Influence of longitudinal wind on mass burning rate of rectangular heptane pool fire with different aspect ratios

Fire is one of the primary disasters that threaten the safe operation of tunnel and underground space. Mass burning rate is a significant parameter in characterizing the behavior of pool fire which is related to thermal feedback, pool shape and ambient wind. Five convection-controlled heptane pool fires are examined inside a longitudinal wind tunnel with aspect ratio of 1, 2, 4, 8, and 16. The variation of burning rate with longitudinal wind is divided into increasing regime at v < 0.96 m/s, decreasing regime at 0.96 <= v < 1.98 m/s, and slightly-fluctuating regime at 1.98 <= v < 2.49 m/s. The effect of longitudinal wind on burning rate is attributed to heat feedback, flow disturbance and oxidizer supply around the flame. The increment of burning rate with wind speed is proved by the liquid evaporation theory. The heat transfer analysis proves that the enlargement rate of burning rate is linearly proportional to a coupling factor of longitudinal air flow speed and aspect ratio in a unified mathematical correlation Delta m''/k' = (2 root n + 1/root n)v which is fully consistent with measurements. The results provide guidance for tunnel fire protection design and prediction of fire development under the condition of vehicle tank leakage inside a tunnel.

Automated summary

Fire is a major threat to the safe operation of tunnels and underground spaces. The mass burning rate, which is related to thermal feedback, pool shape, and ambient wind, is an important parameter in characterizing pool fires. This study examines five convection-controlled heptane pool fires in a longitudinal wind tunnel with different aspect ratios. The burning rate variation with longitudinal wind is divided into three regimes: increasing, decreasing, and slightly-fluctuating. The effect of longitudinal wind on burning rate is attributed to heat feedback, flow disturbance, and oxidizer supply. The results provide guidance for tunnel fire protection design and fire development prediction under the condition of vehicle tank leakage inside a tunnel.