Initial Fuel Temperature Effects on Flame Spread over Aviation Kerosene in Low- and High-Altitude Environments

Abstract

Long-distance petroleum or oil pipelines and aircraft taking off and landing cover a wide range of altitudes in practice. An increase in altitude leads to a decline in atmosphere pressure, as well as a decrease of the partial pressure of oxygen, which may influence the burning behavior of liquid fuels involved in accidental spills. In order to gain understanding on the hazards of spills from aircraft tanks or oil transport networks, experimental work was conducted in Hefei (50 m) and Lhasa (3,650 m) to investigate the effect of initial fuel temperature on flame spread over aviation kerosene both in low- and high-altitude environments. Data shows that flame spread is faster as the initial temperature increases. The transition from liquid-phase to gas-phase-controlled flame spread occurred at the initial fuel temperature of 65°C in Lhasa, but 82.5°C in Hefei. Moreover, for the same initial fuel temperature and under the regime controlled by liquid-phase transport, the rate of flame spread and temperature rise at low altitudes were smaller than those at higher altitudes, while the subsurface convection length and preheating time were larger. Direct evidence was also obtained to show the flame at both altitudes propagated in a pulsating forward-back-forward manner, whereas the average flame pulsation wavelength and frequency at the high altitude were larger than at the low altitude. Theoretical analyse predicts that an increase in initial fuel temperature or altitude led to an increase in fuel evaporation rate, which enhances flame spread and causes unsteady behavior. Given the difference in flame speed, fire accidents at high altitude are potentially more hazardous than those at low-altitude environment.