Prediction of explosion dynamics of H2/NH3/Air using large eddy simulation and thickened flame model

To enhance the safety of hydrogen-ammonia fuel utilization, this study explores the complicated relationship between hydrogen content (α(H 2 )) and explosion dynamics. By integrating an optimized combustion mechanism with large eddy simulation (LES) and thickened flame (TF) models, it uncovers how α(H 2 ) can modulate flame acceleration via regulating chain-branching and nitrogen-chemistry pathways. The LES-TF approach successfully reproduces the crucial explosion parameters, including flame propagation speed, explosion overpressure development, three-dimensional flame structure and radical distribution. Quantitative analysis reveals that increasing α(H 2 ) from 50 % to 75 % causes the reaction flux of H 2 - H to surge by 110 %, while the sensitivity coefficient of the chain-propagating reaction OH + H 2 ⇌ H + H 2 O increases by 63.2 %. The key findings indicate that increasing the hydrogen volume fraction (α(H 2 )) significantly enhances laminar burning velocity (LBV) by promoting the radical-driven chain branching reactions while simultaneously suppressing the influence of nitrogen chemical pathways. The flow fields in the burned zones significantly influence flame evolution and radical distributions during flame acceleration, particularly during the formation of “tulip” flames. The intricate interplay of radical mass fractions and flow fields modulates explosion behavior. This work can establish a predictive approach for H 2 /NH 3 /air explosion and provide guidelines for mitigating explosion risk in fuel storage systems.