Experimental study of evaporation and ignition characteristics of RP-3 fuel on hot surfaces of different sizes

During aircraft operation, leakage of liquid fuel onto hot surfaces can lead to severe safety incidents. High-temperature components of aircraft (e.g., engine casings, tail nozzles, and fuel pipeline assemblies) vary significantly in size and shape, which may markedly influence the evaporation and ignition behaviors of leaking fuel. Therefore, this study experimentally investigated the evaporation and ignition characteristics of RP-3 fuel leaked onto hot surfaces of varying sizes (diameter = 4, 8, 12 cm). The experimental results indicated notable differences in evaporation and ignition characteristics across the tested surface sizes. As the hot surface size increased, the minimum hot surface ignition temperature and the ignition temperature threshold range decreased. The ignition delay time monotonically decreased with increasing hot surface temperature (T_S) and surface size. By comparing the average evaporation rates for different surface sizes, it was found that within the temperature range of T_S = 600–620 °C, the average evaporation rate increased with larger surface sizes. Energy conservation analysis demonstrated a positive correlation between the heat absorption rate of fuel and T_S. Additionally, before ignition, the relative contributions of heat transfer from the upper surface ($Q_{\mathrm{top}}/Q_{\text{total}}$) and the sidewall ($Q_{\text{side}}/Q_{\text{total}}$) of the fuel container were quantitatively analyzed. The results revealed that the proportion of $Q_{\text{side}}$ increased as the hot surface size decreased. This corresponds to higher heat transfer rates. Furthermore, a dimensionless correlation describing the average evaporation rate was developed. It incorporates the effects of varying hot surface sizes and temperatures, with predictions agreeing with the experimental data.