Formulation and evaluation of a high-pressure discrete droplet gasification model for bipropellant liquid rocket combustor modeling applications

This thesis presents the formulation of a high-pressure, discrete droplet gasification submodel for application in a spray combustion CFD code and an evaluation of its potential for use in liquid rocket combustor modeling. Introductory background information and a critical review and survey of the research literature are presented to identify current research status and needs and to assimilate existing knowledge as a basis for model development. The theoretical formulation of a spherically-symmetric, diffusion-transport-controlled, and quasi-steady, time dependent gasification model, with empirical corrections for convective effects, is presented. And thermodynamic vapor-liquid equilibria models, based upon the Redlich-Kwong equation of state with modified mixing rules for high ambient pressures, are described. Computer codes are developed allowing comparison of theoretical predictions with available experimental data for validation. The pressure dependent parametric behavior of an n-pentane droplet vaporizing in hot nitrogen gas is also examined for subcritical, critical, and supercritical pressures. Vapor-liquid equilibria calculations are performed for an oxygen-hydrogen system using quantum gas mixing rules, and the results are utilized in an investigation of LOX droplet behavior when injected into the hydrogen-rich gas of a high-pressure, liquid rocket combustor. In addition, an evaluation of the gasification characteristics of these LOX droplets in the high-frequency, transverse-mode acoustic oscillations of liquid rocket combustion instability is made from which a physical mechanism for the initiation or sustenance of instability, termed punctuated criticality, is proposed. Some droplet size measurements from preliminary, elevated-pressure droplet combustion experiments are given for hydrocarbons burning in air.