Abstract
Hydrogen is emerging as a promising zero-carbon emission energy source for vehicle engines. However, the full potential of hydrogen engines and their economic viability remain uncertain. Additionally, comprehensive data on ultralean combustion performance and emissions as well as strategies for improving HC and CO emissions are lacking. This study addresses these gaps by thoroughly examining hydrogen combustion and emissions in a 1.5 L engine. Incorporating a hydrogen direct injection (HDI) system and an electric supercharger, we investigated emissions under various piston ring tensions during lean limit operations. Our findings reveal that hydrogen exhibits a fast combustion speed in the engine within 20 °CA, along with excellent ultralean burn performance, expanding the lambda limit to 3. As the load increases, the thermal efficiency significantly improves, reaching a maximum of 40.8%. NOx emissions peak at a lambda of 1.1 but decrease notably above 2.7, with levels below 10 ppm. At a lambda near 3, NOx emissions hover between 0 and 5 ppm, approaching zero emissions. Additionally, lubricating oil consumption during engine operation yields a minor HC and CO emissions. Higher tension piston rings result in lower HC and CO emissions, typically below 5 ppm, nearing zero emission levels.