SF_(6) has excellent insulation performance and arc extinguishing ability,and is widely used in the power industry.However,its global warming potential is about 23,500 times that of C0_(2),it can exist stably in the a...SF_(6) has excellent insulation performance and arc extinguishing ability,and is widely used in the power industry.However,its global warming potential is about 23,500 times that of C0_(2),it can exist stably in the atmosphere,it is not easily degradable and is of great potential harm to the environment.Based on pulsed dielectric barrier discharge plasma technology,the effects of H_(2)O and 0_(2) on the degradation of SF_(6) were studied.Studies have shown that H_(2)O can effectively promote the decomposition of SF_(6) and improve its degradation rate and energy efficiency of degradation.Under the action of a pulse input voltage and input frequency of 15 kV and 15 kHz,respectively,when H_(2)O is added alone the effect of 1% H_(2)O is the best,and the rate and energy efficiency of degradation of SF_(6) reach their maximum values,which are 91.9% and 8.25 g kWh^(-1),respectively.The synergistic effect of H_(2)O and O_(2) on the degradation of SF_(6) was similar to that of H_(2)O.When the concentration of H_(2)O and O_(2) was 1%,the system obtained the best rate and energy efficiency of degradation,namely 89.7% and 8.05 g kWh~(-1),respectively.At the same time,different external gases exhibit different capabilities to regulate decomposition products.The addition of H_(2)O can effectively improve the selectivity of S0_(2).Under the synergistic effect of H_(2)O and O_(2),with increase in O_(2) concentration the degradation products gradually transformed into SO_(2)F_(2).From the perspective of harmless treatment of the degradation products of SF_(6),the addition of O_(2) during the SF_(6) degradation process should be avoided.展开更多
Sulfamethoxazole(SMX)is an antibiotic and widely present in aquatic environments,so it presents a serious threat to human health and sustainable development.A dielectric barrier discharge(DBD)plasma jet was utilized t...Sulfamethoxazole(SMX)is an antibiotic and widely present in aquatic environments,so it presents a serious threat to human health and sustainable development.A dielectric barrier discharge(DBD)plasma jet was utilized to degrade aqueous SMX,and the effects of various operating parameters(working gas,discharge power,etc)on SMX degradation performance were studied.The experimental results showed that the DBD plasma jet can obtain a relatively high degradation efficiency for SMX when the discharge power is high with an oxygen atmosphere,the initial concentration of SMX is low,and the aqueous solution is under acidic conditions.The reactive species produced in the liquid phase were detected,and OH radicals and O3were found to play a significant role in the degradation of SMX.Moreover,the process of SMX degradation could be better fitted by the quasi-first-order reaction kinetic equation.The analysis of the SMX degradation process indicated that SMX was gradually decomposed and 4-amino benzene sulfonic acid,benzene sulfonamide,4-nitro SMX,and phenylsulfinyl acid were detected,and thus three possible degradation pathways were finally proposed.The mineralization degree of SMX reached 90.04%after plasma treatment for 20 min,and the toxicity of the solution fluctuated with the discharge time but eventually decreased.展开更多
Ozone(O_(3)) generated by a dielectric barrier discharge(DBD) is widely used in various industrial processes. In this study, NaCl aqueous solution was used as a novel electric power transmission electrode in a DBD rea...Ozone(O_(3)) generated by a dielectric barrier discharge(DBD) is widely used in various industrial processes. In this study, NaCl aqueous solution was used as a novel electric power transmission electrode in a DBD reactor(instead of a traditional metal electrode) for highly efficient ozone generation. The results demonstrated that a high O_(3) yield of 242 g k Wh^(-1) with a concentration of 14.6 g m^(-3)O_(3) was achieved. The power transmission mechanism works because NaCl aqueous solution behaves as a capacitor when an alternating pulse voltage below 8 k Hz is used.Compared with the resistance of the discharge barrier and discharge space, the resistance of NaCl aqueous solution can be ignored, which ensures that O_(3) is generated efficiently. It is expected that O_(3) generation using NaCl aqueous solution as a novel electrode in a DBD reactor could be an alternative technology with good application prospects.展开更多
This paper describes the realization of a homogeneous dielectric barrier discharge(DBD)in argon at atmospheric pressure.The effect of the morphology of the dielectric surface(especially the dielectric surface covered ...This paper describes the realization of a homogeneous dielectric barrier discharge(DBD)in argon at atmospheric pressure.The effect of the morphology of the dielectric surface(especially the dielectric surface covered by hollow ceramic beads(99%Al_(2)O_(3))with different diameters)on discharge is investigated.With different dielectrics,the argon DBD presents two discharge modes:a filamentary mode and a homogeneous mode.Fast photography shows that the filamentary mode operates in a streamer discharge,and the homogeneous mode operates in a Townsend discharge regime.It is found that a homogeneous discharge can be generated within a certain voltage range.The voltage amplitude range decreases,and the breakdown voltage increases with the increase in the mean diameter of the ceramic beads.Waveforms of the total current and optical emission signal present stochastic pulses per half voltage cycle for the filamentary mode,whereas there is one single hump per half voltage cycle for the homogeneous mode.In the homogeneous mode,the intensity of the optical emission decreases with the mean diameter of the ceramic beads.The optical emission spectrum is mainly composed of atomic lines of argon and the second positive system of molecular nitrogen.It reveals that the electron density decreases with the increasing mean diameter of the ceramic beads.The vibrational temperature increases with the increasing mean diameter of the ceramic beads.It is believed that a large number of microdischarges are formed,and smaller ceramic beads have a larger activation surface area and more point discharge.Electrons liberated in the shallow well and electrons generated from microdischarges can increase the secondary electron emission coefficient of the cathode and provide initial electrons for discharge continuously.Therefore,the breakdown electric field is reduced,which contributes to easier generation of homogeneous discharge.This is confirmed by the simulation results.展开更多
