Stability of a Turbulent Jet Methane Flame Issuing from an Asymmetrical Nozzles with Sudden Expansion

The effect of quarl (i.e., a sudden expansion) on the stability of turbulent diffusion flame of methane jet issuing from asymmetric nozzles and discharging into still air environment is examined experimentally. The study covers the flame liftoff height and velocity, as well as the reattachment and blowout velocities. Five nozzles with different internal geometries but with similar equivalent exit diameter are tested. The results reveal that the jet flame liftoff height is reduced further when quarl is attached to the exit of the nozzle. Moreover, the stability range of the lifted flame is found to expand when quarl is attached to the nozzle. Quarl leads to an increased flame blowout velocity, which is the upper stability limit, and decreasing the liftoff velocity, which is the lower lifted flame stability limit. This might be of great interest for industrial applications in which a wide stability range of the lifted flame is desired.