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1.
The emission spectra of excited radicals(OH(A~2E),O(3p~3 P),H_α(3P)) and emissive species(N_2~+(B~2∑_u~+),N_2(C_3Π_u)) produced by positive pulsed high-voltage needle-plane corona discharges in atmospheric N_2 and O_2 flows wetted with 10%H_2O at 80 ℃ are used to investigate the relative concentrations of the produced radicals.The results indicate that the tendencies of the concentrations of radicals with discharge conditions are similar to each other due to their similar excitation processes by electron collision.The influence of oxygen flow mixed with the nitrogen flow on the emission intensities of O(3p~5P → 3s~5S_2~.),H_α(3P → 2S),N_2_+(B~2∑_u~+ → X~2∑_g+0-0),and N_2(C~3Π_u → B~3Π_g 1-0) is presented.When the flow rate of oxygen addition is varied from 0-30 ml min~(-1),the emission intensities of O(3p~5P → 3s~5S_2~0.),H_α(3P → 2s),and N_2~+(B~2∑_u~+ →X~2∑_g 0-0) increase and reach a maximum.Then,if the oxygen flow rate increases further,the emission intensities tend to decrease.However,the intensity of N_2(C~3Π_u → B~3Π_g1-0) decreases monotonously with the increasing oxygen flow,which indicates that the electron density decreases with the increasing oxygen flow.By the tendencies of the relative intensities to N_2(C~3Π_u → B~3Π_g 1-0),the concentrations of the total produced O,H,and N_2~+ are shown to increase with the oxygen flow.Based on the reactions for the production of H and O without and with the addition of O_2,the analytic solutions for H and O production are derived in accordance with the experimental results. 相似文献
2.
Zilu ZHAO 《等离子体科学和技术》2018,20(11):115403
In this paper, volume barrier discharge with different gap distances is added on the discharge border of high-voltage electrode of annular surface barrier discharge for generating volume added surface barrier discharge (V-SBD) excited by bipolar nanosecond high-voltage pulse power in atmospheric air. The excited V-SBDs consist of surface barrier discharge (d=0 mm) and volume added surface barrier discharges (d=2 mm and 3 mm). The optical emission spectra are recorded for calculating emission intensities of N2 (C 3Ⅱu →B3Πg ) and N2+ (B 2Σu+ → X 2Σg+ ), and simulating rotational and vibrational temperatures. The influences of gap distance of V-SBD on emission intensity and plasma temperature are also investigated and analyzed. The results show that d=0 mm structure can excite the largest emission intensity of N 2 (C 3 Πu →B 3Πg ), while the existence of volume barrier discharge can delay the occurrence of the peak value of the emission intensity ratio of N2+ (B 2Σu+ → X 2Σg+ )/N 2(C3Πu →B3Πg ) during the rising period of the applied voltage pulse and weaken it during the end period. The increasing factor of emission intensity is effected by the pulse repetition rate. The d=3 mm structure has the highest threshold voltage while it can maintain more emission intensity of N2(C3 Π u →B 3Πg ) than that of d=2 mm structure. The structure of d=2 mm can maintain more increasing factor than that of the d=3 mm structure with varying pulse repetition rate. Besides, the rotational temperatures of three V-SBD structures are slightly affected when the gap distance and pulse repetition rate vary. The vibrational temperatures have decaying tendencies of all three structures with the increasing pulse repetition rate. 相似文献
3.
The plasma characteristics of a gas-liquid phase discharge reactor were investigated by optical and electrical methods.The nozzle-cylinder electrode in the discharge reactor was supplied witha negative nanosecond pulsed generator.The optical emission spectrum diagnosis revealed that OH(A~2∑~+?→?X~2Π,306–309 nm),N~3_2(CΠ→B~3Π_g,337 nm),O(3p~5p→3s~5s~0,777.2 nm)and O(3p~3p→3s~3s~0,844.6 nm)were produced in the discharge plasma channels.The electron temperature(T_e)was calculated from the emission relative intensity ratio between the atomic O 777.2 nm and 844.6 nm,and it increased with the applied voltage and the pulsed frequency and fell within the range of 0.5–0.8 e V.The gas temperature(T_g)that was measured by Lifbase was in a range from 400 K to 600 K. 相似文献
4.
