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Multitarget Evaluation of Hybrid Electric Vehicle Powertrain Architectures considering Fuel Economy and Battery Lifetime

McMaster University-Phillip Kollmeyer, Ali Emadi
Politecnico di Torino-Pier Giuseppe Anselma, Giovanni Belingardi
  • Technical Paper
  • 2020-37-0015
To be published on 2020-06-23 by SAE International in United States
Hybrid Electric Vehicle (HEV) powertrains are characterized by a complex design environment as a result of both the large number of possible layouts and the need for dedicated energy management strategies. When selecting the most suitable hybrid powertrain architecture at early design stage of HEVs, engineers usually focus on fuel economy (directly linked to tailpipe emissions) and vehicle drivability performance solely. However, high voltage batteries are a crucial component of HEVs as well in terms of performance and cost. This paper introduces a multitarget assessment framework for HEV powertrain architectures which considers both fuel economy and battery lifetime. A multi-objective formulation of dynamic programming is initially presented as off-line optimal HEV energy management strategy capable of predicting both fuel economy performance and battery lifetime of HEV powertrain layout options. Subsequently, three different HEV powertrain architectures are considered as test cases for the developed HEV assessment methodology including parallel P2, series-parallel P1P2 and power-split layouts. A comparison of numerical results for the three HEV powertrain test cases is then performed in terms of optimal fuel economy…
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Fuel Consumption and Emission Reduction for Hybrid Electric Vehicles with electrically heated Catalyst

TU Dresden-Frank Atzler
TU Muenchen-Georg Wachtmeister
  • Technical Paper
  • 2020-37-0017
To be published on 2020-06-23 by SAE International in United States
Hybridization is a promising way to further reduce the CO2 emissions of passenger vehicles. However, high engine efficiencies and the reduction of engine load, due to torque assist by an electric motor, cause a decrease of exhaust gas temperature levels. This leads to an increased time to light-off of the catalysts resulting in an overall lower efficiency of the exhaust aftertreatment system. Especially in low load driving conditions, at cold ambient temperatures and on short distance drives, the tailpipe pollutant emissions are severely impacted by these low efficiency levels. To ensure lowest emissions at all driving conditions, catalyst heating methods must be used. In conventional vehicles internal combustion engine measures, e.g. late combustion can be applied. A hybrid system with an electrically heated catalyst enables further methods such as the increase of engine load, the so-called load point shifting by the electric motor or using the energy from the battery for electric catalyst heating. Since these methods result either directly or indirectly in additional fuel consumption there is a conflict of objectives between a fast…
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A Reverse Engineering Method for Powertrain Parameters Characterization Applied to a P2 Plug-In Hybrid Electric Vehicle with Automatic Transmission

FEV Group GmbH-Alessandro Perazzo
Politecnico di Torino-Enrico Galvagno, Federico Millo, Giuseppe DiPierro, Mauro Velardocchia, Gianluca Mari
  • Technical Paper
  • 2020-37-0021
To be published on 2020-06-23 by SAE International in United States
Over the next decade, CO2 legislation will be more demanding and the automotive industry has seen in vehicle electrification a possible solution. This has led to an increasing need for advanced powertrain systems and systematic model-based control approaches, along with additional complexity. This represents a serious challenge for all the OEMs. This paper describes a novel reverse engineering methodology developed to estimate relevant but unknown powertrain data required for fuel consumption-oriented hybrid electric vehicle modelling. The main estimated quantities include high-voltage battery internal resistance, electric motor and transmission efficiency maps, torque converter and lock-up clutch operating maps, internal combustion engine and electric motor mass moment of inertia, and finally front/rear brake torque distribution. This activity introduces a list of limited and dedicated experimental tests, carried out both on road and on a chassis dynamometer, aiming at powertrain characterization thanks to a suitable post-processing algorithm. In this regard, the methodology was tested on a P2 architecture Diesel Plug-in HEV equipped with a 9-speed AT. voltage and current sensors are used to measure the electrical power exchanged…
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Impact of Thermal Management of the Three-Way Catalyst on the Energy Efficiency of a P2 Gasoline FHEV

