Air-Assisted Passive Ionizer for a Charged Pipe

An air-assisted passive ionizer is developed for the elimination of static charges on charged particles accumulated in pipes, hoppers, or silos. The ionizer is a grounded electrode with a sharp tip at which corona discharge takes place due to the electric field produced by the charged particles. A charged plastic pipe was used to test the performance of the passive ionizer. The ionizer was placed in the center of the charged pipe to effectively meet the corona inception conditions. Fast air flow was supplied to the tip of the ionizer to increase the efficiency of static charge elimination. The surface potential distribution of the charged pipe before and after static elimination was measured both with and without the air assist. The results indicate that the air assist plays an important role in the electrostatic elimination process of the charged pipe. A simple model using a charged pipe and a grounded sphere is also proposed. By calculating the electric field strength formed by the charges on the cylinder and its image charges inside the grounded sphere, the electric field distribution in the center axis of the charged pipe could be estimated analytically. The efficiency of charge elimination was found to be a function of the dimension of the charged pipe, the radius of the grounded sphere, and the initial potential at the center of the charged pipe.