High-voltage Plasma Research Articles

High-voltage pulsed plasma generation with frequency control for streamer initiation in liquid phase

Plasma streamers are produced utilizing a high-voltage pulse generator with variable peak-potential difference for up to 20 kV with 200 mJ of pulse energy, 15 microsecond rise time, and adjustable pulse frequency in the range between 1 Hz and 1.5 kHz for corona streamer initiation in liquid phase. The pulsed plasma generator is tested in a pin-to-plate electrode geometry in a sealed reactor filled with deionized water. Streamer geometry information and the resulting electrical waveforms are presented, in addition to quantitative description of temperature variation with respect to pulse frequency and electrical power applied. It is observed that consistent streamers without significant variation in length are obtained within the frequency range analyzed.

Active control of thermoacoustic instability using microsecond plasma discharge

The thermoacoustic instability produced in a simple heat-driven-acoustic-oscillation device (so-called Rijke tube) has been controlled by the periodic plasma discharge. A perforated plate is placed at the upstream of the tube as the heater. Due to the interaction between the heat and acoustic waves, thermoacoustic instabilities occur. The high-voltage microsecond pulsed plasma is generated within pin-to-pin electrodes that are used as an actuator since the pressure wave generated by the plasma is quite strong and able to attenuate the thermoacoustic sound wave in the Rijke tube. However, since the pressure waveform generated by the plasma discharge is different from the sinusoidal signal that is generated by a loudspeaker and widely used as a control actuator, it is necessary to derive the new model from the simplified Rijke tube. The time domain oscillation simulation is conducted, and the phase shift method is used to find appropriate control strategy. The discharge pressure waveform is subsequently fitted with an eighth-order Fourier series, and the overall Fourier signal is adjusted so that the first-order waveform in the discharge was similar to the analog sinusoidal control signal; the control is quite effective. It is known that when the sinusoidal control waveform of same frequency as thermoacoustic instability can meet control requirements, the non-sinusoidal signal can also control the thermoacoustic instability. Finally, according to the simulation results, the high-voltage microsecond plasma discharge is adjusted to the suitable amplitude and phase used for closed-loop control on the thermoacoustic oscillation, which significantly suppressed the instability.

Advanced oxidation treatments of olive mill wastewater

New and innovative advanced oxidative processes for wastewater treatments are currently in the focus of scientific research and development for possible industrial implantation. The main aim of this study was to investigate the effect of cold plasma treatment, high intensity ultrasound and UV radiation with the addition of additives: H2O2, TiO2, FeCl3 x 6H2O on degradation and removal of complex organic compounds from olive mill wastewater (OMWW). Olive mill wastewater represents a potential ecological problem when it is raw disposed into the environment, because of its high organic load. OMWW samples (with and without additives) were treated by high-voltage plasma discharge at frequencies 60 Hz and 120 Hz in combination with pumped gases (nitrogen, air and oxygen) for 30 minutes, by UV radiation for 30 minutes and 10 minutes by high intensity ultrasound. Physico-chemical parameters of quality, chemical oxygen demand (COD), and total dissolved carbon (TOC) were determined. The results have shown the efficacy of plasma treatment in degradation of organic compounds as well as degradation and reduction of polyphenolic compounds. Reduction of colour and total dissolved carbon occurred in all treated samples, mostly with the addition of FeCl3 x 6H2O. Treatment with UV radiation and ultrasound proved to be the most efficient resulting in the 50% reduction of organic compounds after a 10-minute treatment.

Exploring the Potential of High-Voltage Electric Field Cold Plasma (HVCP) Using a Dielectric Barrier Discharge (DBD) as a Plasma Source on the Quality Parameters of Carrot Juice.

The main aim of the current investigation was to contemplate the impact of high-voltage electric field cold plasma (HVCP) on different quality characteristics (enzymes, microbial activities, coloring pigments, ascorbic acid, polyphenolic compounds, °Brix, acidity, and color index) of carrot juice in correlation with thermal processing. A carrot juice (250 mL) sample sealed in pre-sterilized food-grade bottles, which placed between two dielectric quartz plates for HVCP treatment. The gap between the plates was 30 mm, and a stable and uniform plasma dielectric barrier discharge (DBD) generated for 3 and 4 min at 60, 70, and 80 kV. Air was used as a working gas during the DBD-based plasma treatment. The observed rise in temperature was 2–5 °C during the HVCP treatment. A water bath was used to carry out thermal treatment (100 °C for 5 min). The maximum inactivation of enzymes and microorganisms was achieved with thermal treatment and then with HVCP treatment at 70 kV for 4 min. However, maximum retention of coloring compounds, ascorbic acid, total phenols, flavonoids, and tannins was found following HVCP (70 kV for 4 min) treatment compared to thermal treatment. The °Brix, pH, and acidity remained unchanged irrespective of treatments. These findings suggest that HVCP treatment at 70 kV for 4 min may be a good alternative to thermal treatment, and it may successfully be applied in carrot juice production, resulting in reduced enzymes, lower microbial activity, and improved bioactive compounds. The prospects of overcoming the existing conventional physical and chemical methods for sterilization make it a novel and more economical technique to maintain food’s natural nourishment, composition, appearance, structure, and freshness.

