How to achieve low energy consumption and high degradation efficiency(DRE)under mild conditions is an important issue in the field of sulfur hexafluoride(SF_(6))treatment.In this work,a new route of SF_(6)degradation ...How to achieve low energy consumption and high degradation efficiency(DRE)under mild conditions is an important issue in the field of sulfur hexafluoride(SF_(6))treatment.In this work,a new route of SF_(6)degradation promoted by Ni-doped ceria(NiO-CeO_(2))in a packed bed dielectric barrier discharge(PB-DBD)was proposed.The effects of Ni/Ce molar ratio,input power,SF_(6)concentration and flow rate on the DRE of SF_(6)were investigated.Compared with DBD or CeO_(2)-DBD alone,the combination of DBD and NiO-CeO_(2)can significantly promote the SF_(6)degradation at lower input power.The experimental results show that when the dosage of catalyst 1.5NiO-CeO_(2)(Ni/Ce mole ratio is 1.5%)is 5 g,DBD input power is 50 W and SF_(6)(1.5%SF_(6)/98.5%Ar)flow rate is 100 ml·min-1,the highest DRE can reach 97.7%and the energy yield can reach 11.5 g·(kW·h)-1.Adjusting the catalyst dosage according to the flux of SF_(6)(e.g.,using 10 g catalyst to degrade SF_(6)with a concentration of 1.5%and a flow rate of 80 ml·min-1),the DRE of nearly 99%can be achieved for a long time,which is crucial for industrial application.The mechanism deduction shows that the rich surface and mesopores of the catalyst are beneficial to the adsorption of SF_(6)and intermediates,while the doping of Ni can significantly increase the content of oxygen vacancies to improve the degradation.Meanwhile,when NiO-CeO_(2)is activated by DBD,the free O·can further promote the degradation.It is this coupling effect that leads to the high efficiency and low energy consumption of SF_(6)degradation under mild conditions.It can be expected that this coupling technology route will have a good application prospect in the field of SF_(6)treatment.展开更多
Based on a homemade novel dielectric barrier discharge actuator with a rotating high-voltage electrode, this study investigates the influence of electrode rotating speed on the discharge characteristics, and the mecha...Based on a homemade novel dielectric barrier discharge actuator with a rotating high-voltage electrode, this study investigates the influence of electrode rotating speed on the discharge characteristics, and the mechanisms of discharge process under rotary conditions are discussed. The results demonstrate that when the high-voltage electrode is rotating,the distribution patterns of dielectric barrier discharge and the parameters of micro-discharge channels exhibit significant changes. Under a low rotating speed, the discharge patterns present as a series of separated discharge channels, resulting in uniform charge distribution but uneven electric field distribution in the gap. As the rotating speed increases, the electric field and the discharge channels will be affected by the rotation, so the electric field is more evenly distributed in the gap, and the discharge mode changes to a quasi-uniform discharge. With increasing distance from the rotation axis, the electric field strength gradually decreases, and the electric field force experienced by the micro-discharge channels during its formation weakens. Consequently, the average size of the micro-discharge channels increases, indicating that these channels are gradually stretched. The rotation of the electrode generates a significant number of accumulated charges, impacting the number of micro-discharge channels. The number of micro-discharge channels at the center of the electrode increases with rotating speed;however, due to channel stretching, the average size of the micro-discharge channels at the edge of the electrode also increases, leading to a decrease in their overall quantity. The research results reveal the significant impact of the electrode rotation on the characteristics of discharge channels, providing a theoretical basis for further optimal design of the rotating dielectric barrier discharge in various application.展开更多
This article carries out synthetic measurements and analysis of the characteristics of the asymmetric surface dielectric barrier discharge plasma aerodynamic actuation. The rotational and vibrational temperatures of a...This article carries out synthetic measurements and analysis of the characteristics of the asymmetric surface dielectric barrier discharge plasma aerodynamic actuation. The rotational and vibrational temperatures of an N2 （ C3 Ⅱu ） molecule are measured in terms of the optical emission spectra from the N2 second positive system. A simplified collision-radiation model for N2 （C）and N2 ＋ （B）is established on the basis of the ratio of emission intensity at 391.4 nm to that at 380.5 nm and the ratio of emission intensity at 371. 1 nm to that at 380.5 nm for calculating temporal and spatial averaged electron temperatures and densities. Under one atmosphere pressure, the electron temperature and density are on the order of 1.6 eV and 10H cm-3 respectively. The body force induced by the plasma aerodynamic actuation is on the order of tens of mN while the induced flow velocity is around 1.3 m/s. Starting vortex is firstly induced by the actuation ; then it develops into a near-wall jet, about 70 mm downstream of the actuator. Unsteady plasma aerodynamic actuation might stimulate more vortexes in the flow field. The induced flow direction by nanosecond discharge plasma aerodynamic actuation is not parallel, but vertical to the dielectric layer surface.展开更多
Aircraft icing has long been a plague to aviation for its serious threat to flight safety. Even though lots of methods for anti-icing have been in use or studied for quite a long time, new methods are still in great d...Aircraft icing has long been a plague to aviation for its serious threat to flight safety. Even though lots of methods for anti-icing have been in use or studied for quite a long time, new methods are still in great demand for both civil and military aircraft. The current study in this paper uses widely used Dielectric Barrier Discharge（DBD） plasma actuation to anti-ice on a NACA0012 airfoil model with a chord length of 53.5 cm in a closed-circuit icing wind tunnel. An actuator was installed at the leading edge of the airfoil model, and actuated by a pulsed low-temperature plasma power source. The actuator has two types of layout, a striped electrode layout and a meshy electrode layout.The ice accretion process or anti-icing process was recorded by a CCD camera and an infrared camera. Instantaneous pictures and infrared contours show that both types of DBD plasma actuators have the ability for anti-ice under a freestream velocity of 90 m/s, a static temperature of -7℃,an Median Volume droplet Diameter（MVD） of 20 lm, and an Liquid Water Content（LWC） of 0.5 g/m^3. The detected variations of temperatures with time at specific locations reveal that the temperatures oscillate for some time after spraying at first, and then tend to be nearly constant values.This shows that the key point of the anti-icing mechanism with DBD plasma actuation is to achieve a thermal equilibrium on the model surface. Besides, the power consumption in the anti-icing process was estimated in this paper by Lissajous figures measured by an oscilloscope, and it is lower than those of existing anti-icing methods. The experimental results presented in this paper indicate that the DBD plasma anti-icing method is a promising technique in the future.展开更多
