The influence of milliliter-scale oil volume on ignition temperature and fire behavior induced by hot surface

As the common ignition source in the chemical processing industry, hot surfaces could ignite leaking flammable liquid fuels, further causing property damage and casualties. In real fire scenarios, the leakage volume of flammable liquid is typically random. While previous studies have primarily focused on the minimum ignition temperature of flammable liquids, the leakage volume in these studies is relatively small. In order to explore the influence of milliliter-scale leakage volumes (3–9 mL) on the ignition and burning characteristics induced by hot surface, the fire experiment was carried out for transformer oil, where some key parameters were measured and analyzed, including ignition probability, ignition delay time, and fire thermal radiation. Based on hot surface experiments with oil volumes ranging from 3 to 9 mL, it was found that three reaction conditions can be classified for the transformer oil leaking onto hot surfaces, including non-ignition, ignition after long time heating and ignition during the leakage stage. The ignition probability of transformer oil varies with temperature following N-shaped curve, and then traditional prediction model of ignition probability was modified by the single-peak expression. There is a clear negative correlation between the minimum ignition temperature and the volume of oil. The ignition delay time increased as the liquid fuel volume increased for the ignition after long time heating, and the liquid fuel volume had limited influence on the ignition delay time for the ignition during the leakage stage. Furthermore, it was found that the increase in oil volume would contribute to the occurrence of flame overflow. As the volume of leaking oil increases, the maximum radiative heat flux increase exponentially with the surface temperature. The research results provide crucial theoretical support for risk assessment of liquid fuel leakage fire hazards.