Study On Discharge Of High Frequency Rotating Gliding Arc And It’s Application For Methane Dry Reforming

Rotating gliding arc discharge（RGAD）can produce a kind of plasma,which has the characteristics of high temperature plasma and low temperature plasma at normal temperature and pressure.At present,RGAD plasma used in the research of methane reforming,fly ash treatment,waste water degradation and other fields has attracted much attention.The power supply that drives the RGAD is usually DC power supply.The circuit needs to connect a current limiting resistance and the energy loss is large.When the RGAD is driven by a high frequency AC power supply,there is no need to connect a current limiting resistance in the circuit,and the energy efficiency is high.In addition,the energy injected into the reactor by the high frequency AC power is higher than the DC power supply and power frequency power supply,which is conducive to the excitation of chemical reaction.In this study,a RGAD reactor driven by a high frequency AC power was designed.We analyzed the physical characteristics of arc and the distribution of airflow field in the reactor.Besides,this type of discharge was used for methane dry reforming and gas rotating temperature as well as electron density were analyzed by emission spectra.The specific experimental results are shown below.（1）By analyzing the electrical signals and image features in the process of rotating gliding arc discharge,the sliding mode,volt-ampere characteristic and light intensity distribution of arc were studied.The gliding mode of the rotating gliding arc is divided into breakdown gliding（B-G）and steady arc gliding（A-G）mode,and the voltage and current characteristics are different in different gliding modes.In B-G mode,the voltage waveform in positive and negative both have single breakdown,and the current peak value range is 1-40 A.In A-G mode,there is no breakdown in the positive and negative half cycles of voltage waveform,and the current peak ranges from-900 mA to+900 mA.The process of arc from generation to extinction is divided into three phases:arc generation,arc extinction and zero rest,corresponding to three different functional relationships on the volt-ampere characteristic curve.The characteristic curve of the positive and negative volt-ampere characteristic curve is asymmetrical.In the discharge process,the arc light intensity distribution is not uniform,and the most luminous position is always located at root of the cathode arc.（2）The equivalent circuit models before and after discharge were carried out,and Comsol Multiphysics software was used to simulate the distribution of airflow field in the discharge space.In addition,the influence of air flow on the arc parameters was investigated.The narrowest gap between two electrodes is equivalent to a capacitance of 56 pF,which is independent of the gas flow.After the arc generation,the arc is equivalent to a resistance,and the resistance value is related to the arc length.At the same level,the closer to the outer electrode,the greater the gas velocity.On the same longitudinal section,the closer to the tip of the electrode,the smaller the gas velocity.The larger the air flow,the easier the arc develops into A-G mode.When the gas flow increases to a certain value,the arc will always rotate in A-G mode.If the gas flow continues to increase,the arc disconnects and enters the B-G mode.The air flow has no effect on the breakdown voltage.The larger the air flow,the more difficult the arc rotates at top of the electrode.The smaller the voltage,the more difficult the arc moves to top of the electrode.（3）The dry reforming effect of methane under different electrode structures and gas phase parameters was analyzed in RGAD device,and the emission spectra in the discharge process was analyzed.The internal-electrode summit angle of 45°and a higher external electrode are the optimal electrode structure parameters.Total feed flow rate of 3 L/min and CO₂/CH₄ of 3:2 are the optimal gas parameters.The yields of H₂ and CO are 3.1%and 15.9%,respectively,and the energy efficiency is 3.9 mmol/kJ.During the discharge process,the gas rotating temperature is 3200 K,and the electron density is 1.2x10^-14cm^-3.