Flow control using surface Dielectric Barrier Discharge(DBD)plasma actuators driven by a sinusoidal alternating-current power supply has gained significant attention from the aeronautic industry.The induced flow field...Flow control using surface Dielectric Barrier Discharge(DBD)plasma actuators driven by a sinusoidal alternating-current power supply has gained significant attention from the aeronautic industry.The induced flow field of the plasma actuator,with the starting vortex in the wall jet,plays an important role in flow control.However,the energy consumed for producing the induced flow field is only a small fraction of the total energy utilized by the plasma actuator,and most of the total energy is used in gas heating and dielectric heating.Therefore,an in-depth analysis of the thermal characteristics of the plasma actuator is the key to develop its potential capability further.In addition,compared with the investigation on the aerodynamic characteristics of the plasma actuator,there is a relative lack of detail in the study of its thermal characteristics.Understanding the thermal characteristics of the plasma actuator is of great interest for providing a deeper insight into the underlying working principles,advancing its numerical simulation model,prolonging its life,and achieving several potential engineering applications,such as antiicing and deicing.The present paper reviews the thermal characteristics of the plasma actuator,summarizes the influence of the dielectric film and actuation parameters on heating,and discusses the formation and transfer mechanism of the induced heating based on the discharge regimes of the plasma actuator in one cycle.展开更多
MnOx（0.4）-CeO2 was investigated for soot oxidation assisted with a pulse dielectric barrier discharge （DBD）. The catalysts were evaluated and characterized with TPO （temperature programmed oxidation）, X-ray diff...MnOx（0.4）-CeO2 was investigated for soot oxidation assisted with a pulse dielectric barrier discharge （DBD）. The catalysts were evaluated and characterized with TPO （temperature programmed oxidation）, X-ray diffraction （XRD）, Raman and X-ray photo- electron spectroscopy （XPS）. The ignition temperature Ti for soot oxidation decreased from 240.8 to 216.4 ℃ with the increase of the pulse DBD frequencies from 50 to 400 Hz, lower than that of the case without pulse DBD present （253.4 ℃）. The results of XRD, Raman and XPS agreed well with the TPO activities of MnOx（0.4）-CeO2 towards soot oxidation. More solid solution of ceria and manganese, and surface reactive species including 02 , O and Mn4＋ were responsible for the enhancement of soot oxidation due to pulse DBD injection in the present study. For solid solution favors to the activation and transformation of those species, which are be- lieved to be involved in the soot oxidation in a hybrid catalysis-plasma.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
The humidity effects on the benzene decomposition process were investigated by the dielectric barrier discharge（DBD） plasma reactor.The results showed that the water vapor played an important role in the benzene oxi...The humidity effects on the benzene decomposition process were investigated by the dielectric barrier discharge（DBD） plasma reactor.The results showed that the water vapor played an important role in the benzene oxidation process.It was found that there was an optimum humidity value for the benzene removal efficiency,and at around 60% relative humidity（RH）,the optimum benzene removal efficiency was achieved.At a SIE of 378 J/L,the removal efficiency was 66% at 0% RH,while the removal efficiency reached 75.3% at 60% RH and dropped to 69% at 80% RH.Furthermore,the addition of water inhibited the formation of ozone and NO2 remarkably.Both of the concentrations of ozone and NO2 decreased with increasing of the RH at the same specific input energy.At a SIE of 256 J/L,the concentrations of ozone and NO2 were 5.4 mg/L and 1791 ppm under dry conditions,whereas they were only 3.4 mg/L and 1119 ppm at 63.5%RH,respectively.Finally,the outlet gas after benzene degradation was qualitatively analyzed by FT-IR and GC-MS to determine possible intermediate byproducts.The results suggested that the byproducts in decomposition of benzene primarily consisted of phenol and substitutions of phenol.Based on these byproducts a benzene degradation mechanism was proposed.展开更多
The decomposition of trifluoromethane （CHF3） was carried out using non-thermal plasma generated in a dielectric barrier discharge （DBD） reactor. The effects of reactor temperature, electric power, initial concentr...The decomposition of trifluoromethane （CHF3） was carried out using non-thermal plasma generated in a dielectric barrier discharge （DBD） reactor. The effects of reactor temperature, electric power, initial concentration and oxygen content were examined. The DBD reactor was able to completely destroy CHF3 with alumina beads as a packing material. The decomposition efficiency increased with increasing electric power and reactor temperature. The destruction of CHF3 gradually increased with the addition of O2 up to 2%, but further increase in the oxygen content led to a decrease in the decomposition efficiency. The degradation pathways were explained with the identified by-products. The main by-products from CHF3 were found to be COF2, CF4, CO2 and CO although the COF2 and CF4 disappeared when the plasma were combined with alumina catalyst.展开更多
