Assessing fuel economy and NOx emissions of a hydrogen engine bus using neural network algorithms for urban mass transit systems

The transition from compressed natural gas (CNG) to hydrogen has begun in mass transportation applications in Seoul, South Korea. This study investigates the feasibility of using a hydrogen combustion engine for city buses in Seoul. A hydrogen-fueled, six-cylinder, 11,046-cm3 spark-ignition engine equipped with a mixer-type fuel supply system is proposed. An experiment using a single-cylinder engine is performed to obtain operating and perfor-mance maps. These maps are then used in the vehicle simulation model. Combustion characteristics are inves-tigated using three-dimensional numerical simulation validated by the experimental results. A regression analysis is conducted using neural network algorithms to determine the dominant operating parameters on nitric oxides (NOx) emissions, and 373 bus routes in Seoul are analyzed using real-time driving data and recent annual statistics. The vehicle driving simulation using actual Seoul bus driving data reveals an average fleet fuel economy of 121.7 g/km, confirming that hydrogen-engine buses can be more efficient than the CNG buses currently in use. A 70-MPa tank can store 34.78 kg of hydrogen, which yields a maximum travel distance of 388 km longer than the longest route (bus #9411 at 77 km). The result indicates that even a 20-Mpa fuel tank, enabling a bus to travel 144 km, is sufficient for Seoul city buses.

Automated summary

The transition from CNG to hydrogen has started in mass transportation in Seoul. This study explores the feasibility of using a hydrogen combustion engine for city buses and proposes a hydrogen-fueled, spark-ignition engine. Experiment and simulation are conducted to investigate the combustion characteristics, performance, and emissions. Real-time driving data and statistics of 373 bus routes in Seoul are analyzed. It is found that hydrogen-engine buses can be more efficient and a 20-Mpa fuel tank is sufficient for Seoul city buses.