An Experimental Study on Mechanism of Eruptive Fire

ABSTRACT This paper presents a systematical experimental study on eruptive fire over a pine needle fuel bed in trench configuration in still air to elucidate the essential mechanism of eruptive fire. The fire spread characteristics under different slope angles (0–40°) and trench aspect ratios (0.1–0.4) are investigated by a comprehensive analysis of experimental data. The data of fire spread rate and flame depth reveal that eruptive fire is a kind of “sudden accident” that happens when the slope angle reaches a certain critical value. Under such a circumstance, as the flame depth increases after ignition, the fireline intensity increases and finally triggers the fire eruption when it comes to a necessary level. The fire eruption induces a series of changes in burning and fire spread behaviors such as sharp increases in velocity and influence range of the attached flow in the direction of fire spread. Due to the hot gas flow induced by flame attachment, compared to flame radiation, convective heating becomes to play a comparative or even more critical role in fire spread. The influence range of the attached flow increases with the slope angle or aspect ratio of the trench configuration, while for a given terrain slope, there is a ceiling effect of the trench aspect ratio on the fire eruption behavior.