Characteristics of laminar inverse diffusion flame formed in two concentric tubes

CH₄-O₂-N₂ laminar inverse diffusion flames are investigated experimentally on the flame shape, stability and thermal structure. Experimental parameters are the fuel velocity, the fuel mole concentration, the oxidizer velocity, and the oxidizer mole concentration. The results obtained are as follows. In laminar flow region, inverse diffusion flames are categorized into eight types by changing the four parameters. High temperature region moves from the flame tip to the flame base by increasing of the fuel flow rate in the case of inverse diffusion flames, therefore the flames formed in the high fuel concentration are more stable. The inverse diffusion flames have less stable feature compared with the normal diffusion flames formed on the same burner. This is because the flow rate at the flame base of inverse diffusion flames is faster than that of normal diffusion flames.