大气压低温氦等离子体射流的诊断研究

doi:10.3964/j.issn.1000-0593(2021)06-1874-06

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Abstract In order to accelerate the process of helium plasma jet’s engineering，a stable helium plasma jet was produced in the atmosphere through a self-designed coaxial Dielectric Barrier Discharge structure with a discharge frequency of 10 kHz. By analyzing the voltage and current waveform under different working conditions, it can be found that simply increasing the volume flow of helium gas can only increase the current pulse slightly, but has little effect on the discharge time and the number of current pulses. However, when the peak discharge voltage is increased, the current pulse amplitude increases significantly. The types of active particles, electron excitation temperature and electron density of atmospheric pressure helium plasma jet were diagnosed by emission spectroscopy. The results show that the main active particles of helium plasma jet are He I atom, N₂ second positive band system, N⁺₂ first negative band system, hydroxyl (OH), H atom Balmer line system (H_α, H_β) and O atom. It shows that although the purity of the helium gas used in this test has reached 99.99%, there is still a small amount of air remaining. At the same time, the air in the atmosphere will be sucked into the discharge space and be ionized. It can be found that the relative spectral intensity of the main active particles showed an upward trend with the increase of the volume flow of helium gas and the increase of the peak discharge voltage. The electronic excitation temperature under different test conditions was calculated by the Boltzmann slope method between 3 500 to 6 300 K. With the increase of the discharge peak voltage and helium gas’s volume flow rate, the electron excitation temperature basically shows a rising trend. However, due to the presence of a reverse electric field, the electronic excitation temperature may show a downward trend at some certain peak voltages; According to the Stark broadening principle, the electron density of the atmospheric pressure helium plasma jet was calculated, and it is found that the electron density can reach the order of 10¹⁵ cm^-3 while increasing the peak voltage and helium volume flow can effectively increase the electron density in the plasma jet. The study of these parameters is of great significance for the application of helium plasma jets.

Key words：Atmospheric pressure; Heliumdielectric barrier discharge; Emission spectroscopy; Electron excitation temperature; Electron density

Received: 2020-06-18 Accepted: 2020-10-05

ZTFLH:

O433.1

Corresponding Authors: CHEN Lei E-mail: chenleisau@126.com

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https://www.gpxygpfx.com/EN/10.3964/j.issn.1000-0593(2021)06-1874-06 OR https://www.gpxygpfx.com/EN/Y2021/V41/I06/1874