In order to promote an in-depth understanding of the mechanism of leading-edge flow separation control over an airfoil using a symmetrical Dielectric Barrier Discharge(DBD) plasma actuator excited by a steady-mode exc...In order to promote an in-depth understanding of the mechanism of leading-edge flow separation control over an airfoil using a symmetrical Dielectric Barrier Discharge(DBD) plasma actuator excited by a steady-mode excitation, an experimental investigation of an SC(2)-0714 supercritical airfoil with a symmetrical DBD plasma actuator was performed in a closed chamber and a low-speed wind tunnel. The plasma actuator was mounted at the leading edge of the airfoil.Time-resolved Particle Image Velocimetry(PIV) results of the near-wall region in quiescent air suggested that the symmetrical DBD plasma actuator could induce some coherent structures in the separated shear layer, and these structures were linked to a dominant frequency of f0= 39 Hz when the peak-to-peak voltage of the plasma actuator was 9.8 kV. In addition, an analysis of flow structures without and with plasma actuation around the upper side of the airfoil at an angle of attack of18° for a wind speed of 3 m/s(Reynolds number Re = 20000) indicated that the dynamic process of leading-edge flow separation control over an airfoil could be divided into three stages. Initially, this plasma actuator could reinforce the shedding vortices in the separated shear layer. Then, these vortical structures could deflect the separated flow towards the wall by promoting the mixing between the outside flow with a high kinetic energy and the flow near the surface. After that, the plasma actuator induced a series of rolling vortices in the vicinity of the suction side of the airfoil, and these vortical structures could transfer momentum from the leading edge of the airfoil to the separated region, resulting in a reattachment of the separated flow around the airfoil.展开更多
A new method for nitric oxide(NO)removal was developed by combining dielectric barrier discharge(DBD)and negative pulse corona(NPC).The effects of gas composition(O2,CO2,and H2 O)on NO removal were investigated with t...A new method for nitric oxide(NO)removal was developed by combining dielectric barrier discharge(DBD)and negative pulse corona(NPC).The effects of gas composition(O2,CO2,and H2 O)on NO removal were investigated with this method,and the effect of alcohols(methanol and ethanol)addition on NO removal was also investigated as well as the reaction mechanisms to enhance the NO removal efficiency.The experimental results showed that O2,CO2,and H2 O had obvious inhibition effects on NO removal,and the negative effects were in the following order:O2>CO2>H2 O.The addition of methanol or ethanol in the reaction system could mitigate the negative effects of O2,CO2 and H2 O on NO removal,and also eliminated the production of N02.The positive effect of alcohols addition with DBD-NPC denitration method was also validated in the simulated flue gas,in which the NOx(NO,NO2)was mainly converted into N2.展开更多
The homogeneous dielectric barrier discharge(DBD) in atmospheric air is most favorable for polymer surface modification due to the low cost of operation and the ability of ambient on-line continuous uniform processing...The homogeneous dielectric barrier discharge(DBD) in atmospheric air is most favorable for polymer surface modification due to the low cost of operation and the ability of ambient on-line continuous uniform processing.In this paper,polypropylene(PP) films are treated using a homogeneous DBD plasma in atmospheric air.The surface properties of PP films are studied using contact angle and surface energy measurement,scanning electron microscopy (SEM) and Fourier transformed infrared spectroscopy(FTIR),and the aging effect after treatment when the treated materials are exposed to open air is also studied,with the modification mechanism being discussed.It is demonstrated that non-thermal plasmas generated by homogeneous DBD in atmospheric air is an effective way to enhance the surface properties of PP films.After the plasma treatment,the surface of PP film is etched,and oxygen-containing polar groups are introduced into the surface.These two processes can induce a remarkable decrease in water contact angle and a remarkable increase in surface energy,and the surface properties of PP films are improved accordingly.展开更多
A superimposed wire-plate dielectric barrier discharge reactor was used to remove toluene in this study. The effects of oxygen content, gas flow rate, gas initial concentration and with/without catalyst on toluene dec...A superimposed wire-plate dielectric barrier discharge reactor was used to remove toluene in this study. The effects of oxygen content, gas flow rate, gas initial concentration and with/without catalyst on toluene decomposition were investigated. It was found that an optimal toluene removal was achieved when the oxygen content was about 5%. Under this condition, the highest toluene removal efficiency of 80.8% was achieved when the gas concentration was 80 mg/m^3. The toluene removal efficiency decreased with the increase of the gas flow rate and the initial concentration of toluene. In addition, the ozone concentration decreased with the increase of the initial concentration of toluene. It suggested that combining DBD （dielectric barrier discharge） with Co3O4/Al2O3/foam nickel catalyst in-situ could improve the toluene removal efficiency and suppress ozone formation. Products analysis showed that the main products were CO and CO2 when oxygen was more than 5%.展开更多
