An experimental study of air-assist atomizer spray flames

Abstract

Spray flames have, in the past, been modeled and treated as homogeneous turbulent gas diffusion flames based upon the similarities in flame structure. Air-assisted atomizer spray flames, as commonly used in industrial furnaces, boilers, and gas turbine combustors, are shown, in this paper, to have a more complex structure. The swirling motion introduced into the fuel and air flows for the control of flame stability, flame length, combustion intensity and efficiency, causes the structure of air-assist atomizer spray flames to be different from that of turbulent gas diffusion flames. Detailed measurements in air-assist atomizer spray flames have been made using a newly developed non-intrusive light scattering Phase/Doppler detection technique. Based upon the measurements and observations, a physical model of the air-assist atomizer spray flames has been constructed. Detailed comparison of the spray structures in burning and non-burning conditions is presented. The presence of the flame has very little effect on the large drops in the outer edges of the spray, outside the flame zone. The spray structure is, however, drastically changed inside the flame reaction zone, as shown by changes in both the magnitude and shape of the radial distributions of drop number density, liquid flux, mean drop size diameter, and drop mean axial velocity.