Dielectric barrier discharge （DBD） was used for the generation of hydrogen from ethanol reforming. Effects of reaction conditions, such as vaporization temperature, ethanol flow rate, water/ethanol ratio, and additi...Dielectric barrier discharge （DBD） was used for the generation of hydrogen from ethanol reforming. Effects of reaction conditions, such as vaporization temperature, ethanol flow rate, water/ethanol ratio, and addition of oxygen, on the ethanol conversion and hydrogen yield, were studied. The results showed that the increase of ethanol flow rate decreased ethanol conversion and hydrogen yield, and high water/ethanol ratio and addition of oxygen were advantageous. Ethanol conversion and hydrogen yield increased with the vaporization room temperature up to the maximum at first, and then decreased slightly. The maximum hydrogen yield of 31.8% was obtained at an ethanol conversion of 88.4% under the optimum operation conditions of vaporization room temperature of 120 ？C, ethanol flux of 0.18 mL/min, water/ethanol ratio of 7.7 and oxygen volume concentration of 13.3%.展开更多
A coaxial dielectric barrier discharge（DBD） reactor with double layer dielectric barriers has been developed for exhaust gas treatment and excited either by AC power or nanosecond（ns）pulse to generate atmospheric ...A coaxial dielectric barrier discharge（DBD） reactor with double layer dielectric barriers has been developed for exhaust gas treatment and excited either by AC power or nanosecond（ns）pulse to generate atmospheric pressure plasma. The comparative study on the discharge characteristics of the discharge uniformity, power deposition, energy efficiency, and operation temperature between AC and ns pulsed coaxial DBD is carried out in terms of optical and electrical characteristics and operation temperature for optimizing the coaxial DBD reactor performance. The voltages across the air gap and dielectric layer and the conduction and displacement currents are extracted from the applied voltages and measured currents of AC and ns pulsed coaxial DBDs for the calculation of the power depositions and energy efficiencies through an equivalent electrical model. The discharge uniformity and operating temperature of the coaxial DBD reactor are monitored and analyzed by optical images and infrared camera. A heat conduction model is used to calculate the temperature of the internal quartz tube. It is found that the ns pulsed coaxial DBD has a much higher instantaneous power deposition in plasma, a lower total power consumption, and a higher energy efficiency compared with that excited by AC power and is more homogeneous and stable. The temperature of the outside wall of the AC and ns pulse excited coaxial DBD reaches 158 ℃ and 64.3 ℃ after 900 s operation, respectively.The experimental results on the comparison of the discharge characteristics of coaxial DBDs excited by different powers are significant for understanding of the mechanism of DBDs,reducing energy loss, and optimizing the performance of coaxial DBD in industrial applications.展开更多
Dielectric barrier discharge （DBD） plasma was utilized to oxidize NO contained in the exhaust gas to NO2, ultimately improve the selective catalytic reduction of nitrogen oxides （NOx）. In the one case, DBD was cre...Dielectric barrier discharge （DBD） plasma was utilized to oxidize NO contained in the exhaust gas to NO2, ultimately improve the selective catalytic reduction of nitrogen oxides （NOx）. In the one case, DBD was created directly in the exhaust gas （direct application）, and in the an other case, ozone produced by DBD was injected into the exhaust gas （indirect application）. A comparative study between such direct and indirect applications of DBD plasma was made in terms of the NOx removal efficiency and the energy consumption. The NO2 content in the exhaust gas was changed by the voltage applied to the DBD device （for direct application） or by the amount of ozone added to the exhaust gas （for indirect application）. In both cases, NO was easily oxidized to NO2, and the change in NO2 content largely affected the NOx removal performance of the catalytic reactor placed downstream, where both NO and NO2 were reduced to N2 in the presence of ammonia as the reducing agent. The experiments were primarily concerned with the effect of reaction temperature on the catalytic NOx reduction at various NO2 contents. The direct and indirect applications of DBD were found to remarkably improve the catalytic NOx reduction, especially at low temperatures.展开更多
Flow separation, as an aerodynamic phenomenon, occurs in specific conditions. The conditions are studied in a wind tunnel on different airfoils. The phenomenon can be delayed or suppressed by exerting an external mome...Flow separation, as an aerodynamic phenomenon, occurs in specific conditions. The conditions are studied in a wind tunnel on different airfoils. The phenomenon can be delayed or suppressed by exerting an external momentum to the flow. Dielectric barrier discharge actuators arranged in a row of 8 and perpendicular to the flow direction can delay flow separation by exerting the momentum. In this study, a mathematical model is developed to predict a parameter, which is utilized to represent flow separation on an NACA0012 airfoil. The model is based on the neurofuzzy method applied to experimental datasets. The neuro model is trained in different flow conditions and the parameter is measured by pressure sensors.展开更多
Modification of the surface properties of polyethylene （PE） films is studied using air dielectric barrier discharge at atmospheric pressure. The treated samples are examined by Water contact angle measurements, Four...Modification of the surface properties of polyethylene （PE） films is studied using air dielectric barrier discharge at atmospheric pressure. The treated samples are examined by Water contact angle measurements, Fourier transform infrared attenuated total reflection spectroscopy （FTIR-ATR）, X-ray photoelectron spectroscopy （XPS） and scanning electron microscopy （SEM）. With the increase in treating time, the water contact angle changes from 93.2° before treatment to a minimum of 53.3° after a treatment for 50 s. Both ATR and XPS results show some oxidized species are introduced into the sample surface by the plasma treatment and the tendency of the water contact angle with the treating time is the same as that of oxygen concentration on the treated sample surface. SEM result shows the surface roughness of PE samples increases with the treatment time increasing.展开更多