Influence of Combined Effect of Ultra-Sonication and High-Voltage Cold Plasma Treatment on Quality Parameters of Carrot Juice.

Influence of the combined effect of ultra-sonication (US) and high-voltage cold plasma treatment (HVCP) on the quality parameters of fresh carrot juice has been studied. During the treatment of ultra-sonication, carrot juice was subjected to a 0.5 inch probe for 3 min by adjusting the pulse duration 5 s on and off at 20 kHz frequency, amplitude level 80%. The ultrasound intensity was measured by using a thermocouple and was 46 Wcm−2. The temperature was maintained at 10 °C by an automatic control unit. During the treatment of HVCP, carrot juice was then subjected to dielectric barrier discharge (DBD) plasma discharge at 70 kV voltage for 4 min. Significant increases were observed when HVCP treated carrot juice was tested against total carotenoids, lycopene, and lutein when compared to the control treatments. Moreover, this increase was raised to its highest in all pigments, chlorogenic acid, sugar contents, and mineral profile, as the results of ultra-sonication when combined with high voltage atmospheric cold plasma (US-HVCP). Whereas, a significant decreased was observed in Mg, total plate count, yeast, and mold after US-HVCP treatment. Furthermore, results indicated that the combined effect of US-HVCP treatment has improved the quality and led to a higher concentration of lycopene, lutein, chlorogenic acid, and mineral compounds (Na, K, and P). Therefore, the findings of the current study suggested that US-HVCP treatment is a novel combined technique that could provide better quality and more stability during the processing of carrot juice with better physicochemical properties and bio-available nutrients, so this novel processing technique could serve as an alternative to traditional processes.

Obtaining nano-disperse soot from orthoxylene by the high-voltage AC plasma torch

The article deals with the synthesis of fullerene-containing soot using high-voltage AC plasma torch. The plasma torch consists of three electric arc channels with three graphite rod electrodes. Orthoxylene vapors are fed into the arc zone of the plasma torch, and argon is used as a protective gas. In the plasma torch orthoxylene decomposes under the action of an electric arc. The prodused soot contains 5.4% C60 fullerene and 1.6% C70 fullerene.

Study of Runaway Electrons in GOLEM Tokamak

High loop voltage and low-density plasma discharges at the GOLEM tokamak present favorable conditions for the study of the runaway electrons (RE). A probe is being designed and developed for the spectral measurement of the RE energy inside the last closed flux surface of GOLEM tokamak plasma. Design of the probe is based on simulation results of the FLUKA code that estimates the energy absorbed by the scintillating crystals and filters of various densities. In the simulations, graphite, stainless steel and molybdenum were tested to filter the supra-thermal electrons. Since having different light yield, YSO (Y2SiO5:Ce), NaI(Tl) and plastic (EJ-200) scintillating crystals were chosen for the simulations.

Dielectric Barrier Discharge High Voltage Cold Atmospheric Plasma: An Innovative Nonthermal Technology for Extending the Shelf‐Life of Asian Sea Bass Slices

Impact of dielectric barrier discharge high-voltage cold atmospheric plasma (DBD-HVCAP) generated with the mixture of oxygen and argon (10:90) for various treatment times (2.5 to 10 min) on the qualities of Asian sea bass slices during 4°C storage was investigated. Microbial load of slices treated with DBD-HVCAP were lower than the control. The efficacy of bacteria reduction by DBD-HVCAP was dependent on the treatment times (P<0.05). Total viable bacteria count (TVBC) was more than 6.0 Log CFU/g at day 6 for the control kept in air. Slices treated with DBD-HVCAP for all treatment times used had TVBC lower than the limit at day 12. Total volatile nitrogen base content (TVNB) as well as trimethylamine (TMA) content in slices treated with DBD-HVCAP were lower than that of the control throughout the storage. TVNB as well as TMA contents were lower in HVCAP treated slices in a treatment time-dependent manner. Nevertheless, lipid oxidation in samples treated with DBD-HVCAP was higher than that of the control. Polyunsaturated fatty acids were decreased in slices treated with DBD-HVCAP for more than 5 min after 12 days of storage. Therefore DBD-HVCAP treatment for 5 min was demonstrated to be potential means for increasing the shelf-life of Asian sea bass slices with minimal negative effect on chemical and sensory properties, in which they could be stored longer than 12 days at 4°C. PRACTICAL APPLICATION: Microbial inactivation capacity of dielectric barrier discharge high-voltage cold atmospheric plasma (DBD-HVCAP) has been documented with limited information on its application in extending the shelf-life of foods. DBD-HVCAP was demonstrated as an innovative technology for extending the shelf-life of Asian sea bass slices, which could be implemented in seafood industries for assuring safety and extending shelf-life of products. The shelf-life of the slices treated with DBD-HVCAP was extended to 12 days of storage at 4°C as compared to the 6 days of the untreated counterpart.

