Development of a High Power, Low Emissions Heavy Duty Hydrogen Engine

<div class="section abstract"><div class="htmlview paragraph">The hydrogen (H₂) internal combustion engine (ICE) is emerging as an attractive low life-cycle carbon powertrain configuration for applications that require high power, high duty cycle operation. Owing to the relative ease of conversion of heavy duty (HD) diesel ICEs to H₂ and the potential for low exhaust emissions, H₂ ICEs are expected to play a strong role in rapidly decarbonizing hard-to-electrify markets such as off-road, rail, and marine. The conversion of HD diesel ICEs to spark ignited H₂ with port fuel injection is typically accompanied by a de-rating of engine power and torque. This is due to several fuel- and system-related challenges, including the high risk of abnormal combustion resulting from the low auto-ignition energy threshold of H₂, and boost system requirements for highly dilute operation that is used to partially mitigate this abnormal combustion risk. However, HD ICEs must be adapted to a diverse range of vehicle applications, and so increasing ICE displacement to accommodate the de-rating challenge is not a feasible solution. This study details the research and development of a high power, ultra-low nitrogen oxides (NO_x) emissions HD H₂ ICE. The engine, converted from a diesel base, leverages an active pre-chamber ignition system to promote stable dilution limit extension, which lowers combustion temperatures and in-cylinder surface temperatures to reduce abnormal combustion. The ignition system also reduces instability-induced abnormal combustion risk. The resulting H₂ ICE achieves power and torque levels consistent with those of the base diesel ICE, eliminating de-rating. The additional lean stability, especially during transient operation, leads to ultra-low cycle-average NO_x emissions, achieving engine-out NO_x of 0.24 g/kWh on a non-road transient cycle (NRTC) with a preliminary transient calibration. Test data was used to correlate a computational fluid dynamics (CFD) model of the engine, developing a simulation toolset that will be used to guide future optimization of the engine.</div></div>