In this study, nanostructured Fe powders were synthesized following 10 hours of high-energy ball milling with a superimposed dielectric barrier discharge plasma （DBDP）. The mean size of the milled powder was approxi...In this study, nanostructured Fe powders were synthesized following 10 hours of high-energy ball milling with a superimposed dielectric barrier discharge plasma （DBDP）. The mean size of the milled powder was approximately 100 nm with an average grain size of 16.2 nm. The influence of DBDP on the underlying grain refinement mechanisms during ball milling was investigated by scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, X-ray diffraction （XRD） and BET methods. Our results show that the Fe particles displayed an extraordinary plasticity during the early milling stages under the action of DBDP, and that the plastic deformation experienced by the Fe particles during this stage was more severe than that present in normal milling. A high concentration of spherical Fe particles, approximately 50-100 nm in diameter, was documented via TEM. We propose that these spherical particles were generated via high temperature disintegration as a result of DBDP electron bombardment during ball milling. Our results suggest that it may be possible to significantly refine metallic powders during milling via the superimposition of DBDP.展开更多
In this paper, a cylindrical dielectric barrier discharge （DBD） reactor has been developed for the conversion of methane into hydrogen and other valuable chemicals. The effects of a wide range of processing paramete...In this paper, a cylindrical dielectric barrier discharge （DBD） reactor has been developed for the conversion of methane into hydrogen and other valuable chemicals. The effects of a wide range of processing parameters including discharge power, residence time and frequency on the performance of plasma methane conversion reaction have been investigated. The results show that the CH4 DBD could be characterized as a typical filamentary discharge with a microdis-charge zone in each half-cycle of the applied voltage. The conversion of CH4 reaches a maximum of 25.2% at a feed flow rate of 50 mL-min-1, a discharge power of 45 W and an excitation frequency of 20 kHz. It is found that the residence time of methane in the discharge zone has the most significant effect on both methane conversion and hydrogen yield, which are significantly higher at higher residence time.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
The direct conversion of methane using a dielectric barrier discharge has been experimentally studied. Experiments with different values of flow rates and discharge voltages have been performed to investigate the effe...The direct conversion of methane using a dielectric barrier discharge has been experimentally studied. Experiments with different values of flow rates and discharge voltages have been performed to investigate the effects on the conversion and reaction products both qualitatively and quantitatively. Experimental results indicate that the maximum conversion of methane has been 80% at an input flow rate of 5 ml/min and a discharge voltage of 4 kV. Experimental results also show that the optimum condition has occurred at a high discharge voltage and higher input flow rate. In terms of product distribution, a higher flow rate or shorter residence time can increase the selectivity for higher hydrocarbons. No hydrocarbon product was detected using the thermal method, except hydrogen and carbon. Increasing selectivity for ethane was found when Pt and Ru catalysts presented in the plasma reaction. Hydrogenation of acetylene in the catalyst surface could have been the reason for this phenomenon as the selectivity for acetylene in the products was decreasing.展开更多
Plasma flow control（PFC） is a promising active flow control method with its unique advantages including the absence of moving components, fast response, easy implementation, and stable operation. The effectiveness o...Plasma flow control（PFC） is a promising active flow control method with its unique advantages including the absence of moving components, fast response, easy implementation, and stable operation. The effectiveness of plasma flow control by microsecond dielectric barrier discharge（μs-DBD）, and by nanosecond dielectric barrier discharge（NS-DBD） are compared through the wind tunnel tests, showing a similar performance between μs-DBD and NS-DBD. Furthermore, theμs-DBD is implemented on an unmanned aerial vehicle（UAV）, which is a scaled model of a newly developed amphibious plane. The wingspan of the model is 2.87 m, and the airspeed is no less than 30 m/s. The flight data, static pressure data,and Tufts images are recorded and analyzed in detail. Results of the flight test show that the μs-DBD works well on board without affecting the normal operation of the UAV model. When the actuators are turned on, the stall angle and maximum lift coefficient can be improved by 1.3° and 10.4%, and the static pressure at the leading edge of the wing can be reduced effectively in a proper range of angle of attack, which shows the ability of μs-DBD to act as plasma slats. The rolling moment produced by left-side μs-DBD actuation is greater than that produced by the maximum deflection of ailerons,which indicates the potential of μs-DBD to act as plasma ailerons. The results verify the feasibility and efficacy of μs-DBD plasma flow control in a real flight and lay the foundation for the full-sized airplane application.展开更多
The physicochemical processes of dielectric barrier discharge （DBD） such as insitu formation of chemically active species and emission of ultraviolet （UV）/visible light were utilized for the treatment of a simulat...The physicochemical processes of dielectric barrier discharge （DBD） such as insitu formation of chemically active species and emission of ultraviolet （UV）/visible light were utilized for the treatment of a simulated wastewater formed with Acid Red 4 as the model organic contaminant. The chemically active species （mostly ozone） produced in the DBD reactor were well distributed in the wastewater using a porous gas diffuser, thereby increasing the gas-liquid contact area. For the purpose of making the best use of the light emission, a titanium oxide-based photocatalyst was incorporated in the wastewater treating system. The experimental parameters chosen were the voltage applied to the DBD reactor, the initial pH of the wastewater, and the concentration of hydrogen peroxide added to the wastewater. The results have clearly shown that the present system capable of degrading organic contaminants in two ways （photocatalysis and ozonation） may be a promising wastewater treatment technology.展开更多
基金financial support from the National Natural Science Foundation of China(U23A20105).
