Discharge Tube Diameter Research Articles

Study on the characteristics and predictive model of autoignition induced by shock wave from high-pressure hydrogen leakage

Faced with climate change and increasing environmental pollution, countries around the world are actively exploring strategies for clean, renewable energy. However, under high-pressure conditions, hydrogen leaks can lead to spontaneous combustion, which significantly raises the safety risk of hydrogen applications. This study employs fluid dynamic simulation methods to investigate the development process of shock waves within tubes. It analyzes the effect of release conditions on the propagation speed and shock wave intensity, revealing the impact of shock wave intensity on the temperature distribution and gas composition variation within the hydrogen-air mixture boundary layer. The results show that the tube length and bends have relatively little impact on the shock waves, while discharge pressure and tube diameter significantly affect the propagation speed and intensity of shock waves. Combined with dimensional analysis and data fitting, a predictive model for autoignition of high-pressure hydrogen leakage is established: (Pr/Pa)((DXrx(H₂)rO₂))/Vs2) = 1505(X/D)−1.329.

Plasma Characterization of Microwave Plasma jet at Atmospheric Pressure

The microwave induced plasma jet (MIPJ) system was built using local materials and based on a tapered waveguide. The parameters of this plasma were determined like electron temperature Te, electron density ne. the other parameters such as plasma frequency( fp), the Debye length( λD), and the number of particles in the Debye sphere( Nd) It has also been studied. The study were done at different Ar flow rate ranging from (2-10) l/m and a discharge tube diameter ranging from (2-10) mm. all of these parameters were determined depending on the MIPJ spectrum. it turned out that there is a high possibility of controlling the parameters of MIPJ through manipulating these parameters.

Электрические характеристики высокочастотного индуктора индукционного разряда низкого давления в замкнутых бесферритных трубках

The effect the high-frequency field frequency and lamp design parameters have on the performance characteristics of the inductor of a ferrite-free inductively-coupled closed-loop tube is studied within the framework of a transformer model. The discharge was excided in tubes with diameters equal to 16, 25 and 38 mm in a mixture of mercury vapour (~ 0.01 mm Hg) and argon (0.6 mm Hg) at driving frequencies equal to 1.7, 3.4 and 8.5 MHz and plasma power equal to 25–200 W by means of an induction coil containing 1, 2 and 3 turns, and placed over the closed-loop tube inner perimeter. It has been found that the dependences of inductor high-frequency current and voltage, and power loss in the coil wire on the discharge plasma power have a minimum, which shifts toward lower power levels with increasing the driving frequency and discharge tube diameter. The minimal values of coil current, voltage, and power losses decrease with increasing the driving frequency, tube diameter and number of coil turns. The prediction results are in satisfactory qualitative agreement with the experimental data; the mismatches are supposedly due to the assumptions adopted in the model, according to which the skin effect and electric field spatial inhomogeneity were not taken into account.

Development and Optimization of Single Filament Plasma Jets for Wastewater Decontamination

New efficient depollution techniques for water decontamination, purification and disinfection are being sought to replace those classic methods (chemical, filtration, ozonisation, photochemical reactions) that have deficiency for some substances. The use of plasma technologies, discharges in, or in contact with, wastewater are promising approaches for the decomposition of pollutants by highly oxidative radicals, charged particles, UV radiation, etc. produced by plasma. In the present study we report on the potential of radiofrequency single and multiple filamentary Dielectric Barrier Discharge (DBD) jets for the decolorization of methylene blue (MB) dye in water solutions. Optical emission spectroscopy (OES) investigations were performed for the characterization of plasma evolving in air, and in liquid. The decolorization process was monitored by absorption spectroscopy. We determined the decolorization time, according to a variety of external parameters. The key parameters for obtaining the maximum decolorization rate were identified as being the discharge tube diameter, tube nature (glass/ceramic), the injected power in the discharge, the type of reactive gas and the number of filamentary plasma jets.

