Electrical Characteristics of Pulsed Corona Discharge Plasmas in Chitosan Solution

Pulsed discharge plasma has exhibited active potential to prepare low molecular weight chitosan. In the present study, the viscosity of ehitosan solution was decreased noticeably after treated with pulsed corona discharge plasma. An experimental investigation on electrical characteristics of pulsed corona discharge plasma in chitosan solution was conducted with a view toward getting insight into discharge process. Factors affecting I-V curve, single pulse injec- tion energy and pulse width were studied. Experimental results showed positive effect of pulsed peak voltage on discharge plasma in chitosan solution. Pulse-forming capacitor greatly influenced the discharge form, and 4 nF was observed as a suitable value for efficiently generating stable discharge plasmas. As the electrode distance was larger than 10 ram, it had slight impact on dis- charge plasma due to the excellent conductive-property of chitosan solution. The injection energy significantly increased with air flow rate, while the pulse width hardly changed as the air flow rate increased from 0.5 m^3/h to 1.0 m^3/h. This study is expected to provide reference for promoting the application of pulsed corona discharge plasma to ehitosan solution treatment.     

Degradation of Synthetic Dyeing Wastewater by Underwater Electrical Discharge Processes

Electrical discharge treatments of synthetic dyeing wastewater were carried out with two different systems: underwater pulsed electrical discharge (UPED) and underwater dielectric barrier discharge (UDBD). Reactive Blue 4 (RB4) and Acid Red 4 (AR4) were used as model contaminants for the synthetic wastewater. The performance of the aforementioned systems was compared with respect to the chromaticity removal and the energy requirement. The results showed that the present electrical discharge systems were very effective for degradation of the dyes. The dependences of the dye degradation rate on treatment time, initial dye concentration, electrical energy, and the type of working gas including air, O 2 , and N 2 were examined. The change in the initial dye concentration did not largely affect the degradation of either RB4 or AR4. The energy delivered to the UPED system was only partially utilized for generating reactive species capable of degrading the dyes, leading to higher energy requirement than the UDBD system. Among the working gases, the best performance was observed with O 2 . As the degradation proceeded, the concentration of total dissolved solids and the solution conductivity kept increasing while pH showed a decreasing trend, revealing that the dyes were effectively mineralized.     

Influence of Additive Gas on Electrical and Optical Characteristics of Non-equilibrium Atmospheric Pressure Argon Plasma Jet

Electrical and optical properties of an argon plasma jet were characterized. In particular, effects of an additive gas, namely nitrogen or oxygen, on these prop...     

Electrical Characteristics of Pseudoglow Discharges in Helium under Atmospheric Pressure

A pseudoglow discharge behaviour is achieved at a 2.0-mm dielectric-dielectric electrode gap in pure helium under atmospheric pressure. An experimental study of the pseudoglow discharges is presented. The electrical characteristics and the discharge photos of the pseudoglow discharges are analyzed and discussed. The current-voltage parameters of the pseudoglow dis- charges are considered in regard to the influence on their behaviour.     

Discharge Characteristics of Series Surface/Packed-Bed Discharge Reactor Diven by Bipolar Pulsed Power

The discharge characteristics of the series surface/packed-bed discharge(SSPBD)reactor driven by bipolar pulse power were systemically investigated in this study.In order to evaluate the advantages of the SSPBD reactor,it was compared with traditional surface discharge(SD) reactor and packed-bed discharge(PBD) reactor in terms of the discharge voltage,discharge current,and ozone formation.The SSPBD reactor exhibited a faster rising time and lower tail voltage than the SD and PBD reactors.The distribution of the active species generated in different discharge regions of the SSPBD reactor was analyzed by optical emission spectra and ozone analysis.It was found that the packed-bed discharge region(3.5 mg/L),rather than the surface discharge region(1.3 mg/L) in the SSPBD reactor played a more important role in ozone generation.The optical emission spectroscopy analysis indicated that more intense peaks of the active species(e.g.N_2 and OI) in the optical emission spectra were observed in the packed-bed region.     

