Characteristics Of Gas Discharge Research Articles

Assessment of the gas discharge characteristics during gas recovery by hydrate decomposition

Hydrate-based gas separation is a novel approach for the capture and recovery of hydrofluorocarbons. The gas discharge characteristics during hydrate decomposition need to be clarified for the efficient recovery of hydrofluorocarbons. In this study, we investigated the mass transfer characteristics during the gas recovery from hydrate particles by decomposing the HFC134a hydrates. First, the volumetric mass transfer coefficient was estimated from the gas recovery rate during the HFC134a hydrate slurry. The hydrate particles enhanced the gas recovery performance of the overall apparatus. Next, the mass transfer coefficient between hydrate and liquid was calculated. Ascending bubbles and the resulting change in the dispersion state of the particles significantly affected the mass transfer. Finally, we developed a mass transfer correlation equation between the solid and liquid phases by dimensionless numbers based on Kolmogorov’s theory. The experimental equation predicted the Sherwood number with ±40 % accuracy and an average absolute relative error of 19.0 %. The dispersion state of the hydrate particles was a significant factor in the estimation.

Issues of gas film stability with performance characteristics in u-ECDM: A review of existing approaches and preliminary investigation on proposed stable & sustainable approach

Micro-featured devices (made of glass and its composites) are becoming increasingly necessary for Micro Electro-Mechanical Systems (MEMS) and healthcare devices with the emergence of technology. Due to limitations of existing methods, Micro Electro Chemical Discharge Machining (μ-ECDM) is an evolving technique for difficult to micro machine materials like glass. However, improper flushing and unstable electrolytic conditions in the processing zone percolates the efficacy, accuracy, and repeatability of μ-ECDM. Consequently, deteriorating the sustainability and industrial feasibility of this process. To cope up with these problems, various approaches like ultrasonic assistance, rotary mode, magneto hydrodynamic are integrated and investigated with μ-ECDM in the literature. Although these approaches achieved the intended objectives but do not assure the stability and sustainability of the process, which are essential for industrial feasibility in the present scenario. The present review has stressed upon the effects of existing approaches on gas film formation, discharge characteristics and performance outcomes. Systematic review methodology indicated the extensive usage of ultrasonic vibrations in μ-ECDM and, the studies on the stability/sustainability of μ-ECDM process are neglected. According to literature and preliminary investigation, problems pertaining to the rising electrolyte temperature and heterogeneous electrolyte concentration are the attributed reasons, which affects the stability as well as sustainability. Therefore, the present review proposed an innovative approach to achieve the stability and sustainability of μ-ECDM process by controlling the electrolytic conditions (termed as controlled-ECDM). A preliminary experimental investigation witnessed the enhancement of process performance and quality characteristics in controlled-ECDM.

Применение метода газоразрядной визуализации для оценки скрытых дефектов семян

The gas-discharge visualization (GDV, electrophotography) method allows recording and quantifying the glow that occurs near the surface of the object (seed), when placing it in an electromagnetic field of high intensity. The hidden defects – emptiness of Pinus sibirica Du Tour seeds and biogenic damage (by phytopathogenic bacteria Pantoea ananatis) of Zea mays L. seeds were revealed and analyzed by the method of gas discharge visualization in combination with automatic analysis of digital gas-discharge images. It is shown that empty seeds have reduced values of the averaged intensity of digital gas discharge images. According to the data obtained, the methods of gas-discharge imaging (electrophotography) and microfocus radiography showed high efficiency (> 90%) of accuracy in the detection of empty seeds of Pinus sibirica. It was found that the sample of Zea mays seeds (hybrid Krasnodarskiy 194 MV) was characterized by reduced values of the average intensity of gas-discharge images, as well as the average brightness of digital X-ray images, compared with the other three seed samples. The seed sample of hybrid Krasnodarskiy 194 MB was characterized by the worst sowing qualities: emergence rate, germination, root length and shoot length. It was shown that the Krasnodarskiy 194 MB seeds were affected by phytopathogenic bacteria Pantoea ananatis. The average inverse correlations of a number of characteristics of gas-discharge glow (area, total intensity) with the standard deviation of brightness of digital X-ray images, as well as weak reliable correlation of most gas-discharge characteristics with seeding qualities were found. Comparative assessment of gas discharge indices and seedlings germination as integral indices for evaluation of biological completeness of Zea mays seeds was carried out. Research has confirmed that the method of gas discharge visualization in combination with automatic analysis of digital gas-discharge images can be used as an effective additional tool for rapid detection of defective seeds.

