Jae-Duk Moon

An EHD gas pump utilizing a ring/needle electrode

An electrohydrodynamic (EHD) gas pump, utilizing a ring/needle electrode, has been proposed and the effect of the ring electrode to the flow velocity and yield of flow generation of the EHD gas pump was investigated. The needle/ring is used as a corona discharge electrode and the mesh is used as the ion collecting electrode. It was observed that the proposed type of EHD gas pump can generate a higher flow velocity and yield of flow generation as compared with that from the same EHD gas pump without the ring electrode. As a result, a maximum flow velocity of VW=4.54 m/s from the proposed EHD gas pump can be obtained at V=15.0 kV, which is 1.2 times higher than that of VW =3.82 m/s of the same needle-to-mesh type EHD gas pump without the ring electrode. With the ring electrode, the yield of flow generation of YW=46.15 m/Ws can be obtained at V=11 kV, which is 2.5 times higher than that of the design without the ring electrode of YW=18.41 m/Ws. These enhancements, however, may be due to the effect of the ring electrode installed near the needle electrode.

Electrostatic Precipitation of Carbon Soot from Diesel Engine Exhaust

A moving belt-type electrostatic precipitator (MBEP) has been developed for the control of diesel engine particulates. It indicates 95-percent collection performance for soot with 1-¿m mass- median diameter (MMD) when used in combination with a pre- agglomeration system consisting of a precharger and a parallel-plane collector. The insulators supporting the discharge electrode were located outside the precipitator so that they were not subjected to soot contamination. The very fluffy conductive soot collected on the moving belt was brought to the rollers where it was pressed and scraped off. The soot deposition on the discharge electrode could be corrected by using a fishbonelike multineedle discharge electrode. Very active coronas from its sharp needle points produced a remarkable self-cleaning effect by corona-induced oxidation of the soot.

An EHD Gas Pump Utilizing a Wet Porous Point Electrode

A point-to-mesh type electrohydrodynamic (EHD) gas pump, utilizing a wet porous point electrode, has been proposed, and the effect of the wet porous point electrode on the gas flow velocity and flow generation yield of the EHD gas pump was investigated. The wet porous point is used as a corona discharge electrode, and the mesh is used as an ion collecting electrode. It was observed that the EHD gas pump with the wet porous point electrode can generate a higher gas flow velocity and flow generation yield than the same design EHD gas pump with a non-porous metal point electrode. As a result with the wet porous electrode, a peak gas flow velocity of VW = 2.54, 2.74, and 1.93 m/s has been obtained for positive, negative, and ac corona discharges. This is 1.95, 1.31, and 1.30 times higher than the velocity VW = 1.30, 2.09, and 1.49 m/s measured with the same design EHD gas pump and a non-porous metal point electrode. At 0.1 W of input corona power for dc and ac powers, the flow generation yields of Y = 13.88, 12.80, and 11.70 m/s/W were obtained with the wet porous point electrode for the positive, negative, and ac corona discharges, which are 1.23, 1.24, and 1.15 times higher as compared with those of the metal point electrode with Y = 11.32, 10.29, and 10.20 m/s/W, respectively. These enhancements may be due to the elevated input corona powers and the water particles generated from the wet porous point electrode.

Effective Ozone Generation With a Wire–Wire-Type Nonthermal Plasma Reactor With a Slit Barrier

The corona discharge and ozone generation characteristics of a wire-wire-type nonthermal plasma reactor (PR), with a slit dielectric barrier, have been experimentally investigated. When a slit mica barrier is installed between corona wires, a significant increase in the generation of ozone could be obtained. From the photographs of the corona discharges, this type of nonthermal PR with a slit barrier (SB) produces two corona discharges, one from the corona wires and another from the slits of the SB. This second corona discharge is caused by the rapid relaxing of the charges, which are migrated from the corona wire and stored on the surface of the barrier, through the slits. As a result, the proposed nonthermal PR has the potential to significantly increase ozone production, and it may be useful as an effective means for removing pollutant gases.

A capacitive type of electrostatic spraying nozzle

Abstract Many toxic pesticides are dispensed to protect food crops from pests in farm fields. Greater than 90% of pesticides are commonly applied as aqueous-based sprays. When dispensed with conventional nozzles, a large portion of the spray is often lost as airborne drifts of droplets. In addition, there is a lack of deposition onto the plants due to the rapid gravitational settling of droplets beneath the soil surface. Thus, target deposition efficiencies poorer than 25% are often encountered in agricultural pesticides. Electrostatic spraying technology offers a very favorable means of increasing pesticide droplet deposition onto biological surfaces of living crops. More than a doubling in efficiency is a reasonable goal. In this paper, a new capacitive type of electrostatic spraying nozzle, which utilizes a ring induction electrode installed on the outside of a nozzle frame cone and a pulsed voltage, is proposed and studied experimentally. The results of this study indicate that the proposed capacitive type of electrostatic spraying nozzle exhibits a large current deposition of aqueous sprays on the sample target. Thus, it has promise to be applied as an effective electrostatic spraying nozzle.