A new phenomenon that a filament discharged only once instead of twice in a cycle of the applied voltage is observed in a square grid pattern in a dielectric barrier discharge(DBD)with a larger gas gap,which is named ...A new phenomenon that a filament discharged only once instead of twice in a cycle of the applied voltage is observed in a square grid pattern in a dielectric barrier discharge(DBD)with a larger gas gap,which is named intermittent discharge.Its spatiotemporal dynamics and the formation mechanism are studied by the multiple photomultiplier tubes and an intensified charge-coupled device.Corresponding to the positions of spots in the picture with an exposure time of 40 ms,there are some bright spots(discharge spots)and black spots(non-discharged spots)in the instantaneous image with an exposure time of 10μs(a half cycle of the applied voltage).There are at least two bright spots around one black spot and vice versa.The surface discharges(SDS)can be observed between any two adjacent spots.The intensity of the SDSbetween the bright spot and the black spot is 2.5 times greater than that between two adjacent bright spots,which indicates that the SDSare directional-selective.The intermittent discharge with positive(negative)current polarity changes to that with negative(positive)current polarity,after it sustains up to 14 voltage cycles at the longest.The spatial distribution of the electric field component is calculated through COMSOL software to solve the Poisson equation numerically.It is found that the inhomogeneous distribution of surface electric field is caused by the inhomogeneous distribution of wall charges,which leads to direction-selective SDS.The intermittent discharge is formed by the competition between the direction-selective SDSand volume discharges(VDS)in DBD.This is the reason why the intermittent discharge is generated.展开更多
Nanosecond(ns)pulsed dielectric barrier discharge(DBD)is considered as a promising method to produce controllable large-volume and high activity low-temperature plasma at atmospheric pressure,which makes it suitable f...Nanosecond(ns)pulsed dielectric barrier discharge(DBD)is considered as a promising method to produce controllable large-volume and high activity low-temperature plasma at atmospheric pressure,which makes it suitable for wide applications.In this work,the ns pulse power supply is used to excite Ar DBD and the influences of the pulse parameters(voltage amplitude,pulse width,pulse rise and fall times)on the DBD uniformity are investigated.The gas gap voltage(Ug)and conduct current(Ig)are separated from the measured voltage and current waveforms to analyze the influence of electrical parameters.The spectral line intensity ratio of two Ar excited species is used as an indicator of the electron temperature(Te).The time resolved discharge processes are recorded by an intensified charge-coupled device camera and a one-dimensional fluid model is employed to simulate the spatial and temporal distributions of electrons,ions,metastable argon atoms and Te.Combining the experimental and numerical results,the mechanism of the pulse parameters influencing on the discharge uniformity is discussed.It is shown that the space electric field intensity and the space particles'densities are mainly responsible for the variation of discharge uniformity.With the increase of voltage and pulse width,the electric field intensity and the density of space particles increased,which results in the discharge mode transition from non-uniform to uniform,and then non-uniform.Furthermore,the extension of pulse rise and fall times leads to the discharge transition from uniform to nonuniform.The results are helpful to reveal the mechanism of ns pulsed DBD mode transition and to realize controllable and uniform plasma sources at atmospheric pressure.展开更多
An experimental system was established to explore the plasma flow control effect for helicopter rotors in hover mode.With the plasma actuator applied at the leading edge of the rotor blades,alternating current dielect...An experimental system was established to explore the plasma flow control effect for helicopter rotors in hover mode.With the plasma actuator applied at the leading edge of the rotor blades,alternating current dielectric barrier discharge(AC-DBD) plasma actuation was generated by a sinusoidal AC high-voltage generator.By direct force measurement,the influence of actuation parameters on the aerodynamic performance of the rotor was investigated at a tip Reynolds number of 1.7 × 105.AC-DBD actuation can delay the blade stall to more than 3° with a 20%increase of about in the thrust coefficient at the post-stall pitch.At a constant motor power driving the rotor,AC-DBD actuation could reduce the rotor’s torque at the stalled pitch and increase the rotational speed of the rotor.Also,AC-DBD actuation could maintain a relatively high hover efficiency of the rotor at large collective pitches.In a wide range of actuation parameters,AC-DBD plasma actuation could improve the rotor’s aerodynamic performance at large blade pitches.High-speed photography of the tuft motion on the blade’s upper surface showed that AC-DBD plasma actuation could promote the reattachment of the blade’s separation flow.展开更多
In order to better analyze the characteristics of particle distribution and its influencing factors in the ionized space during the process of coaxial dielectric barrier discharge,a self-designed two-dimensional axisy...In order to better analyze the characteristics of particle distribution and its influencing factors in the ionized space during the process of coaxial dielectric barrier discharge,a self-designed two-dimensional axisymmetric structure exciter was used to carry out optical diagnosis,with the electron temperature calculated through Gaussian fitting.A plasma model was applied to conduct research on the discharge process through numerical simulation,with the changes in electron density and electron temperature were analyzed by using different discharge parameters.The research results show that with an increase in discharge voltage,pressure inside the reactor and relative permittivity,the discharge process is promoted.In addition,a rise in current density leads to an increase in the number of charged particles on the surface of the medium during the discharge process,while a rise in discharge intensity causes an increase in the electron density.Electron temperature decreases due to the increased loss of collision energy between particles.These results were confirmed by comparing experimental data with simulation results.展开更多
