Abstract
Despite progress in laser-based and computational tools, an accessible model that relies on fundamentals and offers a reasonably accurate estimation of droplet size and velocity is lacking, primarily due to entangled complex breakup mechanisms. Therefore, this study aims at using the integral form of the conservation equations to create a system of equations by solving which, the far-field secondary atomization can be analyzed through predicting droplet size and velocity distributions of the involved phases. To validate the model predictions, experiments are conducted at ambient conditions using water, methanol, and acetone as model fluids with varying formulation properties, such as density, viscosity, and surface tension. Droplet size distribution and velocity are measured with laser diffraction and a high-speed camera, respectively. Finally, an attempt is made to utilize non-scaled parameters to characterize the atomization process, useful for extrapolating the sensitivity analysis to other scales. The merit of this model lies in its simplicity for use in process control and optimization.
Highlights
The conversion of bulk liquid into sprays via two-fluid nozzles is of current importance in several industrial applications, such as electronic equipment, desalination, petroleum refining, fire extinguishing, chemical combustion, gas turbines, diesel engines, spray painting, solid dose manufacturing units and agriculture, as in crop spraying
The current study focuses on the two-fluid nozzle design, whereby the atomization process is dictated by the balance between several different forces
Shaded areas represented the margin of error associated with each measurement
Summary
The conversion of bulk liquid into sprays via two-fluid nozzles is of current importance in several industrial applications, such as electronic equipment, desalination, petroleum refining, fire extinguishing, chemical combustion, gas turbines, diesel engines, spray painting, solid dose manufacturing units (e.g., spray drying, fluidized bed, and pan coating) and agriculture, as in crop spraying. Two-fluid nozzles ( known as air blast, pneumatic and co-axial atomizers in other industries) are overwhelmingly used in pharmaceutics from the laboratory, all the way to commercial scales [1,2,3] This spray technology relies on the breakup of liquid through impact with high-speed gas at the orifice [4]. The droplet size distribution and velocity of the droplet stream impacted the residence time and drying rates, which may, in turn, influence the spatial particulate physical structure and chemical homogeneity [7]. This can further prove costly in high-value particles, Fluids 2020, 5, 231; doi:10.3390/fluids5040231 www.mdpi.com/journal/fluids
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