A sliding discharge-type EHD gas pump utilizing a saw-toothed-plate discharge electrode

A sliding discharge-type electrohydrodynamic (EHD) gas pump, utilizing a discrete saw-toothed-plate electrode as a discharge electrode instead of a smooth conventional-plate electrode, has been developed. The effect of the saw-toothed-plate electrode on the gas flow velocity and yield of flow generation of the EHD gas pump were investigated. It was observed that the EHD gas pump can generate a higher gas flow velocity and yield of flow generation than the same design EHD gas pump with the conventionalplate electrode. As a result, a peak gas flow velocity of VG=1.65 m/s from the EHD gas pump with the saw-toothed-plate electrode can be obtained for VP=12.0 kV, which is 2.39 times higher than that of VG =0.69 m/s of the same design EHD gas pump with the conventional-plate electrode. With the saw-toothed-plate electrode, the yield of flow generation of YG=0.435 m/Ws can be obtained for V=8.0 kV, which is 4.53 times higher than that of the same design EHD gas pump with the conventional-plate electrode of YG=0.096 m/Ws. These enhancements are due to the effect of the saw-toothed-plate electrode being utilized instead of the conventional-plate electrode.

Control of corona characteristics with third electrode and bias voltage

A novel corona control system consisting of a point-to-plate air gap with a cylindrical third electrode has been proposed. Negative and positive coronas from a point-to-plate air gap with a cylindrical third electrode set up close to the corona point of the needle have been investigated with emphasis on the role of the cylindrical third electrode, the bias voltage amplitude and polarity. It was found that the point-to-plate air gap with the cylindrical third electrode had a negative resistance characteristic on its I-V characteristic for negative polarity discharge, which is very different from the same electrode system without the third electrode. Discharge characteristics of the needle point, such as the corona onset voltage and the corona activity, could be controlled by adjusting the field intensity of the corona point by changing the corona point height from the third electrode and varying the bias voltage amplitude and polarity of the third electrode. >

Discharges of point-to-plate gaps in pure water

A preliminary study on conduct ions and discharges of three kinds of gaps-a conventional point-to-plate gap, a conventional point-to-plate gap with field controlling electrode, and a hole-to-plate gap with field controlling electrode in pure water-was conducted to check the potential of the latter as ozone generators. The hole-to-plate gap with a finer hole diameter showed very low breakdown voltages in pure water which could be due to the presence of a stable gas cavity in the hole where partial breakdown could take place easily, the oxygen molecules could be broken down into oxygen atoms, and concurrently ozone could be produced effectively in the hole cavity. The hole-to-plate gap with the field controlling electrode could potentially be used as an ozone generator utilizing the two ozone generating mechanisms of electrolysis and corona discharge, whereas conventional ones are just one of these mechanisms.<<ETX>>

A miniature size electrostatic induction motor

A miniature electrostatic induction type motor has been fabricated, and parameters influencing the motor speed, such as voltage and frequency of the three-phase AC power supply, the resistivity and relative dielectric constant of the rotor surface materials, the relaxation time constants, and the resistivity of the rotor liner materials have been studied. The no load motor speed was proportional to the applied three-phase AC voltage. The motor speed increased linearly with increase of the applied frequency of the three-phase AC power supply, having a critical frequency at the higher frequency where partial discharges take place in the air gap between the rotor and the stator. This characteristic makes it possible to control the speed linearly by changing the applied frequency. The maximum no-load rotor speed of the motor tested was about 5500 RPM at an applied voltage of 4.5 kV and a frequency of 220 Hz for a rotor surface material of BaTiO/sub 3/ 80% in the resin binder layered on the copper-foil rotor liner material.<<ETX>>

SO/sub 2/ and CO gas removal and discharge characteristics of a nonthermal plasma reactor in a crossed DC magnetic field

Discharge and SO/sub 2/ and CO gas removal characteristics of a wire-to-cylinder type nonthermal plasma reactor in a crossed DC magnetic field have been investigated. The experiment has been emphasized on the applying of a crossed magnetic field, which would induce the cyclotron and drift motions of electrons making the residual time longer in the air gap space, and it enhances the energy of electrons and the electrophysicochemical actions to remove pollutant gases effectively. It is found that the corona onset voltage and the breakdown voltage were decreased with increasing the crossed magnetic field. As a result, a higher ozone generation of 20-30% can be obtained with DC corona discharges in the DC current-induced magnetic field, and a very high removal efficiency of almost 100% for the initial fed SO/sub 2/ gas of 120 ppm and CO gas of 1000 ppm was achieved at 900 G of the magnetic flux density.