A basic hybrid rocket oxidizer delivery system utilizes the self-pressurizing nature of a liquid oxidizer at ambient temperatures in conjunction with a non-condensable pressurant to provide a high oxidizer tank pressure that drives liquid oxidizer flow to the combustion chamber. In this study, the oxidizer fluid is nitrous oxide which produces high vapor pressures at ambient temperatures, and helium is the pressurant. The goal of this thesis is to provide a theoretical model that predicts the pressure draining history of the oxidizer tank to within ± 5% of experiment. The validity of simple thermodynamically-based models has not been considered for self-pressurizing, draining propellant tanks under high pressure conditions. In this study, two models are produced, both assuming thermodynamic equilibrium states at every point in time throughout draining. The first model assumes the P-V-T behavior of the nitrous oxide/helium mixture is ideal; the second model assumes that the mixture adheres to the non-ideal Peng-Robinson equation-of-state. Both models are compared to experimental data from pure nitrous oxide draining tests, published in G. Zilliac and M. Karabeyoglu (Modeling of Propellant Tank Pressurization, AIAA 2005-3549, 41st AIAA/ASME/ASEE Joint Propulsion Conference). Theoretical draining histories for the Peregrine hybrid sounding rocket (a joint effort between NASA Ames Research Center and Stanford University), soon to be launched from NASA Wallops Flight Facility, have also been examined. A variety of comparisons with available experimental data, theoretical sensitivity studies, and theoretical launch data demonstrates that the non-ideal draining model provides favorable agreement. The additional complexity introduced by a non-ideal equation-of-state is necessary due to the high pressures encountered in the tank during draining. It is found that despite the highly nonlinear nature of the draining process, the liquid flow rate from the tank remains reasonably constant, which is a highly desirable characteristic of a rocket oxidizer delivery system.
Library of Congress Subject Headings
Hybrid propellant rockets--Design and construction--Mathematical models; Rockets (Aeronautics)--Fuel tanks--Mathematical models; Propellants--Mathematical models; Rocket engines--Combustion--Mathematical models
Department, Program, or Center
Mechanical Engineering (KGCOE)
Fernandez, Margaret Mary, "Propellant tank pressurization modeling for a hybrid rocket" (2009). Thesis. Rochester Institute of Technology. Accessed from
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