INFLUENCE OF BOUNDARY-INDUCED LOSSES ON THE STRUCTURE AND DYNAMICS OFFLAME-BALLS

A theory of finite-size premixed flamelets (''flameballs''), in which the only processes involved are heat conduction, Arrhenius kinetics an d diffusion of a light scarce reactant, is extended to account for the presence of a neighbouring cold impermeable wall. Using activation en ergy asymptotics we show that: (i) owing to its conductive and diffusi ve influences, the wall leads to two branches of stationnary, approxim ately spherical, flame balls when it is sufficiently remote. (ii) a no n-linear equation with memory effects governs the flame radial dynamic s. (iii) only a Lewis-number-dependent part of the upper branch allows for steady states that are stable against radial disturbances. (iv) a long the unstable part of the upper branch, the instability is of osci llatory type. (v) by contrast to what happens when near-field volumetr ic losses are accounted for, no three-dimensional instability shows up .