Helium plasma jets generated by micro-hollow cathode discharge(MHCD) with the squarewave power source of different polarities are investigated in this work. The effects of positive and negative polarity pulses on the ...Helium plasma jets generated by micro-hollow cathode discharge(MHCD) with the squarewave power source of different polarities are investigated in this work. The effects of positive and negative polarity pulses on the MHCD and plasma jet were compared, and the time-resolved optical emission spectra of excited species(N_(2)^(+) and O) were studied. The results confirm that the electric field is a key factor for the propagation of the jet during the rising edge of the positive current pulse, while the gas expansion is mainly important for the jet propagation during the current stable phase. The time-resolved spectra show that the generation of specie O in the jetdriven by the electric field is more efficient.展开更多
Considering the feature of distributions of parameters within the micro-hollow cathode discharge, we use a simple method to separate the sheath region characterized by drastic changes of plasma parameters and the bulk...Considering the feature of distributions of parameters within the micro-hollow cathode discharge, we use a simple method to separate the sheath region characterized by drastic changes of plasma parameters and the bulk plasma region characterized by smooth changes of plasma parameters. A zero-dimensional chemical kinetic model is used to analyze the dissociation mechanism of CO2 in the bulk plasma region of a micro-hollow cathode discharge and is validated by comparisons with previous modeling and experimental results. The analysis of the chemical kinetic processes has shown that the electron impact dissociation and heavy species impact dissociation are dominant in different stages of the rnicro-hollow cathode discharge process for a given applied voltage. The analysis of energy consumption distributions under different applied voltages reveals that the main reason of the conversion improvement with the increase of the applied voltage is that more input energy is distributed to the heavy species impact dissociation.展开更多
In this paper,the air plasma jet produced by micro-hollow cathode discharge(MHCD)is investigated.The discharge is powered by a positive nanosecond pulse high voltage supply.The waveforms of the discharge,the images of...In this paper,the air plasma jet produced by micro-hollow cathode discharge(MHCD)is investigated.The discharge is powered by a positive nanosecond pulse high voltage supply.The waveforms of the discharge,the images of the jet,the evolution of the plasma bullet and the reactive species are obtained to analyze the characteristics of the MHCD plasma jet.It is found that the length of the plasma jet is almost proportional to the air flow rate of 2–6 slm.Two plasma bullets appear one after another during a single period of the voltage waveform,and both of the two plasma bullets are formed during the positive pulse voltage off.The propagation velocity of the two plasma bullets is on the order of several hundred m/s,which is approximate to that of the air flow.These results indicate that the gas flow has an important influence on the formation of this MHCD plasma jet.展开更多
The mechanism of micro-hollow cathode discharge at atmospheric pressure is investigated through simulations using two-dimensional fluid model combined with a transport model for metastable atoms.In the simulations,ele...The mechanism of micro-hollow cathode discharge at atmospheric pressure is investigated through simulations using two-dimensional fluid model combined with a transport model for metastable atoms.In the simulations,electric potential,electric field,particle density,and mean electron energy of the discharge are calculated.The results show that the two characteristic regions of the discharge,i.e.cathode drop and negative glow can be distinguished in the simulation.The cathode drop is characterized by strong electric field and high mean electron energy,while quasi-neutral plasma of high density and exists in the negative glow.The peak value of electron density can reach the order of 1017cm-3.The electron temperature varies from several eV to tens of eV.The influence of cathode dimension on the discharge characteristics is also investigated.展开更多
The effects of parameters such as pressure,first anode radius,and the cavity diameter on the micro-hollow cathode sustained glow discharge are investigated by using a two-dimensional self-consistent fluid model in pur...The effects of parameters such as pressure,first anode radius,and the cavity diameter on the micro-hollow cathode sustained glow discharge are investigated by using a two-dimensional self-consistent fluid model in pure argon.The results indicate that the three parameters influence the discharge in the regions inside and outside of the cavity.Under a fixed voltage on each electrode,a larger volume of high density plasma can be produced in the region between the first and the second anodes by selecting the appropriate pressure,the higher first anode,and the appropriate cavity diameter.As the pressure increases,the electron density inside the hollow cathode,the high density plasma volume between the first anode and second anodes,and the radial electric field in the cathode cavity initially increase and subsequently decrease.As the cavity diameter increases,the high-density plasma volume between the first and second anodes initially increases and subsequently decreases;whereas the electron density inside the hollow cathode decreases.As the first anode radius increases,the electron density increases both inside and outside of the cavity.Moreover,the increase of the electron density is more obvious in the microcathode sustained region than in the micro cavity region.The results reveal that the discharge inside the cavity interacts with that outside the cavity.The strong hollow cathode effect and the high-density plasma inside the cavity favor the formation of a sustained discharge between the first anode and the second anodes.Results also show that the radial boundary conditions exert a considerably weaker influence on the discharge except for a little change in the region close to the radial boundary.展开更多