We report five types of patterns with square symmetry,including three novel types obtained by inserting a specially designed grid photonic crystal(PC)into a dielectric barrier discharge system.They are studied using a...We report five types of patterns with square symmetry,including three novel types obtained by inserting a specially designed grid photonic crystal(PC)into a dielectric barrier discharge system.They are studied using an intensified charge-coupled device camera and photomultiplier tubes.The three novel types of patterns are a square pattern with one structure,a square superlattice pattern with four sublattices and a(1/4)K_(grid)(K_(grid)is the basic wave vector of the grid),and another square pattern with a complex inversion discharge sequence.From the application viewpoint,the five types of patterns can be used as plasma photonic crystals(PPCs).Their band diagrams under a transverse-magnetic wave simulated by the finite element method show that there are a large number of band gaps.Compared with the original PC with only a unidirectional band gap,the five types of PPCs have tunable and omnidirectional band gaps,which is very important in controlling the propagation of electromagnetic waves in the mm-wave region.The experimental results enrich the pattern types in the dielectric barrier discharge system and provide a method for obtaining PPCs with symmetry controllability and bandgap tunability.展开更多
Improving energy efficiency in plasma NO removal is a critical issue.When the surface dielectric barrier discharge(SDBD)device is considered as a combination of multiple plasma actuators,the induced plasma aerodynamic...Improving energy efficiency in plasma NO removal is a critical issue.When the surface dielectric barrier discharge(SDBD)device is considered as a combination of multiple plasma actuators,the induced plasma aerodynamic effect cannot be ignored,which can affect the mass transfer,then affect the chemical reactions.Five SDBD devices with different electrode arrangements are studied for NO conversion.They correspond to different flow patterns.We find that the energy efficiency in an SDBD device with a common structure(Type 1)is 28%lower than that in SDBD devices with a special arrangement(Types 2–5).Two reasons may explain the results.First,fewer active species are produced in Type 1 because the development of discharge is hindered by the mutually exclusive electric field forces caused by the symmetrically distributed charged particles.Second,the plasma wind induced by the plasma actuator can enhance the mass and heat transfer.The mixing of reactants and products is better in Types 2–5 than Type 1 due to higher turbulence kinetic energy.展开更多
Surface modification techniques with plasma are widely investigated to improve the surface insulation capability of polymers under dry conditions,while the relationship between treatment method,surface physical and ch...Surface modification techniques with plasma are widely investigated to improve the surface insulation capability of polymers under dry conditions,while the relationship between treatment method,surface physical and chemical properties,and wet flashover voltage is still unclear for inorganic ceramics.In this work,the surface insulation properties of ceramics under wet conditions are improved using nanosecond-pulsed dielectric barrier discharge with polydimethylsiloxane(PDMS)as the precursor.The relationships between PDMS concentration and the water contact angle,dry and wet flashover voltages are obtained to acquire the optimal concentration.The surface charge dissipation test and surface physio-chemical property measurement with SEM,AFM,XPS are carried out to further explore the mechanism of surface insulation enhancement.The results show that film deposition with micron thickness and superhydrophobicity occurs at the PDMS concentration of 1.5%.The dry flashover voltage is increased by 14.6%due to the induction of deep traps,while the wet flashover voltage is increased by 66.7%.The gap between dry-wet flashover voltage is decreased by 62.3%compared with the untreated one due to the self-cleaning effect.展开更多
The paper presents comparative kinetic characteristics of the decomposition of 2,4-dichlorophenol in a dielectric barrier discharge and a combined plasma-catalytic process. Vermiculite containing 5% zirconium was used...The paper presents comparative kinetic characteristics of the decomposition of 2,4-dichlorophenol in a dielectric barrier discharge and a combined plasma-catalytic process. Vermiculite containing 5% zirconium was used as a catalyst. The destruction processes of 2,4-DCP proceed efficiently, the degree of decomposition increases in the combined plasma-catalytic process by a factor of 1.33 and reaches 80%. The experimental results were processed according to the first-order kinetic law (R<sup>2</sup> > 0.97), according to which the effective constants (0.36 ± 0.04) and (0.51 ± 0.03) s<sup>-1</sup> and the decomposition rates of 2,4-DCP (106 and 123 μmol/l·s) when treating model solutions without a catalyst and with vermiculite + Zr 5%, respectively, and the energy costs are 0.012 and 0.017 molecules/100eV. The main decomposition products present in the solution have been determined to be carboxylic acids, aldehydes, the contribution of which does not exceed 2%, as well as chloride ions, and in the gas phase they are carbon dioxide and molecular chlorine (the share of which does not exceed 1.5% of total chlorine content in the system).展开更多
Fluoride rubber F2311film,an alternating copolymer of CF2-CFCI（CTFE）andCH2-CF2（VF2）components,was treated by atmospheric pressure dielectric barrier discharge（DBD）in air.The surface structure,topography and surf...Fluoride rubber F2311film,an alternating copolymer of CF2-CFCI（CTFE）andCH2-CF2（VF2）components,was treated by atmospheric pressure dielectric barrier discharge（DBD）in air.The surface structure,topography and surface chemistry of the treated F2311filmswere characterized by contact angle measurement,atomic force microscopy（AFM）,and X-rayphotoelectron spectroscopy（XPS）,respectively.The experimental results showed that a shorttime air plasma treatment led to morphological,wettability and chemical changes in the F2311films.The surface hydrophilicity increased greatly after the plasma treatment,the static watercontact angle decreased from 98.6° to 32°,and oxygen containing groups（C=O,O-C=O,etc.）were introduced.Atomic force microscopy revealed that plasma produced by DBD etched F2311films obviously.The roughness of the samples increased remarkably with the formation of peaksand valleys on the treated surfaces.The increased surface wettability may be correlated with boththe introduction of hydrophilic groups due to air plasma oxidation of the surface and the changein surface morphology etched by DBD.展开更多
