Том 49, № 5 (2023)

Plasma accelerators that form high-speed plasma jets due to the force action of their own magnetic field operate at high currents. Because of that, current spots with a high current density may occur on their electrodes, which lead to erosion of the electrodes and limit their life-time. In this work, the current modes of a plasma accelerator were investigated both without current spots and with current spots on the electrodes. In the latter case, the dynamics of current spots in the course of plasma acceleration was explored. This issue was studied by the example of a high-current (I ≤ 25 kA) pulse discharge created between two long (l = 30 cm) and parallel stainless-steel electrodes of cylindrical shape of 10 mm in a diameter. Two distances between the cylinders’ axes, h = 30 and 22 mm, were used. Two discharge zone configurations were investigated. In one of them, the discharge zone is not confined by side dielectric walls. In other one, the discharge zone is confined with transparent dielectric walls spaced by 12 mm. The high-current discharge was studied in nitrogen and helium at moderate pressures from P = 4 to 50 Torr. The high current was provided due to the discharging of a capacitor battery C = 1000 µF charged up to the voltage U ≤ 5 kV. At the very beginning, the discharge was initiated locally at one end of the electrodes, and then the formed plasma quickly moves toward the opposite end under strong force influence of its own magnetic field. Eventually, plasma clot is flying out of the discharge zone.

The rate of iron corrosion in a low-temperature plasma of moist air formed under the action of a fast electron beam, depending on the relative air humidity, was measured. It is shown that a beam of fast electrons (radioactive β-radiation) significantly intensifies the corrosion of iron in a plasma-forming gas medium in which oxygen and water vapour are simultaneously present. It has been established that the rate of corrosion under conditions of radioactive irradiation increases sharply when the relative air humidity exceeds 10%. Numerical simulation of the ionic composition of the plasma is carried out taking into account 12 types of positive and 12 types of negative hydrated ions at different intensities of the external ionization source and at different values of relative humidity from 10–6 to 100%. A hypothesis has been put forward about the determining role of cluster hydrated ions, which are formed in the plasma of moist air at atmospheric pressure, in heterogeneous processes of iron oxidation.

Results of numerical simulation using Plasmaero CFD code are presented for direct current (DC) discharge in a high-speed airflow. Modelling of plasma was performed using single-fluid MHD approach and detailed plasma-chemistry. As a result of simulation, the dynamics of DC discharge was obtained which corresponds to dynamics of this object registered during previous experimental study including such effect as the discharge re-breakdown. Concentration of atomic oxygen in different parts of discharge and near them was obtained and analysed. The influence estimation of obtained atomic oxygen concentration on the fuel mixture induction time was performed using zero-dimensional calculation. It was shown that atomic oxygen generation by DC discharge dramatically reduce the ignition delay that could be important for combustion stimulation in a high-speed flow.

An effect of dielectric barrier discharge on laminar transonic buffet at low Reynolds numbers of (0.5–0.7) × 106 was studied experimentally. Experiments were performed using high-speed schlieren imaging and PIV method. An actuator based on a dielectric barrier discharge was placed near the leading edge of the airfoil. The effect of the discharge frequency on transonic buffet was investigated. Transonic laminar buffet was found to be highly sensitive to perturbations created by low-power electrical discharge.

The concept of plasma mass separation of substances in a configuration with a potential well implies the creation of specialized plasma sources that comply with a number of requirements. The following can be distinguished as the main ones: a high degree of ionization of the plasma flow, single ionization, the possibility of working with a complex mixture of oxides and metals as a working substance, high productivity rate (up to 1 kg/h), kinetic energy at the level of several tens of electron-volts. One possible application of this concept is the separation of spent nuclear fuel. The conversion of condensed matter into a low-temperature plasma flow and its further injection into the separation chamber is the initial stage of the concept and it largely determines the efficiency of the technological process. This paper presents the results of studies of the energy distribution of lead ions in the plasma jet of a plasma source created on the basis of a non-self-sustained arc discharge with a hot cathode in a magnetic field. The influence of this distribution on the separation process was analyzed.

The mutual influence of electric discharge and air-droplet flow formed by a centrifugal nozzle when a conductive liquid (solution of sodium chloride in water) is supplied to it under pressure was investigated. Using the method of digital double microphotography with further computer processing of photographs, the main characteristics of the spray in the presence of an electric discharge and without it were obtained: the mean diameter, the Sauter mean diameter, the distribution of the velocity vector components by the droplet diameter and others. It is shown that the presence of liquid spray leads to a decrease in the effective value of the breakdown electric field strength. Also it was found that the energy release into the air-droplet flow leads to a change in the value of the Sauter mean diameter, and the presence of a high voltage in the measurement region leads to the acceleration of drops of a relatively small diameter.

This work is devoted to the study of the properties of a discharge in a supersonic air flow and the problem of determining the temperature of a contracted (thin cylindrical) plasma channel with a radial temperature distribution. The paper considers a direct discharge 30 mm long far from the channel walls in the core of a supersonic flow with the following parameters: Mach number M = 2, flow rate V ~ 500 m/s, stagnation temperature T0 = 300 K, and static gas pressure Pst = 22 kPa. The axisymmetric geometry of the ex-periments with two coaxial electrodes located parallel to the flow was chosen to avoid the appearance of a part of the current channel perpendicular to the flow and the corresponding discharge pulsations. The current–voltage characteristic was obtained, and the dependences of the temperature of the electric discharge plasma on the electrical parameters of the discharge were obtained using emission spectroscopy. Also, with the help of shadow visualization and high-speed shooting, an estimate was obtained of the thickness of the thermal cone and the discharge channel and their dependence on the discharge current.