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
5.
《等离子体科学和技术》2016,18(1):79-85
In this paper,nitrogen dielectric barrier discharge(DBD) plasma was generated in a quartz tube with coaxial wire-cylinder electrodes at atmospheric pressure.By varying the nitrogen gas flow(FN) in the range of 0-1 m3/h,the plasma optical emission spectra(OES) were measured and studied.The vibration(T_(vib)) and rotation temperature(T_(rot)) of nitrogen were obtained,by fitting the rovibronic bands of N_2(C~3∏_u-B~3∏_g,0-1),and by the Boltzmann plot method for purposes of comparison.T_(vib) increased up to 2481 K with increasing nitrogen flow till0.2 m3/h,and then decreased with further increasing FN,while Trot decreased monotonously and approached to-350 K for FN ≥ 0.6 m~3/h.The intensity of N_2(C~3∏_u-B~3∏_g,0-0,1-0,0-3) and N_2~+(B~2∑_u~+-X~2Σ_g~+,0-0) exhibited similar evolution with increasing FN to those of the T_(vib) and Trot,respectively.The discharge photos revealed that the discharge filaments gradually decreased with increasing FN,and eventually disappeared,which implied that a discharge mode transition emerged with increasing FN.The possible mechanism for the discharge mode transition is studied in detail according to the vibration(T_(vib)) and rotation temperature(T_(rot)) of nitrogen. 相似文献
6.
In this paper,high resolution temporal-spatial diagnostics are employed to research the optical characteristics of nanosecond pulsed dielectric barrier discharge in needle-plate electrode configuration.Temporal-spatial distributions of discharge images,the emission intensities of opticaI emission spectra,and plasma vibrational and rotational temperatures are investigated.By analyzing the evolution of vibrational and rotational temperatures in space and time dimensions,the energy distribution and energy transfer process in plasma are also discussed.It is found that a diffuse structure with high density plasma concentrated in the region near the needle tip can be presented in nanosecond pulsed discharge,and an obvious energy transfer from electronic energy to vibration energy can be observed in each discharge pulse. 相似文献
7.
Junxia RAN 《等离子体科学和技术》2020,22(10):105401
Fast photography and optical emission spectroscopy are implemented in a 5 mm neon gap dielectric barrier discharge (DBD) at atmospheric pressure with quartz glass used as the dielectric layer. Results show that it starts with a Townsend discharge and ends at a sub-normal glow discharge in neon DBD. Based on the Townsend discharge, the first ionization coefficient of neon is measured. The measurements are consistent with those at low pressure. Optical emission spectroscopy indicates that the spectra are mainly composed of atomic lines of neon, molecular bands and molecular ion bands originating from inevitable gas impurities (mainly nitrogen). Moreover, spectral lines emitted from atomic neon corresponding to the transitions (2p5 3p → 2p5 3s) are predominant. Although the second positive system of N2(C3Πu → B3Πg) is observed, their intensities are too weak compared with neon's spectrum. The molecular nitrogen ion line of 391.4 nm is observed. It reveals that Penning ionization between high energy neon excited states and the inevitable gas impurities plays an important role in the value of the α coefficient. 相似文献
8.
A dielectric barrier surface discharge device was used to investigate the transition from a filamentary discharge to a glow discharge in air at different gas pressures. Discharge images and waveforms of the applied voltage and discharge current were recorded simultaneously, and it was found that the discharge could transit from filamentary to glow with the decrease in pressure. Optical emission spectra during the transition from a filamentary discharge to a glow one were recorded. Excited electron temperature can be determined from the ratios of the relative intensities of spectral lines while molecular vibration temperature can be measured by analysing spectral lines of the N2 second positive band system. The results show that both the excited temperature and molecular vibration temperature increase with the decrease in the gas pressure. Qualitative explanations are given. 相似文献
9.
