采用切向气流和磁场协同驱动的旋转滑动弧氩等离子体,先通过光谱分析法计算了其电子温度和电子密度,了解其物理特性,将其应用于甲烷裂解制氢,研究了进气流量和CH_4/Ar比对反应效果的影响。结果表明,该滑动弧系统电子温度为1.0-2.0 e V,...采用切向气流和磁场协同驱动的旋转滑动弧氩等离子体,先通过光谱分析法计算了其电子温度和电子密度,了解其物理特性,将其应用于甲烷裂解制氢,研究了进气流量和CH_4/Ar比对反应效果的影响。结果表明,该滑动弧系统电子温度为1.0-2.0 e V,电子密度高达1015cm^(-3),是介于热与低温等离子体之间的一种等离子体形式,具有独特的物理特性,可以在达到较高反应效率的同时,保持较大的处理量;在CH_4裂解制氢实验中,CH_4转化率可达22.1%-70.2%,并随进气流量和CH_4/Ar比的增大均逐渐降低;H_2选择性为21.2%-61.2%,并随进气流量的增大先基本不变后有所增大,随CH_4/Ar比的增大逐渐降低;与应用于甲烷裂解的不同形式的低温等离子体对比(如微波、射频、介质阻挡放电等)可以发现,旋转滑动弧在获得较高甲烷转化率、较高H_2选择性和较低制氢能耗的同时,还可以保持较大的处理量,即进气流量可达6-20 L/min。展开更多
In this work, a novel direct current （DC） atmospheric pressure rotating gliding arc （RGA） plasma reactor has been developed for plasma-assisted chemical reactions. The influence of the gas composition and the gas ...In this work, a novel direct current （DC） atmospheric pressure rotating gliding arc （RGA） plasma reactor has been developed for plasma-assisted chemical reactions. The influence of the gas composition and the gas flow rate on the arc dynamic behaviour and the formation of reactive species in the N2 and air gliding arc plasmas has been investigated by means of electrical signals, high speed photography, and optical emission spectroscopic diagnostics. Compared to conventional gliding arc reactors with knife-shaped electrodes which generally require a high flow rate （e.g., 10-20 L/min） to maintain a long arc length and reasonable plasma discharge zone, in this RGA system, a lower gas flow rate （e.g., 2 L/min） can also generate a larger effective plasma reaction zone with a longer arc length for chemical reactions. Two different motion patterns can be clearly observed in the N2 and air RGA plasmas. The time-resolved arc voltage signals show that three different arc dynamic modes, the arc restrike mode, takeover mode, and combined modes, can be clearly identified in the RGA plasmas. The occurrence of different motion and arc dynamic modes is strongly dependent on the composition of the working gas and gas flow rate.展开更多
The effects of feed gas flow rate and operating current on the electrical characteristics and dynamic behavior of a rotating gliding arc （RGA） plasma codriven by a magnetic field and tangential flow were investigate...The effects of feed gas flow rate and operating current on the electrical characteristics and dynamic behavior of a rotating gliding arc （RGA） plasma codriven by a magnetic field and tangential flow were investigated.The operating current has been shown to significantly affect the time-resolved voltage waveforms of the discharge,particularly at flow rate =21 min^-1.When the current was lower than 140 mA,sinusoidal waveforms with regular variation periods of 13.5-17.0 ms can be observed （flow rate =21 min^-1）.The restrike mode characterized by serial sudden drops of voltage appeared under all studied conditions.Increasing the flow rate from 8 to 121 min^-1 （at the same current） led to a shift of arc rotation mode which would then result in a significant drop of discharge voltage （around 120-200 V）.For a given flow rate,the reduction of current resulted in a nearly linear increase of voltage.展开更多
The use of atmospheric rotating gliding arc(RGA)plasma is proposed as a facile,scalable and catalyst-free approach to synthesizing hydrogen(H2)and graphene sheets from coalbed methane(CBM).CH4 is used as a CBM surroga...The use of atmospheric rotating gliding arc(RGA)plasma is proposed as a facile,scalable and catalyst-free approach to synthesizing hydrogen(H2)and graphene sheets from coalbed methane(CBM).CH4 is used as a CBM surrogate.Based on a previous investigation of discharge properties,product distribution and energy efficiency,the operating parameters such as CH4 concentration,applied voltage and gas flow rate can effectively affect the CH4 conversion rate,the selectivity of H2 and the properties of solid generated carbon.Nevertheless,the basic properties of RGA plasma and its role in CH4 conversion are scarcely mentioned.In the present work,a 3D RGA model,with a detailed nonequilibrium CH4/Ar plasma chemistry,is developed to validate the previous experiments on CBM conversion,aiming in particular at the distribution of H2 and other gas products.Our results demonstrate that the dynamics of RGA is derived from the joint effects of electron convection,electron migration and electron diffusion,and is prominently determined by the variation of the gas flow rate and applied voltage.Subsequently,a combined experimental and chemical kinetical simulation is performed to analyze the selectivity of gas products in an RGA reaction,taking into consideration the formation and loss pathways of crucial targeted substances(such as CH4,C2H2,H2 and H radicals)and corresponding contribution rates.Additionally,the effects of operating conditions on the properties of solid products are investigated by scanning electron microscopy(SEM)and Raman spectroscopy.The results show that increasing the applied voltage and decreasing CH4 concentration will change the solid carbon from its initial spherical structure into folded multilayer graphene sheets,while the size of the graphene sheets is slightly affected by the change in gas flow rate.展开更多
