Models used at onera to interpret combustion phenomena in heterogeneous solid propellants

Abstract

The experimental study of the combustion of ammonium perchlorate (AP) spheres and square cross-section rods in a combustible medium was carried out to pressure levels as high as 80 atmospheres. The domain of combustion of AP as a function of pressure and of the dilution ratio of methane are determined. The effect of copper chromite (CC) on the flame flashback velocity and on the combustion constant is indicated; it is attributed partially to a catalysing effect in the gaseous phase but more particularly to a modification of the emissivity and absorption coefficients of the surface of the solid and of the reaction zones. The effect of the local mixing ratio on the AP regression rate is important. The study of the combustion of binder rods placed against AP rods is presented. Between 1 and 20 atmospheres, the nature of the fuel determines the flame flashback velocity, whereas this flashback velocity is not influenced by the nature of the fuel between 20 and 100 atmospheres (except with polyisobutylene). In the presence of a liquid fuel such as dimethylhydrazine, AP gives results which differ but little from those obtained with solid fuels.