Improving the efficiency of the internal combustion engine is important for reducing carbon dioxide emissions in the transport sector. Various types of hybrid electric vehicles have been proposed to increase the fuel economy of the internal combustion engine-based vehicle. In a series hybrid electric vehicle, the shaft of the internal combustion engine is separated from the vehicle drive shaft. This means that even if the engine rotation speed changes within a single cycle, the vehicle power transmission is not greatly influenced by the internal combustion engine drive shaft. Therefore, it is possible to improve efficiency by modulating the speed in a single cycle of the engine. To investigate the effect of speed profile modulation on SI engine net indicated efficiency, we have optimized the intracycle speed profile of the SI engine through simulation. Simulation results show that the net indicated efficiency is improved under various speed and intake manifold pressure conditions due to combustion phasing enhancement under a high intake manifold pressure and low speed condition and improvement of heat loss and pumping work in a low intake manifold pressure condition.
Keywords Energy analysis, SI engine, series HEV, Trajectory optimization, Zero-dimensional model