Droplet size spectra produced by air-assisted atomizers

Abstract

Droplet size spectra produced by air-shear, spinning disc and rotary cage atomizers operated with and without air-assistance were measured using a Malvern † † Malvern Instruments Ltd, Spring Lane South, Malvern, Worcestershire, U.K. laser particle size analyser. Empirical models were developed using multiple linear regression to relate liquid viscosity (μ), density (ρ), surface tension (σ), flow rate ( Q), airstream velocity ( U) and rotation rate ( N) to the droplet size spectra parameters volume median diameter (VMD) and the ratio of volume and number median diameters (VMD:NMD ratio). In agreement with most previous atomization studies, the VMD showed strong negative correlation with U and N and relatively weak positive correlation with Q, μ, ρ and σ. The VMD:NMD ratio could generally not be modelled as accurately as the VMD. The rotary atomizers generally gave droplet spectra with lower VMD and VMD:NMD ratio values than the straight jet air-shear nozzle.