Challenges with the self-consistent implementation of closure models for anomalous electron transport in fluid simulations of Hall thrusters

Marks, Thomas A.; Jorns, Benjamin

doi:10.1088/1361-6595/accd18

Cited by 14 publications

(4 citation statements)

References 39 publications

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“…Since lateral walls are dielectric, it must be satisfied I zi + I ze = I d = const. Figure 7 plots I zi (z) and the three contributions to equation (15). These current balances for ions and electrons are satisfied by the PIC solution with errors lower than 5%.…”

Section: Current and Energy Balancesmentioning

confidence: 84%

“…They still miss the azimuthal effects, the main one being the presence of high-frequency nonlinear azimuthal instabilities, which are considered the most plausible cause of the 'anomalous' stationary cross-field transport of electrons [13]. Axial, radial and axial-radial models include this anomalous transport with simple empirical models [1], fitting either performance figures [12] or axial profiles [14,15].…”

Section: Introductionmentioning

confidence: 99%

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Non-Maxwellian electron effects on the macroscopic response of a Hall thruster discharge from an axial–radial kinetic model

Marín-Cebrián,

Bello-Benítez,

Domínguez-Vázquez

et al. 2024

Plasma Sources Sci. Technol.

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A 2D axial-radial particle-in-cell (PIC) model of a Hall thruster discharge has been developed to analyze (mainly) the fluid equations satisfied by the azimuthally-averaged slow dynamics of electrons. Their weak collisionality together with a strong interaction with the thruster walls lead to a non-Maxwellian velocity distribution function (VDF). Consequently, the resulting macroscopic response differs from a conventional collisional fluid. First, the gyrotropic (diagonal) part of the pressure tensor is anisotropic. Second, its gyroviscous part, although small, is relevant in the azimuthal momentum balance, where the dominant contributions are orders of magnitude lower than in the axial momentum balance. Third, the heat flux vector does not satisfy simple laws, although convective and conductive behaviors can be identified for the parallel and perpendicular components, respectively. And fourth, the electron wall interaction parameters can differ largely from the classical sheath theory, based on near Maxwellian VDF. Furthermore, these effects behave differently in the near-anode and near-exit regions of the channel. Still, the profiles of basic plasma magnitudes agree well with those of 1D axial fluid models. To facilitate the interpretation of the plasma response, a quasiplanar geometry, a purely-radial magnetic field, and a simple empirical model of cross-field transport were used; but realistic configurations and a more elaborated anomalous diffusion formulation can be incorporated. Computational time was controlled by using an augmented vacuum permittivity and a stationary depletion law for neutrals.

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Section: Current and Energy Balancesmentioning

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Non-Maxwellian electron effects on the macroscopic response of a Hall thruster discharge from an axial–radial kinetic model

Marín-Cebrián,

Bello-Benítez,

Domínguez-Vázquez

et al. 2024

Plasma Sources Sci. Technol.

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“…In practice, the user can adjust the eight free parameters in this model to match the experimentally measured quantities of interest such as current and thrust. Similar piecewise anomalous transport profiles have been previously used to simulate a number of Hall thrusters in Hall2De [35,44].…”

Section: Anomalous Electron Transportmentioning

confidence: 99%

“…This set of spatiallyresolved data has become one of the standard references for calibrating the electron collision frequency as it varies axially [35]. To quantify the agreement between the simulation and the experimentally-measured ion velocities, we define the integrated velocity residual (IVR) [44]:…”

Section: Metrics For Calibrating Anomalous Collision Frequencymentioning

confidence: 99%

Trends in mass utilization of a magnetically shielded Hall thruster operating on xenon and krypton

Su,

Marks,

Jorns

2024

Plasma Sources Sci. Technol.

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The trends in mass utilization with increasing discharge voltage and current are investigated for a magnetically shielded Hall thruster operating on xenon and krypton. A 9-kW class shielded thruster is operated with discharge voltages from 300 to 600 V and discharge currents from 15 to 30 A on xenon and krypton. Experimental measurements of discharge current, thrust, anode efficiency, and ion velocity as a function of axial position are used to calibrate a multi-fluid 2D Hall thruster code at all operating conditions. The results of these calibrated simulations are employed to interrogate the plasma properties inside the thruster channel. A simplified 0D model for mass utilization evaluated on spatial averages of the simulated plasma parameters is employed to interpret the response of this efficiency mode with power for each propellant. It is found that with both higher voltage and current, mass utilization increases for both gases and their relative gap in this efficiency decreases. This can be attributed to the higher plasma densities and ionization rate coefficients at high voltage, and solely to higher plasma densities at high current. The driving factors for the increase in mass utilization are examined in the context of its nonlinear response to internal plasma properties. The behavior of mass utilization is also discussed in context of the gap in overall efficiency between the propellants. Finally, the implications of these results for improving the performance of high power Hall thrusters operating on krypton are examined.

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Predicting Performance of Hall Effect Ion Source Using Machine Learning

Park,

Doh,

Lee

et al. 2024

Advanced Intelligent Systems

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Accurate performance prediction methods are essential for the development of high‐efficiency Hall effect ion sources, which are employed in industries ranging from material surface treatment to spacecraft electric propulsion (known as Hall thrusters). Traditional methods rely on simplified scaling laws and computationally intensive numerical simulations. Herein, a robust machine learning model is introduced that uses a neural network ensemble to predict the performance of Hall effect ion sources based on design parameters such as discharge channel dimensions and magnetic field structure. The neural networks are trained using 18 000 data points generated from numerical simulations with input powers ranging from sub‐kW‐ to kW‐class. The accuracy of the developed machine learning model is demonstrated using untrained 700 W‐ and 1 kW‐class Hall effect ion sources, producing results with deviations of less than 10% compared to the experimentally measured thrust and discharge current, thus surpassing the accuracy of conventional scaling laws. As a high‐fidelity surrogate for numerical simulations, the proposed prediction tool provides high prediction accuracy and calculation speed, offering an excellent complement to conventional scaling laws and enhancing the understanding of Hall effect ion source performance characteristics.

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Challenges with the self-consistent implementation of closure models for anomalous electron transport in fluid simulations of Hall thrusters

Cited by 14 publications

References 39 publications

Non-Maxwellian electron effects on the macroscopic response of a Hall thruster discharge from an axial–radial kinetic model

Non-Maxwellian electron effects on the macroscopic response of a Hall thruster discharge from an axial–radial kinetic model

Trends in mass utilization of a magnetically shielded Hall thruster operating on xenon and krypton

Predicting Performance of Hall Effect Ion Source Using Machine Learning

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