Characterizing burning behaviour of convection-controlled pool fires at sub-atmospheric pressure by stagnation theory

Pool fires play a critical role in examining the burning behaviour of diffusion flames and are sensitive to changes in scale and environmental conditions. Understanding the evolution of pool fires under low-pressure conditions, common in plateau or flight scenarios, is essential for both fire safety and energy utilization. This study investigates the effects of pressure on pool fires through a series of small-scale experiments carried out in a pressure chamber that provides stable conditions ranging from 95 kPa to 40 kPa. Pool scales between 7 cm and 16 cm were examined, a range dominated by convective heat transfer. Methanol and heptane were chosen to discern fuel-specific variations in burning behaviour under decreased pressure. The findings demonstrate an increase in the axial flame temperature with reducing pressure, while radiative output exhibits an inverse relationship with pressure. Additionally, convective heat transfer toward surroundings appears to rise with decreasing pressure. A modified stagnation theory solution is proposed to model the mass burning rate of convection-controlled pool fires under low pressure, which shows satisfactory agreement with the experimental data. This research could potentially contribute to the comprehension of pool fires and the safety of energy in sub-atmospheric pressure conditions in the future.