Experimental study on the early stage of upward flame spread with cross air flow

In this work, experiments were conducted to study the upward flame spread with cross wind at an early stage (prior to the acceleration of pyrolysis spread rate of the wide slab). An exponential model was fitted to the experimental data of the spread rate of pyrolysis front and the dimensionless cross wind speed, which showed satisfactory results. The pyrolysis front tilt angle showed a decreasing trend with a low cross wind speed. However, at high cross wind speeds, the pyrolysis tilt angle exhibited an increasing trend with the maximum value of 45°. The flame lengths increased with the cross wind for narrower slabs, whereas the phenomenon was most pronounced for the narrowest slab. Additionally, the flame length did not exhibit the lengthening phenomenon for the wider slab (0.1 m). Furthermore, the flame tilt angle did not exhibit significant change over time (even along the pyrolysis length). The correlation of flame tilt angle with the cross wind speed and width was also obtained in this study. The flame tilt angle presented a power-law increase with respect to the dimensionless cross wind speed.