Twin-Fluid Atomization and Novel Lifted Swirl-Stabilized Spray Flames

The effects of swirl configuration and airflow distribution on the structure of swirl-stabilized spray flames are investigated in a combustor featuring a twin-fluid fuel atomization nozzle, coannular airstreams, and helical-vane swirl assemblies. The flames investigated are similar to those employed in gas turbine combustion engines. A novel lifted swirl-stabilized spray flame, obtained with a particular set of experimental conditions, is described. Three-dimensional particle image velocimetry data are used to analyze the structure of the airflow associated with the lifted flame. The lifting effect is shown to result from an interaction between the atomization airstream and the recirculation zone in the flow, which creates two distinct recirculation regions. Only the larger far-field recirculation zone is able to stabilize combustion effectively, and the structure of the airflow is found to determine the regions of heat release associated with the flame. Detailed information on the structure and characteristics of the fuel spray, obtained using phase-Doppler particle analysis, is also presented. The twin-fluid atomization approach is shown to provide effective atomization over a wide range of operating conditions, while simultaneously allowing a great degree of control over the flame structure.