Gas phase ignition theory for homogeneous propellants under shock tube conditions

Theoretical characteristics of the ignition phenomenon, wherein a homogeneous propellant is exposed to stagnant gas after a shock reflection, derived by a combination of numerical and approximate techniques, are discussed. The one-dimensional model considered variable gas density, simultaneous diffusion and chemical reaction, self-determining (feedback) conditions at the solid-gas interface, and various solid and gas phase compositions. The descriptive equations were integrable over the whole time to achieve steady combustion of the solid, giving a complete spectrum of ignition results. In particular, approaching the steady state, a predictable, inverse square dependence on external oxidizer mole fraction was found for the ignition delay. This was true with large external oxidizer mole fractions, even with feedback operative, and resulted n a twin reaction zone structure which disappeared at low oxidizer mole fractious. This effect was found for a wide range of gas phase stoichiometry and solid composition. Further data are presented for a wide range of pyrolysis rates of the solid.