Numerical Study of the Suitable Precharger Grounded Electrode Length in Two-Stage-Type Electrostatic Precipitators

The two-stage-type electrostatic precipitator has been used only in limited applications because of its need to accommodate a large flow rate with its compact size. A two-stage-type electrostatic precipitator comprises a precharger and a collecting unit. The grounded electrode in the precharger is generally designed to be quite short. Previous studies on the influence of the grounded electrode length in the precharger on collection efficiency have reported that the amount of particle charge through the precharger decreases for grounded electrodes that are 20- or 80-mm long. The electric field and space charge distributions were calculated for various grounded electrode lengths using the finite-element method, where the ion density distribution was used as the space charge distribution. For a 20-mm-long grounded electrode, the electric field intensity around the high-voltage wire electrode decreased. Additionally, the electric field intensity distribution at close proximity to the grounded electrode has two additional peaks due to the edges of the electrode. With the 80-mm-long grounded electrode, the peaks of the electric field intensity distribution were outside of the high-ion-density region. These results show that the optimal grounded electrode length for particle charging is about three times the distance between the grounded electrode and the high-voltage wire electrode.