Both experimental and simulated studies of microdischarge(MD)are carried out in a dielectric barrier discharge with a pin-to-pin gap of 3.5 mm,ignited by a sinusoidal voltage with a peak voltage of 10 kV and a driving...Both experimental and simulated studies of microdischarge(MD)are carried out in a dielectric barrier discharge with a pin-to-pin gap of 3.5 mm,ignited by a sinusoidal voltage with a peak voltage of 10 kV and a driving frequency of 5 kHz.Statistical results have shown that the probability of the single current pulse in the positive half-period(HP)reaches 73.6%under these conditions.Experimental results show that great luminous intensity is concentrated on the dielectric surface and the tip of the metal electrode.A 1D plasma fluid model is implemented by coupling the species continuity equations,electron energy density equations,Poisson equation,and Helmholtz equations to analyze the MD dynamics on the microscale.The simulated results are in good qualitative agreement with the experimental results.The simulated results show that the MD dynamics can be divided into three phases:the Townsend phase,the streamer propagation phase,and the discharge decay phase.During the streamer propagation phase,the electric field and electron density increase with the streamer propagation from the anode to the cathode,and their maximal values reach 625.48 Td and 2.31×10^(19)m^(-3),as well as 790.13 Td and 3.58×10^(19)m^(-3)in the positive and negative HP,respectively.Furthermore,a transient glow-like discharge is detected around the anode during the same period of streamer propagation.The formation of transient glow-like discharge is attributed to electrons drifting back to the anode,which is driven by the residual voltage in the air gap.展开更多
In this paper, a two-dimensional axisymmetric fluid model was established to investigate the influence of nitrogen impurity content on the discharge pattern and the relevant discharge characteristics in an atmosphere ...In this paper, a two-dimensional axisymmetric fluid model was established to investigate the influence of nitrogen impurity content on the discharge pattern and the relevant discharge characteristics in an atmosphere pressure helium dielectric barrier discharge(DBD). The results indicated that when the nitrogen content was increased from 1 to 100 ppm, the discharge pattern evolved from a concentric-ring pattern into a uniform pattern, and then returned to the concentricring pattern. In this process, the discharge mode at the current peak moment transformed from glow mode into Townsend mode, and then returned to glow mode. Further analyses revealed that with the increase of impurity level, the rate of Penning ionization at the pre-ionization stage increased at first and decreased afterwards, resulting in a similar evolution pattern of seed electron level. This evolution trend was believed to be resulted from the competition between the N2 partial pressure and the consumption rate of metastable species. Moreover, the discharge uniformity was found positively correlated with the spatial uniformity of seed electron density as well as the seed electron level. The reason for this correlation was explained by the reduction of radial electric field strength and the promotion of seed electron uniformity as pre-ionization level increases. The results obtained in this work may help better understand the pattern formation mechanism of atmospheric helium DBD under the variation of N2 impurity level, thereby providing a possible means of regulating the discharge performance in practical application scenarios.展开更多
We reported a coaxial,micro-dielectric barrier discharge(micro-DBD)reactor and a conventional DBD reactor for the direct conversion of methane into higher hydrocarbons at atmospheric pressure.The effects of input powe...We reported a coaxial,micro-dielectric barrier discharge(micro-DBD)reactor and a conventional DBD reactor for the direct conversion of methane into higher hydrocarbons at atmospheric pressure.The effects of input power,residence time,discharge gap and external electrode length were investigated for methane conversion and product selectivity.We found the conversion of methane in a micro-DBD reactor was higher than that in a conventional DBD reactor.And at an input power of 25.0 W,the conversion of methane and the total C2+C3 selectivity reached 25.10% and 80.27%,respectively,with a micro-DBD reactor of 0.4 mm discharge gap.Finally,a nonlinear multiple regression model was used to study the correlations between both methane conversion and product selectivity and various system variables.The calculated data were obtained using SPSS 12.0 software.The regression analysis illustrated the correlations between system variables and both methane conversion and product selectivity.展开更多
A superimposed wire-plate dielectric barrier discharge reactor was use d to remove toluene in this study. The effects of oxygen content, gas flow rate, gas initial concentration and with/without catalyst on toluene de...A superimposed wire-plate dielectric barrier discharge reactor was use d to remove toluene in this study. The effects of oxygen content, gas flow rate, gas initial concentration and with/without catalyst on toluene decomposition we re investigated. It was found that an optimal toluene removal was achieved when the oxygen content was about 5%. Under this condition, the highest toluene remov al efficiency of 80.8% was achieved when the gas concentration was 80 mg/m3. The toluene removal efficiency decreased with the increase of the gas flow rate and the initial concentration of toluene. In addition, the ozone concentration decr eased with the increase of the initial concentration of toluene. It suggested th at combining DBD(dielectric barrier discharge) with Co3O4/Al2O3/foam nickel cata lyst in-situ could improve the toluene removal efficiency and suppress ozone for mation. Products analysis showed that the main products were CO and CO2 when oxy gen was more than 5%.展开更多
Atmospheric pressure helium/water dielectric barrier discharge(DBD) plasma is used to investigate the generation of reactive species in a gas–liquid interface and in a liquid. The emission intensity of the reactive s...Atmospheric pressure helium/water dielectric barrier discharge(DBD) plasma is used to investigate the generation of reactive species in a gas–liquid interface and in a liquid. The emission intensity of the reactive species is measured by optical emission spectroscopy(OES)with different discharge powers at the gas–liquid interface. Spectrophotometry is used to analyze the reactive species induced by the plasma in the liquid. The concentration of OH radicals reaches 2.2 μm after 3 min of discharge treatment. In addition, the concentration of primary longlived reactive species such as H_2O_2, NO_3^- and O_3 are measured based on plasma treatment time.After 5 min of discharge treatment, the concentration of H_2O_2, NO_3^-, and O_3 increased from 0 mg?·?L^(-1) to 96 mg?·?L^(-1), 19.5 mg?·?L^(-1), and 3.5 mg?·?L^(-1), respectively. The water treated by plasma still contained a considerable concentration of reactive species after 6 h of storage. The results will contribute to optimizing the DBD plasma system for biological decontamination.展开更多
