Chemical kinetics of ignition of n-hexane by a moving hot sphere - Chemical Kinetics in Shock and Detonation Wave

The risk of accidental ignition of flammable mixtures by a hot surface is of particular importance for the commercial aviation industry. In the case of a lightning strike on the aircraft structure, hot particles might be ejected from the inner fuel tank surface and could potentially ignite the flammable vapor space of a fuel tank. Quantifying the risk of ignition of aviation fuels by hot particles is thus a key issue for both engineering design and safety analyses. In the present study, the kinetics of the ignition of n-hexane by a moving hot sphere has been analyzed. Non-reactive two-dimensional simulations have been performed to quantify the condition of temperature that the fluid experiences as it is heated by the hot sphere. Using these temperature profiles, the chemical activity predicted by several detailed reaction mechanisms as well as a one-step model has been studied. The results suggest that under the conditions presently considered, the low-temperature chemistry does not play a significant role in the ignition process due to the very short period spent by the mixture below 1000 K. Below the ignition threshold, the chemical activity is very low and the mixture essentially undergoes pyrolysis and partial oxidation.