Oxygen vacancy OV plays an important role in a flash sintering (FS) process. In defect engineering, the methods of creating oxygen vacancy defects include doping, heating, and etching, and all of them often have compl...Oxygen vacancy OV plays an important role in a flash sintering (FS) process. In defect engineering, the methods of creating oxygen vacancy defects include doping, heating, and etching, and all of them often have complex processes or equipment. In this study, we used dielectric barrier discharge (DBD) as a new defect engineering technology to increase oxygen vacancy concentrations of green billets with different ceramics (ZnO, TiO_(2), and 3 mol% yttria-stabilized zirconia (3YSZ)). With an alternating current (AC) power supply of 10 kHz, low-temperature plasma was generated, and a specimen could be treated in different atmospheres. The effect of the DBD treatment was influenced by atmosphere, treatment time, and voltage amplitude of the power supply. After the DBD treatment, the oxygen vacancy defect concentration in ZnO samples increased significantly, and a resistance test showed that conductivity of the samples increased by 2–3 orders of magnitude. Moreover, the onset electric field (E) of ZnO FS decreased from 5.17 to 0.86 kV/cm at room temperature (RT);while in the whole FS, the max power dissipation decreased from 563.17 to 27.94 W. The defect concentration and conductivity of the green billets for TiO_(2) and 3YSZ were also changed by the DBD, and then the FS process was modified. It is a new technology to treat the green billet of ceramics in very short time, applicable to other ceramics, and beneficial to regulate the FS process.展开更多
In this work,a bright and dark concentric-ring pattern is reported in a dielectric barrier discharge for the first time.The spatiotemporal dynamics of the bright and dark concentric-ring pattern are investigated with ...In this work,a bright and dark concentric-ring pattern is reported in a dielectric barrier discharge for the first time.The spatiotemporal dynamics of the bright and dark concentric-ring pattern are investigated with an intensified charge-coupled device and photomultiplier tubes.The results indicate that the bright and dark concentric-ring pattern is composed of three concentric-ring sublattices.These are bright concentric-ring structures,dark concentric-ring structures and wider concentric-ring structures,respectively.The bright concentric-ring structures and dark concentricring structures are alternately distributed.The bright concentric-ring structures are located at the centre of the wider concentric-ring structures.The wider concentric-ring structures first form from the outer edge and gradually develop to the centre.The essence of all three concentric-ring structures is the individual discharge filaments.The optical emission spectra of different sublattices are acquired and analysed.It is found that the plasma parameters of the three concentricring sublattices are different.Finally,the formation mechanism of the bright and dark concentricring pattern is discussed.展开更多
The destruction of gaseous styrene was studied using a low-temperature plasma induced by tubular multilayer dielectric barrier discharge（DBD）.The results indicate that the applied voltage,gas flow rate,inlet styrene...The destruction of gaseous styrene was studied using a low-temperature plasma induced by tubular multilayer dielectric barrier discharge（DBD）.The results indicate that the applied voltage,gas flow rate,inlet styrene concentration and reactor configuration play important roles in styrene removal efficiency （ηstyrene） and energy yield（EY）.Values of ηstyrene and EY reached 96%and 15567 mg/kWh when the applied voltage,gas flow rate,inlet styrene concentration and layers of quartz tubes were set at 10.8 kV,5.0 m/s,229 mg/m^3 and 5 layers,respectively.A qualitative analysis of the byproducts and a detailed discussion of the reaction mechanism are also presented.The results could facilitate industrial applications of the new DBD reactor for waste gas treatment.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
Effects of carrier gas composition（N2/air） on NH3 production, energy efficiency regarding NH3 production and byproducts formation from plasma-catalytic decomposition of urea were systematically investigated using an...Effects of carrier gas composition（N2/air） on NH3 production, energy efficiency regarding NH3 production and byproducts formation from plasma-catalytic decomposition of urea were systematically investigated using an Al2 O3-packed dielectric barrier discharge（DBD） reactor at room temperature. Results show that the presence of O2 in the carrier gas accelerates the conversion of urea but leads to less generation of NH3. The final yield of NH3 in the gas phase decreased from 70.5%, 78.7%, 66.6% and 67.2% to 54.1%, 51.7%, 49.6% and 53.4% for applied voltages of 17, 19, 21 and 23 kV, respectively when air was used as the carrier gas instead of N2.From the viewpoint of energy savings, however, air carrier gas is better than N2 due to reduced energy consumption and increased energy efficiency for decomposition of a fixed amount of urea. Carrier gas composition has little influence on the major decomposition pathways of urea under the synergetic effects of plasma and Al2 O3 catalyst to give NH3 and CO2 as the main products. Compared to a small amount of N2 O formed with N2 as the carrier gas, however,more byproducts including N2O and NO2 in the gas phase and NH4 NO3 in solid deposits were produced with air as the carrier gas, probably due to the unproductive consumption of NH3, the possible intermediate HNCO and even urea by the abundant active oxygen species and nitrogen oxides generated in air-DBD plasma.展开更多
Process scale-up remains a considerable challenge for environmental applications of non-thermal plasmas.Undersanding the impact of reactor hydrodynamics in the performance of the process is a key step to overcome this...Process scale-up remains a considerable challenge for environmental applications of non-thermal plasmas.Undersanding the impact of reactor hydrodynamics in the performance of the process is a key step to overcome this challenge.In this work,we apply chemical engineering concepts to analyse the impact that different non-thermal plasma reactor configurations and regimes,such as laminar or plug flow,may have on the reactor performance.We do this in the particular context of the removal of pollutants by non-thermal plasmas,for which a simplified model is available.We generalise this model to different reactor configurations and,under certain hypotheses,we show that a reactor in the laminar regime may have a behaviour significantly different from one in the plug flow regime,often assumed in the non-thermal plasma literature.On the other hand,we show that a packed-bed reactor behaves very similarly to one in the plug flow regime.Beyond those results,the reader will find in this work a quick introduction to chemical reaction engineering concepts.展开更多
