Bifurcation in Heterogeneous Combustion
Heterogeneous combustion takes place at the interface separating two different physical phases. The burning of solid propellants for rocket propulsion represents typically this type of combustion. So-called composite solid propellants are mixtures of finely ground salts, such as NH4ClO4 (ammonium Perchlorate = AP), and a polymer binder (for instance polybutadiene) in a ratio of order 4:1. At operational pressures combustion of AP-based solid propellants takes place in a thin zone close to the interface solid/gas. On the solid surface itself the polymer pyrolyzes forming gaseous products, and the AP decomposes into NH3 and HClO4 that react exothermically between themselves and with the polymer vapor in a diffusion flame. Details of the physics and chemistry of this type of combustion may be found elsewhere1-2. The purpose of this study is to present a mathematical model of the solid phase-gas system reacting at the interface, and to show that depending on the external variables (pressure, heat flux by radiation) and on the physico-chemical characteristics of the propellant (energy content, activation energies of the condensed phase decomposition reaction, etc.) burning occurs in different regimes.
KeywordsBurning Rate Bifurcation Diagram Condensed Phase Bifurcation Parameter Solid Propellant
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