  The non linear description of laminar premixed flames has been very
successful, because of the existence of model equations describing the dynamics
of these flames. The Michelson Sivashinsky equation is the most well known of
these equations, and has been used in different geometries, including
three-dimensional quasi-planar and spherical flames. Another interesting model,
usually known as the Frankel equation,which could in principle take into
account large deviations of the flame front, has been used for the moment only
for two-dimensional expanding and Bunsen flames. We report here for the first
time numerical solutions of this equation for three-dimensional flames.
