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

• Published in: Energy (Oxford) Vol. 275; p. 127517
• Main Authors: Kim, Seongsu, Kim, Junghwan
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.07.2023
• Subjects: 1D simulation; combustion; Driving simulation; energy; Engine development; Hydrogen; Mixer-type fuel supply; natural gas; regression analysis; simulation models; South Korea; spark ignition engines; transportation; Urban mass transport system; South Korea; Driving simulation; Hydrogen; Mixer-type fuel supply; Engine development; Urban mass transport system; 1D simulation
• ISSN: 0360-5442
• DOI: 10.1016/j.energy.2023.127517

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 performance maps. These maps are then used in the vehicle simulation model. Combustion characteristics are investigated 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. •Feasibility of hydrogen combustion engine is investigated for a city bus in Seoul.•Neural networks reveal four dominant parameters in NOx emission prediction.•Hydrogen-engine buses are found to be more efficient than the CNG buses.•The predicted maximum travel distance of 388 km is longer than the longest route.•The amount of hydrogen needed for four major lines is 63,128 tons per year.