The intrinsic influence mechanism of HENG explosion under different hydrogen blending ratios and equivalence ratios: A combined ReaxFF and MD study

Abstract

To uncover the underlying reaction mechanism and evolution mechanism of hydrogen-enriched natural gas (HENG) explosions, this study employed reactive force field–molecular dynamics (ReaxFF-MD) to investigate the molecular reactive thermodynamic behavior of HENG at various hydrogen blending ratios and equivalence ratios. An evolution pathway for carbon-containing substances was constructed, elucidating the microscopic mechanism of HENG explosions at the atomic level. The results indicated that the microscopic oxidation process in the typical explosion of HENG system can be divided into five stages: initiation, methane excitation, hydrogen augmentation, hydroxyl oscillation, and burnout. The primary evolution pathway of carbon containing substances can be summarized as: CH₄ → ·CH₃ → CH₂O → ·CHO → CO → CO₂. The presence of hydrogen molecules can reduce both the excitation time of methane (T1) and the time for methyl radicals to reach their first peak (T2). As the number of hydrogen molecules increases, the oscillation amplitude of H and ·OH radicals intensifies during the reaction, enhancing the explosive reactivity of the system. A reduction in the oxygen content shortens the system's initiation time; however, it also leads to earlier termination of the system's oxidation process. This study provides an atomic-level explanation of the explosion behavior of HENG, offering scientific guidance for effective accident prevention and management, as well as a theoretical foundation for the development of explosion suppression technologies.