共查询到20条相似文献，搜索用时 0 毫秒
1.
Yiwen LI 《等离子体科学和技术》2019,21(6):65502-131
Development of magnetohydrodynamic acceleration technology is expected to improve wind tunnel simulation capability and testing capability. The underlying premise is to produce uniform and stable plasma in supersonic air flow, and gas discharge is an effective way to achieve this. A nanosecond pulsed discharge experimental system under supersonic conditions was established, and a pin-to-plate nanosecond pulsed discharge experiment in Mach 2 air flow was performed to verify that the proposed method produced uniform and stable plasma under supersonic conditions. The results show that the discharge under supersonic conditions was stable overall, but uniformity was not as good as that under static conditions. Increasing the number of pins improved discharge uniformity, but reduced discharge intensity and hence plasma density. Under multi-pin conditions at 1000 Hz, the discharge was almost completely corona discharge, with the main current component being the displacement current, which was smaller than that under static conditions. 相似文献
2.
Helium plasma jets generated by micro-hollow cathode discharge (MHCD) with the square-wave power source of different polarities are investigated in this work. The effects of positive and negative polarity pulses on the MHCD and plasma jet were compared, and the time-resolved optical emission spectra of excited species (N2+ and O) were studied. The results confirm that the electric field is a key factor for the propagation of the jet during the rising edge of the positive current pulse, while the gas expansion is mainly important for the jet propagation during the current stable phase. The time-resolved spectra show that the generation of specie O in the jet-driven by the electric field is more efficient. 相似文献
3.
Shuqun WU 《等离子体科学和技术》2019,21(7):74007-64
In this work, a typical pin-to-pin plasma synthetic jet in static air is excited by a pulsed DC power supply. The influences of the pulse rising time, the amplitude and the repetition frequency of the pulse voltage on the jet flow have been investigated. First, using a high-speed Schlieren imaging technique, the induced shock waves and the fast jet flow generated by the plasma synthetic jet are characterized. With a deposited energy of 44 mJ per pulse, the velocity of the shock wave and the maximum velocity of the jet flow reach 320 m s−1 and 100 m s−1, respectively. Second, when the applied voltage increases from 12.8 kV to 16 kV, the maximum jet velocity increases from 66 m s−1 to 93 m s−1. On the other hand, as the pulse rising time varies from 50 ns to 500 ns, or the pulse repetition frequency increases from 5 Hz to 40 Hz, the jet velocity induced by the plasma synthetic jet is weakly dependent. In addition, a comparative study of the plasma synthetic jets using three commercial pulsed power supplies (XJ-15, NPG- 18, and PG-30) is implemented. It reveals that the maximum jet velocity of 120 m s−1 is obtained in the case of PG-30, with the longest pulse rising time and the lowest breakdown voltage, while the maximum velocity of 33 m s−1 is detected in the case of NPG-18, even though it has the shortest pulse rising time and the highest breakdown voltage. 相似文献
4.
HU Guanghai 《等离子体科学和技术》2016,18(9):918-923
Plasma source is the most important part of the laboratory plasma platform for fundamental plasma experimental research. Barium oxide coated cathode plasma source is well recognized as an effective technique due to its high electron emission current. An indirectly heated oxide coated cathode plasma source has been constructed on a linear magnetized plasma device. The electron emission current density can reach 2 A/cm 2 to 6 A/cm 2 in pulsed mode within pulse length 5–20 ms. A 10 cm diameter, 2 m long plasma column with density 10 18 m −3 to 10 19 m 3 and electron temperature Te ≈ 3–7 eV is produced. The spatial uniformity of the emission ability is less than 4% and the discharge reproducibility is better than 97%. With a wide range of the plasma parameters, this kind of plasma source provides great flexibility for many basic plasma investigations. The detail of construction and initial characterization of oxide coated cathode are described in this paper. 相似文献
5.
YANG Lanlan 《等离子体科学和技术》2015,17(1):25-31
A two-dimensional self-consistent fluid model is used to investigate the effects of DC-voltage polarity in plasma initiation and propagation of helium plasma jet.The simulation results indicate that the difference in initial breakdown for the positive jet and negative jet leads to a difference in the electron density of about 4 orders of magnitude,even with the same initial electric field,which also influences the subsequent propagation.In the propagation process of negative jets,the ionization process exists in a longer gas channel behind the streamer head.In addition,the drift process to the infinite grounded electrode driven by the electric field results in higher energy consumption in the ionization process.However,in the positive jet,the ionization process mainly exists in the streamer head.Therefore,the differences in the initial breakdown and propagation process make the electric field intensity and the ionization weaker in the streamer head of the negative jet,which explains the weaker and shorter appearance of the negative jet compared to the positive jet.Our model can adequately reproduce the experimental results,viz.a bullet-like propagation in the positive jet and a continuous plasma plume in the negative jet.Furthermore,it also indicates that the streamer velocity shows the same variations as the electron drift velocity for both positive and negative jets. 相似文献
6.
