Near-limit oscillations of spherical diffusion flames

We examine the dynamic characteristics of a droplet of liquid fuel burning in a reduced oxidant environment. The study is motivated by the experimental observations of candle flames in microgravity, which bear some similarity to the spherical diffusion flame that surrounds a burning liquid fuel droplet. The microgravity experiments reveal that when the oxidant concentration in the chamber is sufficiently low, oscillations develop prior to extinction. A similar phenomena is predicted here. An oscillatory state results for a sufficiently low oxidant concentration when radiative losses from the flame are appreciable. The frequencies of oscillations we predict are in good agreement with the experimental observations.