In this paper, the AC-excited helium discharges generated between the powered needle electrode enclosed in a conical quartz tube and the grounded de-ionized water electrode are investigated.The current and voltage waveforms exhibit a transition from the glow-like to streamer-like mode discharges, which forms a stable cone-shaped structure at the gas–liquid interface. In this region,the air and water vapor diffusion initiate various physical–chemical processes leading to substantial changes of the primary species emission intensities(e.g., OH, N_2, NO, and O) and the rotational temperatures. The experimentally measured rotational temperature at the gas–liquid interface is 870 K from the N_2(C–B) band with a power input of 26 W. With the prolongation of the discharge time, significant changes in the discharge voltage and current, discharge emission patterns, instantaneous concentrations of the secondary species(e.g., H_2O_2,NO_2~-, and NO_3~-) in the liquid phase, p H values and electrical conductivities of the liquids are observed experimentally. The present study is helpful for deepening the understandings to the basic physical–chemical processes in the discharges in contact with liquids, especially to those occurring in the vicinity of the gas–liquid interface, and also for promoting existing and potential applications of such type of discharges in the fields of environmental protection, biomedicine,agriculture, and so on. 相似文献
10.
Jianping LIANG Xiongfeng ZHOU Zilu ZHAO Hao YUAN Hongli WANG Wenchun WANG Dezheng YANG 《等离子体科学和技术》2021,23(9):123-134
In this paper,unipolar pulse (including positive pulse and negative pulse) and bipolar pulse voltage are employed to generate diffuse gas-liquid discharge in atmospheric N2 with a trumpet-shaped quartz tube.The current-voltage waveforms,optical emission spectra of excited state active species,FTIR spectra of exhaust gas components,plasma gas temperature,and aqueous H2O2,NO2-,and NO3-production are compared in three pulse modes,meanwhile,the effects of pulse peak voltage and gas flow rate on the production of reactive species are studied.The results show that two obvious discharges occur in each voltage pulse in unipolar pulse driven discharge,differently,in bipolar pulse driven discharge,only one main discharge appears in a single voltage pulse time.The intensities of active species (OH(A),and O(3p)) in all three pulsed discharge increase with the rise of pulse peak voltage and have the highest value at 200 ml min-1 of gas flow rate.The absorbance intensities of NO2 and N2O increase with the increase of pulse peak voltage and decrease with the increase of gas flow rate.Under the same discharge conditions,the bipolar pulse driven discharge shows lower breakdown voltage,and higher intensities of excited species (N2(C),OH(A),and O(3p)),nitrogen oxides (NO2,NO,and N2O),and higher production of aqueous H2O2,NO2-,and NO3-compared with both unipolar positive and negative discharges. 相似文献
11.
In this paper,a low pressure Ar/N2 shock plasma jet with clearly multicycle alternating zones produced by a DC cascade arc discharge has been investigated by an emission spectral method combined with Abel inversion analysis.Plasma emission intensity,electron,vibrational and rotational temperatures of the shock plasma have been measured in the expansion and compression zones.The results indicate that the ranges of the measured electron temperature,vibrational temperature and rotational temperature are 1.1 eV to 1.6 eV,0.2 eV to 0.7 eV and 0.19 eV to 0.22 eV,respectively,and it is found for the first time that the vibrational and rotational temperatures increase while the electron temperature decreases in the compression zones.The electron temperature departs from the vibrational and the rotational temperatures due to non-equilibrium plasma efects.Electrons and heavy particles could not completely exchange energy via collisions in the shock plasma jet under the low pressure of 620 Pa or so. 相似文献
12.
A direct-current air plasma jet operated underwater presents three stable modes including an intermittently-pulsed discharge, a periodically-pulsed discharge and a continuous discharge with increasing the power voltage. The three discharge modes have different appearances for the plasma plumes. Moreover, gap voltage-current characteristics indicate that the continuous discharge is in a normal glow regime. Spectral lines from reactive species(OH, N_2, N_2~+, H_α,and O) have been revealed in the emission spectrum of the plasma jet operated underwater.Spectral intensities emitted from OH radical and oxygen atom increase with increasing the power voltage or the gas flow rate, indicating that reactive species are abundant. These reactive species cause the degradation of the methylene blue dye in solution. Effects of the experimental parameters such as the power voltage, the gas flow rate and the treatment time are investigated on the degradation efficiency. Results indicate that the degradation efficiency increases with increasing the power voltage, the gas flow rate or the treatment time. Compared with degradation in the intermittently-pulsed mode or the periodically-pulsed one, it is more efficient in the continuous mode, reaching 98% after 21 min treatment. 相似文献
13.
