Revealing reaction kinetics in ammonium perchlorate (AP) combustion using an EM-HyChem approach

The combustion kinetics of ammonium perchlorate (AP), a key oxidizer in solid propellants, remain debated due to the complexity of its solid-phase decomposition. In this study, the reaction kinetics of AP is resolved by decoupling the complex combustion process into solid-phase pyrolysis and gas-phase oxidation sub-processes, proposed as EM-HyChem approach. By this approach, the key pyrolysis products and reaction mechanisms are identified through molecular dynamics simulations. The chemical reaction neural network model is then employed to extract the rate parameters in pyrolysis model from thermogravimetric experiments. Subsequently, the pyrolysis model is coupled with an oxidation model for the pyrolysis products to build a kinetic model for AP. The kinetic model is used to simulate AP laminar flame via a one-dimensional method. Predicted burning rates, surface temperatures, and species profiles show good agreement with results from other experimental measurements and models. Sensitivity analysis of kinetic parameters provides insights into the factors contributing to the N-shaped curve of the AP burning rate.