The purpose of this article is to show the validity of the simulation result for particle charge and trajectory in an electrostatic precipitator (ESP) with multiple wire electrodes, and the effect of the number of wire electrodes on the relationship between collection efficiency and discharge power. The ESP in this article has wires-and-plates configuration. The potential, the electric field intensity, the negative ion density, the ionic gas flow, the charge of the particles and the charged particle trajectory in the ESP were calculated. In the experiment, the charged particle trajectory was measured by a particle image velocimetry (PIV). In addition, the analysis and the experimental collection efficiencies as a function of input power in the ESPs with a single wire electrode and three wire electrodes were compared, and the effect of the number of wire electrodes on the power consumption was investigated. As a result, the x and y components of the particle velocity measured using the PIV almost agreed with the simulated result. The validity of the simulation result for charged particle trajectory, which was calculated by fitting the analyzed corona current to the experimental value, in an ESP with multiple wire electrodes was demonstrated. Also, both analysis and experimental collection efficiencies by the ESP with three wire electrodes were greater than those with the single wire electrode at the same input power. An analysis revealed that this was because the residence time of the particles in the ESP with three wire electrodes was longer than that with the single wire electrode.

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 pre-charger and a collecting unit. The grounded electrode in the pre-charger is generally designed to be quite short. Previous studies on the influence of the grounded electrode length in the pre-charger on collection efficiency have reported that the amount of particle charge through the pre-charger 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.

Exhaust gases from internal combustion engines contain fine carbon particles. If a biofuel is used as the engine fuel for low-carbon emission, the exhaust gas still contains numerous carbon particles. For example, the ceramic filters currently used in automobiles with diesel engines trap these carbon particles, which are then burned during the filter regeneration process, thus releasing additional CO₂. Electrostatic precipitators are generally suitable to achieve low particle concentrations and large treatment quantities. However, low-resistivity particles, such as carbon particles, cause re-entrainment phenomena in electrostatic precipitators. In this study, we develop an electrostatic precipitator to collect fine carbon particles. Woodceramics were used for the grounded electrode in the precipitator to collect carbon particles on the carbon electrode. Woodceramics are eco-friendly materials, made from sawdust. The electrical resistivity and surface roughness of the woodceramics are varied by the firing temperature in the production process. Woodceramics electrodes feature higher resistivity and roughness as compared to stainless-steel electrodes. We evaluated the influence of woodceramics electrodes on the electric field formed by electrostatic precipitators and calculated the corresponding charge distribution. Furthermore, the particle-collection efficiency of the developed system was evaluated using an experimental apparatus.

Electrostatic Precipitators (ESP) are used extensively for decontaminating of industrial gaseous pollution and air cleaning of building. One application of the ESP is decontaminating polluted gases and increasing the visibility index in expressway tunnels. However, the collection efficiency of large particle decreases due to particle re-entrainment phenomena, since lots of particles in expressway tunnels are made of carbon that has low resistivity. Therefore, large particle has the adverse effect of decreasing visibility index. It is important to prevent re-entrainment for increasing the visibility index. In this work, we discussed the method preventing particle re-entrainment, and devised applying rectangular AC high voltage to the collecting electrodes. DC voltage is applied to precharger in all test conditions. The collection efficiency of large particle decreases due to particle re-entrainment with DC high voltage applied to electrode in collecting section. However, when rectangular AC high voltage applied to the collecting electrodes, the collection efficiency of large particles improves with increasing frequency. The re-entrainment phenomena are prevented on applying rectangular AC high voltage (1Hz). And then, the collection efficiency of submicron particles on applying rectangular AC high voltage (1Hz) is as high as DC high voltage.