For improving the energy efficiency of plasma volatile organic compounds( VOCs) decomposition, a pulse modulated power is used to drive the dielectric barrier discharge( DBD) plasma to treat benzene. Through the chang...For improving the energy efficiency of plasma volatile organic compounds( VOCs) decomposition, a pulse modulated power is used to drive the dielectric barrier discharge( DBD) plasma to treat benzene. Through the change of pulse duty cycle,the pulse modulation effect on benzene removal energy efficiency was investigated. The results show that pulse modulation can improve the energy yield and reduce the temperature of the chamber wall. There is an optimal duty cycle for achieving the maximum energy yield at a certain discharge voltage. The effect of initial benzene concentration on the decomposition efficiency and carbon selectivity in pulse modulation plasma were studied. The results indicate that the removal efficiency and carbon balance increase with the specific input energy( SIE) and decrease with the concentration. The energy yield increases with increasing initial concentration and achieves maximum around 180 J / L SIE for all initial concentrations.展开更多
The wind tunnel test was conducted with an NACA 0012 airfoil to explore the flow control effects on airfoil dynamic stall by NS-DBD plasma actuation. Firstly, light and deep dynamic stall states were set, based on the...The wind tunnel test was conducted with an NACA 0012 airfoil to explore the flow control effects on airfoil dynamic stall by NS-DBD plasma actuation. Firstly, light and deep dynamic stall states were set, based on the static stall characteristics of airfoil at a Reynolds number of 5.8 × 105. Then, the flow control effect of NS-DBD on dynamic stall was studied and the influence law of three typical reduced frequencies (k = 0.05, k = 0.05, and k = 0.15) was examined at various dimensionless actuation frequencies (F+ = 1, F+ = 2, and F+ = 3). For both light and deep dynamic stall states, NS-DBD had almost no effect on upstroke. However, the lift coefficients on downstroke were increased significantly and the flow control effect at F+ = 1 is the best. The flow control effect of the light stall state is more obvious than that of deep stall state under the same actuation conditions. For the same stall state, with the reduced frequency increasing, the control effect became worse. Based on the in being principles of flow separation control by NS-DBD, the mechanism of dynamic stall control was discussed and the influence of reduced frequency on the dynamic flow control was analyzed. Different from the static airfoil flow separation control, the separated angle of leading-edge shear layer for the airfoil in dynamic stall state is larger and flow control with dynamic oscillation is more difficult. The separated angle is closely related to the effective angle of attack, so the effect of dynamic stall control is greatly dependent on the history of angles of attack.展开更多
A numerical investigation is conducted to explore the evolution of a plasma discharge and its interaction with the fluid flow based on a self-consistent fluid model which couples the discharge dynamics with the fluid ...A numerical investigation is conducted to explore the evolution of a plasma discharge and its interaction with the fluid flow based on a self-consistent fluid model which couples the discharge dynamics with the fluid dynamics.The effects of the applied voltage on the distribution of velocity and temperature in initially static air are parainetrically studied.Furthermore,the spatial structure of plasma discharge and the resulting force contours in streamwise and normal directions are discussed in detail.The result shows that the plasma actuator produces a net force that should always be directed away from the exposed electrode,which results in an ionic wind pushing particles into a jet downstream of the actuator.When the energy added by the plasma is taken into account,the ambient air temperature is increased slightly around the electrode,but the velocity is almost not affected.Therefore it is unlikely that the induced flow is buoyancy driven.For the operating voltages considered in this paper,the maximum induced velocity is found to follow a power law,i.e.,it is proportional to the applied voltage to the 3.5 power.This promises an efficient application in the flow control with plasma actuators.展开更多
Electric discharge in and in contact with water can accompany ultraviolet（UV）radiation and electron impact, which can generate a large number of active species such as hydroxyl radicals（OH）, oxygen radical（O）, o...Electric discharge in and in contact with water can accompany ultraviolet（UV）radiation and electron impact, which can generate a large number of active species such as hydroxyl radicals（OH）, oxygen radical（O）, ozone（O_3） and hydrogen peroxide（H_2O_2）. In this paper, a nonthermal plasma processing system was established by means of dielectric barrier discharge（DBD）arrays in water mist spray. The relationship between droplet size and water content was examined,and the effects of the concentrations of oxides in both treated water and gas were investigated under different water content and discharge time. The relative intensity of UV spectra from DBD in water mist was a function of water content. The concentrations of both O_3 and nitrogen dioxide（NO_2） in DBD room decreased with increasing water content. Moreover, the concentrations of H_2O_2, O_3 and nitrogen oxides（NOx） in treated water decreased with increasing water content,and all the ones enhanced after discharge. The experimental results were further analyzed by chemical reaction equations and commented by physical principles as much as possible. At last,the water containing phenol was tested in this system for the concentration from 100 mg/L to9.8 mg/L in a period of 35 min.展开更多
