23. Internationales Stuttgarter Symposium

Automobil- und Motorentechnik

4. - 5. Juli 2023

Session: ZERO-IMPACT-EMISSIONS I | | 13:30 - 14:00

NOx Emissions Reduction Strategies for Spark-Ignited Hydrogen Internal Combustion Engines

Julian Wallace, Southwest Research Institute

Hydrogen-fueled internal combustion engines have the potential to soon become a key part of the global transportation sector decarbonization process. A common trend in the industry is to operate spark ignition (SI) hydrogen engines with an air-fuel ratio lean of stoichiometric with a lambda value greater than two. Running this lean reduces the propensity of abnormal combustion events and lowers NOx production, but typically results in reduced power density due to the limitations of boosting systems. An effective method for increasing power density for is to operate closer to stoichiometric, but this requires additional strategies for NOx reduction. In this research, the effectiveness of various NOx emissions reduction strategies for less-lean SI hydrogen operation (with a lambda value between 1 and 2) was evaluated. The study was conducted using a 1.3 L single-cylinder research engine at the Southwest Research Institute (SwRI) that was configured to run on either port fuel injection (PFI) or direct injection (DI) hydrogen. The NOx mitigation strategies tested included water injection, exhaust gas recirculation (EGR), and charge stratification using a combination of PFI and DI fueling. These strategies were evaluated on their abilities to simultaneously reduce knock and NOx emissions while running the engine at less lean conditions compared to conventional PFI operation.