Measurements of the droplet size and velocity distributions in the sprays produced by a range of pressure nozzle designs operating with a range of spray liquids.

摘要

Measurements of droplet size distributions are well established as the basis for classifying the performance of agricultural spray nozzles but it is also recognised that the velocity of droplets is a major factor influencing droplet trajectories and spray behavior at a target surface. The work reported in this paper used a double imaging spray analyser to measure droplet size and velocity distributions in the sprays generated by different agricultural spray nozzle designs operating with a range of spray liquids. Comparative measurements of the droplet size distributions were also made with a laser diffraction instrument and the data relating to droplet size and velocity distributions were correlated with the results from standardised wind tunnel tests to determine the drift risk associated with the sprays. The results showed that although the droplets from air-induction nozzles travelled at lower vertical velocities, the larger sizes of droplets from this nozzle design meant that kinetic energy in the spray was comparable with that from conventional nozzle designs. The quantity of spray liquid in droplets <100 micro m in diameter was shown to correlate well with measured airborne spray profiles in wind tunnel experiments for the pressure nozzles with spray angles in the range 100-120 degrees as used in this study.