The decolorization of reactive blue 19(RB-19)as a model dye from aqueous solutions has been studied by means of the dielectric barrier discharge(DBD)process.The independent parameters of input power,initial dye concen...The decolorization of reactive blue 19(RB-19)as a model dye from aqueous solutions has been studied by means of the dielectric barrier discharge(DBD)process.The independent parameters of input power,initial dye concentration and initial pH value were evaluated respectively.Experimental data were optimized by means of a 33 factorial design and response surface methodology(RSM).The dye was quickly removed during the treatment,yielding 96.9%of decolorization efficiency under optimized conditions.Therefore,the total organic carbon(TOC)and chemical oxygen demand(CODcr)results indicated that only the chromophore was destroyed rather than completed oxidation.This was confirmed with UV-vis and tertiary butanol assessments during the DBD treatment.展开更多
In this paper,an absorption spectroscopy measurement method was applied on two atmospheric pressure plasma sources to determine their production of nitric oxide.The concentrations are essential for evaluating the plas...In this paper,an absorption spectroscopy measurement method was applied on two atmospheric pressure plasma sources to determine their production of nitric oxide.The concentrations are essential for evaluating the plasma sources based on the principle of the Dielectric Barrier Discharge（DBD）for applications in plasma medicine.The described method is based on a setup with an electrodeless discharge lamp filled with a mixture of oxygen and nitrogen.One of the emitted wavelengths is an important resonance wavelength of nitric oxide（λ = 226.2 nm）.By comparing the absorption behaviour at the minimum and maximum of the spectral absorption cross section of nitric oxide around that wavelength,and measuring the change in intensity by the absorbing plasma,the concentration of nitric oxide inside the plasma can be calculated.The produced nitric oxide concentrations depend on the pulse duration and are in the range of 180 ppm to 1400 ppm,so that a distance of about 10 cm to the respiratory tract is enough to conform to the VDI Guideline 2310.展开更多
The effect on the germination and seedling growth of radish(Raphanus sativus)seeds were examined employing a dielectric barrier discharge(DBD)at atmospheric pressure and room temperature for various treatment time.DBD...The effect on the germination and seedling growth of radish(Raphanus sativus)seeds were examined employing a dielectric barrier discharge(DBD)at atmospheric pressure and room temperature for various treatment time.DBD plasma using argon gas of flow rate 21 m^(-1)was employed in this study.Radish seeds were treated with DBD plasma for 1-5 min,respectively.Germination characteristics,seedling growth parameters,the contact angle of the seed coat,water uptake capacity,mass loss,the temperature of the seeds,chlorophyll,and carotenoid contents of the seedlings were measured before and after the DBD plasma treatments.Plasma treatment of radish seeds significantly increased germination-related characters,including germination percentage,fresh and dry weight,vigor index,and total carotenoids contents.However,the cumulative production rate was found to be decreased.Results from the experiment indicate an acceleration in the water uptake of the radish seeds and make the seed surface hydrophilic by plasma treatment.Scanning electron microscopy analysis showed that etching effects on the seed coat occurred after the argon plasma treatments,which affected the wettability of the radish seed.The experimental findings showed that seeds being treated by DBD plasma for 2 and 3 min had a positive effect on the germination and seedling growth of radish.展开更多
A Dielectric Barrier Discharge(DBD) plasma actuator can create a body force which locally accelerates the base flow leading to an attenuation of broadband disturbance to delay the transition. In this study, numerical ...A Dielectric Barrier Discharge(DBD) plasma actuator can create a body force which locally accelerates the base flow leading to an attenuation of broadband disturbance to delay the transition. In this study, numerical simulation on an NLF0416 airfoil is conducted to investigate transition delay and drag reduction by a DBD plasma actuator. To simulate plasma’s effect more accurately, boundary-layer data is acquired from Reynolds Averaged Navier Stocks(RANS) equations instead of laminar boundary layer equations, although RANS equations need a much finer boundary-layer grid, and the linear stability analysis method is used to analyze the boundary layer and get the transition point. In this study, the influences of different actuation intensities and positions are investigated, and results show that if the actuation intensity is stronger and the actuation position is closer to the base transition point, more drag reduction can be obtained. However, the efficiency of plasma transition delay is really low. For example, when the actuation voltage is 16 k V,the actuation frequency is 1 k Hz, and the main Mach number is 0.1, the saved power due to drag reduction is about 5.09 W, but the power consumed is about 32.61 W, and the efficiency is just15.6%.展开更多