Research on Discharge Characteristics in Ultra-high Pressure Gases (Supercritical Fluids): A Brief Review

This paper provides a review of the research on discharge characteristics in ultra high pressure gases (supercritical fluids) and discusses different applications in various fields. Followed by a summary on the investigations performed on the application of supercritical fluids for power switching purposes. A brief overview of the open research questions related to characterization of ultra high pressure switching arcs concludes the paper.

Gas Production Characteristics of UHV Oil immersed Shunt Reactor with Vibration Defects

The special multi-air gap structure of Ultra high voltage (UHV) oil-immersed shunt reactor determines that its magnetic leakage is far greater than that of a power transformer of the same voltage level, and it is more prone to vibration and other problems. Overheating and suspended discharge caused by vibration are important sources of excessive gas production in UHV shunt reactors. In this paper, the source of gas production under reactor vibration is analyzed, and a reactor defect simulation gas production platform is built. Using oil chromatography analysis, partial discharge detection, and other means, the gas production characteristics, discharge characteristics and insulation degradation characteristics of typical defects such as suspended discharge and partial overheating under vibration have been experimentally studied. Then, the correlation analysis model between the vibration type, intensity, overheating degree, and the reactor performance change was established. Finally, the gas production and discharge characteristics of the reactor under different defect types were obtained. Besides, gas production characteristics under vibration with 50 Hz, 100 Hz, and 150 Hz were carried out, and it was found that the gas will continue to increase with the increase of vibration frequency, and the growth has been stabilized after exceeding 100 Hz. The relevant research results of this paper can provide technical support for the application of UHV oil-immersed shunt reactor state assessment and diagnosis, and improve the level of equipment operation and maintenance.

Pulsed Gas Discharge Driven by Bipolar Solid-State Linear Transformer Driver

Pulsed gas discharge has been studied using a pulsed power generator with a bipolar solid-state linear transformer driver (SSLTD) scheme. Taking advantage of the output flexibility of the bipolar SSLTD, we have studied the residual charges phenomenon by the coaxial discharge load. The experiment result shows that for two consecutive positive pulses discharge, the current of the second positive pulse is usually lower than that of the first pulse for the same voltage amplitude. However, a middle negative pulse applied between the first and second pulse can increase the current of the second positive pulse. An explanation for this phenomenon has been explored using a 1-D model that considers the effect of residual charge left by the previous pulse discharge. According to the explanation of our 1-D discharge model, this phenomenon may be caused by the residual charge distorting the discharge electric field strength. The findings obtained by this article will help us understand the fundamental characteristics of pulsed atmospheric pressure gas discharge.

Analysis of gas discharge characteristics across micro-gap under different pressures

To study the process of micro-gap gas discharge under different pressures, the experimental of the micro-discharges for the gaps ranging from 1 to 100 μm under 1–100 kPa is presented and the results are discussed. The curves of breakdown voltage with the pd value at different gaps are drawn and there are multiple breakdown voltages under the same pd value. As the decrease of the gaps, the deviation between the breakdown curve and the traditional Paschen curve increases when the electrode distance is less than 100 μm and the pd value is less than about 80 Pa·cm. The breakdown field strength and the ratio of effective secondary coefficient of field emission to Townsend’s secondary coefficient are estimated at different pressures and different electrode gaps. The ion-enhanced field effect has been found to play an important role in field emission in several microns of electrode gaps.