文摘How to achieve low energy consumption and high degradation efficiency(DRE)under mild conditions is an important issue in the field of sulfur hexafluoride(SF_(6))treatment.In this work,a new route of SF_(6)degradation promoted by Ni-doped ceria(NiO-CeO_(2))in a packed bed dielectric barrier discharge(PB-DBD)was proposed.The effects of Ni/Ce molar ratio,input power,SF_(6)concentration and flow rate on the DRE of SF_(6)were investigated.Compared with DBD or CeO_(2)-DBD alone,the combination of DBD and NiO-CeO_(2)can significantly promote the SF_(6)degradation at lower input power.The experimental results show that when the dosage of catalyst 1.5NiO-CeO_(2)(Ni/Ce mole ratio is 1.5%)is 5 g,DBD input power is 50 W and SF_(6)(1.5%SF_(6)/98.5%Ar)flow rate is 100 ml·min-1,the highest DRE can reach 97.7%and the energy yield can reach 11.5 g·(kW·h)-1.Adjusting the catalyst dosage according to the flux of SF_(6)(e.g.,using 10 g catalyst to degrade SF_(6)with a concentration of 1.5%and a flow rate of 80 ml·min-1),the DRE of nearly 99%can be achieved for a long time,which is crucial for industrial application.The mechanism deduction shows that the rich surface and mesopores of the catalyst are beneficial to the adsorption of SF_(6)and intermediates,while the doping of Ni can significantly increase the content of oxygen vacancies to improve the degradation.Meanwhile,when NiO-CeO_(2)is activated by DBD,the free O·can further promote the degradation.It is this coupling effect that leads to the high efficiency and low energy consumption of SF_(6)degradation under mild conditions.It can be expected that this coupling technology route will have a good application prospect in the field of SF_(6)treatment.
基金Project supported by the National Natural Science Foundation of China (Grant No. 52377135)。
文摘Based on a homemade novel dielectric barrier discharge actuator with a rotating high-voltage electrode, this study investigates the influence of electrode rotating speed on the discharge characteristics, and the mechanisms of discharge process under rotary conditions are discussed. The results demonstrate that when the high-voltage electrode is rotating,the distribution patterns of dielectric barrier discharge and the parameters of micro-discharge channels exhibit significant changes. Under a low rotating speed, the discharge patterns present as a series of separated discharge channels, resulting in uniform charge distribution but uneven electric field distribution in the gap. As the rotating speed increases, the electric field and the discharge channels will be affected by the rotation, so the electric field is more evenly distributed in the gap, and the discharge mode changes to a quasi-uniform discharge. With increasing distance from the rotation axis, the electric field strength gradually decreases, and the electric field force experienced by the micro-discharge channels during its formation weakens. Consequently, the average size of the micro-discharge channels increases, indicating that these channels are gradually stretched. The rotation of the electrode generates a significant number of accumulated charges, impacting the number of micro-discharge channels. The number of micro-discharge channels at the center of the electrode increases with rotating speed;however, due to channel stretching, the average size of the micro-discharge channels at the edge of the electrode also increases, leading to a decrease in their overall quantity. The research results reveal the significant impact of the electrode rotation on the characteristics of discharge channels, providing a theoretical basis for further optimal design of the rotating dielectric barrier discharge in various application.
基金National Natural Science Foundation of China(50906100)China Postdoctoral Science Foundation(20090450373)
文摘This article carries out synthetic measurements and analysis of the characteristics of the asymmetric surface dielectric barrier discharge plasma aerodynamic actuation. The rotational and vibrational temperatures of an N2 （ C3 Ⅱu ） molecule are measured in terms of the optical emission spectra from the N2 second positive system. A simplified collision-radiation model for N2 （C）and N2 ＋ （B）is established on the basis of the ratio of emission intensity at 391.4 nm to that at 380.5 nm and the ratio of emission intensity at 371. 1 nm to that at 380.5 nm for calculating temporal and spatial averaged electron temperatures and densities. Under one atmosphere pressure, the electron temperature and density are on the order of 1.6 eV and 10H cm-3 respectively. The body force induced by the plasma aerodynamic actuation is on the order of tens of mN while the induced flow velocity is around 1.3 m/s. Starting vortex is firstly induced by the actuation ; then it develops into a near-wall jet, about 70 mm downstream of the actuator. Unsteady plasma aerodynamic actuation might stimulate more vortexes in the flow field. The induced flow direction by nanosecond discharge plasma aerodynamic actuation is not parallel, but vertical to the dielectric layer surface.