文摘采用切向气流和磁场协同驱动的旋转滑动弧氩等离子体,先通过光谱分析法计算了其电子温度和电子密度,了解其物理特性,将其应用于甲烷裂解制氢,研究了进气流量和CH_4/Ar比对反应效果的影响。结果表明,该滑动弧系统电子温度为1.0-2.0 e V,电子密度高达1015cm^(-3),是介于热与低温等离子体之间的一种等离子体形式,具有独特的物理特性,可以在达到较高反应效率的同时,保持较大的处理量;在CH_4裂解制氢实验中,CH_4转化率可达22.1%-70.2%,并随进气流量和CH_4/Ar比的增大均逐渐降低;H_2选择性为21.2%-61.2%,并随进气流量的增大先基本不变后有所增大,随CH_4/Ar比的增大逐渐降低;与应用于甲烷裂解的不同形式的低温等离子体对比(如微波、射频、介质阻挡放电等)可以发现,旋转滑动弧在获得较高甲烷转化率、较高H_2选择性和较低制氢能耗的同时,还可以保持较大的处理量,即进气流量可达6-20 L/min。
基金supported by National Natural Science Foundation of China(No.51576174)the Specialized Research Fund for the Doctoral Program of Higher Education of China(No.20120101110099)the Fundamental Research Funds for the Central Universities(No.2015FZA4011)
文摘In this work, a novel direct current （DC） atmospheric pressure rotating gliding arc （RGA） plasma reactor has been developed for plasma-assisted chemical reactions. The influence of the gas composition and the gas flow rate on the arc dynamic behaviour and the formation of reactive species in the N2 and air gliding arc plasmas has been investigated by means of electrical signals, high speed photography, and optical emission spectroscopic diagnostics. Compared to conventional gliding arc reactors with knife-shaped electrodes which generally require a high flow rate （e.g., 10-20 L/min） to maintain a long arc length and reasonable plasma discharge zone, in this RGA system, a lower gas flow rate （e.g., 2 L/min） can also generate a larger effective plasma reaction zone with a longer arc length for chemical reactions. Two different motion patterns can be clearly observed in the N2 and air RGA plasmas. The time-resolved arc voltage signals show that three different arc dynamic modes, the arc restrike mode, takeover mode, and combined modes, can be clearly identified in the RGA plasmas. The occurrence of different motion and arc dynamic modes is strongly dependent on the composition of the working gas and gas flow rate.
基金supported by National Natural Science Foundation of China(51576174)
文摘The effects of feed gas flow rate and operating current on the electrical characteristics and dynamic behavior of a rotating gliding arc （RGA） plasma codriven by a magnetic field and tangential flow were investigated.The operating current has been shown to significantly affect the time-resolved voltage waveforms of the discharge,particularly at flow rate =21 min^-1.When the current was lower than 140 mA,sinusoidal waveforms with regular variation periods of 13.5-17.0 ms can be observed （flow rate =21 min^-1）.The restrike mode characterized by serial sudden drops of voltage appeared under all studied conditions.Increasing the flow rate from 8 to 121 min^-1 （at the same current） led to a shift of arc rotation mode which would then result in a significant drop of discharge voltage （around 120-200 V）.For a given flow rate,the reduction of current resulted in a nearly linear increase of voltage.
基金supported by the Foundation for Innovative Research Groups of National Natural Science Foundation of China (No. 51621005)China Postdoctoral Science Foundation (No. 2018M630672)
文摘The use of atmospheric rotating gliding arc(RGA)plasma is proposed as a facile,scalable and catalyst-free approach to synthesizing hydrogen(H2)and graphene sheets from coalbed methane(CBM).CH4 is used as a CBM surrogate.Based on a previous investigation of discharge properties,product distribution and energy efficiency,the operating parameters such as CH4 concentration,applied voltage and gas flow rate can effectively affect the CH4 conversion rate,the selectivity of H2 and the properties of solid generated carbon.Nevertheless,the basic properties of RGA plasma and its role in CH4 conversion are scarcely mentioned.In the present work,a 3D RGA model,with a detailed nonequilibrium CH4/Ar plasma chemistry,is developed to validate the previous experiments on CBM conversion,aiming in particular at the distribution of H2 and other gas products.Our results demonstrate that the dynamics of RGA is derived from the joint effects of electron convection,electron migration and electron diffusion,and is prominently determined by the variation of the gas flow rate and applied voltage.Subsequently,a combined experimental and chemical kinetical simulation is performed to analyze the selectivity of gas products in an RGA reaction,taking into consideration the formation and loss pathways of crucial targeted substances(such as CH4,C2H2,H2 and H radicals)and corresponding contribution rates.Additionally,the effects of operating conditions on the properties of solid products are investigated by scanning electron microscopy(SEM)and Raman spectroscopy.The results show that increasing the applied voltage and decreasing CH4 concentration will change the solid carbon from its initial spherical structure into folded multilayer graphene sheets,while the size of the graphene sheets is slightly affected by the change in gas flow rate.
