The electron drift velocity, electron energy distribution function （EEDF）, densitynormalized effective ionization coefficient and density-normalized longitudinal diffusion velocity are calculated in SF6-O2 and SFs-A...The electron drift velocity, electron energy distribution function （EEDF）, densitynormalized effective ionization coefficient and density-normalized longitudinal diffusion velocity are calculated in SF6-O2 and SFs-Air mixtures. The experimental results from a pulsed Townsend discharge are plotted for comparison with the numerical results. The reduced field strength varies from 40 Td to 500 Td （1 Townsend=10-17 V.cm2） and the SF6 concentration ranges from 10% to 100%. A Boltzmann equation associated with the two-term spherical harmonic expansion approximation is utilized to gain the swarm parameters in steady-state Townsend. Results show that the accuracy of the Boltzlnann solution with a two-term expansion in calculating the electron drift velocity, electron energy distribution function, and density-normalized effective ionization coefficient is acceptable. The effective ionization coefficient presents a distinct relationship with the SF6 content in the mixtures. Moreover, the E/Ncr values in SF6-Air mixtures are higher than those in SF6-O2 mixtures and the calculated value E/Ncr in SF6-O2 and SF6-Air mixtures is lower than the measured value in SFB-N2. Parametric studies conducted on these parameters using the Boltzmann analysis offer substantial insight into the plasma physics, as well as a basis to explore the ozone generation process.展开更多
A comprehensive dynamic model consisting of 66 reactions and 24 species is developed to investigate the dynamic characteristics of ozone generation by positive pulsed dielectric barrier discharge（DBD） using parallel...A comprehensive dynamic model consisting of 66 reactions and 24 species is developed to investigate the dynamic characteristics of ozone generation by positive pulsed dielectric barrier discharge（DBD） using parallel-plate reactor in air.The electron energy conservation equation is coupled to the electron continuity equation,the heavy species continuity equation,and Poisson＇s equation for a better description.The reliability of the model is experimentally confirmed.The model can be used to predict the temporal and spatial evolution of species,as well as streamer propagation.The simulation results show that electron density increases nearly exponentially in the direction to the anode at the electron avalanche.Streamer propagation velocity is about 5.26×104m/s from anode to cathode in the simulated condition.The primary positive ion,negative ion,and excited species are O_2~＋,O_3^-and O_2（1？g） in pulsed DBD in air,respectively.N_2 O has the largest density among nitrogen oxides.e and N_2~＋densities in the streamer head increase gradually to maximum values with the development of the streamer.Meanwhile,the O_2~＋,O,O_3,N_2（A^3Σ） and N_2 O densities reach maximum values in the vicinity of the anode.展开更多
In this paper,three dielectric barrier discharge(DBD)configurations,which were plain DBD with no packing,DBD with packed pure quartz fibers and DBD with packed loaded quartz fibers,were employed to investigate the eff...In this paper,three dielectric barrier discharge(DBD)configurations,which were plain DBD with no packing,DBD with packed pure quartz fibers and DBD with packed loaded quartz fibers,were employed to investigate the effect and catalytic mechanism of catalyst materials in a packed-bed ozone generator.From the experimental results,it was clear that the DBD configuration with packed pure fibers and packed loaded fibers promotes ozone generation.For the packed-bed reactor,ozone concentration and ozone yield were enhanced by an increase of electric field in the discharge gap with the packed-bed effect.Meanwhile,the enhancement of ozone concentration and yield for the DBD reactor packed by loaded fibers with silica nanoparticles was due to the catalysis of silica nanoparticles on the fiber surface.The adsorption of silica nanoparticles on the fiber surface can prolong the retention time of active species and enhance surface reactions.展开更多
基金supported by National Natural Science Foundation of China(Nos.11105067 and 51366012)Jiangxi Province Young Scientists(Jinggang Star)Cultivation Plan of China(No.2013BCB23008)
文摘The electron drift velocity, electron energy distribution function （EEDF）, densitynormalized effective ionization coefficient and density-normalized longitudinal diffusion velocity are calculated in SF6-O2 and SFs-Air mixtures. The experimental results from a pulsed Townsend discharge are plotted for comparison with the numerical results. The reduced field strength varies from 40 Td to 500 Td （1 Townsend=10-17 V.cm2） and the SF6 concentration ranges from 10% to 100%. A Boltzmann equation associated with the two-term spherical harmonic expansion approximation is utilized to gain the swarm parameters in steady-state Townsend. Results show that the accuracy of the Boltzlnann solution with a two-term expansion in calculating the electron drift velocity, electron energy distribution function, and density-normalized effective ionization coefficient is acceptable. The effective ionization coefficient presents a distinct relationship with the SF6 content in the mixtures. Moreover, the E/Ncr values in SF6-Air mixtures are higher than those in SF6-O2 mixtures and the calculated value E/Ncr in SF6-O2 and SF6-Air mixtures is lower than the measured value in SFB-N2. Parametric studies conducted on these parameters using the Boltzmann analysis offer substantial insight into the plasma physics, as well as a basis to explore the ozone generation process.
基金supported by National Natural Science Foundation of China(Nos.51366012 and 11105067)Jiangxi Province Young Scientists(Jinggang Star)Cultivation Plan of China(No.20133BCB23008)+1 种基金Natural Science Foundation of Jiangxi,China(No.20151BAB206047)Jiangxi Province Higher School Science and Technology Landing Plan of China(No.KJLD-14015)
文摘A comprehensive dynamic model consisting of 66 reactions and 24 species is developed to investigate the dynamic characteristics of ozone generation by positive pulsed dielectric barrier discharge（DBD） using parallel-plate reactor in air.The electron energy conservation equation is coupled to the electron continuity equation,the heavy species continuity equation,and Poisson＇s equation for a better description.The reliability of the model is experimentally confirmed.The model can be used to predict the temporal and spatial evolution of species,as well as streamer propagation.The simulation results show that electron density increases nearly exponentially in the direction to the anode at the electron avalanche.Streamer propagation velocity is about 5.26×104m/s from anode to cathode in the simulated condition.The primary positive ion,negative ion,and excited species are O_2~＋,O_3^-and O_2（1？g） in pulsed DBD in air,respectively.N_2 O has the largest density among nitrogen oxides.e and N_2~＋densities in the streamer head increase gradually to maximum values with the development of the streamer.Meanwhile,the O_2~＋,O,O_3,N_2（A^3Σ） and N_2 O densities reach maximum values in the vicinity of the anode.
基金supported by National Natural Science Foundation of China(No.51867018)Jiangxi Province’s Major Subject Academic and Technical Leader Training ProgramLeading Talent Project(No.20204BCJ22016)the Innovation Fund Designed for Graduate Students of Jiangxi Province,China(No.YC2020-S118)。
文摘In this paper,three dielectric barrier discharge(DBD)configurations,which were plain DBD with no packing,DBD with packed pure quartz fibers and DBD with packed loaded quartz fibers,were employed to investigate the effect and catalytic mechanism of catalyst materials in a packed-bed ozone generator.From the experimental results,it was clear that the DBD configuration with packed pure fibers and packed loaded fibers promotes ozone generation.For the packed-bed reactor,ozone concentration and ozone yield were enhanced by an increase of electric field in the discharge gap with the packed-bed effect.Meanwhile,the enhancement of ozone concentration and yield for the DBD reactor packed by loaded fibers with silica nanoparticles was due to the catalysis of silica nanoparticles on the fiber surface.The adsorption of silica nanoparticles on the fiber surface can prolong the retention time of active species and enhance surface reactions.