基金supported by the National Natural Science Foundation of China (No.11472221)
文摘Aircraft icing has long been a plague to aviation for its serious threat to flight safety. Even though lots of methods for anti-icing have been in use or studied for quite a long time, new methods are still in great demand for both civil and military aircraft. The current study in this paper uses widely used Dielectric Barrier Discharge（DBD） plasma actuation to anti-ice on a NACA0012 airfoil model with a chord length of 53.5 cm in a closed-circuit icing wind tunnel. An actuator was installed at the leading edge of the airfoil model, and actuated by a pulsed low-temperature plasma power source. The actuator has two types of layout, a striped electrode layout and a meshy electrode layout.The ice accretion process or anti-icing process was recorded by a CCD camera and an infrared camera. Instantaneous pictures and infrared contours show that both types of DBD plasma actuators have the ability for anti-ice under a freestream velocity of 90 m/s, a static temperature of -7℃,an Median Volume droplet Diameter（MVD） of 20 lm, and an Liquid Water Content（LWC） of 0.5 g/m^3. The detected variations of temperatures with time at specific locations reveal that the temperatures oscillate for some time after spraying at first, and then tend to be nearly constant values.This shows that the key point of the anti-icing mechanism with DBD plasma actuation is to achieve a thermal equilibrium on the model surface. Besides, the power consumption in the anti-icing process was estimated in this paper by Lissajous figures measured by an oscilloscope, and it is lower than those of existing anti-icing methods. The experimental results presented in this paper indicate that the DBD plasma anti-icing method is a promising technique in the future.
基金support by the National Natural Science Foundation of China(No.11902336)State Key Laboratory of Aerodynamics Foundation of China(Nos.SKLA2019020201,JBKYC190103)+1 种基金CARDC Fundamental and Frontier Technology Research Fund,China(No.PJD20180144)China Scholarship Council.
文摘Flow control using surface Dielectric Barrier Discharge(DBD)plasma actuators driven by a sinusoidal alternating-current power supply has gained significant attention from the aeronautic industry.The induced flow field of the plasma actuator,with the starting vortex in the wall jet,plays an important role in flow control.However,the energy consumed for producing the induced flow field is only a small fraction of the total energy utilized by the plasma actuator,and most of the total energy is used in gas heating and dielectric heating.Therefore,an in-depth analysis of the thermal characteristics of the plasma actuator is the key to develop its potential capability further.In addition,compared with the investigation on the aerodynamic characteristics of the plasma actuator,there is a relative lack of detail in the study of its thermal characteristics.Understanding the thermal characteristics of the plasma actuator is of great interest for providing a deeper insight into the underlying working principles,advancing its numerical simulation model,prolonging its life,and achieving several potential engineering applications,such as antiicing and deicing.The present paper reviews the thermal characteristics of the plasma actuator,summarizes the influence of the dielectric film and actuation parameters on heating,and discusses the formation and transfer mechanism of the induced heating based on the discharge regimes of the plasma actuator in one cycle.
基金supported by National Natural Science Foundation of China(51108187,50978103,21207039)Guangdong High Education Engineering Technology Research Center for Air Pollution Control Program(GCZX-A0903)the Fundamental Research Funds for the Central Universities(2012ZM0041)
文摘MnOx（0.4）-CeO2 was investigated for soot oxidation assisted with a pulse dielectric barrier discharge （DBD）. The catalysts were evaluated and characterized with TPO （temperature programmed oxidation）, X-ray diffraction （XRD）, Raman and X-ray photo- electron spectroscopy （XPS）. The ignition temperature Ti for soot oxidation decreased from 240.8 to 216.4 ℃ with the increase of the pulse DBD frequencies from 50 to 400 Hz, lower than that of the case without pulse DBD present （253.4 ℃）. The results of XRD, Raman and XPS agreed well with the TPO activities of MnOx（0.4）-CeO2 towards soot oxidation. More solid solution of ceria and manganese, and surface reactive species including 02 , O and Mn4＋ were responsible for the enhancement of soot oxidation due to pulse DBD injection in the present study. For solid solution favors to the activation and transformation of those species, which are be- lieved to be involved in the soot oxidation in a hybrid catalysis-plasma.
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 National Natural Science Foundation of China(Nos.11205007 and 11205029)
文摘The humidity effects on the benzene decomposition process were investigated by the dielectric barrier discharge（DBD） plasma reactor.The results showed that the water vapor played an important role in the benzene oxidation process.It was found that there was an optimum humidity value for the benzene removal efficiency,and at around 60% relative humidity（RH）,the optimum benzene removal efficiency was achieved.At a SIE of 378 J/L,the removal efficiency was 66% at 0% RH,while the removal efficiency reached 75.3% at 60% RH and dropped to 69% at 80% RH.Furthermore,the addition of water inhibited the formation of ozone and NO2 remarkably.Both of the concentrations of ozone and NO2 decreased with increasing of the RH at the same specific input energy.At a SIE of 256 J/L,the concentrations of ozone and NO2 were 5.4 mg/L and 1791 ppm under dry conditions,whereas they were only 3.4 mg/L and 1119 ppm at 63.5%RH,respectively.Finally,the outlet gas after benzene degradation was qualitatively analyzed by FT-IR and GC-MS to determine possible intermediate byproducts.The results suggested that the byproducts in decomposition of benzene primarily consisted of phenol and substitutions of phenol.Based on these byproducts a benzene degradation mechanism was proposed.
