Abstract: PMMA(Polymethyl Methacrylate) panels (8 cm×10 cm×1 cm) are used as experimental materials to carry out vertical fire spread experiments with different fuel spacing (0~10 cm) to analyze changes in flame height, burning rate, pyrolysis front position and ignition delay time. It is found that with the increase of fuel spacing, the net flame height and burning rate of the solid surface both increase first and then decrease. In addition, the flame "ignition delay" occurs during the spreading process of the adjacent solid fuel surface, and its ignition delay time increases exponentially with the increase of the fuel spacing.

Key words: fuel spacing, vertical combustion, flame height, burning rate, ignition delay time