The Effect of cold microwave plasma on Hormones and Living tissues of mouse females Using Digital Image Processing

The microwave plasma now been used in medical application helping to cut without any damage to the health tissue. The microwaves plasma system worked with 2.45 GHz microwaves frequency, 170 Volt applied voltage, 2 ℓ/min argon gas flow rate and 10 mm discharge tube diameter. Eight female albino mice were divided into two groups one control and one treated with microwaves plasma at 60 second. the results were positive and significantly increase in the follicular stimulating hormone (FSH) and the luteinizing hormone (LH) level. Digital image processing and Histopathology of the uterus is applied to search of effect of the microwave plasma on this organ. The segmentation process represented by thresholding is applied as a first step in the pre-processing. The statistical features is used to explained the changes which occur in the Uterus of the mice.

Электрические и излучательные характеристики индуктивных бесферритных ртутных УФ-ламп в замкнутых трубках

Electric and radiation characteristics of ultraviolet (UV) radiation (254 nm) sources employing ferrite-free inductively-coupled discharge excited in the closed-loop quartz tube with a help of a 3-turn induction coil disposed along the tube “inner” perimeter were experimentally studied. The inductive discharge was excited in the mixture of mercury vapor (~ 0,01 torr) and argon (1,0 torr) at a frequency of  1,7 MHz and RF power of 90-160 W. It was experimentally shown that in the lamp with discharge tube of 25 mm in diam., induction coil power losses and plasma RF electric field dependencies on lamp power had minima while discharge current and lamp UV radiation generation efficiency dependencies on lamp power had maxima. UV radiation flux grew with lamp power from 28 to 72 W while plasma UV radiation generation efficiency grew from 52 to 65%. The decrease of discharge tube diameter to 16 mm caused the increase of coil power losses and plasma RF electric field but did not affect UV radiation flux and lamp and plasma UV radiation generation efficiencies

Conversion of CO2 to CH4 by a Pulsed Hydrogen Plasma Shower Method

Aims: To suppress the emission of CO 2 to the environment and to save the consumption of fossil fuels, CO 2 was converted to CH 4 by a newly developed hydrogen shower method with a hydrogen pulse plasma. Study Design: Research study. Place and Duration of Study: This study was performed for 2013 - 2015 at Department of Electrical Engineering, Tohoku University, Sendai, Miyagi, Japan. Methodology: The experiment was carried out in a small chamber which was divided into two parts by an orifice disc of 3-mm-thickness stainless plate with one 0.5-mm-diameter hole at the center. Hydrogen gas was supplied from the left part, where hydrogen radicals of H* and H 2* were produced by a pulse discharge. Hydrogen radicals were supplied through the orifice from the left part to the right part as a hydrogen radical shower. Carbon dioxide was directly supplied to the right reaction part, where CO 2 was able to collide with hydrogen radicals and as a result CH 4 was produced. Results: Dependences of CO 2 decomposition ratio α, methane selectivity β, and energy efficiency γ on hydrogen flow rate, electrode distance, discharge tube diameter, applied voltage, electrode diameter, and gas feeding type were investigated. Methane was produced from carbon dioxide by Original Research Article

Investigation of capillary nanosecond discharges in air at moderate pressure: comparison of experiments and 2D numerical modelling

Nanosecond electrical discharges in the form of ionization waves are of interest for rapidly ionizing and exciting complex gas mixtures to initiate chemical reactions. Operating with a small discharge tube diameter can significantly increase the specific energy deposition and so enable optimization of the initiation process. Analysis of the uniformity of energy release in small diameter capillary tubes will aid in this optimization. In this paper, results for the experimentally derived characteristics of nanosecond capillary discharges in air at moderate pressure are presented and compared with results from a two-dimensional model. The quartz capillary tube, having inner and outer diameters of 1.5 and 3.4 mm, is about 80 mm long and filled with synthetic dry air at 27 mbar. The capillary tube with two electrodes at the ends is inserted into a break of the central wire of a long coaxial cable. A metal screen around the tube is connected to the cable ground shield. The discharge is driven by a 19 kV 35 ns voltage pulse applied to the powered electrode. The experimental measurements are conducted primarily by using a calibrated capacitive probe and back current shunts. The numerical modelling focuses on the fast ionization wave (FIW) and the plasma properties in the immediate afterglow after the conductive plasma channel has been established between the two electrodes. The FIW produces a highly focused region of electric field on the tube axis that sustains the ionization wave that eventually bridges the electrode gap. Results from the model predict FIW propagation speed and current rise time that agree with the experiment.

