A model for double base propellant combustion

Abstract

A model has been developed to describe the combustion of double base propellants with a primary objective to develop a better understanding of the combustion mechanisms of double base propellants in both condensed and gas phases. The gas phase in double base propellants sustains two flames which are separated by a dark zone at low pressure. At high pressure, the secondary flame merges into the primary flame, eliminating the dark zone. The proposed model calculates the temperature profile in both the condensed phase and through both flames of the gas phase. the model solves the energy equations and species equations for both the condensed and gas phases separately, and then matches the boundary conditions between the two phases. The model assumes that there are three parallel reactions occurring in the condensed phase; a zero order degradation reaction, a first order reaction with NO 2 , and a second order reaction of complex aldehyde species. The gas phase kinetics are summarized with four reactions; a first order NO 2 reaction, a second order reaction of aldehydes, a first order NO-carbon reaction, and a second order NO reduction reaction. p In the past, several models have been developed to predict the burning rate of double base propellant as a function of pressure and initial temperature. Increasingly numerous experimental results (most from Kubota and Zenin) provide a well established data base which, along with increased computing capability, now allow one to verify the reliability of numerical models using a much broader variety of experimental data. A complete model must determine the burning rate as a function of pressure and initial temperature. In this study, the behavior of each reaction zone through the propellant combustion wave has been examined.