Interactive influences of convective flow and initial droplet diameter on isolated droplet burning rate

In quiescent ambiences the burning rate of an isolated liquid fuel droplet varies with the droplet’s initial diameter d0 due to the close surrounding of the droplet in the flame and the subsequent strong action of flame heat, in balance with its loss to ambience, on burning. Suppressing the influence of d0 on burning rate was recognized in this communication through burning the droplet in a forced convective flow that sweeps the flame off the droplet to weaken the action of flame heat on burning. The d0-dependent k0, however, affected the correlation k=k0(1+C·Re0.5) for the burning rate in convective flows, where k0 and k are the burning rate constants, respectively, in the equi-temperature quiescent and convective-flow ambiences, and Re is the flow’s Reynolds number with respect to d0. Different correlation constants C were acquired when using different d0 and its corresponding k0 to fit the correlation. In hot conditions (633 K in this article) k0 is bigger for larger d0, causing a smaller constant C when taking a larger d0 for the correlation. Against this, k0 is lower for larger d0 in room-temperature ambiences, which resulted in the mutual compensation of the effects from k0 and d0 on C such that C is basically independent of the values of d0 and k0. Besides, the communication showed that C was larger for the gas flow with a higher temperature, revealing an increase in the effect of Re on burning with raising the gas temperature.