Optimizing hydrogen direct injection and NOx emissions via injection-ignition timing strategies in spark-ignition

Abstract The utilization of hydrogen presents a promising solution for achieving carbon neutrality. Hydrogen exhibits a significantly higher combustion rate and flame propagation speed, approximately 5 to 8 times greater than that of gasoline. However, hydrogen combustion can lead to increased NOx emissions due to high combustion temperatures. With precise control of injection and ignition parameters, a stable and efficient combustion will be able to be managed in direct-injection hydrogen engines. This study aims to propose optimal ignition and injection timing strategies for hydrogen in spark-ignition engines, with the objectives of minimizing NOx emissions and maximizing engine efficiency. The research is conducted through simulations using Converge CFD software, based on the specifications of a 1.6-liter, four-cylinder Campro engine parameter. The focus is on direct-injection hydrogen combustion under moderate engine speed conditions at 2000 RPM, examining the effects of varying injection and ignition timings to achieve optimal combustion performance. The results show that early injections improve combustion efficiency due to more complete combustion and slight increase in NOx emissions. Similarly, advanced ignition timing enhances combustion efficiency but also contributes to higher NOx levels. This study concludes that a combined strategy of optimized injection and ignition timing effectively balances thermal efficiency and NOx emission control in directinjection hydrogen engines.