基金supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF)funded by the Ministry of Education,Science and Technology (Grant Number 2010-0021672)
文摘The decomposition of trifluoromethane （CHF3） was carried out using non-thermal plasma generated in a dielectric barrier discharge （DBD） reactor. The effects of reactor temperature, electric power, initial concentration and oxygen content were examined. The DBD reactor was able to completely destroy CHF3 with alumina beads as a packing material. The decomposition efficiency increased with increasing electric power and reactor temperature. The destruction of CHF3 gradually increased with the addition of O2 up to 2%, but further increase in the oxygen content led to a decrease in the decomposition efficiency. The degradation pathways were explained with the identified by-products. The main by-products from CHF3 were found to be COF2, CF4, CO2 and CO although the COF2 and CF4 disappeared when the plasma were combined with alumina catalyst.
基金supported by the National Natural Science Foundation of China No.20606023
文摘Dielectric barrier discharge （DBD） was used for the generation of hydrogen from ethanol reforming. Effects of reaction conditions, such as vaporization temperature, ethanol flow rate, water/ethanol ratio, and addition of oxygen, on the ethanol conversion and hydrogen yield, were studied. The results showed that the increase of ethanol flow rate decreased ethanol conversion and hydrogen yield, and high water/ethanol ratio and addition of oxygen were advantageous. Ethanol conversion and hydrogen yield increased with the vaporization room temperature up to the maximum at first, and then decreased slightly. The maximum hydrogen yield of 31.8% was obtained at an ethanol conversion of 88.4% under the optimum operation conditions of vaporization room temperature of 120 ？C, ethanol flux of 0.18 mL/min, water/ethanol ratio of 7.7 and oxygen volume concentration of 13.3%.
基金supported by National Natural Science Foundation of China(Nos.51777091 and 51677083)
文摘A coaxial dielectric barrier discharge（DBD） reactor with double layer dielectric barriers has been developed for exhaust gas treatment and excited either by AC power or nanosecond（ns）pulse to generate atmospheric pressure plasma. The comparative study on the discharge characteristics of the discharge uniformity, power deposition, energy efficiency, and operation temperature between AC and ns pulsed coaxial DBD is carried out in terms of optical and electrical characteristics and operation temperature for optimizing the coaxial DBD reactor performance. The voltages across the air gap and dielectric layer and the conduction and displacement currents are extracted from the applied voltages and measured currents of AC and ns pulsed coaxial DBDs for the calculation of the power depositions and energy efficiencies through an equivalent electrical model. The discharge uniformity and operating temperature of the coaxial DBD reactor are monitored and analyzed by optical images and infrared camera. A heat conduction model is used to calculate the temperature of the internal quartz tube. It is found that the ns pulsed coaxial DBD has a much higher instantaneous power deposition in plasma, a lower total power consumption, and a higher energy efficiency compared with that excited by AC power and is more homogeneous and stable. The temperature of the outside wall of the AC and ns pulse excited coaxial DBD reaches 158 ℃ and 64.3 ℃ after 900 s operation, respectively.The experimental results on the comparison of the discharge characteristics of coaxial DBDs excited by different powers are significant for understanding of the mechanism of DBDs,reducing energy loss, and optimizing the performance of coaxial DBD in industrial applications.
文摘Dielectric barrier discharge （DBD） plasma was utilized to oxidize NO contained in the exhaust gas to NO2, ultimately improve the selective catalytic reduction of nitrogen oxides （NOx）. In the one case, DBD was created directly in the exhaust gas （direct application）, and in the an other case, ozone produced by DBD was injected into the exhaust gas （indirect application）. A comparative study between such direct and indirect applications of DBD plasma was made in terms of the NOx removal efficiency and the energy consumption. The NO2 content in the exhaust gas was changed by the voltage applied to the DBD device （for direct application） or by the amount of ozone added to the exhaust gas （for indirect application）. In both cases, NO was easily oxidized to NO2, and the change in NO2 content largely affected the NOx removal performance of the catalytic reactor placed downstream, where both NO and NO2 were reduced to N2 in the presence of ammonia as the reducing agent. The experiments were primarily concerned with the effect of reaction temperature on the catalytic NOx reduction at various NO2 contents. The direct and indirect applications of DBD were found to remarkably improve the catalytic NOx reduction, especially at low temperatures.
基金co-supported by University of Tehran and the Dana Research Laboratory of Amirkabir University of Technology in Iran
文摘Flow separation, as an aerodynamic phenomenon, occurs in specific conditions. The conditions are studied in a wind tunnel on different airfoils. The phenomenon can be delayed or suppressed by exerting an external momentum to the flow. Dielectric barrier discharge actuators arranged in a row of 8 and perpendicular to the flow direction can delay flow separation by exerting the momentum. In this study, a mathematical model is developed to predict a parameter, which is utilized to represent flow separation on an NACA0012 airfoil. The model is based on the neurofuzzy method applied to experimental datasets. The neuro model is trained in different flow conditions and the parameter is measured by pressure sensors.
基金the Science Development Foundation of the Engineering and Technical College of Chengdu University of Technology of China(Nos.C122007025,C122007018)
文摘Modification of the surface properties of polyethylene （PE） films is studied using air dielectric barrier discharge at atmospheric pressure. The treated samples are examined by Water contact angle measurements, Fourier transform infrared attenuated total reflection spectroscopy （FTIR-ATR）, X-ray photoelectron spectroscopy （XPS） and scanning electron microscopy （SEM）. With the increase in treating time, the water contact angle changes from 93.2° before treatment to a minimum of 53.3° after a treatment for 50 s. Both ATR and XPS results show some oxidized species are introduced into the sample surface by the plasma treatment and the tendency of the water contact angle with the treating time is the same as that of oxygen concentration on the treated sample surface. SEM result shows the surface roughness of PE samples increases with the treatment time increasing.
