Effervescent atomization is a twin fluid atomization mechanism which is based on the injection of gas into a liquid stream at an upstream location of the exit nozzle. This atomization mechanism is capable of producing droplets with Sauter Mean Diameter (SMD) comparable to other types of atomizers but at lower injection pressures. For the conditions investigated in this paper, liquid at the nozzle exit is an annular film surrounding the gas phase. A shadowgraph system is used to visualize particles shape and study droplets evolution in the spray field. Measurement of droplet SMD and centricity has been conducted at several axial and radial locations for different Gas-Liquid Ratios (GLRs). The shadowgraphy images reveal some non-spherical droplets which consist of both elliptical and coalescing droplets. Results also demonstrate that higher numbers of non-spherical droplets are observed at the near nozzle region and at higher liquid flow rate. In this work, spatial structure of the liquid phase velocity field has also been studied using a StereoPIV technique. The velocity field from StereoPIV measurements has been compared with the shadowgraphy velocity results averaged over different droplet size classes. This comparison has been conducted for the atomizer operating at different GLRs. Comparison of the results demonstrates that at the far-field, StereoPIV velocity field measurement is biased toward the velocity of droplets size classes which have relatively higher probability.

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