Injection Temperature and Scheme Effects on Neutral Flow Dynamics in Hall Thrusters

Neutral flow dynamics within Hall thrusters is studied using the direct simulation Monte Carlo method, with a primary focus on assessing the influence of diverse thruster channel geometries and injection schemes. Special emphasis is given to iodine flow. In this regard, the initial analysis covers the theoretical framework required to model dissociation into atomic state and molecular collision parameters. Numerical simulations explore the cases of axial and radial propellant injection with conventional discharge channel configuration, followed by the implementation of a buffer volume directly downstream of the injection point. It is found that the axial injection scheme exhibits the highest degree of radial nonuniformity in terms of neutral density and the shortest characteristic residence time. Substantial improvements for both metrics can be achieved by utilizing a radial injection scheme or integrating a buffer volume. The latter approach results in a superior density uniformity across the channel width, particularly in the region near the anode, although at a slightly lower density for the same propellant flow rate.