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In this work, the effects of orifice divergence on spray characteristics have been reported. Parameters such as spray cone angle, liquid sheet thickness, coefficient of discharge, break-up length, and Sauter mean diameter are greatly affected by the half divergence angle [Formula: see text] at orifice exit. An experimental investigation is carried out in which water sprays from five atomizers having half divergence angle values of 0°, 5°, 10°, 15°, and 20° are studied at different injection pressures. Image processing techniques are used to measure spray cone angle and break-up length from spray images, whereas the sheet thickness outside the orifice exit is obtained using the scattered light from a thin Nd-YAG Laser beam. Phase Doppler interferometry is also used to obtain the Sauter mean diameter at different axial locations. A few numerical simulations based on the volume of fluid method are included to obtain physical insight of the liquid film development and air core flow inside the atomizer. It is observed that the liquid sheet thickness as well as tangential and radial components of velocity at orifice exit are modified drastically with a change in half divergence angle. As a consequence, the droplet size distribution is also altered by variation in the nozzle divergence angle. The mechanism responsible for such variations in the spray behavior is identified as the formation of an air core or air cone inside the liquid injector as a result of the swirl imparted to the liquid flow.

In this work, interactions between cold spray and swirl airflow are characterized experimentally and numerically for various air swirler geometries. The number of vanes, vane angle, vane curvature, and air velocity are varied for the swirling airflow. Spray visualization and phase Doppler interferometry techniques have been employed to obtain important parameters such as spray cone angle and mean drop size. In the numerical work, the Realizable kÀe turbulence model has been employed along with the Linearized Instability Sheet Atomization and Taylor Analogy Breakup to simulate spray field. The predicted results for the airflow field compare well with available experimental results in published literature. Good match is also found between the present predictions and measured spray data. The radial distribution of Sauter mean diameter exhibits peak values at the periphery of the spray near the injector, due to liquid swirl. The peak Sauter mean diameter shifts to the spray axis, beyond the recirculation zone, due to entrainment of droplets by the swirling air stream. The volume fraction of droplets exhibits multi-modal distribution, due to the interactions between spray droplets and recirculating airflow. A curved swirler gives rise to finer spray compared to a flat swirler, due to lower losses and better utilization of momentum.

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