Convection-Diffusion Controlled Laminar Micro Flames

Small laminar diffusion flames (flame height ≃2–3 mm) established by a fuel jet issuing into a quiescent medium are investigated. It was found that for these flames buoyancy effects disappeared as the flame size decreased (Fr≫1), and diffusive transport of the fuel was comparable to the convective transport of the fuel. The effect of buoyancy on these flames was studied by examining the flame shape for horizontally oriented burners. A phenomenological model was developed (based on experimentally determined flame shapes) to compare diffusion and convection transport effects. Finally, the flame shapes were theoretically determined by solving the conservation equations using similarity methods. It was seen that when the axial diffusion (in momentum and species equations) terms are included in the conservation equations, the calculated flame shape is in better agreement (as compared to without the axial diffusion term) with the experimentally measured flame shape.