Monopropellant Decomposition in a Reactive Atmosphere†

Abstract

The quasi-steady decomposition of a monopropellant is considered when the monopropellant reacts with the ambient atmosphere in a one-step irreversible process. The solution is characterized by the variation of the vaporization rate M with two Damköhler numbers, D ₁ and D ₂, the first a measure of the monopropellant reaction rate and the second a measure of the bipropellant reaction rate. Three possible asymptotic limits are described in the double-equilibrium limit D ₁→∞, D ₂→∞, and necessary and sufficient conditions on the various parameters of the problem are given for these limits to exist. Large activation-energy asymptotics is used to elucidate one of these limits which would otherwise be intractable. The relation of the three limits to known results for pure monopropellant and pure bipropellant burning is clarified by an analysis when just one of the Damkohler numbers is infinite. In particular a complete discussion of the variation of M with D ₂ in the limit D ₁→ ∞ is given when the bipropellant activation energy is large; while the variation of M with D ₁ in the limit D ₂ → ∞ is conjectured from known results for large monopropellant activation energy.