Although Hybrid Electric Vehicles (HEVs) represent one of the key technologies to reduce CO₂ emissions, their effective potential in real world driving conditions strongly depends on the performance of their Energy Management System (EMS) and on its capability to maximize the efficiency of the powertrain in real life as well as during Type Approval (TA) tests. Attempting to close the gap between TA and real world CO₂ emissions, the European Commission has decided to introduce from September 2017 the Worldwide Harmonized Light duty Test Procedure (WLTP), replacing the previous procedure based on the New European Driving Cycle (NEDC). The aim of this work is the analysis of the impact of different driving cycles and operating conditions on CO₂ emissions and on energy management strategies of a Euro-6 HEV through the limited number of information available from the chassis dyno tests. The vehicle was tested considering different initial battery State of Charge (SOC), ranging from 40% to 65%, and engine coolant temperatures, from −7 °C to 70 °C. The change of test conditions from NEDC to WLTP was shown to lead to a significant reduction of the electric drive and to about a 30% increase of CO₂ emissions. However, since the specific energy demand of WLTP is about 50% higher than that of NEDC, these results demonstrate that the EMS strategies of the tested vehicle can achieve, in test conditions closer to real life, even higher efficiency levels than those that are currently evaluated on the NEDC, and prove the effectiveness of HEV technology to reduce CO₂ emissions.

A plug-in hybrid electric powertrain, as one of the most promising solutions to increase the fuel economy and to meet the stringent requirements of low emissions urban zones, has been investigated and developed for a light duty commercial vehicle application in this work. The plug-in hybrid electric powertrain combines an advanced small diesel internal combustion engine with a high energy battery pack, capable to assure an extended range in pure electric mode for specific areas, like the low/zero emissions urban zones. Since the right size of the powertrain components is essential to fully exploit the benefits of the hybridization, an advanced methodology has been proposed to optimize the design of the plug-in hybrid powertrain at an early phase. This methodology is based on the genetic algorithm approach for the choice of the powertrain component characteristics, combined with a quasi-optimal energy management strategy that is the Equivalent fuel Consumption Management Strategy (ECMS). The performance of the hybrid electric powertrain which was designed through the proposed methodology were then assessed and analyzed over the Worldwide Harmonized Light Duty Driving Cycle (WLTC) by means of a simulation model, thus demonstrating its effectiveness in addressing the issue of the powertrain components sizing from the early stage of the design process. GRAPHICAL ABSTRACT

Electric vehicles (EVs) are attractive to reduce the pollution levels of urban areas thanks to their zero tail pipe emissions and to the possibility to rely on renewable energies for the electricity production. However, the market penetration of such vehicles is restricted by their limited range capabilities and by the lack of fast charging infrastructures. The Range Extended (R-EX) hybrid technology represents a valuable option to address these issues, since it offers the benefits of an EV, such as the electric driving for medium distances, while still maintaining the internal combustion engine, which can be operated at its optimal efficiency to recharge the battery, thus eliminating the driver's range anxiety. This article illustrates the design of the Energy Management System (EMS) of an R-EX Ultra-Light Vehicle (ULV), applying a heuristic approach based on the results obtained from the Dynamic Programming (DP) optimization, maximising the overall powertrain efficiency as function of trip information.

The target for future cooling systems is to control the fluid temperatures and flows through a demand oriented control of the engine cooling to minimize energy demand and to achieve comfort, emissions, or service life advantages.The scope of this work is to create a complete engine thermal model (including both cooling and lubrication circuits) able to reproduce engine warm up along the New European Driving Cycle in order to assess the impact of different thermal management concepts on fuel consumption. The engine cylinder structure was modeled through a finite element representation of cylinder liner, piston and head in order to simulate the cylinder heat exchange to coolant or oil flow circuits and to predict heat distribution during transient conditions. Heat exchanges with other components (EGR cooler, turbo cooler, oil cooler) were also taken into account. The thermal model was indirectly integrated with the engine model to evaluate the heat generated by the combustion process: the combustion gas temperatures and convective heat exchange coefficients between gas and walls were obtained from the results of detailed engine model simulation. The main advantage of this approach is the lower computational time in comparison with direct integration. The cooling system analyzed in this work presents some innovative technologies in terms of thermal-management, such as a controlled water pump (Switchable Water Pump) and an electronically controlled thermostat. Through the simulation, it was therefore possible to assess the impact of different control strategies of the cooling system control. In particular, it was possible to evaluate solutions capable to control the engine warm up, in order to reduce the fuel consumption and increase the overall efficiency of the engine during the driving cycle.

Until 2017 in Europe the Type Approval (TA) procedure for light duty vehicles for the determination of pollutant emissions and fuel consumption was based on the New European Driving Cycle (NEDC), a test cycle performed on a chassis dynamometer. However several studies highlighted significant discrepancies in terms of CO₂ emissions between the TA test and the real world, due to the limited representativeness of the test procedure. Therefore, the European authorities decided to introduce a new, up-to date, test procedure capable to closer represent real world driving conditions, called Worldwide Harmonized Light Vehicles Test Procedure (WLTP). This work aims to analyze the effects of the new WLTP on vehicle CO₂ emissions through both experimental and simulation investigations on two different Euro 5 vehicles, a petrol and a diesel car, representatives of average European passenger cars. The study also considers the effect of the engine warm-up and the impact of the start-stop technology in this new TA scenario. Since the WLTP imposes higher test mass and Road Loads (RLs), as well as higher driving cycle dynamics, a 44% cycle energy demand increase for the petrol car and a 23% increase for the diesel car were found. However, CO₂ emissions increased in the same proportion only for the diesel car, while they increased only by 10% for the petrol car, thanks to the improvement of the average internal combustion engine efficiency along the WLTC cycle. Finally, the effectiveness of the start-stop in terms of fuel (or CO₂) savings, was found to be almost halved for both vehicles when passing from the NEDC to the WLTP.