A New Gaskinetic Model to Analyze Background Flow Effects on Weak Gaseous Jet Flows from Electric Propulsion Devices

Chunpei Cai

doi:10.3390/aerospace4010005

Abstract

Recent work on studying rarefied background and jet flow interactions is reported. A new gaskinetic method is developed to investigate two closely related problems. The first problem is how a collisionless background flow can affect a highly rarefied jet flow. The rarefied jet and background flow conditions are assumed available and described with seven parameters. Gaskinetic theories are applied and formulas are obtained for the mixture properties. Simulations are performed to validate these expressions, and excellent agreement is obtained. The second problem is to recover the collisionless background and jet flow parameters with limited measurements. A group of linearized equations are derived for the flowfield properties. The solving process includes initial estimations on the seven parameters, followed with iterations. Numerical tests are performed and the results indicate the procedure is accurate and efficient. The new method and expressions can reduce the amount of experimental work and numerical simulations to analyze facility effects. Parameter studies with particle simulations may require several months; however, the new methods may require minutes. These methods can be used to quantify and predict jet performance, vacuum chamber designs and optimization. Applications may be for many societies using vacuum conditions.

Highlights

For many engineering applications under near vacuum conditions, such as molecular beams [1], materials processing inside vacuum chambers [2], and electric propulsion (EP) devices in a space environment [3], there are always dilute background flows
For plume investigations, which are important to the rocket industry, the cosine law model [4] is a good example for modeling the background flow effects
The purpose of this paper is to address this issue by developing new and unique models to analyze dilute background flow effects on dilute weak jet flows

Summary

Introduction

For many engineering applications under near vacuum conditions, such as molecular beams [1], materials processing inside vacuum chambers [2], and electric propulsion (EP) devices in a space environment [3], there are always dilute background flows. For plume investigations, which are important to the rocket industry, the cosine law model [4] is a good example for modeling the background flow effects. These rarefied background flows have specific density, velocities, temperature, and flow directions. A spacecraft, e.g., satellite, space shuttle, or a space station, may have many small EP devices for station-keeping or primary propulsion missions At different orbits, such as a low Earth orbit or the Earth geostationary orbit, the local atmosphere densities, velocities, orientation angles, and temperatures are different; the performances of EP devices may be different from those inside a ground test vacuum chamber. A certain amount of background gas may enter the EP devices, and the mass flow ratio can be computed as: ṁb ṁ j q βb π R0

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Conclusion