Plasma dynamics, instabilities and OH generation in a pulsed atmospheric pressure plasma with liquid cathode: a diagnostic study

While plasma-liquid interactions have been an important focus in the plasma research community, the impact of the strong coupling between plasma and liquid on plasma properties and processes remains not fully understood. In this work, we report on the impact of the applied voltage, pulse width and liquid conductivity on the plasma morphology and the OH generation for a positive pulsed DC atmospheric pressure plasma jet with He-0.1% H2O mixture interacting with a liquid cathode. We adopted diagnostic techniques of fast imaging, 2D laser induced fluorescence (LIF) of OH and Thomson scattering spectroscopy. We show that plasma instabilities and enhanced evaporation occur and have a significant impact on the OH generation. At elevated plasma energies, it is found that the plasma contracts due to a thermal instability through Ohmic heating and the contraction coincides with a depletion in the OH density in the core due to electron impact dissociation. For lower plasma energies, the instability is suppressed/delayed by the equivalent series resistor of the liquid electrode. An estimation of the energy flux from the plasma to the liquid shows that the energy flux of the ions released into the liquid by positive ion hydration is dominant, and significantly larger than the energy needed to evaporate sufficient amount of water to account for the measured H2O concentration increase near the plasma-liquid interface.

Electric field strength in a discharge with a liquid electrolyte cathode in air at atmospheric pressure

The electric field strength in the channel of a discharge with a liquid electrolyte cathode at atmospheric pressure in air with the current in range of 20–90 mA is measured. The dependences of the electric field strength on the value of the discharge current are found for aqueous solutions with different compositions and with different pH values, but with the same specific conductivity of 300 μS/cm. It is shown that these dependences don’t differ by much from eachother. The dependence of the electric field strength in a discharge with a liquid cathode on the discharge current, averaged over the composition of the solution, is obtained.

Study of the factors that determine the transfer of water and organic compounds into the gas phase from aqueous solutions in a discharge with a liquid cathode

A study was performed to investigate the transfer of organic compounds and water from an aqueous solution to the gas phase under the action of a direct current discharge, in which an aqueous solution that contains organic compounds plays the role of a cathode. The effect of the area of the free surface of a liquid in various reactors, as well as the effect of the stirring mode of a solution near the surface of a liquid on the rate of transfer of water and organic compounds under the action of a discharge of this type, have been investigated. It is shown that a change in the area of the free surface of a liquid has no significant effect on the rate of transfer of water and organic compounds from solution to the gas phase under the action of a direct current discharge with a liquid cathode. It is shown that the stirring mode and the temperature of the solution, on the contrary, have a very significant effect on the rate of nonequilibrium transfer of both water and organic compounds from solution to the gas phase under the action of a discharge with a liquid cathode.

On the application of a discharge with liquid electrodes for polishing metal surfaces

The work investigates the electrical parameters of the discharge plasma with a liquid cathode and a combined porous anode. The discharge is carried out in the vertical position of the plasma column, has a volumetric multichannel structure with a pronounced diffuse structure of the electrode spots. The influence of the porous element on the stabilization of the discharge characteristics is revealed. Discharges with a liquid electrolyte cathode continue to be of great interest from the point of view of practical application and are studied in a wide range of changes in physical and geometric characteristics [1 - 4]. Discharge plasma with a liquid cathode can be most effectively used for cleaning, polishing, with simultaneous removal of fractured and relief layers, hardening, gas saturation, surface activation, improvement of mechanical and other characteristics of agricultural machinery parts. In this work, for plasma polishing, parts of the bearing assemblies of disc harrows were selected.

Simplified and rapid determination of Ca, K, Mg, and Na in fruit juices by flowing liquid cathode atmospheric glow discharge optical emission spectrometry

Atmospheric pressure glow discharge (APGD) microplasma, sustained between a flowing liquid cathode (FLC) and a tungsten anode, was applied for the determination of Ca, K, Mg, and Na in fruit juices with a simplified sample preparation procedure.

Parameters of a gas discharge with a liquid electrode in the process of gasification of hydrocarbon-containing waste

A plasma generator with a liquid cathode has been developed and investigated, which makes it possible to create a plasma flow from electrolyte vapors with a temperature of up to 1800°C with a mass flow rate of up to 3.0 g/s for the gasification of carbon-containing waste. An electrolyte in the form of a solution of Glauber salt in distilled water with a concentration of 0.5-1.0 kg/m3 by weight was used. The current-voltage characteristics of the discharge are constructed. The optimal electrical and thermal parameters of the plasma flow are determined experimentally.

The application of tetramethylammonium hydroxide for generating atmospheric pressure glow discharge in contact with alkalized flowing liquid cathode solutions – evaluation of the analytical performance

The analytical performance of flowing liquid cathode atmospheric pressure glow discharge (FLC-APGD), generated in contact with alkalized solutions for the determination of selected elements by optical emission spectrometry (OES) was assessed.