Experimental investigation on fluid structure and full-cone spray characteristics of a jet-swirl atomizer using shadowgraph technique

Abstract

Full-cone spray is quite important in spray cooling and catalytic combustion applications; however, it is not extensively studied. Besides, the liquid spray is relatively a non-uniform structure especially along longitudinal axis which includes different sizes and distribution of droplets. The few published experimental studies are limited to calculate some of the spray characteristics on a certain plane located downstream of the nozzle exit. Therefore, the spray parameters representing fluid structure, droplets mean diameter, and their distribution in different cross sections from nozzle exit are considered in this study. Accordingly, a jet-swirl atomizer with pressure-swirl full-cone spray is investigated where all important full-cone spray characteristics are considered at different planes from nozzle exit. The spray images are obtained with a shadowgraph technique and are analyzed to obtain the Sauter mean diameter (SMD), D₁₀, and droplet size distribution along with the spray structure, spray cone angle, and discharge coefficient. The experimental results are verified based on the pre-published numerical studies on the same atomizer. The experimental and numerical results show good agreement. Moreover, the results show that the SMD is increased by moving away from center of spray to its edges, and the droplets number density is increased in central regions. The increased droplets number density leads to the greater external forces which create smaller droplets. In contrast, larger particles exist in peripheral parts due to the less droplets concentration. Furthermore, and far away from the exit nozzle, the SMD values are decreased due to the increased aerodynamic forces and oscillations. The droplets dispersion including spray density in radial and axial directions is also observed using spray density images.