Droplet generation and characterization using a piezoelectric droplet generator and high speed imaging techniques

• Single droplets were generated using a droplet generator in Droplet-On Demand and continuous mode.
• Droplet characteristics were evaluated with a high speed image acquisition and processing system.
• Droplets from 134.1 to 461.5 μm in DOD and from 167.2 to 458.6 μm in continuous mode were produced.
• Droplet velocities from 0.08 to 1.8 m/s in DOD and from 1.8 to 4.7 m/s in continuous mode were produced.

Accurate spray (droplet) characterization helps in the better understanding of the pesticide spray application process. The goal of this research was to evaluate the characteristics of a single droplet generated using a piezoelectric single droplet generator in 2 modes: Droplet-On-Demand (DOD) and continuous with 4 different orifice sizes. The droplet generator can produce a single droplet, or a continuous stream of uniformly sized droplets. Using a high speed imaging system and image processing algorithms, the effects of pulse width and pulse amplitude in DOD mode and of frequency and pulse amplitude in continuous mode on droplet characteristics (droplet size, droplet velocity and inter droplet spacing) were investigated for different orifice sizes. The system was able to produce droplet diameters within the range from 134.1 to 461.5 μm in DOD, and from 167.2 to 458.6 μm in continuous mode. In addition, droplet velocities ranged from 0.08 to 1.8 m/s in DOD mode and from 1.8 to 4.7 m/s in continuous mode. Validation using a droplet weighing method showed good agreement with the droplet image analysis results.