The effect of gas injection on energy characteristics of high-current gas discharge with liquid electrolyte cathode

A gas discharge with flowing liquid electrolyte cathode was studied experimentally in high-current combustion conditions under conditions of gas injection into the discharge chamber. The interelectrode distance was 20 cm. Aqueous solutions of sodium chloride with specific electrical conductivity of 10–12 mS/cm were used as electrolyte. The discharge current varied within 14-20 A. The studies were carried out with air blowing at a mass flow rate of up to 2.2 g/s. It is shown that air blowing leads to an increase in the discharge current and decrease heat losses through electrodes.

Analysis of ArF excimer laser system discharge characteristics in different buffer gases

Excimer laser is the current mainstream source of international semiconductor lithography. The stable operation of the laser system directly affects the working efficiency of the semiconductor lithography machine, so it is very important to optimize the laser system. The buffer gas commonly used in ArF excimer laser systems is He, Ne. In the early years, Shinjin Nagai and Mieko Ohwa have studied the output characteristics of the system when using He or Ne as a buffer gas from the aspect of pump efficiency and gain coefficient, and pointed out that using Ne instead of He has no obvious advantages in terms of efficiency. However, when Ne is used as the buffer gas, the reaction between Ne and electrons is more complicated. In addition to direct ionization and excitation reactions, it also contains a large amount of step ionization and secondary ionization, which releases free electrons. The stability of the system is improved, when Ne is used as the buffer gas. The ArF excimer laser system discharge characteristics in different buffer gases are analyzed based on fluid model in the paper. The role of photoionization is discussed. The simulation results show that the width of the electron depletion layer and the cathode sheath are both smaller, and the discharge stability is higher when Ne is used as the buffer gas. The expansion of the discharge region is accelerated and the threshold voltage of the discharge is reduced by adding Xe into Ne to trigger photoionization. The excimer laser discharge process is very complicated and is affected by many factors. Only two factors of the buffer gas and the photoionization process are studied in this paper. The simulation model will be extended from one-dimensional case to two-dimensional case in the future, and multiple physical factors of the ArF excimer laser system will be considered.

Parameterized Nanosecond Pulse Realization Through Parametrical Modulation of Timing Sequence of Switches in Marx Circuit

The characteristics of gas discharge are closely related to the features of high-voltage pulses, especially to the rising and falling time of pulse. A parameterized pulse control method based on improved Marx generator is proposed to obtain parameterized nanosecond high-voltage pulses to match different discharge circumstances. Different parameters of nanosecond pulses are realized in real time by parametrical modulating timing sequences of switches in an improved Marx generator. Experimental results indicate that the ability of generating pulses is with 0–20 kV amplitude, 0–1 ms width (flat top), 50–500 ns or faster rising/falling time, below 5% overshoot, and a maximum 5 kHz repetitive frequency at 20 kV on a matched 0–100 pF capacitance load. The shape of pulse waveform including triangular, rectangular, or the combination of the two kinds of pulse waveform can be achieved. The discharge characteristics in the dielectric barrier discharge device driven by the parameterized pulse, especially changing the rising time of pulse, are investigated. The uniform discharge is observed, and the discharge intensity is doubled while reducing the rising time of pulse from 500 to 50 ns, and the intensity of the N2 spectrum increased to 2.5 times.

Comparing properties of dc discharges in tubes possessing a hollow cathode or anode in an undergraduate laboratory

In this paper, we suggest a simple experiment to study the properties of a dc glow discharge in tubes with a ‘hollow cathode and flat anode’ and a ‘hollow anode and flat cathode’ design in the course of undergraduate laboratory work devoted to the research into the characteristics of gas discharges. The work is aimed at observing a phenomenon where employing the tube with a hollow cathode furnishes a much larger discharge current than one can get with a hollow anode design or that with both flat electrodes. Within the certain pressure range (27–40 Pa under our conditions) two negative glows overlap at the center of the cavity resulting in a considerable (several times) increase in the discharge current. The anode shape does not practically affect the discharge current value that is manifested by the fact that current–voltage characteristics for both flat electrodes and the hollow anode design almost coincide.

