State-Specific Kinetic Modeling of Atomic H for H$_2$/ He Entry Flows

TL;DR

This paper develops a detailed kinetic model for atomic hydrogen in H2/He entry flows, validated against shock tube experiments, improving predictions of ionization and radiation profiles.

Contribution

It introduces a state-specific kinetic model for atomic H in H2/He mixtures, validated with shock simulations and experimental data, highlighting discrepancies in heavy-particle-impact rates.

Findings

The model reasonably reproduces experimental radiance profiles.

Discrepancies in heavy-particle-impact rate data are identified.

The model shows improved accuracy over previous models.

Abstract

An 11-species thermochemical model for H$_2$/ He mixtures with state-specific kinetics for atomic H is developed and used to simulate 1-D shocks at conditions relevant for ice and gas giant entry flows. To implement this kinetic model, a literature review of the state-specific excitation and ionization rate constants of atomic H is first performed. While electron-impact rate constants from various sources are found to be in good agreement, large discrepancies are found in the limited data available on heavy-particle-impact rate constants. To validate the kinetic model, 1-D steady shocks are simulated using a space-marching code that explicitly accounts for shock tube boundary layer effects. The resulting radiance profiles are compared to experimental data from the NASA Ames Electric Arc Shock Tube (EAST) facility, and are found to reproduce the measured values reasonably accurately while capturing the distinct induction zone behavior observed in the experiments. A sensitivity analysis of the kinetic rates and boundary layer treatment reveals avenues for further improvement of the model. Finally, a comparison to alternate models from the literature underscores the improved accuracy of the present model in predicting ionization and radiation profiles.