Correlations to predict droplet size in ultrasonic atomisation

Area of Science:

• Fluid dynamics
• Acoustics
• Materials science

Background:

• Conventional two-fluid nozzles use high-velocity air for liquid atomization.
• Ultrasonic energy offers potential for finer, more spherical, and uniformly sized droplets.
• Ultrasound-induced atomization results in lower droplet momentum, beneficial for coating and granulation.

Purpose of the Study:

• To develop a universal correlation for predicting droplet size in ultrasonic atomization.
• To account for physico-chemical and ultrasonic parameters influencing droplet formation.
• To establish robust correlations for designing ultrasonic atomizers.

Main Methods:

• Design and utilization of an ultrasonic probe sonicator for liquid atomization.
• Droplet size measurement using filter paper and image analysis.
• Evaluation of measurement technique with high-speed photography.
• Development of dimensionless numbers incorporating ultrasonic parameters.

Main Results:

• A universal correlation for droplet size prediction was proposed, considering liquid properties (flow rate, viscosity, density, surface tension) and ultrasonic properties (amplitude, frequency, vibrating surface area).
• Dimensionless numbers incorporating ultrasonic parameters were defined.
• Correlations based on dimensionless numbers and Davies approach showed acceptable deviation for droplet size prediction.
• An empirical correlation from experimental data was also proposed.

Conclusions:

• The proposed universal correlations are robust and applicable to various ultrasonic atomizer designs.
• The study provides a significant contribution to understanding and predicting ultrasonic atomization processes.
• The developed correlations can aid in the design of efficient ultrasonic atomizers for diverse applications.