Merging of two opposite-spreading flames on kerosene under parallel and perpendicular wind

Liquid fuels such as aviation kerosene are highly flammable and volatile, showing a significant risk of fire and explosion. This work conducted experiments on the spread of two flames toward each other and merging behavior of RP-5 aviation kerosene under parallel and perpendicular winds. Under the parallel wind ( ), at ≤ 0.5 m/s, the dual effects of heat plume collision-induced heat dispersion and insufficient fuel vapor diffusion significantly suppressed the merging speed of two flames. At > 0.5 m/s, the spread rate is enhanced by concurrent wind through flame stretching and combustion area enlargement, while the flame leading edge is continuously blown off by the opposed wind. Meanwhile, the flame merging point gradually shifts toward the leeward side with increasing . Under the perpendicular wind ( ), spread behavior at low-wind speeds resembles that under parallel wind. At > 0.5 m/s, symmetric vortices are formed to improve oxygen-fuel mixing efficiency and superimpose radiant heat, which promotes the flame spread more than the concurrent wind. The gas-liquid two-phase temperature distribution reveals the dynamic heat transfer process: the gas-phase temperature rises rapidly, while the liquid-phase temperature exhibits a delayed response. Finally, a prediction model of flame spread rate is developed. • Investigate two flames spreading toward each other under different wind speeds and directions. • Reveal flame spread mechanism over liquid fuel under parallel and perpendicular winds. • Discover oscillated flame spread over liquid fuel under concurrent-opposed airflow competition. • Develop a prediction model of average flame spread rate with an accuracy of 30%.