TANG Jingfeng 《等离子体科学和技术》2016,18(3):273-277
Atmospheric pressure discharges excited by repetitive nanosecond pulses have attracted significant attention for various applications.In this paper,a plate-plate discharge with airflows is excited by a repetitive nanosecond pulse generator.Under different experiment conditions,the applied voltages,discharge currents,and discharge images are recorded.The plasma images presented here indicate that the volume discharge modes vary with airflow speeds,and a diffuse and homogeneous volume discharge occurs at the speed of more than 35 m/s.The role of airflows provides different effects on the 2-stage pulse discharges.The 1st pulse currents nearly maintain consistency for different airflow speeds.However,the 2nd pulse current has a change trend of first decreasing and then rapidly increasing,and the value difference for 2nd pulse currents is about 20 A under different airflows.In addition,the experimental results are discussed according to the electrical parameters and discharge images. 相似文献
7.
8.
Non-thermal plasma surface modification for epoxy resin(EP)to improve the insulation properties has wide application prospects in gas insulated switchgear and gas insulatedtransmission line.In this paper,a pulsed Ar dual dielectrics atmospheric-pressure plasma jet(APPJ)was used for Si C_xH_yO_zthin film deposition on EP samples.The film deposition was optimized by varying the treatment time while other parameters were kept at constants(treatment distance:10 mm,precursor flow rate:0.6 l min~(-1),maximum instantaneous power:3.08 k W and single pulse energy:0.18 m J).It was found that the maximum value of flashover voltages for negative and positive voltage were improved by 18%and 13%when the deposition time was3 min,respectively.The flashover voltage reduced as treatment time increased.Moreover,all the surface conductivity,surface charge dissipation rate and surface trap level distribution reached an optimal value when thin film deposition time was 3 min.Other measurements,such as atomic force microscopy and scanning electron microscope for EP surface morphology,Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy for EP surface compositions,optical emission spectra for APPJ deposition process were carried out to better understand the deposition processes and mechanisms.The results indicated that the original organic groups(C–H,C–C,C=O,C=C)were gradually replaced by the Si containing inorganic groups(Si–O–Si and Si–OH).The reduction of C=O in ester group and C=C in p-substituted benzene of the EP samples might be responsible for shallowing the trap level and then enhancing the flashover voltage.However,when the plasma treatment time was longer than 3 min,the significant increase of the surface roughness might increase the trap level depth and then deteriorate the flashover performance. 相似文献
9.
A line-to-plate reactor was set-up in the experimental study on the application of nanosecond pulsed corona discharge plasma technology in environmental pollution control. Investigation on the attenuation and distortion of the amplitude of the pulse wave front and the discharge image as well as the waveform along the corona wire was conducted. The results show that the wave front decreases sharply during the corona discharge along the corona wire. The higher the amplitude of the applied pulse is, the more the amplitude of the wave front decreased. The wave attenuation responds in a lower corona discharge inversely. To get a higher efficiency of the line-to-plate reactor a sharp attenuation of the corona has to be considered in practical design. 相似文献
10.
An application of magnetic field to the nanosecond pulse corona discharge is investigated. A cylinder reactor with different corona electrodes is set up for experimental study. A magnetic field with its direction perpendicular to the corona discharge is applied. Different discharge images are taken under single nanosecond pulse with a high sensitive UV-visible light imagine recorder. Experimental results show that with a cross magnetic field the nanosecond corona discharge both generates paths and develops homogeneously in space more than that without the magnetic field. The results may lead to a possibility to apply a cross magnetic field on nanosecond pulse corona discharge for getting higher desulfurization efficiency. 相似文献
11.
The Experimental Investigations of Dielectric Barrier Discharge and Pulse Corona Discharge in Air Cleaning 总被引：2，自引：0，他引：2
The dielectric barrier discharge (DBD) and pulse corona discharge(POD) plasmagenerator was used to remove NHa, H2S, C7H8 etc. from atmosphere. The principle and charac-teristic of the two ways was discussed in the article. The test shows the result of PCD is betterthan that of DBD. 相似文献
12.