Study the effect of cathode geometry on I-V characteristics of nitrogen dc glow discharge

In this paper, the I-V characteristic of a dc glow discharge are studied with the aim of determine the performance a good parametersfor stable operation of the plasma. Nitrogen plasma produced by dc glow discharge is the investigated with a manypurpose of studying plasma phenomena, the discharge system consists of two electrodes, the cathode forms various geometrical shapes and anode as a disc- shaped with diameter (8.8cm). The electrodes are enclosed in a large cylindrical glass chamber of pyrex filled with nitrogen gas. Two important physical parameters affecting the condition of the discharge are the gas pressure and constant inter-electrode distance. The discharge current-voltage (I-V) characteristic curves of the discharge were measured at variable pressure and the inter-electrode spacing, Current-voltage characteristics visualization of the discharge indicate that the discharge is take place in the normal glow region. The (I-V) characteristics of nitrogen gas discharge were deduced as a plasma system operated in normal glow discharge nitrogen, which is very important parameter in the sputtering and deposition. Also, the discharge current is increased for nitrogen plasma discharge with the increasing of the working pressure lead to increase the deposition rate.DIO.: http://dx.doi.org/10.31257/2018/JKP/2019/110110

Examination of digital X-ray and gas discharge characteristics of English oak acorns (Quercus robur L.) for assessment of their sowing qualities

Examination of digital X-ray and gas discharge characteristics of English oak acorns (Quercus robur L.) for assessment of their sowing qualities

A theoretical model for effect of electron radial diffusion on breakdown characteristics of DC Townsend discharge in uniform axial magnetic field

The breakdown characteristics of gas discharge between two parallel disks including the electron losses in the discharge process due to radial diffusion have been discussed. A theoretical approach was established to determine the fraction of electrons lost from the discharge cell due to radial diffusion. Then, the dependency of the effective secondary electron emission coefficient on the inter-electrode spacing d, the electrode radius R, and the axial magnetic field B was studied. A particle-in-cell, Monte Carlo collision technique was employed to obtain the values of electron loss coefficient, δ, for d from 1 cm to 10 cm, R between 1 and 10 cm, B up to 300 G, and the gas pressures from 50 mTorr to 250 mTorr. The results show that the loss of the electrons increases exponentially with the distance d, while it decreases by increasing R. Based on the model, the applied magnetic field lowers the Paschen curve that is in agreement with the experimental data.

An investigation on optical properties of capacitive coupled radio-frequency mixture plasma with Langmuir probe

The properties of Capacitively Coupled Radio Frequency (CCRF) plasmas for mixture gases have not already been known. Therefore, our goal in this paper is to understand the characteristics of mixture gas discharges in the different ratio of capacitive coupled discharge at low pressure. For this aim, the single Langmuir probe can be used to estimate the electron temperature and the electron density of the mixture discharge in a capacitive coupled discharge plasma system at low pressure. The characteristics of helium (He) and electronegative oxygen (O2) mixture plasma is determined by the single Langmuir probe. The ratio of the ion saturation current to electron saturation current is investigated with obtaining values from this probe. The optical emission measurements have been taken to minimize the deficiency of the Langmuir probe diagnostics.

Dark-to-arc transition in field emission dominated atmospheric microdischarges

We study the voltage-current characteristics of gas discharges driven by field emission of electrons at the microscale. Particle-in-cell with Monte Carlo collision calculations are first verified by comparison with breakdown voltage measurements and then used to investigate atmospheric discharges in nitrogen at gaps from 1 to 10 μm. The results indicate the absence of the classical glow discharge regime because field electron emission replaces secondary electron emission as the discharge sustaining mechanism. Additionally, the onset of arcing is significantly delayed due to rarefied effects in electron transport. While field emission reduces the breakdown voltage, the power required to sustain an arc of the same density in microgaps is as much as 30% higher than at macroscale.