基金supported by Guizhou Province (Ceneral), grant/award number Qian Ke He Zhi Cheng [2022] General 207, National Natural Science Foundation of China (No. 52307170)Natural Science Foundation of Hubei Province, China (No. 2023AFB382)。
文摘SF_(6) has excellent insulation performance and arc extinguishing ability,and is widely used in the power industry.However,its global warming potential is about 23,500 times that of C0_(2),it can exist stably in the atmosphere,it is not easily degradable and is of great potential harm to the environment.Based on pulsed dielectric barrier discharge plasma technology,the effects of H_(2)O and 0_(2) on the degradation of SF_(6) were studied.Studies have shown that H_(2)O can effectively promote the decomposition of SF_(6) and improve its degradation rate and energy efficiency of degradation.Under the action of a pulse input voltage and input frequency of 15 kV and 15 kHz,respectively,when H_(2)O is added alone the effect of 1% H_(2)O is the best,and the rate and energy efficiency of degradation of SF_(6) reach their maximum values,which are 91.9% and 8.25 g kWh^(-1),respectively.The synergistic effect of H_(2)O and O_(2) on the degradation of SF_(6) was similar to that of H_(2)O.When the concentration of H_(2)O and O_(2) was 1%,the system obtained the best rate and energy efficiency of degradation,namely 89.7% and 8.05 g kWh~(-1),respectively.At the same time,different external gases exhibit different capabilities to regulate decomposition products.The addition of H_(2)O can effectively improve the selectivity of S0_(2).Under the synergistic effect of H_(2)O and O_(2),with increase in O_(2) concentration the degradation products gradually transformed into SO_(2)F_(2).From the perspective of harmless treatment of the degradation products of SF_(6),the addition of O_(2) during the SF_(6) degradation process should be avoided.
基金supported jointly by National Natural Science Foundation of China(Nos.U20A20372,51807046,51777206)the Natural Science Foundation of Anhui Province(Nos.2108085MD136,1908085MA29)。
文摘Sulfamethoxazole(SMX)is an antibiotic and widely present in aquatic environments,so it presents a serious threat to human health and sustainable development.A dielectric barrier discharge(DBD)plasma jet was utilized to degrade aqueous SMX,and the effects of various operating parameters(working gas,discharge power,etc)on SMX degradation performance were studied.The experimental results showed that the DBD plasma jet can obtain a relatively high degradation efficiency for SMX when the discharge power is high with an oxygen atmosphere,the initial concentration of SMX is low,and the aqueous solution is under acidic conditions.The reactive species produced in the liquid phase were detected,and OH radicals and O3were found to play a significant role in the degradation of SMX.Moreover,the process of SMX degradation could be better fitted by the quasi-first-order reaction kinetic equation.The analysis of the SMX degradation process indicated that SMX was gradually decomposed and 4-amino benzene sulfonic acid,benzene sulfonamide,4-nitro SMX,and phenylsulfinyl acid were detected,and thus three possible degradation pathways were finally proposed.The mineralization degree of SMX reached 90.04%after plasma treatment for 20 min,and the toxicity of the solution fluctuated with the discharge time but eventually decreased.
基金supported by National Natural Science Foundation of China (Nos. 12075037 and 22206013)the Natural Science Foundation of Jiangsu Province (No. BK20210857)the Leading Innovative Talents Cultivation Project of Changzhou City (No. CQ20210083)。
文摘Ozone(O_(3)) generated by a dielectric barrier discharge(DBD) is widely used in various industrial processes. In this study, NaCl aqueous solution was used as a novel electric power transmission electrode in a DBD reactor(instead of a traditional metal electrode) for highly efficient ozone generation. The results demonstrated that a high O_(3) yield of 242 g k Wh^(-1) with a concentration of 14.6 g m^(-3)O_(3) was achieved. The power transmission mechanism works because NaCl aqueous solution behaves as a capacitor when an alternating pulse voltage below 8 k Hz is used.Compared with the resistance of the discharge barrier and discharge space, the resistance of NaCl aqueous solution can be ignored, which ensures that O_(3) is generated efficiently. It is expected that O_(3) generation using NaCl aqueous solution as a novel electrode in a DBD reactor could be an alternative technology with good application prospects.
基金supported by National Natural Science Foundation of China(Nos.11875121,51977057,11575050,11875014)the Hebei Province Natural Science Foundation(No.A2022201036)。
文摘This paper describes the realization of a homogeneous dielectric barrier discharge(DBD)in argon at atmospheric pressure.The effect of the morphology of the dielectric surface(especially the dielectric surface covered by hollow ceramic beads(99%Al_(2)O_(3))with different diameters)on discharge is investigated.With different dielectrics,the argon DBD presents two discharge modes:a filamentary mode and a homogeneous mode.Fast photography shows that the filamentary mode operates in a streamer discharge,and the homogeneous mode operates in a Townsend discharge regime.It is found that a homogeneous discharge can be generated within a certain voltage range.The voltage amplitude range decreases,and the breakdown voltage increases with the increase in the mean diameter of the ceramic beads.Waveforms of the total current and optical emission signal present stochastic pulses per half voltage cycle for the filamentary mode,whereas there is one single hump per half voltage cycle for the homogeneous mode.In the homogeneous mode,the intensity of the optical emission decreases with the mean diameter of the ceramic beads.The optical emission spectrum is mainly composed of atomic lines of argon and the second positive system of molecular nitrogen.It reveals that the electron density decreases with the increasing mean diameter of the ceramic beads.The vibrational temperature increases with the increasing mean diameter of the ceramic beads.It is believed that a large number of microdischarges are formed,and smaller ceramic beads have a larger activation surface area and more point discharge.Electrons liberated in the shallow well and electrons generated from microdischarges can increase the secondary electron emission coefficient of the cathode and provide initial electrons for discharge continuously.Therefore,the breakdown electric field is reduced,which contributes to easier generation of homogeneous discharge.This is confirmed by the simulation results.
