The effect of space charge on the performance of an electrostatic induction charging spray nozzle

In an electrostatic induction-charging spray nozzle, it is generally believed that the space charge formed by the charged spray cloud suppresses the nozzleʹs internal induction-charging field, causing the space charge cloud current to reduce as the nozzle-to-target distance increases. Experiments reported here show that the space charge does not affect the total current induced upon the liquid; rather, it affects the distribution between the space charge cloud current and the electrode leakage current. The main reason for this reduction of the space cloud current is that a small number of highly charged droplets escape the air entrainment by the repulsion of the space charge field and are repelled radially or are deposited on the nozzleʹs external surface, adding to the electrode leakage current. The stronger the space charge field, the more droplets are repelled to the nozzleʹs surface. The result of this “feedback” phenomenon is that under constant atomizing air pressure and within a certain voltage range, the space charge effect makes the target current to be constant at a certain distance away from the nozzle, irrespective of the electrode voltage. Raising the electrode voltage will not increase the target current.