Kinetic analysis of the factors limiting the output power of the Ne–CuBr UV laser

The parametric optimization of the Ne–CuBr UV laser excited by longitudinal pulsed discharge is analysed by using a self-consistent kinetic model. Consistent characteristics of the optimization process are obtained by comparing with the experimental results. Simulation results show that neon ions come into being along with considerable depletion of the ground-state copper atoms. And the optimization of the discharge tube diameter is the tradeoff between the specific output photon density and the total active volume. Both the optimal neon gas pressure and the optimal reservoir temperature result from the balance between the neon ion density and the ground-state copper atom density to arrive at a maximum of their product.

Kinetics of the active medium of a He—Sr+ recombination laser: 2. Achievable energy characteristics

The mechanisms limiting the improvement of the energy characteristics of He—Sr+ recombination lasers with increasing pressure, active volume, and pulse repetition rate are analysed. It is found that the existence of optimal pressure is related to the cooling rate limitation for electrons at high pressures arising from the heating action of the trailing edge of a current pulse and that the average power saturation with increasing discharge tube diameter and pulse repetition rate occurs due to the formation of radial nonuniformity as well as due to the growth of the electron temperature in the afterglow. Calculations involving a mathematical model showed that the attainable maximum of the linear power is equal to ≈6.2 W m-1 for self-heating active elements of BeO ceramics and to ≈7.8 W m-1 with its surface blackened, to ≈7.7 W m-1 for an independent introduction of the vapour and to ≈9.4 W m-1 in combination with blackening, to ≈17 W m-1 for intense forced cooling of the active elements of cylindrical geometry and to ≈29 W m-1 with active elements of rectangular cross section for a wall dimension ratio of 1:3. We demonstrate the feasibility of raising the output power by ≈21% in the excitation of the active medium by pulse bursts with a short interpulse separation.

Experimental Investigation of Transformer Coupled Toroidal Discharges

The transformer coupled toroidal discharge (TCTD) was studied experimentally in the mixture of mercury vapours with argon and in pure neon. New experimental data on electric fleld strength and emission yield to visible and UV-range were obtained as functions of the discharge parameters. It was proved that the dependencies of electrical and optical characteristics of TCTD on the discharge current, gas pressure and tube diameter are close to those of dc arc discharges in mercury vapour and neon correspondingly. The possible reasons for parameter deviations were considered.

Experimental study of transformer-coupled toroidal discharge in mercury vapour

Experimental investigations of the transformer-coupled toroidal discharge (TCTD) in a mixture of argon and mercury vapour were carried out for a wide range of discharge parameters: mercury vapour pressure (0.1–40 000 Pa), discharge current (1–260 A), diameter of a gas-discharge tube (20–75 mm) and current frequency (10–250 kHz). New experimental data on electric field strength and emission yield to visible and UV-range were obtained as functions of the discharge parameters. It was proved that the dependences of electrical and optical characteristics of TCTD on the discharge current, vapour pressure and tube diameter are close to those of dc arc discharges in mercury vapour. The possible reasons for parameter deviations were considered. Also, the effect of the reduction of emissivity for the visible triplet of mercury spectrum (404.7, 435.8, 546.1 nm) with the excitation potential of 7.73 eV was discovered under certain conditions: mercury vapour pressure is higher than 10 kPa, and the specific power is above 50 W cm−1.