《等离子体科学和技术》2019,21(12):125404-49
In order to form an atmospheric-pressure plasma jet without airflow, a needle–ring electrode structure is proposed in this paper. When heteropolar potentials are applied to a needle and a ring, a marked electric field strength enhancement around the needle's pointed end has been found. When the same potential is applied to both the needle and the ring, the lateral electric field strength for the needle can be weakened. By using the above two methods, an increase of the difference between the pointed end electric field strength and the lateral one is achieved and stable plasma jets are formed. A symmetrical space electric field distribution is established at the pointed end of the needles when several sets of heteropolar needle–ring electrodes are uniformly arranged, which is conducive to forming a uniform array plasma jet. Under DC discharge conditions, a safe and stable plasma jet of high density and an array plasma jet are successfully achieved. 相似文献
13.
A high-voltage transverse pulsed nanosecond discharge with a slotted hollow cathode was found to be a source of high-energy (few kV) ribbon electron beams.Conditions for the formation and extinction of electron beams were experimentally studied in discharges in helium at pressures of 1-100 Torr.It was found that interaction of fast electrons with a non-uniform electric field near the slotted cathode led to limitation of the magnitude of the discharge current.A physical model was developed to describe the discharge current self-limitation that was in satisfactory agreement with the experimental results.Some technical solutions that are expected to increase the upper current limits in transverse nanosecond discharge are discussed. 相似文献
14.
Atmospheric gas-liquid discharge with argon as a working gas is presented by employed nanosecond pulse power. The discharge is presented in a glow-like mode. The discharge powers are determined to be less than 1 W, and remains almost constant when the discharge duration time increases. Bountiful active species are determined by capturing optical emission spectra,and their main generation processes are also discussed. The plasma gas temperature is calculated as 350 K by comparing the experimental spectra and the simulated ones of N_2(C~3Ⅱ_g→B~3Ⅱ_g, Δv =-2). The time resolved vibrational and rotational temperature is researched to present the stability of discharge when pulse voltage and discharge duration vary.The electron density is determined to be 10~(16) cm~(-3) according to the Stark broadening effect of the H_α line. 相似文献
15.
The pumped system of the XeCl excimer laser has been designed and applied to analyze UV XeC1 laser spectroscopy characteristics. Under the proportion of mixed gas of HCI：Xe：He = 0.1%： 1% ：98.9%, excimer laser light was generated by stable glow discharge process. The laser spectrum, pulse duration, and laser power properties were obtained. The result shows that this XeCI excimer laser exhibits unique spectral properties, with two peaks between 307.7 nm and 308.5 nm at high pressure with a pumped power of 1.3959 MW/cm^3. The transition relies on the strongest transitions between B-X and C-X. The maximum-intensity transition of spectroscopy is B to X energy levels. The laser parameters are as follows： minimal duration of 15.42 ns, a repetition rate from 0.5 Hz to 5 Hz, single pulse stable power of 400 m J, and beam divergence angle of 3 mrad. The laser can be used to study UV spectroscopy, laser ablation sampling and sputtered pinnate form. 相似文献
16.
A coaxial dielectric barrier discharge(DBD) reactor with double layer dielectric barriers has been developed for exhaust gas treatment and excited either by AC power or nanosecond(ns)pulse to generate atmospheric pressure plasma. The comparative study on the discharge characteristics of the discharge uniformity, power deposition, energy efficiency, and operation temperature between AC and ns pulsed coaxial DBD is carried out in terms of optical and electrical characteristics and operation temperature for optimizing the coaxial DBD reactor performance. The voltages across the air gap and dielectric layer and the conduction and displacement currents are extracted from the applied voltages and measured currents of AC and ns pulsed coaxial DBDs for the calculation of the power depositions and energy efficiencies through an equivalent electrical model. The discharge uniformity and operating temperature of the coaxial DBD reactor are monitored and analyzed by optical images and infrared camera. A heat conduction model is used to calculate the temperature of the internal quartz tube. It is found that the ns pulsed coaxial DBD has a much higher instantaneous power deposition in plasma, a lower total power consumption, and a higher energy efficiency compared with that excited by AC power and is more homogeneous and stable. The temperature of the outside wall of the AC and ns pulse excited coaxial DBD reaches 158 ℃ and 64.3 ℃ after 900 s operation, respectively.The experimental results on the comparison of the discharge characteristics of coaxial DBDs excited by different powers are significant for understanding of the mechanism of DBDs,reducing energy loss, and optimizing the performance of coaxial DBD in industrial applications. 相似文献
17.