Università del Salento-Marco Benegiamo, Andrea Valletta, Antonio Carlucci
Università di Roma Tor Vergata-Vincenzo Mulone
  • Technical Paper
  • 2020-37-0019
To be published on 2020-06-23 by SAE International in United States
Gasoline Full Hybrid Electric Vehicles (FHEVs) are recognized as a cost-effective solution to comply with upcoming emissions legislation. However, several studies have highlighted that frequent start-and-stops worsen the HC tail-pipe emissions, especially when the light-off temperature of the three-way catalyst (TWC) has not been reached. In fact, strategies only addressing the minimization of fuel consumption tend to delay engine activation and hence TWC warming, especially during urban driving. Goal of the present research is therefore to develop an on-line powertrain management strategy accounting also for TWC temperature, in order to reduce the time needed to reach TWC light-off temperature. A catalyst model is incorporated into the model of the powertrain where torque-split is performed by an adaptive equivalent consumption minimization strategy (A-ECMS). The developed A-ECMS operates on a domain of power-split combinations between electric machine and internal combustion engine, which, aside from satisfying the torque demand, also ensure a controlled ICE torque derivative as well as a controlled ICE start-and-stop frequency. Hence, the algorithm which is extended for TWC thermal management, incorporates a penalty on…
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Simplified Cost-effective Aftertreatment System for Electrified Diesel Applications

Exothermia SA-Dimitrios Karamitros, Christos Avgerinos, Stavros Skarlis, Grigorios Koltsakis
GM Global Propulsion System-Giuseppe Previtero, Fransesco Bechis
  • Technical Paper
  • 2020-37-0023
To be published on 2020-06-23 by SAE International in United States
The Diesel powertrain remains an important CO2 reduction technology in specific market segments due to its inherent thermodynamic combustion efficiency advantages. Diesel powertrain hybridization can bring further potential for CO2 emissions reduction. However, the associated reduction in the exhaust gas temperature may negatively impact the performance of the exhaust aftertreatment (EAT) system and challenge the abatement of other emissions, especially NOx. Considering that active urea-SCR systems may be required to ensure compliance with the legislative limits, the total cost of the hybrid Diesel powertrain is expected to increase even more, therefore making it less commercially attractive. We present a model-based analysis of a 48V Diesel mild hybrid electric vehicle (MHEV) which is combined with an exhaust aftertreatment (EAT) system using Lean-NOx trap (LNT) technology. The overall de-NOx performance is further enhanced with the addition of passive SCR catalysts to benefit from the on-board ammonia formation during rich combustion events. Since the modeling framework is fully physico-chemically informed, it allows the investigation of various topologies, catalyst geometrical and chemical properties. Moreover, the model includes a simplified…
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Assessment of the Potential of Power to Gas Fuels for Replacement of Fossile Fuels in Switzerland

EMPA-Panayotis Dimopoulos Eggenschwiler, Florian Kiefer, Karin Schröter, Christian Bach
  • Technical Paper
  • 2020-37-0027
To be published on 2020-06-23 by SAE International in United States
In Switzerland, road traffic is responsible for one third of greenhouse gas emissions respectively 40% of the CO2 emissions and therefore accounts for the largest single share of all sectors. These emissions have even increased slightly since 1990 (from 15.5 to 16.2 million tCO2). Private individual road transport achieves a mileage of approximatively 91.0 billion pkm (person-kilometer) and 17.2 billion tkm (tons-kilometer) per year. Therefore, 3.3 billion liters of gasoline and 3.2 billion liters of diesel are used, resulting in 16.2 million tCO2 emissions in total. Thereof, 10.2 million tons of CO2 are emitted by passenger cars and 1.7 million tons by trucks, the two most important means of transport concerning CO2 emissions. The rest is produced by vans, buses, motorcycles, railways and shipping, national air traffic and fuel tourism. The passenger cars are the most relevant application in terms of CO2 emissions with a share of 63% of the road vehicle CO2 emissions. To comply with the 95 g/km target, low CO2 vehicles have to be introduced. In the following, the number of such…
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A Theoretical and Experimental Analysis of the Coulomb Counting Method and Estimation of the Electrified-Vehicles Electricity Balance Over the WLTP