A new combined reactor with Hg/Ar electrodeless ultraviolet(EDUV)activated by DBD for 3,4-dichlorodiphenyl ether abatement is presented.The effect of specific input energy and feeding gas component on 3,4-dichlorodiph...A new combined reactor with Hg/Ar electrodeless ultraviolet(EDUV)activated by DBD for 3,4-dichlorodiphenyl ether abatement is presented.The effect of specific input energy and feeding gas component on 3,4-dichlorodiphenyl ether removal efficiency has been explored.Compared with a single DBD system,this new combined process performed a significant promotion on 3,4-dichlorodiphenyl ether abatement.Experiment results verified that active oxygen clearly contributed to the synergistic activity of DBD-EDUV system.Results of emission spectra showed that UV radiation of 253.7 nm could be detected in the DBD-EDUV system.Further,the products of DBD-EDUV process were analyzed via gas chromatographymass spectrometer(GC-MS)to reveal involved decomposition mechanism.展开更多
基金supported by the Equipment Investigation in Advance of China(No.51313010204)
文摘In order to promote an in-depth understanding of the mechanism of leading-edge flow separation control over an airfoil using a symmetrical Dielectric Barrier Discharge(DBD) plasma actuator excited by a steady-mode excitation, an experimental investigation of an SC(2)-0714 supercritical airfoil with a symmetrical DBD plasma actuator was performed in a closed chamber and a low-speed wind tunnel. The plasma actuator was mounted at the leading edge of the airfoil.Time-resolved Particle Image Velocimetry(PIV) results of the near-wall region in quiescent air suggested that the symmetrical DBD plasma actuator could induce some coherent structures in the separated shear layer, and these structures were linked to a dominant frequency of f0= 39 Hz when the peak-to-peak voltage of the plasma actuator was 9.8 kV. In addition, an analysis of flow structures without and with plasma actuation around the upper side of the airfoil at an angle of attack of18° for a wind speed of 3 m/s(Reynolds number Re = 20000) indicated that the dynamic process of leading-edge flow separation control over an airfoil could be divided into three stages. Initially, this plasma actuator could reinforce the shedding vortices in the separated shear layer. Then, these vortical structures could deflect the separated flow towards the wall by promoting the mixing between the outside flow with a high kinetic energy and the flow near the surface. After that, the plasma actuator induced a series of rolling vortices in the vicinity of the suction side of the airfoil, and these vortical structures could transfer momentum from the leading edge of the airfoil to the separated region, resulting in a reattachment of the separated flow around the airfoil.
基金Supported by the National Natural Science Foundation of China(21536009)the Science and Technology Plan Projects of Shaanxi Province(2017ZDCXL-GY-10-03).
文摘A new method for nitric oxide(NO)removal was developed by combining dielectric barrier discharge(DBD)and negative pulse corona(NPC).The effects of gas composition(O2,CO2,and H2 O)on NO removal were investigated with this method,and the effect of alcohols(methanol and ethanol)addition on NO removal was also investigated as well as the reaction mechanisms to enhance the NO removal efficiency.The experimental results showed that O2,CO2,and H2 O had obvious inhibition effects on NO removal,and the negative effects were in the following order:O2>CO2>H2 O.The addition of methanol or ethanol in the reaction system could mitigate the negative effects of O2,CO2 and H2 O on NO removal,and also eliminated the production of N02.The positive effect of alcohols addition with DBD-NPC denitration method was also validated in the simulated flue gas,in which the NOx(NO,NO2)was mainly converted into N2.
基金Supported by National Natural Science Foundation of China(50707012),State Key Laboratory of Electrical Insulation and Power Equipment(EIPE11205),"Qing Lan Project"in Jiangsu Province of China.
文摘The homogeneous dielectric barrier discharge(DBD) in atmospheric air is most favorable for polymer surface modification due to the low cost of operation and the ability of ambient on-line continuous uniform processing.In this paper,polypropylene(PP) films are treated using a homogeneous DBD plasma in atmospheric air.The surface properties of PP films are studied using contact angle and surface energy measurement,scanning electron microscopy (SEM) and Fourier transformed infrared spectroscopy(FTIR),and the aging effect after treatment when the treated materials are exposed to open air is also studied,with the modification mechanism being discussed.It is demonstrated that non-thermal plasmas generated by homogeneous DBD in atmospheric air is an effective way to enhance the surface properties of PP films.After the plasma treatment,the surface of PP film is etched,and oxygen-containing polar groups are introduced into the surface.These two processes can induce a remarkable decrease in water contact angle and a remarkable increase in surface energy,and the surface properties of PP films are improved accordingly.
文摘A superimposed wire-plate dielectric barrier discharge reactor was used to remove toluene in this study. The effects of oxygen content, gas flow rate, gas initial concentration and with/without catalyst on toluene decomposition were investigated. It was found that an optimal toluene removal was achieved when the oxygen content was about 5%. Under this condition, the highest toluene removal efficiency of 80.8% was achieved when the gas concentration was 80 mg/m^3. The toluene removal efficiency decreased with the increase of the gas flow rate and the initial concentration of toluene. In addition, the ozone concentration decreased with the increase of the initial concentration of toluene. It suggested that combining DBD （dielectric barrier discharge） with Co3O4/Al2O3/foam nickel catalyst in-situ could improve the toluene removal efficiency and suppress ozone formation. Products analysis showed that the main products were CO and CO2 when oxygen was more than 5%.
基金supported by the National Natural Science Foundation of China(No.52077118)the Guangdong Basic and Applied Basic Research Foundation(No.2021A1515011778)State Key Laboratory of Power System Operation and Control,Tsinghua University(No.SKLD22KM01).
