Electrostatic sprayer for agricultural application
In order to protect food and fibre crops against insect, disease and weed pests, usage of agricultural chemicals such as insecticides, fungicides and herbicide is essential. Entomological studies have established that in numerous cases, smaller droplets of pesticide spray provide greater biological efficacy per unit mass of pesticide than do the larger droplets for achieving insect control but drift was the major problem. Thus, the recent concept of spraying is to spray the target pest more efficiently by selecting optimum droplet size and density for maximum retention and coverage. Some cases in rather old data, 95% of the chemical applied can be wasted to the ground or at most 50% of mass transfer onto the desired plant. Electrostatic spraying would offer a possible solution to those environmental problems; by reducing spray drift and improving coverage of chemical to target plant. These application areas broadly include ground equipment for spraying plants of row crops, orchards and greenhouse, even aircraft spraying.
An inductive electrostatic sprayer was designed by Weidong, et al. The test result showed that the charge-to-mass ratio could reach 0.951 mC/ Kg when electrostatic voltage was 20 kV and working pressure was 0.25 to 0.4 MPa. The particle size distribution of charged droplets were more concentrated than that of uncharged droplets, the axial velocity of charged droplets was faster than that of uncharged droplets, and the velocity distribution uniformity was also improved. The average deposition rate under charging conditions was 14% higher than that in uncharged conditions. Moreover, the deposit rate of the back of the leaf was evident.
Previously designed and constructed electrostatic sprayer was evaluated in order to quantify the charging of droplets (Maynagh, et al). Liquid atomization was achieved by using an ultrasonic nozzle. The maximum flow rate of nozzle was 25 ml/ minute and vibration frequency was about 30 kHz. The induction method was used for charging the output droplets. The independent parameters in this study included: voltage at four levels of 1.5, 3, 5 and 7 kV; air flow speed at six levels of 14, 14.9, 17, 20.2, 21.6 and 23 ms-1; charging electrode radius in two levels of 10 and 15 mm, horizontal distance between the electrode and nozzle tip at four levels of 1.5, 6, 10 and 15 mm; and liquid flow rate at three levels of 5, 12 and 25 ml/ minutes. The maximum charging occurred at 5 ml/ min flow rate, voltage of 7 kV, air flow speed of 23 ms-1 and the resulting current was 0.24 μA. On dividing the electrical current by the liquid flow rate and changing the scale, the mean charge to mass ratio was 1.032 μC g-1.
Jai W; Xue F; Qui B. (2013). Design and Performance of Inductive Electrostatic Sprayer. Journal of Applied Sciences, Engineering and Technology 5(21): 5102-5106.
Maynagh B. M; Ghobadian B; Jahannama M. R. and Hashjin T. T. (2009). Effect of