Study on the Critical Flame Spread Along Inclined and Discrete Thermally-Thin Paper

Abstract

Flame spread over discrete solids with different inclination angles is a typical phenomenon in fire scenarios. In this study, the phenomenon of flame spread over thin fuels separated by critical air gaps with different inclination angles is experimentally investigated. In this paper, experiments with inclinations angles from 0° to 75°were designed to capture the critical gap sizes, the flame morphology, the gap temperature, the hot air flow around the fuel, and the flame spread rate during the flame spread process. The results show that the critical fuel coverages are from 0.5 to 0.95 for different inclination angles. There is a special phenomenon of flame splitting during critical flame spread. The temperature variations within the gap are analyzed and the rate of temperature rise increased with the increase of tilt angle. Visualizing the flow field around the fuel using a schlieren system enhances the understanding of flame-spreading mechanisms influenced by tilt angle and critical gap. The size of the hot gas flow layer above and below the fuel both increases with the increase of inclination angle. The proposed model reveals a correlation between flame spread rate at critical fuel coverage and fuel tilt angle, alongside flame pyrolysis length.