Thermal decomposition, flame propagation, and combustion reactions behaviours of stearic acid by experiments and molecular dynamic simulation

To better look into the thermal decomposition and combustion progress of stearic acid (C18H36O2), the experi-mental tests and Reaction Force Field (ReaxFF) molecular dynamics simulation were conducted. Also, an investigation into the Hame propagation characteristics and the reaction mechanisms of stearic acid was explored under different conditions. The thermal decomposition activation energy of stearic acid obtained by the TG tests was 105.01 kJ/mol. This is consistent with the initial decomposition stage reaction activation energy calculated to be 94.273 kJ/mol in the simulation. The Hame propagation process of stearic acid combustion was explored and involved three stages: the Hame growth stage, the stable Hame stage, and the Hame decay stage. The Hame growth stage was subdivided into the Hame growth inside the tube, upper the tube, and mushroom-shaped cloud. Besides, the Hame growth stage could correspond to three Hame propagation velocity peaks. Furthermore, the simplified reaction mechanism scheme for stearic acid radicals could explain the macro Hame propagation be-haviours. The main reaction pathway through which the C18H36O2 molecules were decomposed into C2H4 and center dot C2H3, center dot C2H5, and other free radicals was found to correspond to the initial Hame growth stage, and the Hame decay stage was dominated by the generation of final reaction products (H2O, CO2, and CO2, etc.). Concerning the overall reaction mechanism, the unburned stearic acid was continuously ignited, and the combustion products were continuously generated at the same time, thereby corresponding to the stable Hame propagation stage. According to the Hame propagation process and the simulation results, combustion reaction mechanisms of stearic acid were constructed.