Optimization of the parallel and mild hybrid vehicle platforms operating under conventional and advanced combustion modes

Abstract

The stringent regulations, increased global temperature and customer demand for high fuel economy have led to rapid developments of different alternative propulsion solutions in the last decade, with special attention to the electrified vehicles. The combination of electric machines with conventional powertrains allows to diversify the powertrain architectures. In addition, alternative combustion modes as reactivity controlled compression ignition (RCCI) have been shown to provide simultaneous ultralow NOx and soot emissions with similar or better thermal efficiency than conventional diesel combustion (CDC). Therefore, the combination of both technologies creates a promising horizon to be implemented in commercial vehicles of the near future. In this work, experimental and numerical simulations were combined to study the potential of the parallel full hybrid electric vehicle (P2-FHEV) and mild hybrid vehicle (MHEV) to obtain lower fuel consumption and NOx emissions than a conventional powertrain in the Worldwide Harmonized Light Vehicles Cycle (WLTC). The hybrid vehicles are simulated with both CDC and diesel-gasoline RCCI combustion engines as power source. Each powertrain was optimized in terms of components (battery, electric motors...) capacity, internal combustion engine operative points, energy management strategy and gear ratios. The results show a significant fuel consumption reduction as the complexity of the hybrid system increases. The parallel architecture, which represents the most complex hybrid system tested in this work, allows obtaining a fuel consumption reduction of around 20% as compared to CDC. The dual-mode CDC-RCCI concept showed improvements in NOx and soot emissions with comparable values in terms of energy consumption and CO2 emissions than CDC. Additionally, the mild hybrid technology with the functionality of start-stop, torque assist and regenerative braking showed an acceptable balance between complexity and fuel consumption gain.

Perspectives and Challenges of Vehicle Electrification: An Academic Review

“…The level of influence of the combustion engine on the propulsion system of these vehicles is what will determine their degree of hybridization. The combination of the two types of engines in a hybrid vehicle makes the car more efficient, adding less fuel consumption since the electric motor is assisting the combustion engine (Benajes et al, 2019).…”

“…Mallig et al (2016) also bring as a diversification option the use of hybrid vehicles capable of associating benefits from more than one type of technology. Benajes et al (2019) highlight that Hybrid electrics combine an electric battery with a combustion engine or generator. These solutions overcome range limitations and, at the same time, allow driving on electric power for most of the total mileage.…”

Increased Internal Combustion Engine Efficiency with Optimized Valve Timings in Extended Stroke Operation

“…Fuel efficiency further improves by use of start-stop systems, which have become standard equipment in the automotive sector [30]. Furthermore, with an electric motor present in the power train, a shift of the operating point is possible, leading to improved fuel economy [31,32]. As internal combustion engines are very likely to play an important role in future mobility, especially in long-distance applications, the decarbonization of fuel plays an important role.…”

A Novel Two-Zone Thermodynamic Model for Spark-Ignition Engines Based on an Idealized Thermodynamic Process

“…The innovative technologies make combustion engines more flexible and efficient. However, these innovative technologies really work effectively only under the proper design of the control system and its related management strategies [5].…”