Electrophysical and thermal characteristics of a jet discharge with a liquid (non-metallic) cathode

Аuthors

Belgibaev E. R., Petryakov S. Y., Gaisin A. F.^*, Kayumov R. R.

Kazan National Research Technical University named after A.N. Tupolev, Kazan, Russia

*e-mail: almaz87@mail.ru

Abstract

The paper presents the results of an experimental investigation of the electrophysical and thermal characteristics of a jet discharge with a liquid (non-metallic) cathode formed on a wetted organic glass surface under atmospheric pressure conditions. This paper belongs to the field of fluid, gas, and low temperature plasma mechanics. The study was aimed at obtaining a comprehensive description of the interaction between electrical, thermal, hydrodynamic, and plasma-chemical processes occurring in the “plasma–jet–surface” system. The experimental setup included a jet of 4 % NaCl aqueous solu-tion acting as a liquid cathode and a wetted dielectric surface serving as a liquid anode. High-speed video recording, infrared thermography, oscillographic diagnostics, and optical emission spectroscopy with instrumental function correction were employed to investigate discharge behavior and plasma pa-rameters. The discharge demonstrated a pronounced pulsed mode of operation with current pulse du-rations of approximately 3–30 ms. At an applied voltage of 200 V, mainly ohmic conduction with ra-re spark events was observed, while increasing the voltage to 500–1000 V resulted in the formation of a stable ring-shaped discharge accompanied by current pulses in the range of 0,2–2,4 A. The current–voltage characteristic was found to be nonlinear, reflecting transitions from electrolyte conduction to mixed discharge regimes and finally to stable ring plasma burning. High-speed imaging revealed that the luminous discharge region was localized along the front of a circular hydrodynamic wave formed by the spreading electrolyte film. Such localization contributed to the concentration of current density and heat flux in a narrow annular zone. Optical emission spectra showed the presence of H I, Na I, K I, Cu I, O I atomic lines and OH(A–X), N₂⁺(C–B) molecular bands. Electron concentration estimated from Stark broadening of Balmer hydrogen lines was in the range of ~10¹⁵–10¹⁶ cm⁻³. Rotational and vibrational temperatures determined by fitting OH(A–X) spectra using the LIFBASE package were Tr ≈ 3450 K and Tv ≈ 4600 K, indicating pronounced non-equilibrium plasma conditions. The ob-tained results demonstrate the prospects of jet plasma discharges with liquid non-metallic cathodes for loca-lized plasma-liquid processing, surface modification, and thermophysical treatment technologies.

Keywords:

jet discharge, liquid (non-metallic) cathode, plasma-liquid processing; ring discharge, circular hydro-dynamic wave, current-voltage characteristic, pulse current, infrared thermography, optical emission spectroscopy, Stark broadening, electron concentration, rotational temperature, vibrational tempera-ture

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