Optimization of the gas exchange process in a H2 V8 6.6 ℓ 2-stroke heavy-duty spark ignition engine

Ultra-lean hydrogen spark-ignition combustion is a well-established route to near-zero pollutant emissions while enabling high brake thermal efficiency. However, in conventional 4-stroke engines, its effectiveness is limited by the need for very high volumetric efficiency to prevent abrupt performance drops. Turbocharging mitigates this drawback but often fails to guarantee both low-end torque and high maximum power. A 2-stroke cycle offers a compelling alternative, as it can potentially match both the emissions/efficiency and the performance targets. This work explores a novel hydrogen-fuelled 2-stroke valved engine concept, based on the conversion of a stock Duramax V8 6.6 ℓ Diesel engine by GM. The proposed architecture employs poppet valves for both intake and exhaust, dual stage boosting, and minimal modifications aside from redesigning the cylinder head. A combined 0D-1D/3D-CFD methodology is applied to optimize scavenging and fuel-air mixing. 3D-CFD simulations are focused on the in-cylinder flow and mixture formation, while 0D 1D models, calibrated against the 3D-CFD results, are employed to predict brake performance. Scavenging is assessed at three full-load operating points (1200, 1600, 3000 rpm), and mixture homogeneity at spark timing is evaluated at 3000 rpm for different hydrogen injection timings. Results show that shrouded intake valves and a shallow piston bowl strengthen the down-draft tumble vortex, reduce short-circuiting, and promote turbulence-driven mixture homogenization. The findings demonstrate the feasibility of a high-performance, ultra-low emission hydrogen 2-stroke engine architecture, showing a promising pathway for future heavy-duty applications. • From diesel to H 2 2S SI valved engine with minimum modifications. • Integrated 0D-1D/3D-CFD analysis of scavenging and gas mixing. • Very high tumble promotes gas mixing and combustion. • Shrouded valves and ducted injection almost cancel fuel short circuit. • High power density and BTE along with near zero emissions.