基金National Natural Science Foundation of China(No.12075075)The Natural Science Foundation of Hebei Province,China(Nos.2020201016 and A2018201154).
文摘A new phenomenon that a filament discharged only once instead of twice in a cycle of the applied voltage is observed in a square grid pattern in a dielectric barrier discharge(DBD)with a larger gas gap,which is named intermittent discharge.Its spatiotemporal dynamics and the formation mechanism are studied by the multiple photomultiplier tubes and an intensified charge-coupled device.Corresponding to the positions of spots in the picture with an exposure time of 40 ms,there are some bright spots(discharge spots)and black spots(non-discharged spots)in the instantaneous image with an exposure time of 10μs(a half cycle of the applied voltage).There are at least two bright spots around one black spot and vice versa.The surface discharges(SDS)can be observed between any two adjacent spots.The intensity of the SDSbetween the bright spot and the black spot is 2.5 times greater than that between two adjacent bright spots,which indicates that the SDSare directional-selective.The intermittent discharge with positive(negative)current polarity changes to that with negative(positive)current polarity,after it sustains up to 14 voltage cycles at the longest.The spatial distribution of the electric field component is calculated through COMSOL software to solve the Poisson equation numerically.It is found that the inhomogeneous distribution of surface electric field is caused by the inhomogeneous distribution of wall charges,which leads to direction-selective SDS.The intermittent discharge is formed by the competition between the direction-selective SDSand volume discharges(VDS)in DBD.This is the reason why the intermittent discharge is generated.
基金supported by National Natural Science Foundation of China(Nos.52177148,51777091 and 52037004)Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX23_1449)。
文摘Nanosecond(ns)pulsed dielectric barrier discharge(DBD)is considered as a promising method to produce controllable large-volume and high activity low-temperature plasma at atmospheric pressure,which makes it suitable for wide applications.In this work,the ns pulse power supply is used to excite Ar DBD and the influences of the pulse parameters(voltage amplitude,pulse width,pulse rise and fall times)on the DBD uniformity are investigated.The gas gap voltage(Ug)and conduct current(Ig)are separated from the measured voltage and current waveforms to analyze the influence of electrical parameters.The spectral line intensity ratio of two Ar excited species is used as an indicator of the electron temperature(Te).The time resolved discharge processes are recorded by an intensified charge-coupled device camera and a one-dimensional fluid model is employed to simulate the spatial and temporal distributions of electrons,ions,metastable argon atoms and Te.Combining the experimental and numerical results,the mechanism of the pulse parameters influencing on the discharge uniformity is discussed.It is shown that the space electric field intensity and the space particles'densities are mainly responsible for the variation of discharge uniformity.With the increase of voltage and pulse width,the electric field intensity and the density of space particles increased,which results in the discharge mode transition from non-uniform to uniform,and then non-uniform.Furthermore,the extension of pulse rise and fall times leads to the discharge transition from uniform to nonuniform.The results are helpful to reveal the mechanism of ns pulsed DBD mode transition and to realize controllable and uniform plasma sources at atmospheric pressure.
文摘An experimental system was established to explore the plasma flow control effect for helicopter rotors in hover mode.With the plasma actuator applied at the leading edge of the rotor blades,alternating current dielectric barrier discharge(AC-DBD) plasma actuation was generated by a sinusoidal AC high-voltage generator.By direct force measurement,the influence of actuation parameters on the aerodynamic performance of the rotor was investigated at a tip Reynolds number of 1.7 × 105.AC-DBD actuation can delay the blade stall to more than 3° with a 20%increase of about in the thrust coefficient at the post-stall pitch.At a constant motor power driving the rotor,AC-DBD actuation could reduce the rotor’s torque at the stalled pitch and increase the rotational speed of the rotor.Also,AC-DBD actuation could maintain a relatively high hover efficiency of the rotor at large collective pitches.In a wide range of actuation parameters,AC-DBD plasma actuation could improve the rotor’s aerodynamic performance at large blade pitches.High-speed photography of the tuft motion on the blade’s upper surface showed that AC-DBD plasma actuation could promote the reattachment of the blade’s separation flow.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.51509035 and 51409158)the Project of Shenyang Science and Technology Bureau (Grant No.RC200010)the National Natural Science Foundation of Liaoning Province of China (Grant No.2020-KF-13-03)。
文摘In order to better analyze the characteristics of particle distribution and its influencing factors in the ionized space during the process of coaxial dielectric barrier discharge,a self-designed two-dimensional axisymmetric structure exciter was used to carry out optical diagnosis,with the electron temperature calculated through Gaussian fitting.A plasma model was applied to conduct research on the discharge process through numerical simulation,with the changes in electron density and electron temperature were analyzed by using different discharge parameters.The research results show that with an increase in discharge voltage,pressure inside the reactor and relative permittivity,the discharge process is promoted.In addition,a rise in current density leads to an increase in the number of charged particles on the surface of the medium during the discharge process,while a rise in discharge intensity causes an increase in the electron density.Electron temperature decreases due to the increased loss of collision energy between particles.These results were confirmed by comparing experimental data with simulation results.