文摘Oxygen vacancy OV plays an important role in a flash sintering (FS) process. In defect engineering, the methods of creating oxygen vacancy defects include doping, heating, and etching, and all of them often have complex processes or equipment. In this study, we used dielectric barrier discharge (DBD) as a new defect engineering technology to increase oxygen vacancy concentrations of green billets with different ceramics (ZnO, TiO_(2), and 3 mol% yttria-stabilized zirconia (3YSZ)). With an alternating current (AC) power supply of 10 kHz, low-temperature plasma was generated, and a specimen could be treated in different atmospheres. The effect of the DBD treatment was influenced by atmosphere, treatment time, and voltage amplitude of the power supply. After the DBD treatment, the oxygen vacancy defect concentration in ZnO samples increased significantly, and a resistance test showed that conductivity of the samples increased by 2–3 orders of magnitude. Moreover, the onset electric field (E) of ZnO FS decreased from 5.17 to 0.86 kV/cm at room temperature (RT);while in the whole FS, the max power dissipation decreased from 563.17 to 27.94 W. The defect concentration and conductivity of the green billets for TiO_(2) and 3YSZ were also changed by the DBD, and then the FS process was modified. It is a new technology to treat the green billet of ceramics in very short time, applicable to other ceramics, and beneficial to regulate the FS process.
基金supported by National Natural Science Foundation of China(No.12075075)the Natural Science Foundation of Hebei Province,China(Nos.2020201016,A2018201154,A2023201012)Scientific Research and Innovation Team of Hebei University(No.IT2023B03)。
文摘In this work,a bright and dark concentric-ring pattern is reported in a dielectric barrier discharge for the first time.The spatiotemporal dynamics of the bright and dark concentric-ring pattern are investigated with an intensified charge-coupled device and photomultiplier tubes.The results indicate that the bright and dark concentric-ring pattern is composed of three concentric-ring sublattices.These are bright concentric-ring structures,dark concentric-ring structures and wider concentric-ring structures,respectively.The bright concentric-ring structures and dark concentricring structures are alternately distributed.The bright concentric-ring structures are located at the centre of the wider concentric-ring structures.The wider concentric-ring structures first form from the outer edge and gradually develop to the centre.The essence of all three concentric-ring structures is the individual discharge filaments.The optical emission spectra of different sublattices are acquired and analysed.It is found that the plasma parameters of the three concentricring sublattices are different.Finally,the formation mechanism of the bright and dark concentricring pattern is discussed.
基金supported by Key Project of Science and Technology Commission of Shanghai Municipality(No.13231201903)National Key Technology R&D Program of China(No.2011BAJ07B04)
文摘The destruction of gaseous styrene was studied using a low-temperature plasma induced by tubular multilayer dielectric barrier discharge（DBD）.The results indicate that the applied voltage,gas flow rate,inlet styrene concentration and reactor configuration play important roles in styrene removal efficiency （ηstyrene） and energy yield（EY）.Values of ηstyrene and EY reached 96%and 15567 mg/kWh when the applied voltage,gas flow rate,inlet styrene concentration and layers of quartz tubes were set at 10.8 kV,5.0 m/s,229 mg/m^3 and 5 layers,respectively.A qualitative analysis of the byproducts and a detailed discussion of the reaction mechanism are also presented.The results could facilitate industrial applications of the new DBD reactor for waste gas treatment.
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 the National Natural Science Foundation of China (Nos. 21547004, 51638001)the Beijing Natural Science Foundation (No. 8152011)the Scientific Research Program of Beijing Municipal Education Commission (No. KM201510005009)
文摘Effects of carrier gas composition（N2/air） on NH3 production, energy efficiency regarding NH3 production and byproducts formation from plasma-catalytic decomposition of urea were systematically investigated using an Al2 O3-packed dielectric barrier discharge（DBD） reactor at room temperature. Results show that the presence of O2 in the carrier gas accelerates the conversion of urea but leads to less generation of NH3. The final yield of NH3 in the gas phase decreased from 70.5%, 78.7%, 66.6% and 67.2% to 54.1%, 51.7%, 49.6% and 53.4% for applied voltages of 17, 19, 21 and 23 kV, respectively when air was used as the carrier gas instead of N2.From the viewpoint of energy savings, however, air carrier gas is better than N2 due to reduced energy consumption and increased energy efficiency for decomposition of a fixed amount of urea. Carrier gas composition has little influence on the major decomposition pathways of urea under the synergetic effects of plasma and Al2 O3 catalyst to give NH3 and CO2 as the main products. Compared to a small amount of N2 O formed with N2 as the carrier gas, however,more byproducts including N2O and NO2 in the gas phase and NH4 NO3 in solid deposits were produced with air as the carrier gas, probably due to the unproductive consumption of NH3, the possible intermediate HNCO and even urea by the abundant active oxygen species and nitrogen oxides generated in air-DBD plasma.
