Experimental observation and modeling of solid composite propellants

Trevor Hedman, Purdue University

Abstract

Since the 1960's, composite propellants have been widely used in rocketry applications because of their excellent performance and low cost to implement. Due to their pervasive use, there has been a strong desire for a method to predict the performance of a propellant a priori. The ability to predict performance would accelerate development of solid propellants, minimizing the required amount of costly empirical data. Early flame structure models for composite propellants such as the granular diffusion flame (GDF) and the Beckstead, Derr, Price (BDP) models, were introduced in the 1960's and 1970's respectively. These well-known models involved the development of heuristic relations to predict the burning rate of a composite propellant. Increased computing power in recent years has allowed for more advanced modeling of solid propellants. Models exist today that incorporate detailed chemistry in the gas phase with a simplified geometry as well as a 3-D surface structure using simple chemistry. However, these models lack validation due to the dearth of detailed experimental data on composite propellants. This is due, in part, to the challenging nature of the combustion environment. The flame is particulate heavy, transient, and highly spatially variant. Additionally, composite propellant surface morphology is complex, made up of complex mixtures of oxidizers and fuels. This document summarizes an effort to provide detailed experimental data for todays advanced models that is currently lacking in the literature. Experiments are designed and carried out to quantify the flame structure and surface behavior of various composite propellants. High speed PLIF and high resolution surface imaging are employed at various pressures in order to characterize flame structure and surface behavior. In addition, an attempt is made to begin to improve existing composite propellant models. This is performed by first combining a micro-scale detailed chemistry model and a meso-scale model that includes surface topography. This model is compared with the experimental results and areas for improvement are identified. It is hoped that increased knowledge of the flame structure and surface structure of composite propellants will translate into better a priori predictions of performance eventually.

Degree

Ph.D.

Advisors

Lucht, Purdue University.

Subject Area

Mechanical engineering

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