Jet fuel droplet combustion with and without the convection

Combustion of stationary JP8 and JP8+100 fuel droplets were studied in low convectional environments for the first time. Although usage of these fuels is quite broad and significant, their fundamental physical properties are not well provided. Our goal is to provide practical parameters such as burning rate constants, burning times of jet fuel droplets by the use of the spherical symmetry in low convection. Furthermore, sooting propensity of JP8 and JP8+100 is reported by two approaches; burning in air and in a mixture of 30% oxygen and 70% helium (to suppress soot) at room temperature and 1atm. Low convection was achieved by performing experiments in a drop tower with a drag shield to reduce the gravity level. All experiments were fiber-supported and used the same experimental instruments to remove additional complexities. We also report a preliminary experimental result studied in natural convection (at room temperature and 1atm, air). The examined droplet diameters were from 0.44 to 0.49 mm for low convectional experiments and from 0.52 to 0.80 mm for natural convectional environment. Two different regions reveal very different results. In low gravity, significant droplet heating period and excessive soot for both fuels burning in air were observed. On the other hand, convection seems to overcome droplet heating by strong buoyancy, resulting in faster burning completion. Besides, the O₂/He mixture helps us understand a role of soot on droplet burning by soot control. As a final note, droplet burning for all cases is nonlinear even after the initial heating period. Therefore, the burning rate is time-dependent and increases throughout the burning.