Performance experiment on spray atomization and droplets deposition of wind-curtain electrostatic boom spray

Abstract: To solve the problem of less liquid deposition on the middle and lower plant canopy and uneven distribution of particle diameter by traditional pesticide application methods, this paper conducted the exploratory research about the application of the technology of pneumatic auxiliary spray combined with electrostatic spray. The charge-to-mass ratios of the droplets under different spray pressures and voltages were measured by measurement system. The results indicated that the charge-to-mass ratio increased as the voltage increased and then tended to be stable, yet decreased with the increase of spray pressure. The particle diameter spatial distribution of the droplets under charging or not was measured by Winner318B laser particle size analyzer; the horizontal and longitudinal stent in the system could move precisely so as to adjust the position of the nozzle relative to the measuring line of the laser particle size analyzer. The results showed that the volume median diameters (VMD) of the droplets decreased and then tended to increase when the nozzle moved from 0 to 3 in the horizontal stent; in the condition of no charging, the VMD of the droplets was 108.48 μm and the coefficient of variation of droplet sizes was 11.96%, while in the condition of charging, the VMD of the droplets was 83.67 μm and the coefficient of variation of droplet sizes was 7.48%; and the VMD of the droplets increased when the nozzle moved from 6 to 4 in the longitudinal stent. For analyzing the influence of wind-curtain, spray pressure and voltage on droplets deposition performance, the wind-curtain electrostatic boom spray system was set up and the experiment on droplet deposition performance was conducted. The system used cochineal solution as spraying liquid, and used radermachera hainanensis merr. as simulation target. Layout the film on the upper, middle, lower position plant canopy for collecting the droplets deposited. In order to ensure the accuracy of the experimental data, the droplet collection started after spray being stable with the duration of 20 s, and the film sample was eluted by 50 ml distilled water, the absorbance of the eluant was measured by UV-2100PCS UV-VIS spectrophotometer and then converted into the concentration based on the curve equation. Finally, calculate the unit area droplets deposited amount (UADDA) on plant canopy. The wind-curtain effect (the wind-curtain outlet wind speed was 20 m/s) could improve the UADDA under spray pressure of 0.2 MPa and no voltage, in which the coefficient of variation of droplet deposition distribution under wind-curtain was 0.645, and compared with no wind-curtain, the coefficient of variation declined by 25.95%. The electrostatic effect could also improve the UADDA when spray pressure was 0.2MPa and the wind-curtain outlet wind speed was 20 m/s, in this case, the coefficient of variation of droplet deposition distribution decreased from 0.645 to 0.321, reduced by 50.2%; when droplets were charged, the coefficient of variation of droplet deposition distribution increased as the spray pressure increased. This study provides the theory and design basis for the development of innovative wind-curtain electrostatic boom sprayer and offers the experience for the field test which will be conducted next.