AN EXPERIMENTAL-STUDY ON THE IMPACT OF ACOUSTICS AND SPRAY QUALITY ONTHE EMISSIONS OF CO AND NO FROM AN ETHANOL SPRAY FLAME

The effects of frequency, sound pressure level, excess air, and spray atomization on NO and CO emissions from a spray flame in a Rijke tube combustor were investigated using an electrochemical gas analyzer and a phase-Doppler droplet sizing instrument. A large decrease in NO and CO emissions was observed in the presence of acoustic oscillations. Ta king concentration values at steady conditions as a reference, per cen t reductions in NO and CO varied between 52 and 100%, and 53 and 90% w ith average values of 79 and 73%, respectively. The largest decreases were observed with increases in sound pressure level, followed by incr eases in acoustic frequency, and increases in excess air. Although the overall production of these pollutants is reduced, how much reduction is obtained depends on the nozzle position with respect to the acoust ic field. NO and CO emissions as a function of excess air were also re duced as the spray initial Sauter mean diameter decreased. A combustio n efficiency of 99% for all acoustic modes, compared to 94% for steady operation, was obtained with an excess air of 10%. No significant var iations in the combustion efficiency as a function of acoustic mode we re observed. (C) 1998 Elsevier Science Ltd. All rights reserved.