Macroscopic flame structure in a premixed-spray burner (2nd report, flame propagation speed and droplet cluster disappearance speed)

Both flame propagation speed and droplet cluster disappearance speed in a premixed-spray burner system are experimentally investigated by image processing analysis in an effort to evaluate two-stage flame structure observed in the premixed-spray flame. It is confirmed that flame speed concerned with premixed-mode combustion in the spray flame is approximately 2.0 m/s in average while mean disapperance speed of droplet clusters, which are dominated by diffusion-controlled combustion-mode downstream of the flame, is evaluated as much as 0.45 m/s. Although both speed, Which are supposed to depend on local properties of the spray itself and flow conditions surrounding droplet clusters, are scattered in experiments, it was clarified that both characteristics of premixed-mode and diffusion-mode combustion in spray flames are of much difference in nature.