Premixed flame kernel growth in the presence of a vortex ring

A laminar vortex toroid, representing a building block of turbulence, was studied as it interacts with a lean, premixed, spark-generated flame kernel in a well-controlled environment. Kernel-vortex interactions for four different characteristic length scales (size of vortex), three different characteristic velocity scales (strength of vortex), and three different kernel maturities at the onset of the interaction were measured using an image-intensified high-speed videocamera, operating at 4500 frames/sec. Spark-generated flame kernels were formed in a very weak methane-air mixture (φ = 0.6) to exaggerate the effect of the vortex on the kernel growth. More robust kernels were also studied by increasing φ to 0.8, more than doubling the laminar burning velocity. Lewis number effects were expected to be strong due to the very high curvature. These effects were investigated using a propane-air mixture with φ = 0.7. Global quenching of the flame kernel, local quenching of the kernel, and intensified flame speeds due to the vortex interaction were observed under various experimental conditions. Original is abstract.