Multispecies Reacting Flow Model for the Plasma Efflux of an ETC Igniter - Application to an Open-Air Plasma Jet Impinging on an Instrumented Probe

Abstract : The U.S. Army Research Laboratory (ARL) is investigating the electrothermal-chemical (ETC) gun concept. As part of this program, ARL has recently begun a comprehensive study on the interaction of the plasma efflux from an ETC igniter with solid propellant grains. The goal of this work is to elucidate the relevant physical, mechanical, and chemical mechanisms that underlie the observed ballistic effects in ETC guns that can lead to useful performance gains once an understanding of these mechanisms is achieved. This report describes the first phase of the modeling effort in support of this plasma-propellant interaction project. A time-accurate computational fluid dynamics code was used that included high-temperature thermodynamics, variable specific heats and transport properties (viscosity and thermal conductivity), and finite-rate (nonequilibrium) chemical kinetics. Validation of this code used a series of experiments with an ETC igniter fired into open air, generating an unsteady flowfield in which a measurement probe is placed. Computer simulations revealed important gas dynamic and chemical details of the plasma jet as it interacted with the probe and represented the first such detailed modeling of ETC plasma efflux.