Abstract：
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.
2013, Vol. 50 