Role of combustion air swirl distribution in a burner on secondary atomization of droplets

The effect of high shear in the flow on the spray flame characteristic has been examined. The shear was provided using different swirl combination in the inner and outer swirlers in the double concentric swirl burner. The burner allowed independent control of swirl and combustion airflow in the inner and outer annulus of the burner. Phase Doppler Particle Analyzer (PDPA) laser diagnostics have been used to obtain comprehensive data related to droplet size, velocity, number density, size distribution of droplets. A commercially available twin fluid nozzle has been used in this study. Results have been obtained for a swirl combination of 65degrees in inner swirler and 30degrees in outer swirler (referred to as 65degrees/30degrees). The results are compared with the a swirl combination of 50degrees/30degrees. The results show secondary break-up of the droplets with high shear that was not present with low shear in the flow. They also show new way to obtain smaller size of droplets from a spray. Smaller size of droplets allows one to easily control the size, shape, stability and structure of the spray flames.