Enhancement in spray atomization and droplet dispersal by insertion of perforated plate in swirl air stream

Coaxially fitted atomizer and air swirler configuration is widely used in gas turbine combustors. The present study deals with the experimental analysis of the conjugate effects of coaxial swirling air and grid-generated air turbulence on a liquid spray. A perforated plate (or grid) is placed upstream of an air swirler in a coaxially fitted swirler-atomizer assembly. Grids of different mesh hole diameter and solidity ratio are used to change the turbulence level. A laser Doppler velocimeter (LDV) is used to characterize the airflow field. High-speed imaging and a phase Doppler particle analyzer (PDPA) are used to determine the spray characteristics. It is observed that both the mean and fluctuating air velocity components are altered significantly in the presence of the grid. Moreover, the strength and size of the recirculation zone increase, and the peak locations of mean velocity, velocity fluctuations, and turbulent kinetic energy shift away from the axis. The grid also introduces notable modification to the spray characteristics.