3-DIMENSIONAL (3-D) MODEL OF ELECTRIC-FIELD AND SPACE-CHARGE IN THE BARBED PLATE-TO-PLATE PRECIPITATOR

A finite-element/method-of-characteristics model of three-dimensional (3-D) electrode geometries with corona discharge is used to predict sp ace charge density, current density, electric potential and electric f ield in point-to-plane, single-barb plate-to-plane, and hexagonal mult iple-barbed plate-to-plate geometries. Although a modification of Peek 's formula for the hyperboid-to-plane was initially used to establish a boundary condition at the edge of the corona, predicted total curren t did not agree with measured values. As a result, it was necessary to use measured current-voltage characteristics to establish the space c harge density at the outer surface of the corona sheath. An additional problem in modeling point discharges is specification of shape and si ze of the corona sheath. Both our results and much earlier work by Tri chel suggest that the thickness of the corona sheath cannot be automat ically neglected.