Evaporation and piloted ignition in porous media soaked with heptane

In incidents involving liquid fuel spills, the application of porous media such as sand is widely regarded as an efficient and safe mitigation measure. However, the effectiveness of this approach in preventing ignition has not been thoroughly investigated. This study investigated the evaporation and piloted ignition behavior of quartz sand soaked in heptane (representative flammable liquid) under varying external heat fluxes (10-50 kW/m2) and fuel levels, using a cone calorimeter with electric spark igniter. A numerical model, complemented by theoretical ignition models, was developed to simulate the underlying processes. Results showed that the time required for flash ignition and sustained ignition decreased nonlinearly with increasing external heat flux and fuel level, with sustained ignition times ranging from 28 s to 3400 s. The critical mass flux (the minimum mass flux of fuel gases for which the flame is sustained for at least 5 s) required for sustained ignition remained consistent under different conditions and was accurately predicted by a gas-phase ignition model. By calibrating key parameters and boundary conditions, the numerical model effectively predicted both evaporation rates and temperature evolution. The integration of numerical and ignition models enabled the prediction of sustained ignition times with errors within 20%. The findings of this study provide data and a valuable tool for assessing the ignition behavior of fuel-soaked porous media.