Microhollow cathode discharge (MHCD) plasmas were generated in gas mixtures containing water vapor at pressures of up to 100 kPa of He or 20 kPa of air. The cathode diameter was 1.0 mm with a length of 2.0 mm. The electrical characteristics showed an abnormal glow mode. Spectroscopic measurements were carried out to examine the plasma and radicals. An analysis of the spectral profile of Hα at 656.3 nm enabled a derivation of the electron densities, namely 2×10 14 cm 3 (at 10 kPa) and 6×10 14 cm 3 (at 4 kPa) for the helium and air atmospheres, respectively, in the negative glow region. By comparing the observed OH radical spectra with those calculated by the simulation code LIFBASE, the gas temperature was deduced to be 900 K for 4 kPa of He at a discharge current of 50 mA. 相似文献
18.
Feng LIU 《等离子体科学和技术》2022,24(5):54004
Dielectric barrier discharges (DBDs) have been widely used in ozone synthesis, materials surface treatment, and plasma medicine for their advantages of uniform discharge and high plasma-chemical reactivity. To improve the reactivity of DBDs, in this work, the O2 is added into Ar nanosecond (ns) pulsed and AC DBDs. The uniformity and discharge characteristics of Ar ns pulsed and AC DBDs with different O2 contents are investigated with optical and electrical diagnosis methods. The DBD uniformity is quantitatively analyzed by gray value standard deviation method. The electrical parameters are extracted from voltage and current waveforms separation to characterize the discharge processes and calculate electron density ne. The optical emission spectroscopy is measured to show the plasma reactivity and calculate the trend of electron temperature Te with the ratio of two emission lines. It is found that the ns pulsed DBD has a much better uniformity than AC DBD for the fast rising and falling time. With the addition of O2, the uniformity of ns pulsed DBD gets worse for the space electric field distortion by O2−, which promotes the filamentary formation. While, in AC DBD, the added O2 can reduce the intensity of filaments, which enhances the discharge uniformity. The ns pulsed DBD has a much higher instantaneous power and energy efficiency than AC DBD. The ratio of Ar emission intensities indicates that the Te drops quickly with the addition of O2 both ns pulsed and AC DBDs and the ns pulsed DBD has an obvious higher Te and ne than AC DBD. The results are helpful for the realization of the reactive and uniform low temperature plasma sources. 相似文献
19.
N A ASHURBEKOV;K O IMINOV;K M RABADANOV;G S SHAKHSINOV;M Z ZAKARYAEVA;M B KURBANGADZHIEVA 《等离子体科学和技术》2023,25(3):035405-035405
This article presents the 2D simulation results of a nanosecond pulsed hollow cathode discharge obtained through a combination of fluid and kinetic models. The spatio-temporal evolution of the electron energy distribution function (EEDF) of the plasma column and electrical characteristics of the nanosecond pulsed hollow cathode discharge at a gas pressure of 5 Torr are studied. The results show that the discharge development starts with the formation of an ionization front at the anode surface. The ionization front splits into two parts in the cathode cavity while propagating along its lateral surfaces. The ionization front formation leads to an increase in the fast isotropic EEDF component at its front, as well as in the anisotropic EEDF component. The accelerated electrons enter the cathode cavity, which significantly contributes to the formation of the high-energy EEDF component and EEDF anisotropy. 相似文献
20.
Measurements of the plasma parameters of coaxial gridded hollow electrode alternating current(AC)discharge helium plasma were carried out using an improved probe diagnostic technology.The measurements were performed under well-defined discharge conditions(chamber geometry,input power,AC power frequency,and external electrical characteristics).The problems encountered in describing the characteristics of AC discharge in many probe diagnostic methods were addressed by using an improved probe diagnostics design.This design can also be applied to the measurement of plasma parameters in many kinds of plasma sources in which the probe potential fluctuates with the discharge current.Several parameters of the hollow electrode AC helium discharge plasma were measured,including the plasma density,electron temperature,plasma density profiles,and changes in plasma density at different input power values and helium pressures.The characteristics of the coaxial gridded hollow electrode plasma determined by the experiments are suitable for comparison with plasma simulations,and for use in many applications of hollow cathode plasma. 相似文献