Two-fluid magnetohydrodynamic model of plasma flows in a quasi-steady-state accelerator with a longitudinal magnetic field

Abstract

This paper reports the results of numerical studies of axisymmetric flows in a coaxial plasma accelerator in the presence of a longitudinal magnetic field. The calculations were performed using a two-dimensional two-fluid magnetohydrodynamic model taking into account the Hall effect and the conductivity tensor of the medium. The numerical experiments confirmed the main features of the plasmadynamic processes found previously using analytical and one-fluid models and made it possible to study plasma flows near the electrodes.Key words: plasma flow, magnetohydrodynamic model, Hall effect, plasma accelerator, longitudinal magnetic field.Introduction. In coaxial plasma accelerators [1] with azimuthal magnetic field H ϕ , plasma acceleration is due to the Ampére force. The current crisis phenomenon [1, 2] prevents the attainment of high velocities in accelerators with impermeable electrodes. This phenomenon is caused by the adverse effect of the Hall effect leading to a plasma deficiency near the anode. Large-amplitude oscillations occur in the accelerator. These phenomena exert the greatest effect on the volt-ampere characteristics corresponding to a constant flow rate of matter. If the discharge current in the system is higher than a certain critical value, the discharge voltage begins to grow rapidly and the system prevents the passage of high currents. Overcoming of the current crisis is possible in two-stage systems of the type of quasi-steady-state plasma accelerators (QSPAs) [1-3]. The first stage of QSPAs consists of several small coaxial plasma accelerators for plasma ionization and its preliminary acceleration. The second stage is a large coaxial plasma accelerator connected to an independent electric circuit. Experimental studies of QSPAs have shown a high degree of stability and azimuthal symmetrization of the flows (see, for example, [4,5]). The attained parameters values (particle concentration n 10 20 m −3 , plasma velocity V ≈ 10 4 -10 6 m/sec) indicate that these accelerators are promising for use not only in developing new technologies but also in space engineering, as electrojet plasma engines, and in other areas. Modern QSPAs are designed to use ion current transport with permeable electrodes. In this regime, the electrodes are equipotential surfaces and should be permeable to plasma. The self-consistent plasma flow through the electrodes is due to the Hall effect. Ignoring this effect (V e = V i ), the regime of impermeable continuous equipotential electrodes occurs, which is degenerate in physical practice (V e = V i ). Analytical and numerical studies of processes in accelerators for a dense plasma have been performed for magnetohydrodynamic (MHD) models in the absence of a longitudinal field (see, for example, [6][7][8]).

Design of a Plasma Accelerator Based on Effects of Energy/Momentum Exchange in Crossed Magnetic Fields

“…At the same time, this system provides thrust without the need for additional current and space charge neutralization. It is also worth noting that the similar mechanism of acceleration occurs with a coaxial plasma accelerator [8,9] or a magnetoplasmadynamic thruster [10].…”

Numerical study of the ionization process and radiation transport in the channel of plasma accelerator

“…In some cases it is necessary to use the two-fluid MHD model with the Hall effect (see e.g. [1][2][3]8] ), and also the two-fluid MHD model taking into account the inertia of electrons (see e.g. [24,25] ).…”

“…For these devices we explore the transonic plasma flows including the presence of an additional longitudinal magnetic field [7,8] , the near-electrode processes caused by the Hall effect and leading to the phenomenon of the current crisis [9] , the compressible streams, the radiation transport, the dynamics of impurities, as well as the numerical models of the ionization process corresponding to different levels of complexity [1,3,10,11] . Besides the investigations of the ionization processes, the plasma dynamics and radiation transport are connected with a number of other actual branches of science, and a plenty of publications is devoted to them (see e.g.…”

Experimental Study of Integrated Characteristics of Plasma Stream and Discharge of a Quasi-Stationary High-Current Plasma Accelerator With Its Own Magnetic Field

“…Брушлинским, под руководством которого сформировалось научное направление по математическому моделированию различных задач плазмодинамики и плазмостатики [28,31]. Численным исследованиям динамики потоков в ускорителях также посвящён ряд публикаций [35][36][37][38][39][40][41][42][43].…”