Phase-Resolved Measurement of Atmospheric-Pressure Radio-Frequency Pulsed Discharges in Ar/CH4/CO2 Mixture

The low-pressure atmosphere on Mars, rich in CO2 (~95%), makes the in-situ resource utilization of Martian CO2 and the improvement of oxidation attract widespread attention. It contributes to construct the Mars base which will support the deep space exploration. Conversion of CO2 based on high voltage discharge has the advantages of environmental friendliness, high efficiency and long service life. It has application potential in the in-situ conversion and utilization of Martian CO2 resources. We simulate the CO2 atmosphere of Mars where the pressure is fixed at 1kPa and the temperature is maintained at room temperature. A comparative study was carried out on the discharge characteristics of two typical electrode structures (with/without barrier dielectric) driven by 20kHz AC voltage. Combined with numerical simulation, the CO2 discharge characteristics, products and their conversion pathways were analyzed. The results show that the discharge mode changes from single discharge during each half cycle to multi discharge pulses after adding the barrier dielectric. Each discharge pulse of the multi pulses corresponds to a random discharge channel, which is induced by the distorted electric field of accumulated charge on the dielectric surface and the space charge. The accumulated charge on the dielectric surface promotes the primary discharge and inhibits the secondary discharge. Space charge will be conducive to the occurrence of secondary discharge. The main products in discharge process include CO%2B 2, CO, O2, C, O, etc. Among the products, CO is mainly produced by the attachment decomposition reaction of energetic electrons and CO2 at the boundary of cathode falling zone, and the contribution rate of the reaction can reach about 95%. O2 is mainly generated by the compound decomposition reaction of electrons and CO%2B 2 near the instantaneous anode surface or instantaneous anode side dielectric surface, and the contribution rate of the reaction can reach about 98%. It is further found that the dielectric does not change the generation position and dominant reaction pathway of the two main products, but will reduce the electron density (from 5.6×1016?m-3 to 0.9×1016?m-3) and electron temperature (from 17.2eV to 11.7eV) at the boundary of the cathode falling region, resulting in the reduction of CO production. At the same time, the deposited power is reduced, resulting in insufficient CO%2B 2 yield near the instantaneous anode surface and instantaneous anode side dielectric surface and further reduced O2 generation.

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Section: 模型中电子和离子的边界采用通量边界条件离子通unclassified

Comparative study on discharge characteristics of low pressure CO<sub>2</sub> driven by sinusoidal AC voltage: DBD and bare electrode structure

付强¹,

王聪²,

王语菲³

et al. 2022

Acta Phys. Sin.

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“…In the following discussion, the relationship between OES and gaseous products will be built-up and the reaction pathways will be clarified. As a further step, rotational temperature (T r ) and vibrational temperature (T v ) of CH and C 2 bands are obtained using LIFBASE program [49,50] (with typical fitting result shown in figure 3(g)) and Specair program [51][52][53][54], respectively. Here, T r can be used to estimate the gas temperature (T g ) in collisional high-pressure plasma.…”

Section: Oes and Plasma Characteristicsmentioning

confidence: 99%

“…In fact, the luminous discharge core and dim edge will contribute differently to OES, while the short pulse-on period and long afterglow period can have disparate OES. Of course, we can use temporally and spatially resolved OES diagnostics, as have been performed in our former investigations [35,44,50].…”

Section: D Reaction Kinetics Modelmentioning

confidence: 99%

Reaction mechanism in non-thermal plasma enabled methane conversion: correlation between optical emission spectroscopy and gaseous products

