Stability of Buoyant Inverse Diffusion Methane Flames with Confinement Effects

Experimental and numerical studies were performed to examine the stability of inverse diffusion flames (IDFs) with the focus on the boundary wall effects. A regime diagram for flame stability was obtained based on the visual characteristics of flames and verified by the simulated flow fields. The boundary wall effects were identified and investigated by simulating the IDFs with different outer burner diameters. It was found that the wall-bounded induced shear flows either reduce the flow instability by vorticity diffusion or enhance it by vorticity convection. Based on the experimental and numerical observations, the mechanism of the boundary wall effects on the stability of buoyant IDFs was explained and further extended to general diffusion flames.