Progress in Electron Energy Modeling for Plasma Flows and Discharges

TL;DR

This paper introduces a simplified and more accurate model for electron energy relaxation in plasma flows and discharges, effectively capturing inelastic collision effects using only two key parameters and validated against experimental data.

Contribution

A new formulation of electron energy relaxation terms that simplifies implementation and improves accuracy by relying on reduced electric field and mobility, applicable to various plasma conditions.

Findings

Model accurately predicts electron temperatures in plasma flows.

Validation shows superior performance over previous models.

Effective for both low and high electron temperature regimes.

Abstract

A novel formulation of the electron energy relaxation terms is presented here, which is applicable to plasma flows and discharges wherein the electron temperature could be higher or lower than the gas temperature. It is demonstrated that the electron energy losses due to inelastic collisions can be expressed as a function of only two species-dependent parameters: the reduced electric field and the reduced electron mobility. This formulation is advantageous over previous ones, being simpler to implement and more accurate when experimental data of the reduced electric field and reduced mobility are available. Curve fits to empirical data of these two properties are outlined here for all important air molecular species. The approach accounts for all inelastic electron energy relaxation processes without needing individual cross-sections or rates, reducing potential errors associated with independently handling each process. Several test cases are presented to validate the proposed electron energy source terms including re-entry plasma flows for which the electron temperature is less than the gas temperature, as well as discharges in which the electron temperature reaches values in excess of 30 eV. In all cases, the agreement with experimental data is observed to be very good to excellent, significantly surpassing prior electron energy models for plasma flows