Computational analysis of performance and emissions of spark-ignition engines fueled with ammonia/hydrogen blends

In the current scenario, where automotive companies seek alternatives to fossil fuels to reduce greenhouse gas emissions, ammonia has emerged as a promising carbon-free energy carrier. However, its low reactivity and combustion characteristics pose challenges for direct utilization in internal combustion engines. This study investigates the feasibility of using ammonia–hydrogen blends as fuel for commercially-available automotive turbocharged spark-ignition engines. A computational methodology is employed, combining non-dimensional thermodynamic modeling with 1D simulations and a phenomenological combustion model specifically designed for ammonia–hydrogen blends. The results show that using pure ammonia as fuel has limitations in the low-end region due to compressor surge and, primarily, at low loads due to combustion instabilities. An optimal hydrogen percentage is identified to minimize energy consumption, with its effect becoming more significant at lower engine loads and higher engine speeds. Additionally, increasing the hydrogen percentage in the mixture leads to higher NOx emissions due to increased combustion temperatures. These findings suggest that ammonia–hydrogen blends used in conventional engine systems can be a viable option for reducing greenhouse gas emissions from automotive applications, provided that control strategies are implemented to mitigate emission formation.