Feasibility of Artificial Neural Networks and Fuzzy Logic Models for Prediction of NO$_{X}$ Concentrations in Nonthermal Plasma-Treated Diesel Exhaust

High-voltage discharge-based nonthermal plasma (NTP) treatment for diesel exhaust is a laboratorial proven efficient technique. A prophecy of the treatment results based on the knowledge of its parameters would be a step forward toward bringing it into real-time applications of pollution control. In this paper, artificial neural networks (ANNs) and fuzzy logic model (FLM) have been used to model the NO $_{ X }$ (sum of NO and NO2) concentrations as a function of parameters of the NTP process. A data set of 4032 input–output pairs has been collected by conducting experiments, in which 70% of the data are used for the training of the models derived. The performances of all the considered models have been evaluated by testing them for the remaining 30% of the data, which is novel for the models. Furthermore, a comparison of the models has been made based on the root-mean-square error (RMSE) and mean relative error (MRE), where the FLM has been found to be the better compared to the ANN-based models, i.e., ANN, multilayer perceptrons (MLP), and functional link ANN (FLANN). The RMSE of FLM is 2.53 ppm for a test data of 1210 sets. It can be said from these results that the NO $_{ X }$ concentrations can be predicted using FLM with a good accuracy.

Co-gasification of lignite and used car tires by H2O/air thermal plasma

The article considers a high-voltage AC plasma torch working on a mixture of water vapor and air up to 90 kW. A thermodynamic calculation of the co-gasification of used automobile tires and lignite is presented. Assessment of the operation of the plasma torch working on mixtures of H2O/air at co-gasification of lignite and used car tires shows prospect of these processes implementation.

Current-Assisted Sintering of Combustion-Synthesized β-SiAlON Ceramics

Current-assisted sintering of combustion-synthesized β-Si5AlON7, h-BN, and TiN powders was explored in comparison with conventional sintering. High relative density of product (above 92%) was achieved by using high-voltage electric discharge consolidation (HVEDC) and spark plasma sintering (SPS). Better results were obtained in case of SPS processing.

Fullerenes production by electric arc pyrolysis of methane in an AC three-phase plasma torch

The article deals with a high-voltage three-phase AC plasma torch working as a part of a plasma-chemical facility. The plasma torch consists of three electric arc channels and three rod copper electrodes. The initial breakdown occurs with high voltage (10 kV) provided by a high voltage power supply. The electric arc plasma oxygen-free pyrolysis of methane was realized on the facility. The fullerene-containing fraction was extracted from the carbonaceous material by extraction with orthoxylene. The produced carbon-black and the selected extract were analyzed by modern methods of physical and chemical analysis: scanning electron microscopy, X-ray phase analysis, IR spectroscopy.

Acoustic cavitation assisted plasma for wastewater treatment: Degradation of Rhodamine B in aqueous solution

A novel wastewater treatment process, acoustic cavitation assisted plasma (ACAP) is proposed in this study aiming at expanding the treatable range of water pollutants due to a synergetic effect of ultrasound irradiation and high voltage plasma discharge. In this process, the role of acoustic cavitation is not only to provide generation of chemically active OH radicals, as for example in conventional ultrasonic wastewater treatment techniques, but also to ensure conditions for stable plasma generation in wastewater and, thus, to extend the treatable range of water pollutants. Rhodamine B (RhB) was used as a model pollutant in experiments examining effects of ultrasound amplitude, RhB initial concentration, output voltage, solution pH and electrical conductivity on the RhB degradation efficiency. The results revealed that the ultrasound-assisted plasma generation requires lower output voltages and allows to increase the acceptable range of electrical conductivity of treatable solutions up to 1000 μS/cm, that is about 24 times higher than in the case of conventional plasma discharge treatment. The alkaline and acid medium were found to be favorable for higher degradation efficiency. Additional measurements and results of recent investigations concerning underwater plasma showed that microbubbles presented in cavitation zone could serve as “bridges” making the pulse discharge propagation between the electrodes easier than in the conventional case. Besides, acoustic cavitation assists a faster transition of plasma discharge from ineffective streamer type to more effective spark type that further contributes to the improvement of the treatment performance.