基金supported by the National Natural Science Foundation of China (No.51177008)Natural Science Fundation of Fujian Province(No. 2012J01228)+1 种基金the Program for New Century Excellent Talents in Fujian Province University (No. NCETFJ–Z80136)Fujian Provincial Department of Science & Technology (Nos. 2011J01324 and JK2010030)
文摘In this study, nanostructured Fe powders were synthesized following 10 hours of high-energy ball milling with a superimposed dielectric barrier discharge plasma （DBDP）. The mean size of the milled powder was approximately 100 nm with an average grain size of 16.2 nm. The influence of DBDP on the underlying grain refinement mechanisms during ball milling was investigated by scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, X-ray diffraction （XRD） and BET methods. Our results show that the Fe particles displayed an extraordinary plasticity during the early milling stages under the action of DBDP, and that the plastic deformation experienced by the Fe particles during this stage was more severe than that present in normal milling. A high concentration of spherical Fe particles, approximately 50-100 nm in diameter, was documented via TEM. We propose that these spherical particles were generated via high temperature disintegration as a result of DBDP electron bombardment during ball milling. Our results suggest that it may be possible to significantly refine metallic powders during milling via the superimposition of DBDP.
文摘In this paper, a cylindrical dielectric barrier discharge （DBD） reactor has been developed for the conversion of methane into hydrogen and other valuable chemicals. The effects of a wide range of processing parameters including discharge power, residence time and frequency on the performance of plasma methane conversion reaction have been investigated. The results show that the CH4 DBD could be characterized as a typical filamentary discharge with a microdis-charge zone in each half-cycle of the applied voltage. The conversion of CH4 reaches a maximum of 25.2% at a feed flow rate of 50 mL-min-1, a discharge power of 45 W and an excitation frequency of 20 kHz. It is found that the residence time of methane in the discharge zone has the most significant effect on both methane conversion and hydrogen yield, which are significantly higher at higher residence time.
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The direct conversion of methane using a dielectric barrier discharge has been experimentally studied. Experiments with different values of flow rates and discharge voltages have been performed to investigate the effects on the conversion and reaction products both qualitatively and quantitatively. Experimental results indicate that the maximum conversion of methane has been 80% at an input flow rate of 5 ml/min and a discharge voltage of 4 kV. Experimental results also show that the optimum condition has occurred at a high discharge voltage and higher input flow rate. In terms of product distribution, a higher flow rate or shorter residence time can increase the selectivity for higher hydrocarbons. No hydrocarbon product was detected using the thermal method, except hydrogen and carbon. Increasing selectivity for ethane was found when Pt and Ru catalysts presented in the plasma reaction. Hydrogenation of acetylene in the catalyst surface could have been the reason for this phenomenon as the selectivity for acetylene in the products was decreasing.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51336011 and 51607188)the China Postdoctoral Science Foundation(Grant No.2014M562446)the PhD Research Startup Foundation of Xi’an University of Technology(Grant No.256081802)
文摘Plasma flow control（PFC） is a promising active flow control method with its unique advantages including the absence of moving components, fast response, easy implementation, and stable operation. The effectiveness of plasma flow control by microsecond dielectric barrier discharge（μs-DBD）, and by nanosecond dielectric barrier discharge（NS-DBD） are compared through the wind tunnel tests, showing a similar performance between μs-DBD and NS-DBD. Furthermore, theμs-DBD is implemented on an unmanned aerial vehicle（UAV）, which is a scaled model of a newly developed amphibious plane. The wingspan of the model is 2.87 m, and the airspeed is no less than 30 m/s. The flight data, static pressure data,and Tufts images are recorded and analyzed in detail. Results of the flight test show that the μs-DBD works well on board without affecting the normal operation of the UAV model. When the actuators are turned on, the stall angle and maximum lift coefficient can be improved by 1.3° and 10.4%, and the static pressure at the leading edge of the wing can be reduced effectively in a proper range of angle of attack, which shows the ability of μs-DBD to act as plasma slats. The rolling moment produced by left-side μs-DBD actuation is greater than that produced by the maximum deflection of ailerons,which indicates the potential of μs-DBD to act as plasma ailerons. The results verify the feasibility and efficacy of μs-DBD plasma flow control in a real flight and lay the foundation for the full-sized airplane application.
文摘The physicochemical processes of dielectric barrier discharge （DBD） such as insitu formation of chemically active species and emission of ultraviolet （UV）/visible light were utilized for the treatment of a simulated wastewater formed with Acid Red 4 as the model organic contaminant. The chemically active species （mostly ozone） produced in the DBD reactor were well distributed in the wastewater using a porous gas diffuser, thereby increasing the gas-liquid contact area. For the purpose of making the best use of the light emission, a titanium oxide-based photocatalyst was incorporated in the wastewater treating system. The experimental parameters chosen were the voltage applied to the DBD reactor, the initial pH of the wastewater, and the concentration of hydrogen peroxide added to the wastewater. The results have clearly shown that the present system capable of degrading organic contaminants in two ways （photocatalysis and ozonation） may be a promising wastewater treatment technology.
