Аннотация:

The local and integral characteristics of a direct current electric discharge in a supersonic flow (Mach number M = 2) located longitudinally to the flow between coaxial electrodes are considered. The paper presents the results of two-dimensional modeling in the PlasmAero and FlowVision software complexes, as well as comparison with the data obtained in the experiment. Longitudinal and radial distributions of the characteristics of the gas flow and discharge at discharge currents from 1 to 7 A are presented.

Ключевые слова:

supersonic flow, electrical discharge, plasma, CFD

Основной текст труда

Studies of the characteristics of an electric discharge under high-speed flow conditions have been widely developed since the early 60’s [1], largely due to the urgent need to search for new efficient technologies in the field of combustion, aerospace industry, and energy conversion. Recently, an extended constricted direct current discharge, or arc discharge, is considered mainly in relation to the problems of control of subsonic [2] and supersonic [3] flows, as well as in works on plasma-assisted combustion [4].

In order to obtain detailed information on the local characteristics of the discharge and the gas flow near the discharge, it was decided to consider a direct current discharge in the simplest formulation: in the core of a supersonic flow (i.e., far from the walls), in a configuration between two coaxial electrodes located parallel to the flow. Such a configuration was realized in an experiment in a supersonic wind tunnel IATD-50 of the Joint Institute for High Temperatures of the Russian Academy of Sciences, while the discharge practically did not have a fragment of the current channel perpendicular to the flow. A discharge with a current of 1–7 A was ignited in a supersonic flow (M = 2, Tg = 167 K, *P* = 22 kPa) between thin electrodes (*D *~ 1mm) with a distance of 30mm between them. The flow parameters in the calculations and the geometry of the model were identical to the experimental one. This configuration had axial symmetry and could be calculated in a two-dimensional axisymmetric formulation in the PlasmAero software package (a detailed description of the model used in the calculation is presented in [5]), as well as in the FlowVision software package (a detailed description of the model used in the calculation is presented in [6]). Two different software packages were used for the following reasons: PlasmAero was developed at the Joint Institute for High Temperatures of the Russian Academy of Sciences to solve problems of plasma aerodynamics; the model used in this work takes into account 11 components (N_{2}, O_{2}, NO, N, O, N_{2} +, O_{2} +, NO +, N +, O +, e) and a set of 49 reactions, but there is no possibility of including the turbulence model; FlowVision is a commercial code in which the one-fluid model (MHD approximation) of electrodynamics was recently added by developers, this CFD code includes standard turbulence models and support the ability to perform 3D calculations. Comparison of the calculation results using these two approaches will make it possible to assess the applicability of the FlowVision package for solving the problem of modeling an electric discharge in a flow and subsequent modeling of plasma-assisted combustion.

In the experiment and simulation, a significant influence of the geometry of the problem on the results obtained was noted. In particular, the formation of flow instability is observed in the shear layer at the interface between the gas heated by the discharge and the surrounding cold flow. In the simulation, two-dimensional distributions of temperature, velocity, current density, as well as radial distributions of the mixture components in the discharge region were obtained. The processing and analysis of the results obtained continues.

Грант

This work was supported by the Russian Science Foundation grant no. 21-79-10408

Литература

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