Numerical Calculation And Influence Study Of The Spatial Electric Field In Electrostatic Spraying

The technology of electrostatic spraying is an effective way to reduce droplets drift and decrease pesticide pollution, which is a new development aspect of the high-efficieny and low-pollution spraying. Based on summarizing the development status of electrostatic spraying at home and abroad, the paper compared, analyzed and summed up many research tasks in the future, finding the distributing of the spatial electric field is a key factor affecting the quality of spraying. Because of the existing of the space charges ,the distributing of the field is highly complex. The research in this area is far not deepened both in theory and in tests. For the corona charging method is commonnly used in electrostatic spraying, so the paper is to calculate and study the corona charging field.The spatial field in electrostatic spraying is a resultant field of induced field by electrode with high voltage and that produced by space charges. The parameters of the electrode and the type of the nozzle have great influence on the distributing of the electric field. So a multi-needle electrode annularly arranged was designed and made, the field induced by which is calculated by simulation charge method and a mathematic mode of potential and electric strength was obtained. Selecting the hollow-conical nozzle used most extensively, which forms charged hollow-conical spraying area. A mathematic mode of the electric field also was got produced by the charged spraying area. Then, according to the additive principle, the mathematic mode of spatial field was set. up. Taking advantage of the software matlab, it is got that the value of the potential and electric strength and their distributing figure of the three fields. The mathematic modes were corrected by tests and then the affection of the parameters of the electrode and charged spraying area on the field was studied. Through the work upwards, it is found:(1)The potential and the strength of the field induced by the electrode with highvoltage are determined by the voltage V on electrode, the curvature radius r₀,, the ringelectrode radius r₁, the number of the needle electrode n, and the vertical distance between the center of the ring electrode and the ground H and so on. It is interactional for the three parameters of the curvature radius r₀, the ring electrode radius r₁ and thenumber of the needle electrode n .While the voltage V on electrode and the vertical distance between the center of the ring electrode and the ground H affect the field induced by the electrode independently.(2)The shape of the spraying area and the charges on it determine the field produced by the space charge, so the type of the nozzle can affect the field. To the hollow-conical nozzle, in the inner part of the hollow- conical spraying area, the potential gradually decreases and the field strength increase in radial; in outer part, the change of the potential and the field strength has the contrary rule. Supposed x₀ is a point where the volume is halved, when x≤x₀, both the potential and the field strength gradually decrease along the x axis. When x>x₀ , both the potential and the field strength gradually increase. Near the spraying target, the space charges play an important role.(3)Due to the existing of the space charges, the spatial field is more uniform than the field induced by the electrode. In the process transporting of the droplets from the nozzle to the target, the field induced by the electrode is dominated near the nozzle, while it is defeated by the field produced by the space charges near the spraying targets.