Date of Graduation

1996

Document Type

Thesis

Abstract

The intent of this project was to investigate the flow field and emissions of laterally and radially oscillating natural gas flames produced by slot and axisymmetric fluidic nozzles used as burners. The behavior of flames produced by three nozzles was studied. A parametric study was conducted while visualizing and quantifying the flame flow field and measuring emissions produced by the flame. Nozzle configurations included two different-sized axisymmetric nozzles and one slot nozzle. Flame oscillation frequency varied from zero to 35 Hz; equivalence ratios ranged from 0.6 to 1.4. A focusing Schlieren system was designed, constructed, and used to visualize the flame flow field and flue gas emissions including NO, NO{dollar}\\sb{lcub}\\rm x{rcub},{dollar} CO, CO{dollar}\\sb2,{dollar} and O{dollar}\\sb2{dollar} were measured from the flames. Laser Doppler anemometry was used to quantify flow field velocities with time averaged and conditioned sampled velocities for the steady and 5 and 15 Hz flames. Based upon the results, it was seen that while NO was reduced the greatest percentage for the 5 or 7 Hz oscillating flame in comparison to the steady flame, this decrease in NO was correlated with an increase in CO production, generally at lower equivalence ratios {dollar}(\\Phi\\leq1.0).{dollar} At {dollar}\\Phi{dollar} = 1.2 and 1.4, the decrease in NO did not correspond to an increase in CO. Consequently, burning at higher equivalence ratios was seen as more advantageous due to the production of less NO emissions correlated with less CO emissions. The existence of the low levels of NO, NO{dollar}\\sb{lcub}\\rm x{rcub},{dollar} and CO{dollar}\\sb2{dollar} and the high levels of CO and O{dollar}\\sb2{dollar} for the 5 Hz flame versus the 15 Hz flame at {dollar}\\Phi{dollar} = 0.6 has been attributed to a recirculation of exhaust products induced by the oscillation of the flame. This was evidenced by LDA measurements which showed that zones of negative axial and transverse velocities outside the visible flame boundary, potential areas of recirculation, existed in greater magnitude for the flame oscillated at 5 Hz where NO, NO{dollar}\\sb{lcub}\\rm x{rcub},{dollar} and CO{dollar}\\sb2{dollar} were reduced in comparison to the flame oscillating at 15 Hz where NO, NO{dollar}\\sb{lcub}\\rm x{rcub},{dollar} and CO{dollar}\\sb2{dollar} levels were much higher.

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