Effects of wind speed, spacing distance and heat release rate on the combustion and flame merging characteristics of two extra-thin line fires

This paper investigated the mutual interaction between two extra-thin line fires under different wind speeds of 0.4, 0.6, 0.8, 1.0 and 1.2 m/s by using a small-scale wind tunnel. The experiments involved the spacing distances of 5, 10, 15, 20, 25, 30, 35 and 40 cm, and the heat release rates of 19.4, 25.7 and 32.7 kW, respectively. The results show that the flame merging probability increase, as the wind speed or the heat release rate increases. Compared with the two rectangular or square fires, the flame height and flame length will be smaller at the same heat release rate for the extra-thin line fires. Meanwhile, the line fires will decrease the flame merging, making the downstream flame temperature smaller than that of the upstream at the relatively larger wind speed or heat release rate. The interesting finding is that, with the increase of the heat release rate, the flame inclination angle will increase in the fully merging stage, which is opposite to that of square fires. Correspondingly, the flame merging model is built on the influences of the buoyancy force and inertial force of the horizontal wind, which can give the good explanation on this behavior.