Microgravity investigation of laminar flame propagation in monodisperse gas–droplet mixtures

A model of unsteady-state laminar flame propagation under no-gravity conditions in a mono-disperse mixture of a gaseous oxidizer with droplets of a liquid fuel was developed. The results obtained during our theoretical study of the model were compared with experiments made in microgravity. An explanation for the experimentally measured anomalous non-monotone dependence of the flame propagation velocity on droplet size was given. It was shown that such a dependence could be observed immediately after ignition on segments where the process of flame propagation was unsteady. When the process became self-sustaining and steady, the normal velocity of flame propagation monotonically depended on droplet size (for small droplets, this velocity did not practically change as droplet diameters varied). Thus, it was demonstrated that for a steady-state self-sustained process the flame propagation velocity monotonically decreases on increasing droplet size.