Atmospheric pressure air/Ar/H_2O gliding arc discharge plasma is produced by a pulsed dc power supply. An optical emission spectroscopic(OES) diagnostic technique is used for the characterization of plasmas and for identifications of OH and O radicals along with other species in the plasmas. The OES diagnostic technique reveals the excitation Tx?≈?5550–9000 K, rotational Tr?≈?1350–2700 K and gas Tg?≈?850–1600 K temperatures, and electron density n?(1.1-1.9) ′101 4 cm~(-3) e under different experimental conditions. The production and destruction of OH and O radicals are investigated as functions of applied voltage and air flow rate. Relative intensities of OH and O radicals indicate that their production rates are increased with increasing Ar content in the gas mixture and applied voltage. nereveals that the higher densities of OH and O radicals are produced in the discharge due to more effective electron impact dissociation of H_2O and O_2 molecules caused by higher kinetic energies as gained by electrons from the enhanced electric field as well as by enhanced n e.The productions of OH and O are decreasing with increasing air flow rate due to removal of Joule heat from the discharge region but enhanced air flow rate significantly modifies discharge maintenance properties. Besides, Tgsignificantly reduces with the enhanced air flow rate. This investigation reveals that Ar plays a significant role in the production of OH and O radicals. 相似文献
14.
Nonequilibrium Atmospheric Pressure Ar/O2 Plasma Jet: Properties and Application to Surface Cleaning
《等离子体科学和技术》2016,18(2):168-172
In this study an atmospheric pressure Ar/O_2 plasma jet is generated to study the effects of applied voltage and gas flux rate to the behavior of discharge and the metal surface cleaning.The increase in applied voltage leads to increases of the root mean square(rms) current,the input power and the gas temperature.Furthermore,the optical emission spectra show that the emission intensities of metastable argon and atomic oxygen increase with increasing applied voltage.However,the increase in gas flux rate leads to a reduction of the rms current,the input power and the gas temperature.Furthermore,the emission intensities of metastable argon and atomic oxygen decrease when gas flux rate increases.Contact angles are measured to estimate the cleaning performance,and the results show that the increase of applied voltage can improve the cleaning performance.Nevertheless,the increase of gas flux rate cannot improve the cleaning performance.Contact angles are compared for different input powers and gas flux rates to search for a better understanding of the major mechanism for surface cleaning by plasma jets. 相似文献
15.
《等离子体科学和技术》2021,23(9):95405
In this paper,unipolar pulse (including positive pulse and negative pulse) and bipolar pulse voltage are employed to generate diffuse gas–liquid discharge in atmospheric N_2with a rumpetshaped quartz tube.The current–voltage waveforms,optical emission spectra of excited state active species,FTIR spectra of exhaust gas components,plasma gas temperature,and aqueous H_2O_2,NO_2~-,andNO_3~-production are compared in three pulse modes,meanwhile,the effects of pulse peak voltage and gas flow rate on the production of reactive species are studied.The results show that two obvious discharges occur in each voltage pulse in unipolar pulse driven discharge,differently,in bipolar pulse driven discharge,only one main discharge appears in a single voltage pulse time.The intensities of active species (OH(A),and O(3p)) in all three pulsed discharge increase with the rise of pulse peak voltage and have the highest value at 200 ml min~(-1)of gas flow rate.The absorbance intensities of NO_2and N_2O increase with the increase of pulse peak voltage and decrease with the increase of gas flow rate.Under the same discharge conditions,the bipolar pulse driven discharge shows lower breakdown voltage,and higher intensities of excited species (N_2(C),OH(A),and O(3p)),nitrogen oxides (NO_2,NO,and N_2O),and higher production of aqueous H_2O_2,NO_2~-,andNO_3~-compared with both unipolar positive and negative discharges. 相似文献
16.
