On Instabilities and Flame Structures of Laminar Aerosol Flames

Flame instabilities, characterised by wrinkling and cellular surface structure, increase the burning rate due to the associated increase in surface area. The effect has been shown theoretically and experimentally to be a function of Markstein number and critical Peclet number; the latter marks the flame radius at which cellularity is first observed. Comparisons between gaseous and aerosol flames have shown quantitatively that the presence of liquid droplets influences instabilities by causing earlier onset and more rapid development of cellularity than for gaseous flames, particularly at rich conditions. The Markstein number and Peclet number decrease with increasing droplet diameter as a result of the change in thermal d iffusivity and this leads to an associated decrease in cell size.