Heat and mass transfer of flame spread over jet fuel at sub-flash temperature

Flame propagation over the surface of a liquid fuel is a complicated problem of coupled interactions, including heat transfer, mass transfer, and hydrodynamic processes. Based on some tentative laboratory-scale experiments, the heat and mass transfer mechanisms of flame spread over jet fuel surface at sub-flash temperature are investigated. Results show that an olive-shaped liquid-phase convection flow, which is close to the pool surface, apparently forms during the sub-flash flame spread process. The subsurface convection flow could be separated into two regions: a thin layer of surface tension-driven flow and a thick thermal vortex zone induced by the coupling effects of surface tension and viscous force. Moreover, a theoretical deduction predicts that the velocities of subsurface convection flow are considerably larger than the experimental data, and several probable reasons are proposed to interpret this difference. Furthermore, the magnitude of heat transfer involving in flame spread over liquid fuel decreases as the pool temperature increases, whereas the velocity of flame spread increases with the initial fuel temperature. The liquid-phase convective heat transfer contributes 88% heat flux in the process of flame spreading.