A policy-oriented vehicle simulation approach for estimating the CO2 emissions from Hybrid Light Duty Vehicles

Pollutants emissions and fuel economy tests for passenger cars differ from region to region of the world, since different driving condition and vehicle fleet characterize different geographical areas. In particular, the European type approval procedure for passenger cars uses as reference cycle the New European Driving Cycle (NEDC), which is nowadays not representative of real driving conditions. Therefore, the European Commission has planned to introduce the Worldwide Harmonized Light Duty Test Procedure (WLTP) from September 2017. As a consequence, the CO2 emissions target should be adapted, since the current 2020 goals are based on NEDC assessment. The European Commission and the Joint Research Centre (JRC) are therefore developing a simulation tool called CO2MPAS (CO2 Module for Passenger and commercial vehicles Simulation) for the correlation of CO2 emissions from WLTP to NEDC, which will be used for the type approval of European passenger cars from 2017, avoiding expensive duplicate test campaigns for car manufactures. However, the implementation of CO2MPAS has so far involved solely conventional light duty vehicles. Within this context, a research project has been carried out in closed collaboration between Politecnico di Torino and JRC for the development of CO2MPAS for Hybrid Electric Vehicles (HEVs) and Plug-In Hybrid Electric Vehicles (PHEVs). The correlation model is based on a unique simplified physical approach, which should be able to detect the powertrain behavior along the NEDC cycle from the physical measurements along the new driving cycle, estimating with a good accuracy the CO2 emissions (within ± 3 g/km)

Impact of different driving cycles and operating conditions on CO2 emissions and energy management strategies of a Euro-6 hybrid electric vehicle

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 theWorldwide 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

From NEDC to WLTP: effect on the type-approval CO2 emissions of light-duty vehicles

The present report summarises the work carried out by the European Commission's Joint Research Centre to estimate the impact of the introduction of the new type approval procedure, the Worldwide Light duty vehicle Test Procedure (WLTP), on the European car fleet CO2 emissions. To this aim, a new method for the calculation of the European light duty vehicle fleet CO2 emissions, combining simulation at individual vehicle level with fleet composition data is adopted. The method builds on the work carried out in the development of CO2MPAS, the tool developed by the Joint Research Centre to allow the implementation of European Regulations 1152 and 1153/2017 (which set the conditions to amend the European CO2 targets for passenger cars and light commercial vehicles due to the introduction of the WLTP in the European vehicle type-approval process). Results show an average WLTP to NEDC CO2 emissions ratio in the range 1.1-1.4 depending on the powertrain and on the NEDC CO2 emissions. In particular the ratio tends to be higher for vehicles with lower NEDC CO2 emissions in all powertrains, the only exception being with the plug-in hybrid electric vehicles (PHEVs). In this case, indeed, the WLTP to NEDC CO2 emissions ratio quickly decreases to values that can be also lower than 1 as the electric range of the vehicle increases.JRC.C.4-Sustainable Transpor

Design of the control strategy for a range extended hybrid vehicle by means of dynamic programming optimization

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 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

Numerical Simulation of the Warm-Up of a Passenger Car Diesel Engine Equipped with an Advanced Cooling System

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

Analysis of the Impact of the WLTP Procedure on CO2 Emissions of Passenger Cars

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