Work

Effect of H 2 in fuel-rich NH 3/H 2/air mixtures: Explosion venting experiments and molecular dynamics simulations

Year: 2025

Type: article

Abstract: Ammonia (NH₃) is an important component of low-carbon energy systems, often blended with hydrogen (H₂) to optimize energy utilization efficiency and operated under fuel-rich conditions to reduce nitrogen oxides (NOx) generation. However, the potential explosion safety risks of NH₃/H₂/Air cannot be ignored. In this study, the explosion process of NH₃/H₂/Air premixed gases under fuel-rich conditions is investigated, focusing on H₂ volume fractions of 5%, 10%, 15%, and 20%. The variations in pressure and venting flame characteristics during the process of explosion are analyzed. Meanwhile, the reaction mechanism of the fuel-rich NH₃/H₂/Air system is analyzed from the microscopic perspective through the use of the reactive force field molecular dynamics method. The results indicate that with the increase of the proportion of H₂ in the fuel-rich mixture, the maximum explosion pressure (pmax) and the maximum rate of pressure rise ((dp/dt) max) decrease. At 5%, pmax and (dp/dt) max are 0.22 MPa and 8.10 MPa·s⁻¹, respectively. The first venting flame lengthens at first and then shortens, while the length and velocity of the second venting flame increase. On a microscopic level, the addition of H₂ reduces the decomposition rate of NH₃, increases the generation frequency of •OH and •H in the system, and significantly decreases the amount of NOx produced. Through the analysis of explosion venting and molecular dynamics reaction mechanisms, this study provides strong support for the safe and efficient practical application of fuel-rich NH₃/H₂/Air mixtures in the energy sector.

Source: Safety Emergency Science

DOI: 10.26599/ses.2025.9590009