Analysis on the potential of EGR strategy to reduce fuel consumption in hybrid powertrains based on advanced gasoline engines under simulated driving cycle conditions

Abstract

[EN] The increased concern for environmental problems has boosted the electrification of passenger cars to remove air pollutant emissions from urban areas. Automotive manufacturers have predominantly opted for hybrid powertrains with advanced gasoline engines, because of the current limitations of battery electric vehicles and the higher costs of diesel aftertreatment systems. Meanwhile, the exhaust gas recirculation (EGR) strategy decreases fuel consumption and CO2 emissions in gasoline engines. The powertrain hybridization may increase the EGR benefit in fuel consumption, given that the dependence of internal combustion engine (ICE) operation on the driver¿s power demand is reduced. The ICE can usually operate at medium loads, around its maximum efficiency zone, where the EGR benefit is greater than at low loads. Therefore, this research aimed to quantify the fuel saving achieved with EGR in a gasoline-electric hybrid powertrain under driving cycle conditions. To this end, vehicle 0D simulations were performed using a map-based engine fuel consumption model. Engine tests and 1D simulations were carried out to obtain ICE fuel maps with and without EGR. Besides, the transient performance of the vehicle 0D model was validated with experimental data. Both rule- and optimization-based strategies were used to manage the power split between the engine and electric motor. Modeling results revealed that EGR improves fuel economy by 4.6% in the hybrid powertrain during a WLTP class 3b driving cycle, 2% more than in the conventional one.