Experimental and numerical study on the local extinction mechanisms of ethanol spray swirling flames

This work involved a detailed experimental and numerical investigation of ethanol spray flames in a swirl-stabilized burner to reveal the underlying physics of local extinction. The non-reacting and reacting flows under stable and near-blow-off conditions were analyzed. Experimentally, the particle imaging velocimetry technique was employed to analyze the velocity fields and spray characteristics, while simultaneous planar laser-induced fluorescence of the OH radical was used to measure the flame structure. Numerically, the time-averaged flow fields, flame structure, and droplet–flame–turbulence interactions of different cases were investigated using large eddy simulation coupled with a discrete particle simulation. The comparison between the experimental and numerical studies shows a good agreement on the velocity field, as well as the spray distribution and flame structure. The dynamics of local extinction in the spray swirling flame were elucidated by combining experimental and numerical analyses. Three significant factors contributing to local flame extinctions have been validated, including droplet–chemistry interactions, droplet–flame interactions, and flame–turbulence interactions. Specifically, the local extinction events are primarily initiated by fluctuations in the local mixture fraction near the flame front, high heat loss, and excessive stretch in the shear layer.