• Journal of Korean Society on Water Environment
• /
• v.30 no.4
• /
• pp.394-402
• /
• 2014

High-voltage dielectric discharges are an emerging technique in environmental pollutant degradation, which are characterized by the production of hydroxyl radicals as the primary degradation species. The initiation and propagation of the electrical discharges depends on several physical, chemical, and electrical parameters such as 1st and 2nd voltage of power, gas supply, conductivity and pH. These parameters also influence the physical and chemical characteristics of the discharges, including the production of reactive species such as OH, $H_2O_2$ and $O_3$. The experimental results showed that the optimum 1st voltage and oxygen flow rate for RNO (N-Dimethyl-4-nitrosoaniline, indicator of the generation of OH radical) degradation were 160 V (2nd voltage of is 15 kV) and 4 L/min, respectively. As the 2nd voltage (4 kV to 15 kV) was increase, RNO degradation was increased and, generated $H_2O_2$ and $O_3$ concentration were increased. The conductivity of the solution was not influencing the RNO degradation, $H_2O_2$ and $O_3$ generation. The pH effect on RNO degradation was not high. However, the lower pH and the conductivity, the higher $H_2O_2$ and $O_3$ generation were observed.

• Journal of the Korean Society of Safety
• /
• v.17 no.3
• /
• pp.112-117
• /
• 2002

A comparative investigation of an experimental and a simulation of chemical kinetics for NOx removal from silent(dielectric-barrier) discharges is presented. Several types of dielectric-barrier discharges were implemented depending upon the configuration of electrodes. The simulation was based on an approximate mathematical model for plasma cleaning of waste gas. The influence of non-uniform distributions of species due to the production of primary active particles in the streamer channel was taken into account. A comparison of observed experimental to the calculated removal efficiency of NOx showed acceptable agreement.

• Proceedings of the KIEE Conference
• /
• 2002.07c
• /
• pp.1890-1892
• /
• 2002

The technology of sulfur lamps that has physical and electrical characteristics comparable to current HID source has been reported. The fundamental principles of the operation of microwave discharges that are used to convert microwave energy to broad spectrum visual light are known. In this paper, emission dependance of microwave discharges in mixture content of sulfur with noble gases was studied. It is shown that the excitation of this gaseous mixture is carried out in two phases: (l) ionization of noble gas atoms by a microwave field and (2) the consequent maintenance of slightly ionized nonequilibrium plasma by the field. These two processes have essentially various thresholds for the microwave pump. The purpose of this work is to investigate spectral properties of the high frequency discharges in a mixture sulfur vapors with noble gases.

• Journal of Korean Society on Water Environment
• /
• v.28 no.3
• /
• pp.401-408
• /
• 2012

High-voltage dielectric discharges are an emerging technique in environmental pollutant degradation, which that are characterized by the production of hydroxyl radicals as the primary degradation species. The initiation and propagation of the electrical discharges depends on several physical, chemical, and electrical parameters such as 1st and 2nd voltage of power, gas supply, conductivity and pH. These parameters also influence the physical and chemical characteristics of the discharges, including the production of reactive species such as OH, $H_2O_2$ and $O_3$. The experimental results showed that the optimum 1st voltage and air flow rate for RNO (N-Dimethyl-4-nitrosoaniline, indicator of the generation of OH radical) degradation were 160 V (2nd voltage of is 15 kV) and 4 L/min, respectively. As the increased of the 2nd voltage (4 kV to 15 kV), RNO degradation, $H_2O_2$ and $O_3$ generation were increased. The conductivity of the solution was not influencing the RNO degradation and $H_2O_2$ and $O_3$ generation. The effects pH was not high on RNO degradation. However, the lower pH and the conductivity, the higher $H_2O_2$ and $O_3$ generation were observed.

• Proceedings of the KIEE Conference
• /
• 1992.07b
• /
• pp.980-982
• /
• 1992

This paper deals with the dielectric behaviors of $SF_6$ gas and prebreakdown growth caused by lightning impulse voltages In inhomogeneous field perturbed with a fixed needle-shaped protrusion on the electrode. The measuring interpretation of the external current induced by moving charges is described. The temporal growth of prebreakdown is observed by using a shunt and photomultiplier. The prebreakdown processes are initiated by the first streamer corona at a needle protrusion, the flashover of the main gap in the positive polarity is very sensitive to the local field and propagates into the gap with the leader mechanism. It Is found that the dependence of the prebreakdown phenomena on the polarity of applied voltages is caused by the effect of space charges. In addition, the proposed measuring techniques are very useful to perform the measurements of avalanche currents, corona discharges in inhomogeneous fields and partial discharges in voids.

