Effervescent Atomization of Polyvinylpyrrolidone Solutions: Influence of Liquid Properties and Atomizer Geometry on Liquid Breakup and Spray Characteristics

An effervescent atomizer is a special type of internal mixing pneumatic atomizer with a significantly reduced atomization gas consumption compared to conventional pneumatic atomizers. The influence of the mass fraction of polyvinylpyrrolidone (PVP) K30 in aqueous solutions and the influence of nozzle orifice length on the spray is investigated.
The breakup of PVP K30 solutions is changed significantly by their viscosity which depends on the mass fraction. With increasing viscosity, the breakup changes from complete breakup into drops directly at the nozzle orifice outlet to an incomplete breakup with ligaments present. The corresponding Sauter mean diameter and the standard deviation s2 (representing the width of the drop size distribution) increase with increasing viscosity as well. The air-to-liquid ratio by mass (ALR) has comparably less impact on the breakup at the nozzle orifice outlet. Nevertheless an increasing ALR results in decreasing Sauter mean diameters and standard deviations s2. The atomizer geometry has minor impact on the breakup and the resulting drop size distribution.
The unsteadiness of the spray was quantified by its pulsation frequency. ... mehrComparing Sauter mean diameters and standard deviations s2 with the corresponding pulsation frequencies of the spray allows the conclusion that an increase in pulsation frequency correlates with a reduction of both characteristic values and leads accordingly to a steadier spray. The pulsation frequency can be slightly controlled by the atomizer geometry. The effect of the pulsation frequency on Sauter mean diameter and standard deviation s2 is less distinct than the effect of ALR and mass fraction.