基金supported by National Natural Science Foundation of China(No.12075075)the Natural Science Foundation of Hebei Province, China(Nos.2020201016 and A2018201154)。
文摘We report five types of patterns with square symmetry,including three novel types obtained by inserting a specially designed grid photonic crystal(PC)into a dielectric barrier discharge system.They are studied using an intensified charge-coupled device camera and photomultiplier tubes.The three novel types of patterns are a square pattern with one structure,a square superlattice pattern with four sublattices and a(1/4)K_(grid)(K_(grid)is the basic wave vector of the grid),and another square pattern with a complex inversion discharge sequence.From the application viewpoint,the five types of patterns can be used as plasma photonic crystals(PPCs).Their band diagrams under a transverse-magnetic wave simulated by the finite element method show that there are a large number of band gaps.Compared with the original PC with only a unidirectional band gap,the five types of PPCs have tunable and omnidirectional band gaps,which is very important in controlling the propagation of electromagnetic waves in the mm-wave region.The experimental results enrich the pattern types in the dielectric barrier discharge system and provide a method for obtaining PPCs with symmetry controllability and bandgap tunability.
基金supported by the National Natural Science Foundation of China(60906053,61204069,61274118,61306144,61504079,and 11605112)Scientific and Innovative Action Plan of Shanghai(15DZ1160800 and 17XD1702400)China Postdoctoral Science Foundation(2016 M601595).
文摘Improving energy efficiency in plasma NO removal is a critical issue.When the surface dielectric barrier discharge(SDBD)device is considered as a combination of multiple plasma actuators,the induced plasma aerodynamic effect cannot be ignored,which can affect the mass transfer,then affect the chemical reactions.Five SDBD devices with different electrode arrangements are studied for NO conversion.They correspond to different flow patterns.We find that the energy efficiency in an SDBD device with a common structure(Type 1)is 28%lower than that in SDBD devices with a special arrangement(Types 2–5).Two reasons may explain the results.First,fewer active species are produced in Type 1 because the development of discharge is hindered by the mutually exclusive electric field forces caused by the symmetrically distributed charged particles.Second,the plasma wind induced by the plasma actuator can enhance the mass and heat transfer.The mixing of reactants and products is better in Types 2–5 than Type 1 due to higher turbulence kinetic energy.
基金partially supported by National Natural Science Foundation of China(Nos.51977104,52037004 and 52207160)the Natural Science Foundation of Jiangsu Province(No.BK20220341)。
文摘Surface modification techniques with plasma are widely investigated to improve the surface insulation capability of polymers under dry conditions,while the relationship between treatment method,surface physical and chemical properties,and wet flashover voltage is still unclear for inorganic ceramics.In this work,the surface insulation properties of ceramics under wet conditions are improved using nanosecond-pulsed dielectric barrier discharge with polydimethylsiloxane(PDMS)as the precursor.The relationships between PDMS concentration and the water contact angle,dry and wet flashover voltages are obtained to acquire the optimal concentration.The surface charge dissipation test and surface physio-chemical property measurement with SEM,AFM,XPS are carried out to further explore the mechanism of surface insulation enhancement.The results show that film deposition with micron thickness and superhydrophobicity occurs at the PDMS concentration of 1.5%.The dry flashover voltage is increased by 14.6%due to the induction of deep traps,while the wet flashover voltage is increased by 66.7%.The gap between dry-wet flashover voltage is decreased by 62.3%compared with the untreated one due to the self-cleaning effect.
文摘The paper presents comparative kinetic characteristics of the decomposition of 2,4-dichlorophenol in a dielectric barrier discharge and a combined plasma-catalytic process. Vermiculite containing 5% zirconium was used as a catalyst. The destruction processes of 2,4-DCP proceed efficiently, the degree of decomposition increases in the combined plasma-catalytic process by a factor of 1.33 and reaches 80%. The experimental results were processed according to the first-order kinetic law (R<sup>2</sup> > 0.97), according to which the effective constants (0.36 ± 0.04) and (0.51 ± 0.03) s<sup>-1</sup> and the decomposition rates of 2,4-DCP (106 and 123 μmol/l·s) when treating model solutions without a catalyst and with vermiculite + Zr 5%, respectively, and the energy costs are 0.012 and 0.017 molecules/100eV. The main decomposition products present in the solution have been determined to be carboxylic acids, aldehydes, the contribution of which does not exceed 2%, as well as chloride ions, and in the gas phase they are carbon dioxide and molecular chlorine (the share of which does not exceed 1.5% of total chlorine content in the system).
基金the Joint Foundation of the Council of National Natural Science Foundation of China(NSFC)China Academy of Engineering Physics(CAEP)the National Natural Science Foundation of China(NSAF United Foundation)
文摘Fluoride rubber F2311film,an alternating copolymer of CF2-CFCI（CTFE）andCH2-CF2（VF2）components,was treated by atmospheric pressure dielectric barrier discharge（DBD）in air.The surface structure,topography and surface chemistry of the treated F2311filmswere characterized by contact angle measurement,atomic force microscopy（AFM）,and X-rayphotoelectron spectroscopy（XPS）,respectively.The experimental results showed that a shorttime air plasma treatment led to morphological,wettability and chemical changes in the F2311films.The surface hydrophilicity increased greatly after the plasma treatment,the static watercontact angle decreased from 98.6° to 32°,and oxygen containing groups（C=O,O-C=O,etc.）were introduced.Atomic force microscopy revealed that plasma produced by DBD etched F2311films obviously.The roughness of the samples increased remarkably with the formation of peaksand valleys on the treated surfaces.The increased surface wettability may be correlated with boththe introduction of hydrophilic groups due to air plasma oxidation of the surface and the changein surface morphology etched by DBD.
