Formation of the charged droplet cloud and corona discharge between the cloud and a grounded electrode

The formation of a charged-droplet cloud with high charge density and the corona discharge characteristics between the cloud and a grounded electrode have been investigated. To form a charged-droplet cloud an electrostatic spray system with an airless nozzle is adopted. The spray system consists of an airless nozzle, a ring electrode and a blower. Since an airless nozzle can ejected large amount of droplets at once, a high density cloud can be created. Droplets in the cloud are electrified by means of induction phenomenon with the ring electrode. A blower is used to promote the transportation of the charged droplets and to grow in the charge density of the cloud. As the air-flow is faster, the charge amount of the ejected droplets and the charge density of the cloud increase. The air flow also influences the corona discharge from the grounded electrode to the charged cloud, extremely. The discharge current with air flow becomes several times larger than that without air flow, because the air flow prevents the deposition of charged droplets on the grounded electrode and no small corona discharge from the deposited droplets occurs. It suggests that the air flow is quite effective to make the discharge between a charged-droplet cloud and a grounded electrode