AC plasma torch operating on a mixture of air and methane

The article considers a high-voltage AC plasma torch for air reforming of natural gas. It has two inputs of plasma-forming gases: the electrode zone (for shielding gas) and the arc zone (for the main plasma-forming gas). The voltage drop on the arc increases with increasing methane flow rate due to the formation of hydrogen and intensification of heat transfer.

On Calculation of the Ignition Voltage for a Back-Arc Discharge in a High-Voltage Thermionic Diode

Development of large spacecraft propulsion units involves the creation of high-temperature radiation-resistant systems for current conversion based on thermionic devices of plasma electric power engineering, such as grid-controlled switches and high-voltage plasma thermionic diodes (HVPTD). The current conversion system (CCS) is required to match the electrical parameters of a thermionic conversion power reactor (with an output voltage of 120–150 V) with the parameters of the electric jet engine (having a working voltage of hundreds or thousands of volts). This brings about an urgent issue of calculating the ignition voltage for the back-arc discharge in the interelectrode gap (IEG) of HVPTDs. A semiempirical correlation is proposed for predicting the back-arc discharge ignition voltage as a function of the cesium vapor pressure in IEG and the anode temperature. It can be used by designers of thermionic plasma power engineering devices.

Study of the operation of high-voltage plasma torches with rod electrodes

Study of the operation of high-voltage plasma torches with rod electrodes

Hydrogen Peroxide and Beyond-the Potential of High-voltage Plasma-activated Liquids Against Cancerous Cells.

The use of plasma-activated liquids such as PBS, medium or simply plasma-activated water (PAW) has been receiving increasing attention for applications in cancer treatments. Amongst the reactive species contained in these solutions, hydrogen peroxide appears to play a pivotal role in causing cytotoxic effects. H2O2 concentrations can be correlated with reduced cell viability and growth and used as an indicator of the potential efficacy of a plasma-activated liquid. To investigate the cytotoxic mediators generated in water specific to high-voltage DBD-ACP. Using a high-voltage dielectric barrier atmospheric cold plasma (DBD-ACP) system, we examined PAW-mediated cytotoxic effects on different mammalian cell lines employing a set-up where short-lived reactive species can be discounted and activated liquids with long-term stability are generated. The PAW potency could be modulated using voltage level, treatment time and post-treatment storage time and target-related characteristics such as surface to volume ratio. All of these parameters effected cell viability in a hydrogen peroxide concentration correlated manner. The susceptibility of two cancer cell lines to PAW was similar to that observed for two non-cancer cell lines and the toxicity of plasma-activated water exceeded that of the corresponding hydrogen peroxide concentrations. In cytotoxic plasma activated water an essential role for H2O2 has been demonstrated multi-fold, yet further contributing factors are apparent and remain to be identified.

Investigation of a high voltage AC plasma torch operating on mixtures of methane and other gases

The article considers the high-voltage AC plasma torch working on a mixture of gaseous hydrocarbon (methane, propane-butane) and inert gases (argon). During the burning of the electric arc, methane is transformed into soot containing fullerenes. The composition of the soot was analyzed by optical UV-spectroscopy, IR-spectroscopy and X-ray phase analysis.

Operation of High-Voltage Plasma Torches with Rod Electrodes

The paper deals with single-phase AC plasma torches with rod electrodes made of iron-copper composite material, with air as the plasma-forming gas and an life time of ~200 h. The construction peculiarities of this type of plasma torch and its power-supply systems is described. The experimental results, in particular, the current-voltage and the voltage-flow rate characteristics of the plasma torches, as well as the typical current and voltage oscillograms, are presented.

Breakdown Characteristics of Triggered Pseudospark Discharge-Based Multigap Plasma Cathode Electron Source

Pseudospark (PS) sourced electron beam with high energy can be produced by a multigap PS discharge-based plasma cathode electron (PD-PCE) source under high-voltage operations. The process of successive high-voltage breakdown and plasma formation inside hollow cathode (HC) and in the gaps play significant role for electron beam generation. An investigation has been carried out for the analysis of discharge processes in different multigap PS structures using the 2-D kinetic plasma simulation code. It has been observed that the distribution of equipotential contour lines in the HC cavity as well as gaps is important to investigate the occurrence of the breakdown and plasma generation in the PD-PCE source. The higher equipotential lines start penetrating through the electrode apertures only when the plasma is formed in the adjacent previous gap. The potential lines help the electrons to run out through the electrode apertures and have collision process for the ionization in the next gaps. The radial expansion of the electrons and ions has also been analyzed which depends on the profile of equipotential contour lines. The expansion of ions is relatively more compared to electrons at the time of breakdown and plasma formation in the gaps. The expansions of electrons and ions are less in the first and last gap compared to the intermediate gaps. The equipotential contour lines determine the successive breakdown and discharge processes in the multigap PD-PCE source, which are required for the generation of efficient plasma, and energetic and high-density PS discharge-based electron beams.