Induction charging of flat sprays for space charge generation

Space charges play a key role in many industrial and agricultural applications such as electrostatic painting or application of insecticides in orchards and row crops. For generation of large sized space charge clouds, induction charging is the preferred method. Whereas corona charging often involves voltage in the order of 100 W, induction charging may be achieved with voltages of less than a few thousand volts. The paper presents a novel construction of a spray unit with induction charging suitable for injecting large volumes of ionic space charge into a region. The experimental unit comprises: a flat spray liquid atomizing nozzle with high pressure air; two large size induction electrodes, and, an air curtain surrounding the electrodes to prevent the fine droplets from landing on the electrodes. The two large, flat induction electrodes sandwiching the flat spray have shown to generate excellent induction charging on the spray droplets achieving charge to mass ratios in the order of 4 mC/kg and ionic charge densities of 2 mC/m(3) The studied variables were: pressure and flow of water supply at the nozzle and the pressure and flow of the curtain air. The atomized charged spray cloud of droplets with a mean volume diameter of several micrometers, evaporates at certain distances from the nozzle forming a mixed charged cloud of both water ions and finer water droplets.