Influence of lateral wind and electrostatic voltage on spray drift of electrostatic sprayer

Abstract: In order to study the influence of lateral wind and electrostatic voltage on spray drift of an electrostatic sprayer, the measurement of spray drift was performed through a self-propelled orchard sprayer with a spray boom. The spray boom was equipped with an electrostatic spraying system. The effects of lateral wind (1, 2, 4 m/s constant speed wind and 0-4 m/s non-constant speed wind) and electrostatic voltage (0, 2, 4, 6 and 8 kV) on spray drift were evaluated with the spray pressure at 0.5 MPa by analyzing the spray drift percentage and droplet drift distance. Fan blower provided no boundary planar wind in the form of 1.5 m × 1.5 m. The horizontal distance between the fan and nozzle was 1.0 m. An anemometer was used for wind speed calibration at the nozzle position during the experiment. Droplet size and charge-to-mass ratio were measured under different electrostatic voltages. The spray charge-mass was calculated using the ratio data of spray cloud currently acquired by a system consisted of a Faraday's cage, charge-voltage convertor and data acquisition. The results showed that the droplet size decreased as the electrostatic voltage of constant wind increased, and the charge-to-mass ratio increased as the electrostatic voltage increased and then tended to be stable. The charge-to-mass ratio was not significantly different between dry and wet electrodes at 0-8 k V electrostatic voltages. Electrostatic voltage and lateral wind both had significant impact on the droplet drift distance and spray drift percentage and their interaction was significant (P<0.05). Increasing lateral wind speed of constant wind and electrostatic voltage could improve the spray drift. At the same lateral wind velocity, the droplet drift distance and spray drift percentage still were significantly different (P<0.05) between 6 and 8 kV voltages. When the lateral wind speed was 1 m/s, the droplet drift distance of electrostatic spraying was 0.55 m or less, and the droplet drift percentage was below 15%. When the lateral wind speed was 2 m/s, the droplet drift percentage of 6-8 kV electrostatic spraying was more than 20%, especially the droplet drift percentage of 8 kV electrostatic spraying was 23.9%, which increased by 100.8% compared to that of non-electrostatic spraying. When the lateral wind speed of 4 m/s, the droplet drift distance of 4-8 kV electrostatic spraying was more than 0.9 m, the droplet drift percentage was more than 30%, especially the droplet drift distance and droplet drift percentage of 8 kV electrostatic spraying were 967.2 mm and 35.4%, which increased by 13.7% and 59.5% respectively compared to those of non-electrostatic spraying. It indicated that electrostatic spraying is suitable for working under low wind speed even 0. It suggested that when spraying is conducted under the high wind speed, the low voltage spraying or non-electrostatic spraying should be used. The results can provide a guide for the spray technology parameters optimization, so as to improve the ability of droplet anti-drift.