文摘Process scale-up remains a considerable challenge for environmental applications of non-thermal plasmas.Undersanding the impact of reactor hydrodynamics in the performance of the process is a key step to overcome this challenge.In this work,we apply chemical engineering concepts to analyse the impact that different non-thermal plasma reactor configurations and regimes,such as laminar or plug flow,may have on the reactor performance.We do this in the particular context of the removal of pollutants by non-thermal plasmas,for which a simplified model is available.We generalise this model to different reactor configurations and,under certain hypotheses,we show that a reactor in the laminar regime may have a behaviour significantly different from one in the plug flow regime,often assumed in the non-thermal plasma literature.On the other hand,we show that a packed-bed reactor behaves very similarly to one in the plug flow regime.Beyond those results,the reader will find in this work a quick introduction to chemical reaction engineering concepts.
文摘For improving the energy efficiency of plasma volatile organic compounds( VOCs) decomposition, a pulse modulated power is used to drive the dielectric barrier discharge( DBD) plasma to treat benzene. Through the change of pulse duty cycle,the pulse modulation effect on benzene removal energy efficiency was investigated. The results show that pulse modulation can improve the energy yield and reduce the temperature of the chamber wall. There is an optimal duty cycle for achieving the maximum energy yield at a certain discharge voltage. The effect of initial benzene concentration on the decomposition efficiency and carbon selectivity in pulse modulation plasma were studied. The results indicate that the removal efficiency and carbon balance increase with the specific input energy( SIE) and decrease with the concentration. The energy yield increases with increasing initial concentration and achieves maximum around 180 J / L SIE for all initial concentrations.
基金Project supported by the National Natural Science Foundation of China(Grant No.11802341)the Open Fund from State Key Laboratory of Aerodynamics of China(Grant No.SKLA20180207).
文摘The wind tunnel test was conducted with an NACA 0012 airfoil to explore the flow control effects on airfoil dynamic stall by NS-DBD plasma actuation. Firstly, light and deep dynamic stall states were set, based on the static stall characteristics of airfoil at a Reynolds number of 5.8 × 105. Then, the flow control effect of NS-DBD on dynamic stall was studied and the influence law of three typical reduced frequencies (k = 0.05, k = 0.05, and k = 0.15) was examined at various dimensionless actuation frequencies (F+ = 1, F+ = 2, and F+ = 3). For both light and deep dynamic stall states, NS-DBD had almost no effect on upstroke. However, the lift coefficients on downstroke were increased significantly and the flow control effect at F+ = 1 is the best. The flow control effect of the light stall state is more obvious than that of deep stall state under the same actuation conditions. For the same stall state, with the reduced frequency increasing, the control effect became worse. Based on the in being principles of flow separation control by NS-DBD, the mechanism of dynamic stall control was discussed and the influence of reduced frequency on the dynamic flow control was analyzed. Different from the static airfoil flow separation control, the separated angle of leading-edge shear layer for the airfoil in dynamic stall state is larger and flow control with dynamic oscillation is more difficult. The separated angle is closely related to the effective angle of attack, so the effect of dynamic stall control is greatly dependent on the history of angles of attack.
基金supported by the Foundation for Innovative Research Groups of National Natural Science Foundation of China(No.51121004)National Natural Science Foundation of China(No.50976026)
文摘A numerical investigation is conducted to explore the evolution of a plasma discharge and its interaction with the fluid flow based on a self-consistent fluid model which couples the discharge dynamics with the fluid dynamics.The effects of the applied voltage on the distribution of velocity and temperature in initially static air are parainetrically studied.Furthermore,the spatial structure of plasma discharge and the resulting force contours in streamwise and normal directions are discussed in detail.The result shows that the plasma actuator produces a net force that should always be directed away from the exposed electrode,which results in an ionic wind pushing particles into a jet downstream of the actuator.When the energy added by the plasma is taken into account,the ambient air temperature is increased slightly around the electrode,but the velocity is almost not affected.Therefore it is unlikely that the induced flow is buoyancy driven.For the operating voltages considered in this paper,the maximum induced velocity is found to follow a power law,i.e.,it is proportional to the applied voltage to the 3.5 power.This promises an efficient application in the flow control with plasma actuators.
基金supported by National Natural Science Foundation of China(Nos.11274092,51107033,11404092,11274091)the Nantong Science and Technology Project,China(No.BK2014024)+1 种基金the Open Project of Jiangsu Province Key Laboratory of Environmental Engineering,China(No.KF2014001)the Fundamental Research Funds for the Central Universities,China(No.2014B11414)
文摘Electric discharge in and in contact with water can accompany ultraviolet（UV）radiation and electron impact, which can generate a large number of active species such as hydroxyl radicals（OH）, oxygen radical（O）, ozone（O_3） and hydrogen peroxide（H_2O_2）. In this paper, a nonthermal plasma processing system was established by means of dielectric barrier discharge（DBD）arrays in water mist spray. The relationship between droplet size and water content was examined,and the effects of the concentrations of oxides in both treated water and gas were investigated under different water content and discharge time. The relative intensity of UV spectra from DBD in water mist was a function of water content. The concentrations of both O_3 and nitrogen dioxide（NO_2） in DBD room decreased with increasing water content. Moreover, the concentrations of H_2O_2, O_3 and nitrogen oxides（NOx） in treated water decreased with increasing water content,and all the ones enhanced after discharge. The experimental results were further analyzed by chemical reaction equations and commented by physical principles as much as possible. At last,the water containing phenol was tested in this system for the concentration from 100 mg/L to9.8 mg/L in a period of 35 min.