• Applied Science and Convergence Technology
• /
• v.25 no.6
• /
• pp.138-144
• /
• 2016

The discharge characteristics of pulse-driven coplanar micro barrier discharges for an ultraviolet (UV) light source using Ne-Xe mixture have been investigated using a two-dimensional fluid simulation at near-atmospheric pressure. The densities of electrons, the radiative excited states, the metastable excited states, and the power loss are investigated with the variations of gas pressure and the gap distance. With a fixed gap distance, the number of the radiative states $Xe^*(^3P_1)$ increases with the increasing driving voltage, but this number shows weak dependency on the gas when that pressure is over 400 Torr. However, the number of the radiative states increases with the increase of the gap distance at a fixed voltage, while the power loss decreases. Therefore, a long gap discharge has higher efficiency for UV generation than does a short gap discharge. A slight change in the electrode tilt angle enhances the number of radiative species 2 or 3 times with the same operation conditions. Therefore, the intensity and efficiency of the UV light source can be controlled independently by changing the gap distance and the electrode structure.

• Journal of the Korean institute of surface engineering
• /
• v.44 no.2
• /
• pp.50-54
• /
• 2011

Hydrophobic a-C:F film was coated on polycarbonate film with $CF_4$, $C_2F_6$ and HFC ($C_2F_4H_2$) gas in helium discharge generated by 5~100 kHz AC power supply at atmospheric pressure and room temperature. The highest water contact angle of the a-C:F film formed with $He/C_2F_6$ mixed gas is $155^{\circ}$. X-ray photoelectron spectrum showed that there was 40% of C-$CF_3$ bond at the surface of the super hydrophobic film. The contact angle and deposition rate were decreased with increasing substrate temperature. The contact angle was generally increased with the surface roughness of the film. The contact angle was high when the surface microstructure of the film was fine and sharp at the similar roughness and chemical composition of the surface.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.53 no.7
• /
• pp.377-381
• /
• 2004

A discharge plasma reactor using a ferroelectric pellet packed bed is now used as a removal means of pollutant gases, such as NOx, SOx and VOCs. When an ac voltage is applied to this plasma reactor, then the pellets are polarized, and great electric fields are formed at each top and bottom contact points of the ferroelectric pellets. Thus the points of each pellet become covered with intense corona discharges, where an electrophysicochemical reaction is taking place strongly However these strong discharges also elevate the temperature of the pellets greatly and concurrently decrease the output ozone generation, as a result, the overall removal efficiency of gas becomes decreased greatly A new configuration of discharge plasma reactor using a ferroelectric pellet layer and a wire-to-wire electrode has been proposed and investigated experimentally. It is found that an intensive microdischarge is taking place on the surface of ac corona-charged ferroelectric pellet layer of the proposed reactor, which concurrently enhances the efficiency of plasma generation greatly And, this type of configuration of plasma reactor utilizing a wire-to-wire electrode and a ferroelectric pellet layer could be used as one of effective plasma reactors to remove pollutant gas.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.15 no.2
• /
• pp.31-37
• /
• 2016

In the steam system, a stream trap valve discharges a condensate and a non-condensable gas. It also prevents stream from being leaked. The free float stream trap valve is a mechanical type of stream trap. The valve is opened when a hallow ball is floated due to the density of the condensate through the condensate flows into the valve. On the other hand, when the flow of the condensate is completed, the valve is closed as the float subsides due to the weight of the structure and the stream is blocked. In addition, the bimetal lifts the hallow ball, which discharges the non-condensable gas. In this study, the performance of the properties of the free float stream trap valve, the method of support for three points, and the orifice design are researched. Moreover, the condensate discharge capacity of the free float stream trap valve is calculated from the experiment.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.56 no.9
• /
• pp.1619-1625
• /
• 2007

The gas mixture ratio of PDP discharges plays a very important role in the discharge characteristics of a plasma display panel. The increase of Xe contents results in the increases of luminance and luminous efficiency while it also results in the increase of the breakdown voltage. The addition of He gas increases the brightness and the luminous efficiency. Especially, the luminance and the luminous efficiency have a maximum value when the partial pressure of He is about 10% of the total pressure for a standard plasma display panel with Xe fraction of $10\sim30%$.