Analysis of nozzle geometries for hydrogen direct injection internal combustion engine

This study investigates the influence of injector geometry on hydrogen fuel mixing and combustion performance in a light-duty pent-roof spark-ignition engine under engine-relevant conditions. Using CONVERGE CFD v3.1, simulations were conducted for various injector designs, including hollow-cone and solid multi-hole configurations (ranging from one to ten holes), to analyze their effects on jet dynamics, turbulence, fuel–air mixing, combustion efficiency, and emissions. The results demonstrate that multi-hole injectors significantly enhance hydrogen–air mixing compared to hollow-cone designs, promoting more uniform fuel distribution. The ten-hole injector achieved the most effective mixing, leading to lower combustion temperatures and reduced NO${}_x$ emissions. However, the six-hole injector provided an optimal balance, delivering higher work output while maintaining low emissions and reduced heat transfer losses. Additionally, the study examines the impact of caps on hollow-cone injectors, revealing distinct jet dynamics that require careful design to optimize fuel–air distribution. While the study is limited to simulations conducted under engine-relevant conditions without parametric optimization of operating variables, its scope focuses on evaluating injector and cap modifications to highlight their distinct features. These findings offer new insights into how injector geometry and cap design influence in-cylinder processes and provide guidance for the future development of efficient, low-emission hydrogen-fueled internal combustion engines.