A Computational Investigation of Hydrogen Pre-Chamber and Spark-Ignition Combustion Engines at Different Load Conditions

Efficient powertrains are now critical in the pursuit of a net-zero emissions future. Hydrogen has emerged as a leading alternative fuel due to its superior combustion characteristics, such as fast flame speed, and its potential to support clean, sustainable energy systems. In hydrocarbon premixed combustion, pre-chamber technology has shown significant potential by improving system ignitability, enhancing turbulence and mixing, and mitigating knock tendency. However, in the context of hydrogen combustion—where the inherent fast flame speed may overshadow these advantages—the effectiveness of pre-chamber technology remains unclear. As a result, its application must be carefully scrutinized and compared with conventional spark ignition systems. Direct injection is the preferred fueling method for hydrogen, as it maximizes power density while addressing safety concerns. However, strong stratification in fuel-air distribution can arise, where the enhanced mixing from highly-turbulent pre-chamber jets may offer performance benefits. This study numerically investigates hydrogen combustion under both pre-chamber and spark ignition systems at varying engine loads and a fixed lambda with 3D-CFD simulations. Different loads were achieved by adjusting intake pressure and the total injected hydrogen mass systematically. The results suggest that proper characterization of mixing behavior is critical for achieving stable combustion. At low loads, pre-chamber ignition significantly enhances combustion performance compared to spark ignition, which suffers from high exhaust energy losses due to slower combustion. At medium and high loads, pre-chamber ignition shows promise, particularly when considering NOx emissions reduction strategies, as it enhances system reactivity.