Active Pre-Chamber as a Technology for Addressing Fuel Slip and its Associated Challenges to Lambda Estimation in Hydrogen ICEs

Heavy duty hydrogen (H₂) internal combustion engines (ICEs), typically conversions from base diesel engines, can experience significant deterioration of combustion efficiency with enleanment despite relative engine stability due in part to non-optimized combustion chamber geometry for spark ignited (SI) combustion. This causes un-combusted H₂ to “slip” into the exhaust largely undetected since it is not a typically measured exhaust species. In this study, several implications of H₂ slip in H₂ ICEs are explored. The sensitivity of air fuel ratio (AFR) measurement to H₂ slip is discussed. The challenge this poses for closed-loop transient controls and the impact on nitrogen oxides (NOx) emissions are also shown. Finally, test results from an H₂ ICE using an active pre-chamber highlight the improvement in combustion efficiency and transient stability relative to a baseline SI engine.