The Effect of Inductively Coupled Discharge on Capacitively Coupled Nitrogen-Hydrogen Plasma

A novel technique to generate high-density plasma-called inductively coupled plasma (ICP), enhanced capacitively coupled plasma (CCP)- is successfully developed. The plasma can be generated using different frequency configurations, such as ICP-enhanced single-frequency capacitively coupled plasma (SFCCP) and dual-frequency capacitively coupled plasma (DFCCP). The characteristics of the plasma in the following frequency combinations are mainly investigated using a Langmuir probe, SFCCP (60 MHz), DFCCP (60 MHz, 13.56 MHz), SFCCP (60 MHz) and inductively coupled plasma (13.56 MHz), DFCCP (60 MHz, 13.56 MHz) and inductively coupled plasma (13.56 MHz). In this letter, the nitrogen and hydrogen mixture gas discharge characteristics of different configurations are studied. After the analysis, we can acquire the electron temperature and ion density. Then, the effect of inductively coupled discharge on SFCCP and DFCCP can be summarized. In our preliminary investigations, the main results can be given as follows. ICP can make the density of SFCCP increase and the distribution of the electron temperature in a radial direction more uniform. In addition, ICP not only can make the ion density of DFCCP increase, but also can improve the radial uniformity. Further experiments may be needed to clarify the mechanism.

Structure and Properties of Ti–O–N Coatings Produced by Reactive Magnetron Sputtering

Results of an experimental study of the optical characteristics of gas discharges are presented. The study was aimed at optimizing the operating modes of a mid-frequency magnetron sputtering system to efficiently deposit Ti–O–N coatings. The conditions for maintaining the intensity of the chosen spectroscopic lines that ensure synthesis of titanium oxide and titanium oxynitride coatings have been revealed. The morphology, structure, contact angle, and free surface energy of titanium oxide and titanium oxynitride coatings on type 12Kh18N10T stainless steel substrates were examined by using scanning and transmission electron microscopy and infrared spectroscopy, and by measuring the wetting angle. The results of examination of the structure and properties of the synthesized films and their physicomechanical and optical characteristics are given.

Effects of pressure and electrode resistance on AC-plasma display panels (AC-PDPs) for various panel temperatures

In this study, the effects of panel temperature on AC-plasma display panels (AC-PDPs) were investigated. Macroscopic properties, such as the luminance, discharge delay time lag, and discharge current decreased while the breakdown voltage increased with increasing panel temperature. These data implied that changes in the materials properties with the panel temperature strongly affected the macroscopic properties, including the gas-discharge characteristics of AC-PDPs. The reason can be explained by the change in the collision kinetics due to the increase in the pressure in the AC-PDPs, the voltage drop due to the increase in the resistivity of the metal electrodes, and the decrease in the effective voltage due to the decrease in the surface resistivity of a MgO protective layer. The properties of other components such as the indium-tin-oxide (ITO) transparent electrode and the dielectric layer changed little in the considered temperature range (0 ∼ 80 °C), and, thus, are not thought to affect the macroscopic properties of AC-PDPs with changing panel temperature.

A theoretical approach to electric breakdown behaviour and effective secondary emission coefficient in gas discharge process between two parallel-plane disk electrodes

The gas discharge characteristics are seriously influenced by the effective secondary electron-emission coefficient (γeff) originally defined by Townsend. A theoretical approach has been proposed for the determination of variation of this coefficient as a function of the geometrical parameter d/R (the ratio of inter-electrode distance to electrode radius) in the most practical range of 0.08≤d/R≤1.90. Two geometrical factors gi and gp, which are attributed to ion-induced and photon-induced terms, respectively, were introduced to the effective gamma in parallel-plane arrangement. The factors were theoretically derived and hence the effective gamma and the breakdown voltage for a specified geometrical parameter, such as d/R=0.16, were obtained. Then, the effective gamma and the Paschen curves for various geometrical parameters such as d/R=0.32, 0.63, 1.27, and 1.90 were theoretically reproduced. The obtained results showed quite a good agreement with those reported by other researchers and verified that the proposed gi and gp have properly been introduced and derived.