Han¹,

Huang²,

Liu³

et al. 2021

J. Phys. D: Appl. Phys.

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In this work, the reaction mechanism in non-thermal plasma enabled methane conversion driven by different sources, i.e. microwave discharge, nanosecond pulsed dielectric barrier discharge, and spark discharge, is investigated. The behaviour of reactive species is monitored using the optical emission spectroscopy (OES), while the final gaseous products are analysed with gas-chromatograph. A zero-dimensional (0D) reaction kinetics model is established to reveal the underlying reaction processes. By changing pressure, different plasma modes (diffuse and filamentary) are achieved and the relative emission intensity of different species and distribution of gaseous productions are manipulated. It is found that there is a strong correlation between the intensity-ratio of C2 A → X and CH A → X, gas temperature, and the relative concentration of C2 products in different discharge forms, i.e. higher intensity ratio of C2/CH is associated with higher gas temperature and more unsaturated hydrocarbon products. Assisted with the 0D reaction kinetics model, the relationship between the intermediate species and final products is illustrated. Based on the investigation in this work, it is proposed that intensity ratio of OES can be widely adapted as a non-intrusive and real-time process monitoring in the plasma-enabled methane conversion.

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“…I N THE past ten years, atmospheric pressure radio frequency (RF) glow discharge has become one of the hotspots in the field of discharge and plasma research in the world [1]- [4], which opens new possibilities for numerous applications without the need for expensive vacuum devices, such as sterilization, material modification, deposition of functional films, and nitrogen fixation [5]- [7], especially in the application of plasma biomedicine [3], [8]- [11]. Plasma biomedicine is an innovative and rapidly evolving research field [12], it mainly needs the RF sources to produce the cold atmospheric plasma (CAP) with stability and reactivity in the α mode for different therapeutic settings [13].…”

Section: Introductionmentioning

confidence: 99%

“…By increasing the driving frequency to very-high frequency (VHF) or even ultrahigh frequency (UHF), much more power density can be coupled into the plasmas while the electron density and electron temperature can also be promoted significantly before the discharge evolves into the γ mode [26]- [28]. Pulse modulation is another effective way to refrain from the discharge mode transition, it can greatly reduce the power consumption and enhance the discharge stability by operating the generation of plasmas only in a fraction of RF periods [29]- [32], and experimental and computational studies have shown that the discharge characteristics can be flexibly optimized by introducing control parameters such as duty cycle and modulation frequency [4], [22], [33].…”

Section: Introductionmentioning

confidence: 99%

Comparing Study on Formation of Large Discharge Currents in Atmospheric Pulse-Modulated Radio Frequency Discharges

Gao

Wang

Zhang

2022

IEEE Trans. Plasma Sci.

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In recent years, pulse-modulation is introduced in atmospheric radio frequency (RF) discharges to further control the discharge operation. In this article, a comparing study is performed by a 1-D fluid model to investigate the formation of large discharge currents (LDCs) in the first RF cycle during the power-on phase in an atmospheric pulse-modulated RF discharge controlled by dielectric barriers. The current-voltage characteristics and helium metastable (He * ) distributions show the enhancement of a pulsed voltage on the ignition of RF discharge, which agrees well with the experimental observation. On the other hand, in a dielectric barrier discharge driven by a sinusoidal voltage of 500 MHz, double LDCs are observed in the positive and negative half-cycles, respectively, and the large pulse rise rate of applied voltage essentially influences the distribution of charged particles in the first cycle during the power-on phase. In this study, according to computational data the reverse electric field near the anode contributes greatly to the generation of LDCs in both types of discharge, and the appropriate discharge conditions are suggested to optimize the pulse-modulated RF discharges in applications.

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Phase-Resolved Measurement of Atmospheric-Pressure Radio-Frequency Pulsed Discharges in Ar/CH4/CO2 Mixture

Cited by 17 publications

References 50 publications

Comparative study on discharge characteristics of low pressure CO<sub>2</sub> driven by sinusoidal AC voltage: DBD and bare electrode structure

Comparative study on discharge characteristics of low pressure CO<sub>2</sub> driven by sinusoidal AC voltage: DBD and bare electrode structure

Reaction mechanism in non-thermal plasma enabled methane conversion: correlation between optical emission spectroscopy and gaseous products

Comparing Study on Formation of Large Discharge Currents in Atmospheric Pulse-Modulated Radio Frequency Discharges

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