An Investigation of Methane-Air Nonpremixed Combustion in a Rapid-Mixing Burner

Abstract An experimental analysis was performed on a rapid-mixing burner in which the mixing of methane and air occurs in discrete vortex structures prior to burning. Air is distributed by large vortex structures, and burning of fuel-air are mixtures occurs in smaller eddies. The burner design was evaluated by utilizing various visualization and diagnostic techniques. The advantages and disadvantages of each are discussed. High speed video is employed to evaluate fickering phenomena. Mixing induced by vortex structures is visualized by means of scattering across a laser light sheet. Velocity measurements made with a laser Doppler velocimeter confirm flow divergence and high kinetic energy at the flow edges through which the vortex structures transit. Temperature measurements made with a fast response thermocouple reveal a well-mixed combustion zone. The flame flickers in a manner similar to that occuring in isothermal helium plumes. Therefore, the results present sufficient evidence that a rapid-mixing burner has been successfully devised using radial fuel injection and a noncircular duct cross-section.