Experimental and computational (CFD) investigations were conducted on an Airblast Simplex (ABS) nozzle. A Phase Doppler Particle Analyzer (PDPA) was used to study the main characteristics of the nozzle. Water was used as the test liquid with pressure drops of 68.9, 172.3 & 689 kPa, while the air pressure drops were 2.49 & 34.5 kPa. PDPA data were obtained at three different axial distances from the nozzle exit (x = 2.5 (or 7), 17 & 40 mm). In the numerical simulations, the three-dimensional flow field for both air and liquid was computed. The combination of detailed experimental measurements and CFD provided excellent insight into the physics of the atomizer. The three-dimensional CFD simulation showed distinct jets originating the air swirler and secondary flows that cause multiple peaks in number density, volume flux and velocity distributions. The jets suggest why asymmetric distributions are common in sprays. The jetting effect from the swirler vanes emphasizes the importance of swirler and airflow design on the performance of a spray nozzle. The discrete jetting effect is not visually observable, nor is it easily measured using PDPA.
The ABS nozzle examined has several distinct advantages over a pressure swirl atomizer, including, (1) the distinct sheet from the hollow cone spray is dispersed within 17 mm in all cases studied herein, and (2) the spray volume does not change significantly with increasing air or liquid pressure drop. Therefore, careful design of ABS nozzle results in a spray with nearly constant spray volume and SMD over a wide range of Air/Liquid Ratios.