Influences of Turbulence Characteristic on the Dispersion Behavior of Droplets in the Spray Flame

Abstract

The authors investigated the effect of the turbulence of an air current on droplet dispersion in a spray flame. Wire meshes of different mesh sizes were inserted behind a two-fluid type nozzle each time to vary the air current turbulence characteristics, and then methanol was sprayed to form a spray flame. Droplets in the spray flame were measured with a Phase Doppler Particle Analyzer (PDPA). In the no-reaction field, the turbulence characteristics were measured by using a hot wire anemometer to determine the influences of the turbulence on droplet dispersion in a flame. As the mesh size of the wire mesh was reduced in the investigation, the droplet dispersion was shown to reduce the volume of cluster and also the number density of the droplets. Measuring the turbulence statistics confirmed a decrease of the Stokes number in proportion to the mesh size of the wire mesh. Droplet flying trajectories through turbulence were calculated. According to the calculation results, inserting a finer wire mesh was found to move flying trajectories closer to the streamline of the vortex. When a finer wire mesh was inserted, droplets were drawn closer to the vortex and formed clusters near the vortex. Consequently, droplets were found to disintegrate and disperse under the great influences of a vortex.