Effect of the Mesh Transparency on the Electrical Characteristics of DC Pseudo Discharge

A DC pseudo discharge for air has been studied.Air pressure is used in the range between 0.7 Torr and 12 Torr.The breakdown occurs between a plane cathode and a mesh anode at transparencies of 19%,46%,and 65%.The current-voltage characteristic curves of the discharge,which are measured at different pressures,distances,and mesh transparences,take effect in the region of abnormal glow.The discharge voltage decreases as the air pressure increases,while more voltage is needed to maintain the discharge when either the mesh transparency or the interelectrode distance is increased.An increment of mesh transparency causes high negative potential behind the mesh due to the high concentration of electrons,which accumulate and collide with neutral atoms.Paschen curves deviate from the expected regular one.The left side of Paschen curves appears at inter-electrode distance of 1 mm,whereas the right side appears at inter-electrode distance of 5 mm.The intermediate region is observed only at 3 mm distance between the two electrodes.For the transparency range used in this work,it is found that the decrement of the breakdown voltage,on the right side,depends on the mesh transparency.For different electrode separations,the measured Paschen curves are coincident and deviate from the standard ones of Paschen's law.     

Yield of Ozone,Nitrite Nitrogen and Hydrogen Peroxide Versus Discharge Parameter Using APPJ Under Water

Discharge plasma in and in contact with water can be accompanied with ultraviolet radiation and electron impact,thus can generate hydroxyl radicals,ozone,nitrite nitrogen and hydrogen peroxide.In this paper,a non-equilibrium plasma processing system was established by means of an atmospheric pressure plasma jet immersed in water.The hydroxyl intensities and discharge energy waveforms were tested.The results show that the positive and negative discharge energy peaks were asymmetric,where the positive discharge energy peak was greater than the negative one.Meanwhile,the yield of ozone and nitrite nitrogen was enhanced with the increase of both the treatment time and the discharge energy.Moreover,the p H value of treated water was reduced rapidly and maintained at a lower level.The residual concentration of hydrogen peroxide in APPJ treated water was kept at a low level.Additionally,both the efficiency energy ratio of the yield of ozone and nitrite nitrogen and that of the removal of p-nitrophenol increased as a function of discharge energy and discharge voltage.The experimental results were fully analyzed and the chemical reaction equations and the physical processes of discharges in water were given.     

Effect of Duty Cycle on the Characteristics of Pulse-Modulhted Radio-Frequency Atmospheric Pressure Dielectric Barrier Discharge

Using a one-dimensional fluid model, the pulse-modulated radio-frequency dielectric barrier discharge in atmospheric helium is described. The influences of the pulse duty cycle on the discharge characteristics are studied. The numerical results show that the dependence of discharge characteristics on the duty cycle is sensitive in the region of around 40% duty cycle under the given simulation parameters. In the case of a larger duty cycle, the plasma density is higher, the discharge becomes more intense, but the power consumption is higher. When the duty cycle is lower, one can get a weaker discharge, lower plasma density and higher electron temperature in the bulk plasma. In practical applications, in order to get a higher plasma density and a lower power consumption, it is more important to choose a suitable duty cycle to modulate the RF power supply.     

Discharge Characteristics of SF6 in a Non-Uniform Electric Field Under Repetitive Nanosecond Pulses

The characteristics of high pressure sulphur hexafluoride (SF ₆ ) discharges in a highly non-uniform electric field under repetitive nanosecond pulses are investigated in this paper. The influencing factors on discharge process, such as gas pressure, pulse repetition frequency (PRF), and number of applied pulses, are analyzed. Experimental results show that the corona intensity weakens with the increase of gas pressure and strengthens with the increase of PRF or number of applied pulses. Spark discharge images suggest that a shorter and thicker discharge plasma channel will lead to a larger discharge current. The number of applied pulses to breakdown descends with the increase of PRF and ascends with the rise of gas pressure. The reduced electric field (E/p) decreases with the increase of PRF in all circumstances. The experimental results provide significant supplements to the dielectric characteristics of strongly electronegative gases under repetitive nanosecond pulses.     

Characteristics of a Normal Glow Discharge Excited by DC Voltage in Atmospheric Pressure Air

Atmospheric pressure glow discharges were generated in an air gap between a needle cathode and a water anode. Through changing the ballast resistor and gas gap width between the electrodes, it has been found that the discharges are in normal glow regime judged from the currentvoltage characteristics and visualization of the discharges. Results indicate that the diameter of the positive column increases with increasing discharge current or increasing gap width. Optical emission spectroscopy is used to calculate the electron temperature and vibrational temperature. Both the electron temperature and the vibrational temperature increases with increasing discharge current or increasing gap width. Spatially resolved measurements show that the maxima of electron temperature and vibrational temperature appeared in the vicinity of the needle cathode.