NUMERICAL FIELD CALCULATION IN ELECTROFIL TERS WITH RESPECT TO EQUIVALENT ELECTRICAL OPERATING-CONDITIONS

Earlier investigations of electrostatic precipitators yielded a method to keep grade efficiency independent of absolute precipitator size. A transfer of measuring results from small to larger plants requires a change of precipitator size true to scale. In addition, precipitators have to be operated at a constant dimensionless voltage defined by U/( E0r(SE) in order to provide equivalent electrical operating conditions , i.e. identical spatial distribution of the relative electrical field s. This could be confirmed by analytical field calculations assuming a uniform space charge distribution. Moreover, this paper presents a nu merical simulation method allowing calculation of both the electrical field distribution and the ionic space charge distribution. The method solves alternatingly Poisson's equation by a finite element technique and the equation of continuity. The results show the principal effect of the ionic space charge. This calculation procedure is applied on t hree geometrically similar precipitators of different size. The field gradients and space charge densities were calculated for precipitator operation at constant current density, constant (pseudouniform) field strength and constant dimensionless voltage. The results show that onl y a constant dimensionless voltage leads to identical electrical field distributions.