Effect of supercharging on improving thermal efficiency and modifying combustion characteristics in lean-burn direct-injection near-zero-emission hydrogen engines.

The authors have proposed a new combustion process called the Plume Ignition Combustion Concept (PCC), in which with an optimal combination of hydrogen injection timing and controlled jet geometry, the plume of the hydrogen jet is spark-ignited to accomplish combustion of a rich mixture. This combustion process markedly improves thermal efficiency by reducing cooling loss, which is essential for increasing thermal efficiency in a hydrogen engine while maintaining high power. In order to improve thermal efficiency and reduce NOx formation further, PCC was applied to a lean-burn regime to burn a leaner mixture globally. In this study, the effect of supercharging which was applied to recover the reduced output power due to the leaner mixture on improving thermal efficiency was confirmed along with clarifying the cause. [Display omitted] • Supercharging improves the thermal efficiency, high output, and NOx emissions of a direct-injection hydrogen engine. • Major factors that improve thermal efficiency by supercharge are reduction of cooling loss and unburned hydrogen. • Optimization of SOI timing and λ is important for achieving high efficiency and near-zero NOx emissions. [ABSTRACT FROM AUTHOR]