基金Key Scientific and Technological Project of Henan Province,China(No.162102210084)
文摘The decolorization of reactive blue 19(RB-19)as a model dye from aqueous solutions has been studied by means of the dielectric barrier discharge(DBD)process.The independent parameters of input power,initial dye concentration and initial pH value were evaluated respectively.Experimental data were optimized by means of a 33 factorial design and response surface methodology(RSM).The dye was quickly removed during the treatment,yielding 96.9%of decolorization efficiency under optimized conditions.Therefore,the total organic carbon(TOC)and chemical oxygen demand(CODcr)results indicated that only the chromophore was destroyed rather than completed oxidation.This was confirmed with UV-vis and tertiary butanol assessments during the DBD treatment.
文摘In this paper,an absorption spectroscopy measurement method was applied on two atmospheric pressure plasma sources to determine their production of nitric oxide.The concentrations are essential for evaluating the plasma sources based on the principle of the Dielectric Barrier Discharge（DBD）for applications in plasma medicine.The described method is based on a setup with an electrodeless discharge lamp filled with a mixture of oxygen and nitrogen.One of the emitted wavelengths is an important resonance wavelength of nitric oxide（λ = 226.2 nm）.By comparing the absorption behaviour at the minimum and maximum of the spectral absorption cross section of nitric oxide around that wavelength,and measuring the change in intensity by the absorbing plasma,the concentration of nitric oxide inside the plasma can be calculated.The produced nitric oxide concentrations depend on the pulse duration and are in the range of 180 ppm to 1400 ppm,so that a distance of about 10 cm to the respiratory tract is enough to conform to the VDI Guideline 2310.
基金Nepal Academy of Science and Technology(NAST),Khumaltar,Lalitpur,Nepal for providing financial and technical support。
文摘The effect on the germination and seedling growth of radish(Raphanus sativus)seeds were examined employing a dielectric barrier discharge(DBD)at atmospheric pressure and room temperature for various treatment time.DBD plasma using argon gas of flow rate 21 m^(-1)was employed in this study.Radish seeds were treated with DBD plasma for 1-5 min,respectively.Germination characteristics,seedling growth parameters,the contact angle of the seed coat,water uptake capacity,mass loss,the temperature of the seeds,chlorophyll,and carotenoid contents of the seedlings were measured before and after the DBD plasma treatments.Plasma treatment of radish seeds significantly increased germination-related characters,including germination percentage,fresh and dry weight,vigor index,and total carotenoids contents.However,the cumulative production rate was found to be decreased.Results from the experiment indicate an acceleration in the water uptake of the radish seeds and make the seed surface hydrophilic by plasma treatment.Scanning electron microscopy analysis showed that etching effects on the seed coat occurred after the argon plasma treatments,which affected the wettability of the radish seed.The experimental findings showed that seeds being treated by DBD plasma for 2 and 3 min had a positive effect on the germination and seedling growth of radish.
基金supported by the National Numerical Wind Tunnel Project (No. NNW2018-ZT3B08)。
文摘A Dielectric Barrier Discharge(DBD) plasma actuator can create a body force which locally accelerates the base flow leading to an attenuation of broadband disturbance to delay the transition. In this study, numerical simulation on an NLF0416 airfoil is conducted to investigate transition delay and drag reduction by a DBD plasma actuator. To simulate plasma’s effect more accurately, boundary-layer data is acquired from Reynolds Averaged Navier Stocks(RANS) equations instead of laminar boundary layer equations, although RANS equations need a much finer boundary-layer grid, and the linear stability analysis method is used to analyze the boundary layer and get the transition point. In this study, the influences of different actuation intensities and positions are investigated, and results show that if the actuation intensity is stronger and the actuation position is closer to the base transition point, more drag reduction can be obtained. However, the efficiency of plasma transition delay is really low. For example, when the actuation voltage is 16 k V,the actuation frequency is 1 k Hz, and the main Mach number is 0.1, the saved power due to drag reduction is about 5.09 W, but the power consumed is about 32.61 W, and the efficiency is just15.6%.
基金National Natural Science Foundation of China(No.21577023)the Special Research Project on Causes and Control Technology of Air Pollution(No.2017YFC0212905)the science and technology innovation action project supported by the Science and Technology Commission of Shanghai Municipality(No.18DZ1202605)。
文摘A new combined reactor with Hg/Ar electrodeless ultraviolet(EDUV)activated by DBD for 3,4-dichlorodiphenyl ether abatement is presented.The effect of specific input energy and feeding gas component on 3,4-dichlorodiphenyl ether removal efficiency has been explored.Compared with a single DBD system,this new combined process performed a significant promotion on 3,4-dichlorodiphenyl ether abatement.Experiment results verified that active oxygen clearly contributed to the synergistic activity of DBD-EDUV system.Results of emission spectra showed that UV radiation of 253.7 nm could be detected in the DBD-EDUV system.Further,the products of DBD-EDUV process were analyzed via gas chromatographymass spectrometer(GC-MS)to reveal involved decomposition mechanism.