Experimental Investigation of the Electrical and Optical Characteristics of an Inductively Coupled Discharge in Neon

An experimental investigation of the electrical and optical characteristics of an inductively coupled discharge in neon is performed in a wide range of conditions of discharge burning, namely, discharge tube diameters of 20, 34, and 58 mm, neon pressures of 10 to 600 Pa, discharge currents of 1 to 30 A, and current frequencies of 25 and 250 kHz. The obtained data are compared to the results of investigations of both an inductively coupled discharge in inert gases (Ne, Ar, Kr) at a current frequency of 450 kHz and the positive column of a dc discharge in neon. It is demonstrated that the dependences of the electrical and optical characteristics of an inductively coupled discharge on the discharge strength, tube diameter, and neon pressure qualitatively agree with similar dependences for the positive column of a dc discharge. The effect of the current frequency on the parameters of inductively coupled discharge in neon is revealed.

High power 121.6 nm radiation source

A high power 121.6 nm radiation source based on dielectric barrier discharge (DBD) has been developed. Lamp parameters such as gas pressure, discharge tube diameter, electrode area and gap were optimized to maximize the 121.6 nm radiation power. Higher rf power was coupled to discharge by applying a flexible rf network, which matched the impedance between the source and discharge. The discharge was optimized by simulation using XOOPIC software to model the lamp. The simulation results were in agreement with our experimental measurements. The stable, high power (8 W) radiation source was achieved and it could be used as a reliable source for lithography and other applications.

Measurements and modelling of axial emission profiles in abnormal glow discharges in argon: heavy-particle processes

We report studies on argon glow discharges established between flat disc electrodes, at pressure × electrode separation (pd) values between 45 and 150 Pa cm, with special attention to heavy-particle processes including heavy-particle excitation induced light emission. The discharges are investigated experimentally and also through self-consistent hybrid modelling. The comparison of the experimental and computed light intensity distributions verifies the correctness of the model, which gives a detailed insight into the discharge operation. The efficiency of heavy-particle excitation shows a universal dependence on the reduced electric field. At the higher pd values the scaling of electrical characteristics and light emission intensity with electrode separation is verified, however, additional processes (radial losses of charged particles and reduction of the active cathode area) result in the violation of scaling at the lowest pd value when the discharge tube diameter is kept constant.

The Self-Ballasted Compact Fluorescent Lamp of an "A60" Bulb Shape.

Self-ballasted compact fluorescent lamps (CFLs) have been developed and improved in these twenty years. In Japan, the CFLs that have diffusive glass globes to replace incandescent lamps have been developed, but their sizes were too large to fit in the luminares of incandescent bulbs. Thus, we have developed the self-ballasted CFL of an A60 bulb shape, which has the maximum diameter of φ60 mm and the length of 123 mm. This lamp could be substituted for a 60 W incandescent lamp. In order to realize this lamp size, we optimized the discharge tube diameter, filling gas type and pressure, the shape and making-process of the discharge tube. After all, the triple-U connected tube is selected, which has a decisive advantage against a multi-folded tube on the luminous maintenance during life, but also has a disadvantage on the luminous run-up characteristics. We investigated the behaviors of mercury, especially the mercury diffusion phenomenon released from the auxiliary amalgam-flags after ignition by both experiments and calculation. The luminous run-up characteristic has been much improved.

Influence of the field frequency on the nitrogen atom yield in the remote plasma of an high frequency discharge

An discharge sustained by an electromagnetic surface wave is investigated in order to develop an efficient nitrogen atom source. We take advantage of the flexibility of surface-wave discharges (SWDs) in terms of operating frequency to examine the influence of the field frequency (f = 13.56, 40.68, 440 and 2450 MHz) on the nitrogen atom concentration in the discharge spatial afterglow. The effects of absorbed power (up to 200 W), pressure p (1 to 8 Torr) and discharge tube diameter (4.5 and 15 mm) are also considered. The N atom concentration is determined through emission spectroscopy from the afterglow following validation by NO titration. We find that: (i) the N atom concentration increases with but saturates past a certain power, the value of which decreases with increasing f, (ii) the N atom saturation concentration is at 2450 MHz but only at ; (iii) the vibrational `temperature' of the state in the discharge varies in the same way as the N atom concentration with respect to f and ; (iv) whatever f, saturation of the N atom concentration occurs at a threshold value -600 K of the molecule rotational `temperature' in the discharge, suggesting that too high a gas temperature is the limiting factor of the N atom yield (v) the N atom concentration increases with increasing p and decreasing .

