Effect of swirl chamber length on the atomization characteristics of a pressure-swirl nozzle

Pressure-swirl atomizers are widely used in industrial and engineering applications such as gas turbine combustors. The characteristics of spray generated by a pressure-swirl atomizer with adjustable swirl chamber length were investigated within the range of (0.12 < length/diameter < 0.5) using H₂O as the working fluid. Droplet Sauter mean diameter and velocity components were measured using a phase-Doppler particle analyzer device. The spray cone angle was measured from image processing of images captured by a set of Nd-YAG lasers and a high-speed camera. Results showed that the swirl chamber length/diameter ratio significantly affected the spray characteristics, e.g., droplet size distribution and mean diameter, as well as velocity profile. The spray pattern for the smallest ratio was observed as a hollow-cone type and then was changed to a solid-cone type by increasing the considered parameter. The effective ratio of the swirl chamber was in the range of (0.12 < length/diameter < 0.30), where all the substantial changes occurred.