Numerical analysis of detonation dynamics in ammonia–hydrogen mixtures

Ammonia (NH 3 ) blended with hydrogen (H 2 ) offers a carbon-free energy-conversion pathway for advanced power and propulsion systems. However, the slow chemical kinetics of NH 3 , together with its high ignition energy and narrow flammability limits, pose substantial challenges for detonative combustion. This study investigates detonation propagation in NH 3 –H 2 –O 2 mixtures through two-dimensional simulations of the compressible reactive Navier–Stokes equations with detailed chemical kinetics and species transport. To make these simulations computationally tractable, a sensitivity-enhanced skeletal mechanism, denoted S12R29, is developed from a detailed H 2 oxidation model and extensively validated under post-shock conditions with detailed mechanisms. The reduced mechanism preserves ignition delay and the Chapman–Jouguet (CJ) and von Neumann (VN) prediction accuracies while decreasing computational cost by approximately 73%, enabling systematic simulations over NH 3 /H 2 ratios from 0 to 0.6. Pure H 2 –O 2 mixtures exhibit robust self-sustained detonation with stable Mach-stem and triple-point structures. In contrast, NH 3 -enriched mixtures show progressively reduced wave speeds, lower triple-point density, weakened transverse-wave activity, irregular cellular patterns, and diminished pressure and hydroxyl-radical signatures. A detonation sustainability threshold is identified near NH 3 /H 2 ≈ 0 . 4 2 5 , beyond which self-sustained propagation is no longer maintained under the present conditions. The findings establish quantitative relationships between fuel composition and detonation characteristics, providing fundamental insight into NH 3 -enriched carbon-free fuels for propulsion and safety-critical energy systems.