Cs-Xe dc Gas Discharge as a Fast Highly Nonlinear Volumetric Medium for Microwaves

A plasma of the positive column of a dc gas discharge in a Cs-Xe mixture was shown to provide an effective volumetric nonlinear medium for microwaves. In such a gas-discharge plasma at a xenon pressure 30 Torr and an electron density ${N}_{e}>{10}^{12}{\mathrm{cm}}^{\ensuremath{-}3}$, a uniform spatial distribution of electron density with width about 0.8 of the discharge tube diameter was achieved. Using a 35 GHz microwave beam with intensities up to 0.5 W/c${\mathrm{m}}^{2}$, it has been found that the plasma of the positive column Cs-Xe discharge has a very high nonlinear refractive index ${n}_{2}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\ensuremath{-}0.07{\mathrm{cm}}^{2}/\mathrm{W}$ and a relatively fast response time of less than a millisecond.

Hysteresis effect of corona discharge in a narrow coaxial wire-pipe discharge tube with gas flow

An experimental investigation has been conducted to study corona discharge in a narrow tube. Narrow or capillary corona discharge (discharge tube diameter d/spl ap/1-20 mm) is used for many industrial applications such as flue gas cleaning corona-induced plasma reactors, ion sources, and electrohydrodynamic heat exchangers. In this work, corona discharge characteristics of a narrow coaxial wire-pipe discharge tube with gas flow are experimentally investigated. The results show that, unlike normal corona discharge, a hysteresis in the corona discharge current-voltage characteristic was observed for narrow tube discharges. The onset of the corona discharge was observed to be significantly dependent on the gas temperature and gas flow rates.

Characterization of imprisoned Xe resonant photons in He-Xe and Ne-Xe mixtures

The Holstein's theory of the imprisonment of resonance radiation for pressure-broadened Lorentzian profiles is extended to the Xe-based binary gas mixtures which are widely employed in practical discharge devices. In the binary mixtures, collisions between radiating and buffer atoms modify the emission and absorption spectrum profiles, affecting the imprisonment characteristics. It is found that the imprisonment time Tp is independent of total or partial pressures, provided that the Xe mixture ratio m and discharge tube diameter D are kept constant. Tp is proportional to D1/2. It is also proportional to m1/2 when m is sufficiently small, and becomes independent of m when m approaches unity. The 'broadening coefficients' xi Xe, xi He and xi Ne are defined as degrees of broadening of the Xe emission/absorption profiles due to collisions with Xe, He and Ne, respectively, in terms of half-widths at half-maxima per unit ground state atom density. By measuring Tp using cylindrical discharge tubes of diameters D=2, 5, 10 and 25 mm filled with various mixtures of He-Xe and Ne-Xe, the unknown coefficients are determined to be xi He=1.2*10-16 m3 s-1 and xi Ne=8.0*10-17 m3 s-1. These are 0.059 and 0.039 times that of xi X3, respectively. Knowledge of the coefficients allows us to calculate imprisonment times for any gas mixture and discharge space configuration. A reduction in Tp favours an increase of luminance and luminous efficiency in two ways. One is that luminance saturation with respect to the discharge current becomes less likely to occur, and the other is that, even under the fully saturated condition, luminance is higher with smaller Tp. Smaller Xe mixture ratios and tube diameters favour shortening of Tp. A reduction of m from 1 to 0.01 results, for any value of D, in a decrease in Tp by a factor of 2.6, assuring quicker escape of VUV from the volume. Since neither the total pressure nor Xe, He or Ne partial pressures affect Tp as long as the Xe mixture ratio is kept constant, these pressures can be chosen by considering only the conditions that provide the best discharge.