Numerical study on ammonia/hydrogen supersonic combustion in a strut-based scramjet engine

This study explores ammonia/hydrogen supersonic combustion in a Mach 2.0 strut-based combustor through three-dimensional Reynolds-Averaged Navier–Stokes (RANS) simulations and one-dimensional laminar counterflow flame modeling. The investigation focuses on the effects of ammonia blending ratios (0–0.5) and fuel inlet temperatures (250–600 K) on flame stabilization and pollutant emissions. Results show that increasing ammonia content weakens flame anchoring due to suppressed radical generation (H, OH) and poorer fuel-air mixing, leading to flame extinction at a blending ratio of 0.5, accompanied by a shortened flame length and increased lift-off height. Fuel preheating to 600 K enhances flammability, reducing lift-off height by 42 %, though it decreases heat release by 67 % due to faster decomposition. While NH₃ and NO emissions rise with ammonia blending, preheating suppresses NO via enhanced NH₃ decomposition and inhibited NH→N conversion. These findings provide preliminary insights into the stabilization mechanisms of ammonia-based fuels, supporting the development of low-carbon strategies for scramjet propulsion systems.