Thermal efficiency improvement of a range extender based on the T-GDI engine for a medium-size electric bus using on-board gasoline fuel reforming with steam addition

Electric vehicles (EVs) are becoming increasingly popular in the global automobile industry. A range extender is a generator that increases the mileage of EVs. The engine for a range extender operates in a steady state. Steady conditions are suitable for catalyst-based on-board fuel reforming operations. Hydrogen has unique properties that improve combustion performance, such as fast burning, short quenching distance, and increased flammability. We carried out experiments and analyses to improve the thermal efficiency of a range extender that uses catalyst-based on-board fuel reforming with steam addition. For this study, steam was generated from exhaust-waste heat. Based on a previous study, the power requirement for the range extender of a medium-sized city bus was calculated. Accordingly, the range extender was operated at a brake mean effective pressure (BMEP) of 10 bar and speed of 2000 rpm. The results indicate that reformed H₂ has positive effects on the combustion performance and thermal efficiency of the range extender. Steam addition to the reformer improves the reforming performance and greatly influences the reduction in NO_x emissions. Moreover, steam addition to the reformer leads to an increase in thermal efficiency. However, steam addition cannot affect the thermal efficiency as much as it affects the reforming performance.