European Commission Joint Research-Alessandro Tansini, Georgios Fontaras
Politecnico di Torino-Federico Millo
  • Technical Paper
  • 2020-37-0020
To be published on 2020-06-23 by SAE International in United States
The energy storage devices of electrified vehicles (Hybrid Electric Vehicles and Battery Electric Vehicles) are required to operate with highly dynamic current and power outputs, both for charging and discharging operation. When calculating the vehicle CO2 emissions and electrical energy consumption from a trip, the change in electrical energy content at vehicle-level has to be accounted for. This quantity, referred to as the electricity balance in the WLTP regulation, is normally obtained through a time-integration of the current or power supplied by the vehicle batteries during operation and the efficiency factor is often assumed to be unitary (as in the official type-approval procedure). The Joint Research Centre has collected experimental data from different electrified vehicles with regards to electrical energy use and battery State Of Charge (SOC) profile; the latter was used as a reference to quantify the actual vehicle electricity balance from a trip or driving cycle. In this work, the approach of using a simple Coulomb counting method with unitary efficiency for charging and discharging for the quantification of the vehicle electricity balance…
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Plug-in Electric Vehicles fueled with Green Fuels in LTC mode

Jesus Benajes
Universitat Politecnica de Valencia-Antonio Garcia, Javier Monsalve-Serrano, Santiago Martinez
  • Technical Paper
  • 2020-37-0026
To be published on 2020-06-23 by SAE International in United States
Plug-in Hybrid Electric Vehicles (PHEVs) can be considered as the most promising technology to achieve the European CO2 targets in 2025 together with a moderate infrastructure modification. However, the real benefits, in terms of CO2 emissions, depend on a great extent on the energy source (fuel and electricity mix), user usage, and vehicle design. Moreover, the electrification of the powertrain does not reduce other emissions as NOx and particles (mainly soot). In the last years, low temperature combustion (LTC) modes as the reactivity-controlled compression ignition (RCCI) have shown to achieve ultra-low NOx and soot emission simultaneously due to the use of two fuels with different reactivity and high exhaust gas recirculation (EGR) rates. Therefore, the aim of this work is to assess, through numerical simulations fed with experimental results, the effects of different energy sources on the PHEV performance and emissions. The dual-fuel ICE was fueled with diesel as high reactivity fuel and two different low reactivity fuel: gasoline and ethanol. The powertrains are optimized to meet the European homologation legislation (WLTP) for PHEVs. The…
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HEV Evaluation in Simulation Phase Based on Predicted Sound Behavior

AVL LIST GmbH-Paco Langjahr, Markus Resch, Bernhard Graf
  • Technical Paper
  • 2020-01-1511
To be published on 2020-06-03 by SAE International in United States
Grown interest in complex modern Hybrid Electric Vehicle (HEV) concepts has raised new challenges in the field of NVH. The switch between Internal Combustion Engine (ICE) and Electric Motor (EM) at low speeds produces undesirable vibrations and a sudden raise of noise levels that affects the sound quality and passenger comfort achieved by the close-to-silent electric powertrain operation. Starting the ICE in the most suitable driving situation to create a seamless transition between driving modes can be the key to minimize the NVH quality impact in driver and passenger’s perception in HEVs. To integrate this important aspect in the early stages of the development and design phase, simulation technologies can be used to address the issue. By analyzing NVH measurements, the different noise components of the vehicle operation can be separated into ICE-related noise, EM-related noise and driving noise. To achieve highest system flexibility, these noise components can be synthesized, providing an integral NVH assessment tool that can be adapted to different driving conditions. ICE and EM noise are simulated using additive synthesis of an…
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Refrigerant Valves in AC- and Heat Pump systems for Electric Vehicles

Otto Egelhof GmbH & Co. KG-Eike Willers
Otto Egelhof GmbH&Co. KG-Stephan Wild
  • Technical Paper
  • 2020-28-0038
To be published on 2020-04-30 by SAE International in United States
Abstract The Thermal Management of Electric Vehicles differs strongly from the Thermal Management in IC engine driven vehicles. The Air Conditioning Circuit itself has comparable requirements, however, the electric components and their properties lead to new architectures. Essential is at least a chiller for the conditioning of the battery, which needs to be cooled down to the range of summer ambient temperatures. The respective control devices need to fulfill different basic requirements - Small package - Lightweight - Low noise - Low energy consumption - High control accuracy to play an important role in the Refrigeration architecture of Electric and Hybrid Vehicles. For conventional systems, optimization of package and weight will be achieved by a 75g TXV with a 28 mm thermal head. As soon as a battery also has to be cooled, Shut-Off valves will be implemented in the system in order to manage the respective heat loads according to the needs. For some system configurations, it is important to have a precise electronic control, which is not following the usually fixed superheat characteristic…