Turbulent Spray Flames of Acetone and Ethanol Approaching Extinction

Abstract

This paper presents measurements of mean temperature, axial velocity, turbulence, and droplets fields in pilot-stabilized jet flames of dilute sprays where acetone or ethanol is used as liquid fuel. Laser-induced fluorescence (LIF) is employed to image hydroxyl radical OH which marks the existence of hot regions or reaction zones. Depending on the fuel used, droplets within the flow are delineated by imaging LIF from acetone or Mie scattering. As the jet velocity is increased, the flames gradually approach blow-off in a region further downstream from the stabilizing pilot. It is found that the mean velocity, turbulence, and droplet fields are somewhat similar for both ethanol and acetone flames, and these do not change much with increasing jet velocity, particularly when normalized with the relevant parameters. However, the temperature and reactive fields are varying and undergo departure indicative of nonpremixed to premixed flame behavior depending on the vapor pressure of the fuel and proximity to blow-off. Broad regions of OH as well as breaks in the OH profile marking possible local extinction are observed in the ethanol flames.

Keywords:

• Dilute spray flames
• Laser induced fluorescence
• Turbulent flames

ACKNOWLEDGMENTS

This research was supported by the Australian Research Council. The authors are grateful for constructive comments from Prof. R. W. Bilger, Dr. S. H. Starner and Prof. K. N. Lakshmisha.