Characterization of Nonpremixed Turbulent Bluff-Body Burner Flames. Annual Report, January-December 1989

摘要

The bluff-body flame regimes and blowout limits were correlated to the recirculation zone fuel concentration for both undiluted and diluted fuel jets. Measurements of OH and CH plus CH4 in jet and bluff-body stabilized flames showed similar reaction zone characteristics in these two flames indicating flame zone structure is independent of the large-scale flow dynamics. Flame connectedness and shape are, however, determined by large-scale flow dynamics. CH and OH data in the jet flame were consistent with dissipative eddy model predictions. The effect of confinement at both low (25%) and high (83%) blockage ratios was studied. At low blockage ratio, confinement did not affect the flow pattern or flame stability, while at high blockage ratio, confinement significantly altered flame stability. Nonreacting vortex dynamics model calculations were performed, which revealed the recirculation zone flow dynamics and its quasi-periodic behavior. The calculations showed that the growth and separation of the large-scale vortices become pronounced under selected conditions. These motions would have the potential to extinguish flames.