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 purpose of this study was to investigate the collection characteristics of nanoparticles emitted from a diesel engine in an electrostatic precipitator (ESP). The experimental system consisted of a diesel engine (400 cc) and an ESP; residual fuel oil and light fuel oil were used for the engine. Although, the peak value of distribution decreased as the applied voltage increased due to the electrostatic precipitation effect, the particle concentration, at a size of approximately 20 nm, increased compared with that at 0 kV, in the exhaust gas, from the diesel engine with residual fuel oil. However, the efficiency increased by optimizing the applied voltage, and the total collection efficiency in the exhaust gas, using the residual fuel oil, was 91%. On the other hand, the particle concentration, for particle diameters smaller than 20 nm, did not increase in the exhaust gas from the engine with light fuel oil.

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.