Molecular Dynamics Simulation of Thermal Nonequilibrium and Chemical Reaction Processes in Hydrogen Combustion

Using reactive force field (ReaxFF) and molecular dynamics simulation, we investigate the combustion process of hydrogen-oxygen systems in initial thermal nonequilibrium states with different translational and rovibrational temperatures for oxygen. The system studied in this work contains 300 oxygen molecules and 700 hydrogen molecules with a density of 7 times the air density. For this system, the characteristic relaxation times of oxygen and hydrogen vibrational energies are 0.173 and 0.249 ns, respectively. 0.6% of hydrogen undergoes a chemical reaction with oxygen during the thermal nonequilibrium relaxation stage. For the distribution of translational energy and vibrational energy of oxygen in the thermal nonequilibrium state, the maximum mean error of the statistical distribution in the simulation and the Boltzmann distribution at temperature calculated from the average kinetic energy of molecules is about 2.25 × 10^-5. At the same time, it was observed in the simulation that many-body interactions play a certain role in the combustion process. Furthermore, we compare the ignition time and temperature rise behavior of different combustion mechanisms and molecular dynamics simulations starting from the thermal equilibrium state. These results will provide meaningful references for the construction of thermal nonequilibrium combustion chemical reaction mechanisms.