Diagnosis of Emission Spectroscopy of Helium, Methane and Air Plasma Jets at Atmospheric Pressure
TIAN Fu-chao1, CHEN Lei2*, PEI Huan2, BAI Jie-qi1, ZENG Wen2
1. State Key Laboratory of Coal Mine Safety Technology, China Coal Technology & Engineering Group Shenyang Research Institute, Shenfu Demonstration Zone, Shenyang 113122, China
2. School of Aero-Engine, Shenyang Aerospace University, Shenyang 110136, China
Abstract：With the plasma jet's aid, the liquid's atomization characteristics can be improved to a certain extent. It can be seen that plasma-assisted atomization has the potential to be applied in the field of ultra-fine water mist to suppress gas explosions. However, since various active particles in the plasma jet have a promoting effect on combustion, it is necessary to quantitatively analyze the active particle species in the plasma in the presence of gas. In this study, a DBD discharge study was performed on premixed methane and air under atmospheric pressure using helium as the carrier gas. The needle-ring dielectric barrier plasma generator ionizes the helium/methane-air mixture at a discharge frequency of 10 kHz and atmospheric pressure and generates a stable plasma jet. Diagnosis of the active particle types, vibration temperature and electron excitation temperature of the plasma jet under the conditions of different peak voltages and different mixing volume flow ratios by emission spectroscopy. The results show that the main active particles in the plasma jet are the OH group, the second positive band of N2, the CH group, HeⅠ, and a small number of O atoms. Among them, the methane ionization region is mainly concentrated in the 400 to 600 nm range between. Increasing the peak voltage and the helium mixing volume flow ratio can effectively increase the content of active groups in the isojet. Using the continuous band of the second positive band of N2 to do the least square linear fitting, the vibration temperature of the plasma jet is calculated, and the vibration temperature of the atmospheric pressure helium/air-methane plasma jet is between 2 000 and 4 000 K. The vibration temperature shows an increasing trend with the increase of peak voltage and helium mixing ratio. Using five spectral lines with a large difference in excitation energy of HeⅠatoms to do the least squares linear fitting, the electron excitation temperature of the plasma jet is calculated, and the electron excitation temperature of the atmospheric pressure helium/air-methane plasma jet is obtained. Between 3 500~13 000 K. With the increase of the peak voltage, the electron excitation temperature shows an increasing trend. With the helium mixing ratio increase, the electron excitation temperature shows a decreasing trend. The analysis shows that the increase in the helium volume flow rate Larger will make the airflow in the jet generator faster, take away more heat in the generator, and cause the electron excitation temperature to drop.
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