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.