Ionut Topala Nicoleta Dumitrascu Gheorghe Popa 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2009,267(2):442-445
Plasma polymers of acrylic acid were obtained using an atmospheric pressure discharge system. The plasma polymerization reactor uses a dielectric barrier discharge, with the polyethylene terephthalate dielectric acting as substrate for deposition. The plasma was characterized by specific electrical measurements, monitoring the applied voltage and the discharge current. Based on the spatially resolved optical emission spectroscopy, we analyzed the distribution of the excited species in the discharge gap, specific plasma temperatures (vibrational and gas temperatures) being calculated with the Boltzmann plot method. The properties of the plasma polymer films were investigated by contact angle measurements, infrared and UV-Vis spectroscopy, scanning electron microscopy. The films produced by plasma polymerization at atmospheric pressure showed a hydrophilic character, in correlation with the strong absorbance of OH groups in the FTIR spectrum. Moreover, the surface of the plasma polymers at micrometric scale is smooth and free of defects without particular features. 相似文献
17.
Kefeng SHANG 《等离子体科学和技术》2019,21(7):75502-140
A double-chamber gas-liquid phase DBD reactor (GLDR), consisting of a gas-phase discharge chamber and a gas-liquid discharge chamber in series, was designed to enhance the degradation of benzene and the emission of NOx. The performance of the GLDR on discharge characteristics, reactive species production and benzene degradation was compared to that of the single-chamber gas phase DBD reactor (GPDR). The effects of discharge gap, applied voltage, initial benzene concentration, gas flow rate and solution conductivity on the degradation and energy yield of benzene in the GLDR were investigated. The GLDR presents a higher discharge power, higher benzene degradation and higher energy yield than that of the GPDR. NO2 emission was remarkably inhibited in the GLDR, possibly due to the dissolution of NO2 in water. The benzene degradation efficiency increased with the applied voltage, but decreased with the initial concentration, gas flow rate, and gas discharge gap, while the solution conductivity presented less influence on benzene degradation. The benzene degradation efficiency and the energy yield reached 61.11% and 1.45 g kWh–1 at 4 mm total gas discharge gap, 15 kV applied voltage, 200 ppm benzene concentration, 0.2 L min−1 gas flow rate and 721 μS cm−1 water conductivity. The intermediates and byproducts during benzene degradation were detected by FT-IR, GC-MS and LC-MS primarily, and phenols, COx, and other aromatic substitutes, O3, NOx, etc, were determined as the main intermediates. According to these detected byproducts, a possible benzene degradation mechanism was proposed. 相似文献
18.
This work reports the experimental results on the characteristics of radio frequency dielectric barrier N2 /Ar discharges.Depending on the nitrogen content in the feed gas and the input power,the discharge can operate in two diferent modes: a homogeneous glow discharge and a constricted discharge.With increasing input power,the number of discharge columns increases.The discharge columns have starlike structures and exhibit symmetric self-organized arrangement.Optical emission spectroscopy was performed to estimate the plasma temperature.Spatially resolved gas temperature measurements,determined from NO emission rotational spectroscopy were taken across the 4.4 mm gap filled by the discharge.Gas temperature in the middle of the gas gap is lower than that close to the electrodes. 相似文献
19.
A discharge ignited by an AC power source in contact with deionized water as one of the electrodes is investigated. Immediately after initiation, the discharge exhibits a unique phenomenon: the gasphase discharge is extended into the liquid. Later, a cone-like structure is observed at the liquid surface. Synchronous monitoring of current–voltage characteristics and liquid properties versus time suggests that the discharge shapes are functions of the liquid properties. The spatio-temporal profiles indicate the potential effects of water, ambient air impurities, and metastable argon on the discharge chemistry. This becomes more obvious near the liquid surface due to increasing production of various transient reactive species such as ·OH and NO·. Moreover, it is revealed that thermalization of the rotational population distributions of the rotational states(N' ≤ 6,J'≤13/2) in the Q_1 branch of the OH(A~2∑~+,v'S=0→X~2∏_(3/2),v'=0 ) band ro-vibrational system is influenced by the humid environment near the liquid surface. In addition, the transient behaviors of instantaneous concentrations of long-lived reactive species(LRS) such as H_2O_2,NO_2~-, and-NO_3~- are observed with lengthening the discharge time. The production of multiple transient and LRS proposes AC excited gas–liquid argon discharge as a potential applicant in industrial wastewater cleaning, clinical medicine, and agriculture. 相似文献
20.
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