Simultaneous optimization of water addition and exhaust gas recirculation in a hydrogen-fueled compression-ignition engine: Numerical and experimental analysis

Due to escalating concerns surrounding climate change and its profound implications for human well-being, governments have enacted stringent emission regulations. The aim is to encourage the adoption of alternatives to fossil fuels. In this study, a compression ignition engine was adapted to run primarily on H2, using diesel fuel exclusively for ignition. The research focused on the effects of the simultaneous use of exhaust gas recirculation (EGR) and water injection (WI) on the control of NOx emissions, intake self-ignition and combustion knocking, for different engine operating conditions and various compression ratios (CR). Test results indicate that NOx emissions increased with the H2 fraction. However, when combining WI with EGR, a reduction of over 90% in NOx emissions was achieved, compared to the case of "No water/No EGR" for all CR conditions. The utilization of EGR also demonstrated a positive impact on engine efficiency, with improvements ranging from 5% to 8%. Overall, this study highlights the potential of WI and EGR as an effective strategy to reduce NOx emissions, while improving engine efficiency in hydrogen-fueled compression ignition engines.