Numerical and experimental development of a swirl based hydrogen combustion engine on 15L platform

Ongoing regulatory developments in the transportation sector have increasingly prioritized the reduction of pollutant and greenhouse gas emissions at both the engine and vehicle levels. Within the commercial transport segment, technology adoption trends may differ significantly from those observed in the light-duty vehicle market due to specific constraints related to payload capacity and total cost of ownership. Among the various technological pathways under consideration, hydrogen internal combustion engines (H2-ICEs) are emerging as a viable solution to support decarbonization targets in heavy-duty applications. Nonetheless, load output parity with diesel engines, pre-ignition and compatibility with commercial combustion systems are still areas of attention. This study presents the development of a swirl-based combustion system for hydrogen utilization, building upon an existing production-grade diesel engine platform. The proposed system design methodology incorporates a simulation-driven approach to identify optimal injection and ignition strategies. Two piston concepts were evaluated: a high-turbulence re-entrant bowl and a low-turbulence open bowl configuration, each associated with distinct compression ratios (CR) (12 and 10.5, respectively). Experimental investigations were carried out across a range of equivalence ratios, combustion phasing strategies, and injection timing windows under multiple operating conditions. Results indicate that the baseline piston bowl geometry—adapted from a natural gas engine—exhibited limited load capability (50% of the maximum engine output) due to frequent pre-ignition events. In contrast, the optimized, lower-compression-ratio design enabled over 90% increase in brake mean effective pressure (BMEP), while significantly reducing pre-ignition occurrence However, this improvement in load capacity was accompanied by elevated NOx emissions and an increase of up to 20% in hydrogen emissions, suggesting increased charge stratification with the second combustion system.