Enhancing Combustion Characteristics of Ammonia-Fueled Motorcycle Engines using Multi-Point Ignition Strategy

Abstract

This study presents simulation results on the influence of ignition system configuration on the performance and emissions of an ammonia-fueled motorcycle engine. Two ignition strategies were examined on a Honda engine at 7500 rpm: single-point ignition and three-point distributed ignition. The results indicate that the single-spark configuration failed to overcome ammonia's low laminar flame speed, resulting in a power output of only 4.36 kW (32% lower than that of gasoline). In contrast, the three-spark system significantly enhanced combustion rates, elevating peak pressure to 45.49 bar (exceeding the gasoline baseline of 41.39 bar) and increasing power to 5.36 kW. Although the three-point configuration increased NOx emissions to 908 ppm at an ignition timing of 30°CA, retarding the timing to 20°CA reduced NOx to 294 ppm while maintaining a power output of 4.83 kW.  The findings confirm that multi-point ignition, combined with MBT (Minimum advance for Best Torque) optimization for each ignition configuration, is essential for the practical application of NH₃ in high-speed motorcycle engines.