基金supported by National Natural Science Foundation of China (No. 11975047)。
文摘Helium plasma jets generated by micro-hollow cathode discharge(MHCD) with the squarewave power source of different polarities are investigated in this work. The effects of positive and negative polarity pulses on the MHCD and plasma jet were compared, and the time-resolved optical emission spectra of excited species(N_(2)^(+) and O) were studied. The results confirm that the electric field is a key factor for the propagation of the jet during the rising edge of the positive current pulse, while the gas expansion is mainly important for the jet propagation during the current stable phase. The time-resolved spectra show that the generation of specie O in the jetdriven by the electric field is more efficient.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11575019 and 11275021
文摘Considering the feature of distributions of parameters within the micro-hollow cathode discharge, we use a simple method to separate the sheath region characterized by drastic changes of plasma parameters and the bulk plasma region characterized by smooth changes of plasma parameters. A zero-dimensional chemical kinetic model is used to analyze the dissociation mechanism of CO2 in the bulk plasma region of a micro-hollow cathode discharge and is validated by comparisons with previous modeling and experimental results. The analysis of the chemical kinetic processes has shown that the electron impact dissociation and heavy species impact dissociation are dominant in different stages of the rnicro-hollow cathode discharge process for a given applied voltage. The analysis of energy consumption distributions under different applied voltages reveals that the main reason of the conversion improvement with the increase of the applied voltage is that more input energy is distributed to the heavy species impact dissociation.
基金supported by National Natural Science Foundation of China(No.11475019)。
文摘In this paper,the air plasma jet produced by micro-hollow cathode discharge(MHCD)is investigated.The discharge is powered by a positive nanosecond pulse high voltage supply.The waveforms of the discharge,the images of the jet,the evolution of the plasma bullet and the reactive species are obtained to analyze the characteristics of the MHCD plasma jet.It is found that the length of the plasma jet is almost proportional to the air flow rate of 2–6 slm.Two plasma bullets appear one after another during a single period of the voltage waveform,and both of the two plasma bullets are formed during the positive pulse voltage off.The propagation velocity of the two plasma bullets is on the order of several hundred m/s,which is approximate to that of the air flow.These results indicate that the gas flow has an important influence on the formation of this MHCD plasma jet.
基金Project supported by National Science Foundation of China （11205046, 51077035）, Science Foundation of Hebei Province（A2012201037）, China Postdoctoral Science Foundation（2013M541195）, Science Foundation of Hebei University （2011YYO 1, 2012-237）.
文摘The mechanism of micro-hollow cathode discharge at atmospheric pressure is investigated through simulations using two-dimensional fluid model combined with a transport model for metastable atoms.In the simulations,electric potential,electric field,particle density,and mean electron energy of the discharge are calculated.The results show that the two characteristic regions of the discharge,i.e.cathode drop and negative glow can be distinguished in the simulation.The cathode drop is characterized by strong electric field and high mean electron energy,while quasi-neutral plasma of high density and exists in the negative glow.The peak value of electron density can reach the order of 1017cm-3.The electron temperature varies from several eV to tens of eV.The influence of cathode dimension on the discharge characteristics is also investigated.
基金supported by National Natural Science Foundation of China(Grant Nos.11205046 and 51777051)the Science Foundation of in Hebei province(Grant No.A2016201025)+1 种基金the Post-Graduate’s Innovation Fund Project of Hebei University(Grant No.X201733)the Science Foundation of Hebei University(Grant Nos.2011YY01 and 2012-237)
文摘The effects of parameters such as pressure,first anode radius,and the cavity diameter on the micro-hollow cathode sustained glow discharge are investigated by using a two-dimensional self-consistent fluid model in pure argon.The results indicate that the three parameters influence the discharge in the regions inside and outside of the cavity.Under a fixed voltage on each electrode,a larger volume of high density plasma can be produced in the region between the first and the second anodes by selecting the appropriate pressure,the higher first anode,and the appropriate cavity diameter.As the pressure increases,the electron density inside the hollow cathode,the high density plasma volume between the first anode and second anodes,and the radial electric field in the cathode cavity initially increase and subsequently decrease.As the cavity diameter increases,the high-density plasma volume between the first and second anodes initially increases and subsequently decreases;whereas the electron density inside the hollow cathode decreases.As the first anode radius increases,the electron density increases both inside and outside of the cavity.Moreover,the increase of the electron density is more obvious in the microcathode sustained region than in the micro cavity region.The results reveal that the discharge inside the cavity interacts with that outside the cavity.The strong hollow cathode effect and the high-density plasma inside the cavity favor the formation of a sustained discharge between the first anode and the second anodes.Results also show that the radial boundary conditions exert a considerably weaker influence on the discharge except for a little change in the region close to the radial boundary.
