3-D model of electric field and space charge in the barbed plate-to-plate precipitator

A finite element/method of characteristics model of 3-dimensional electrode geometries with corona discharge is used to predict space charge density, current density, electric potential and electric field in point-to-plane, single barb plate-to-plate, and hexagonal barbed plate-to-plate geometries. Although a modification of Peak's formula for the hyperboid-to-plane was initially used to establish a boundary condition at the edge of the corona, predicted total current did not agree with measured values. As a result, it was necessary to use measured current-voltage characteristics to establish the space charge density at the corona. An additional problem in modeling point discharges is specification of shape and size of the corona sheath. Both our results and much earlier work by Trichel suggest that the thickness of the corona sheath cannot be automatically neglected.