Measurements of the droplet velocities in sprays produced by different designs of agricultural spray nozzle

Measurements of the vertical droplet velocity/size correlations for the reference nozzles used in an agricultural spray nozzle classification scheme showed good agreement between the results obtained with a new design of a double imaging instrument and a Phase Doppler Analyser. Similar measurements with two designs of conventional hydraulic pressure and three designs of air-induction nozzle showed substantial differences in the droplet size/velocity profiles for the different commercial nozzle designs. Velocity distributions with the air-induction nozzle designs were on average 40% less than those of the conventional hydraulic pressure nozzles. Droplet velocities increased with increasing pressure for all nozzles as expected with increases in the order of 23% for an increase in pressure from 3.0 to 5.0 bar for both the conventional and air induction nozzles. Spray fan angle was also indicated as an important parameter influencing droplet velocities. Changes in spray liquid properties that would be typical of different agricultural chemical applications showed some differences in droplet velocities from the nozzles studied with the largest differences of up to 50% measured with a conventional nozzle. Measurements of the airborne flux within a spray made by both the imaging system and conventional collection sampling techniques showed also good agreement.