Developing an electrostatic spray charging system for air-blast sprayers

In this study, an induction-based electrostatic spray charging system was developed to charge droplets produced by standard cone nozzles on conventional air blast sprayers. Different ring-shaped circular electrodes made up of Copper, Aluminum, Brass, and chrome materials were designed and used for charging spray droplets. A Faraday cage was manufactured and used to detect the Charge-to-Mass Ratio (CMR as mC/kg) of charged spray liquid to evaluate the performance of the developed electrostatic system on droplet charging efficiency of spray droplets. To obtain most charging efficiency by this system, many parameters were investigated such as; (1) the effect of high spraying pressures on the charging efficiency and optimum electrode location from the nozzle tip, (2) the impact of electrode characteristics and specifications which were diameter, length, material, shape, and the number of electrodes. Depending on previous parameters, five electrostatic nozzles with the same specifications were designed to develop the electrostatic air blast sprayer. The performance of this electrostatic sprayer in improving droplet deposition was evaluated using artificial and plant targets. According to the results, the charging efficiency increased by increasing the electrode voltage but did not affect by the voltage signal. Spraying pressures from 6 to 9 bars improves the charging efficiency. For pressures such as more than 7 bar, the optimum electrode location stays constant at 25 mm. Neither the ring-shaped electrode material nor its cross-section shape affects the charging efficiency of the spray droplets. Despite reducing the diameter and increasing the length of the ring electrode increases the charging efficiency, they cause electrode wetting at low electrode voltages. The isolated electrode removes the problem of electric leakage, and so, increases the charging efficiency by increasing the high voltage to more levels. The developed electrostatic sprayer increased the droplet deposition on the front and back surfaces of artificial targets by 1.9 and 32.5 times, respectively, and the front (upper) and front (lower) surfaces of the plant leaves by 0.35 and 2.12, respectively.