Stationary spherical diffusion flames can be established with the help
of a spherical burner in which fuel is supplied internally to a stati
onary porous sphere in microgravity. The most important parameter in t
his configuration is the mass flow rate through the sphere, which can
be controlled independently and conveniently. Other relevant parameter
s are the Damkohler number, which is proportional to the ambient press
ure and to the surface area of the sphere, the heat loss to the burner
, and the fuel and oxidant Lewis numbers. In this study we examine the
characteristics of burner-generated diffusion flames as a function of
these parameters, with particular attention given to extinction condi
tions. It is shown that steady flames can be sustained in the vicinity
of the sphere even at sufficiently low injection velocities and that
extinction occurs when excessive reactant leakage through the reaction
zone develops.