基金supported by National Natural Science Foundation of China (Nos. 51877027 and 51877028)financially supported by the Fundamental Research Funds for the Central Universities (No. DUT20ZD202)+1 种基金the Science and Technology Development Fund of Xinjiang Production and Construction (No. 2019BC009)the Dalian High-Level Talents Innovation and Entrepreneurship Project (No. 2018RQ28)
文摘Both experimental and simulated studies of microdischarge(MD)are carried out in a dielectric barrier discharge with a pin-to-pin gap of 3.5 mm,ignited by a sinusoidal voltage with a peak voltage of 10 kV and a driving frequency of 5 kHz.Statistical results have shown that the probability of the single current pulse in the positive half-period(HP)reaches 73.6%under these conditions.Experimental results show that great luminous intensity is concentrated on the dielectric surface and the tip of the metal electrode.A 1D plasma fluid model is implemented by coupling the species continuity equations,electron energy density equations,Poisson equation,and Helmholtz equations to analyze the MD dynamics on the microscale.The simulated results are in good qualitative agreement with the experimental results.The simulated results show that the MD dynamics can be divided into three phases:the Townsend phase,the streamer propagation phase,and the discharge decay phase.During the streamer propagation phase,the electric field and electron density increase with the streamer propagation from the anode to the cathode,and their maximal values reach 625.48 Td and 2.31×10^(19)m^(-3),as well as 790.13 Td and 3.58×10^(19)m^(-3)in the positive and negative HP,respectively.Furthermore,a transient glow-like discharge is detected around the anode during the same period of streamer propagation.The formation of transient glow-like discharge is attributed to electrons drifting back to the anode,which is driven by the residual voltage in the air gap.
基金supported by National Natural Science Foundation of China (Grant No. 51877086)
文摘In this paper, a two-dimensional axisymmetric fluid model was established to investigate the influence of nitrogen impurity content on the discharge pattern and the relevant discharge characteristics in an atmosphere pressure helium dielectric barrier discharge(DBD). The results indicated that when the nitrogen content was increased from 1 to 100 ppm, the discharge pattern evolved from a concentric-ring pattern into a uniform pattern, and then returned to the concentricring pattern. In this process, the discharge mode at the current peak moment transformed from glow mode into Townsend mode, and then returned to glow mode. Further analyses revealed that with the increase of impurity level, the rate of Penning ionization at the pre-ionization stage increased at first and decreased afterwards, resulting in a similar evolution pattern of seed electron level. This evolution trend was believed to be resulted from the competition between the N2 partial pressure and the consumption rate of metastable species. Moreover, the discharge uniformity was found positively correlated with the spatial uniformity of seed electron density as well as the seed electron level. The reason for this correlation was explained by the reduction of radial electric field strength and the promotion of seed electron uniformity as pre-ionization level increases. The results obtained in this work may help better understand the pattern formation mechanism of atmospheric helium DBD under the variation of N2 impurity level, thereby providing a possible means of regulating the discharge performance in practical application scenarios.
基金supported by the National Natural Science Foundation of China (NSFC) under the grant of No.21176175 and No.20606023
文摘We reported a coaxial,micro-dielectric barrier discharge(micro-DBD)reactor and a conventional DBD reactor for the direct conversion of methane into higher hydrocarbons at atmospheric pressure.The effects of input power,residence time,discharge gap and external electrode length were investigated for methane conversion and product selectivity.We found the conversion of methane in a micro-DBD reactor was higher than that in a conventional DBD reactor.And at an input power of 25.0 W,the conversion of methane and the total C2+C3 selectivity reached 25.10% and 80.27%,respectively,with a micro-DBD reactor of 0.4 mm discharge gap.Finally,a nonlinear multiple regression model was used to study the correlations between both methane conversion and product selectivity and various system variables.The calculated data were obtained using SPSS 12.0 software.The regression analysis illustrated the correlations between system variables and both methane conversion and product selectivity.
文摘A superimposed wire-plate dielectric barrier discharge reactor was use d to remove toluene in this study. The effects of oxygen content, gas flow rate, gas initial concentration and with/without catalyst on toluene decomposition we re investigated. It was found that an optimal toluene removal was achieved when the oxygen content was about 5%. Under this condition, the highest toluene remov al efficiency of 80.8% was achieved when the gas concentration was 80 mg/m3. The toluene removal efficiency decreased with the increase of the gas flow rate and the initial concentration of toluene. In addition, the ozone concentration decr eased with the increase of the initial concentration of toluene. It suggested th at combining DBD(dielectric barrier discharge) with Co3O4/Al2O3/foam nickel cata lyst in-situ could improve the toluene removal efficiency and suppress ozone for mation. Products analysis showed that the main products were CO and CO2 when oxy gen was more than 5%.
基金jointly supported by the Science Foundation of the Institute of Plasma Physics, the Chinese Academy of Sciences (No. DSJJ-14-YY02)National Natural Science Foundation of China (Grant Nos. 11475174 and 51777206)
文摘Atmospheric pressure helium/water dielectric barrier discharge(DBD) plasma is used to investigate the generation of reactive species in a gas–liquid interface and in a liquid. The emission intensity of the reactive species is measured by optical emission spectroscopy(OES)with different discharge powers at the gas–liquid interface. Spectrophotometry is used to analyze the reactive species induced by the plasma in the liquid. The concentration of OH radicals reaches 2.2 μm after 3 min of discharge treatment. In addition, the concentration of primary longlived reactive species such as H_2O_2, NO_3^- and O_3 are measured based on plasma treatment time.After 5 min of discharge treatment, the concentration of H_2O_2, NO_3^-, and O_3 increased from 0 mg?·?L^(-1) to 96 mg?·?L^(-1), 19.5 mg?·?L^(-1), and 3.5 mg?·?L^(-1), respectively. The water treated by plasma still contained a considerable concentration of reactive species after 6 h of storage. The results will contribute to optimizing the DBD plasma system for biological decontamination.
