical velocity of tunnel ventilation within the scope of the heat release rate and solves the problem of an infinitely increasing critical speed with the development of the heat release rate in existing models. Because of the two-dimensional nature of this new theory, the effects of tunnel side walls on fire ventilation need to be further studied.%文章介绍了一种新的隧道防火通风理论.与目前通用理论不同的是,该模型没有从Froude相似准则出发,而是通过对基本热流体动力学方程组的简化、分析,揭示了火源放热率与隧道通风速度和隧道高度之间的逻辑关系,提出了以火势为特征的隧道火灾通风理论；依据这一理论,隧道通风临界速度为火势的对数函数,进而解释了大型隧道火灾中临界速度与火源放热率无关这一重要实验现象；利用新的火势概念,该理论给出了定量的火灾分类准则,并从数学上描述了各类火灾的物理特征；与现有实验数据比较,新理论无需任何实验修正,在所有火源放热率范围内成功地预测了隧道通风临界速度,从理论上克服了现有模型中临界速度随放热率无限增大的问题.由于新理论的二维性质,隧道侧壁面对防火通风的影响仍需进一步研究.
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