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Performance Evaluation of an Electric Vehicle with Multiple Electric Machines for Increased Overall Drive Train Efficiency

University of Rome Niccolò Cusano-Laura Tribioli, Daniele Chiappini
University of Ljubljana-Mario Vukotić, Damijan Miljavec
Published 2019-10-07 by SAE International in United States
Proposed solutions for electric vehicles range from the simple single-motor drive coupled to one axle through a mechanical differential, to more complex solutions, such as four in-wheel motors, which ask for electronic torque vectoring. Main reasons for having more than one electric machine are: reduction of the rated power of each motor, which most likely leads to simplification and cost reduction of all the electric drive components; increased reliability of the overall traction system, enhancing fault tolerance ability; increase of the degrees of freedom which allows for control strategy optimization and efficiency improvement. In particular, electrical machines efficiency generally peaks at around 75% of load and this usually leads to machine downsizing to avoid operation in low efficiency regions. The same output performance can be achieved by using two or more electrical machines, rather than only one, of smaller size and running them at unequal load - one of the machines at higher load and the other(s) at lower load.In this paper, the performance of an electric vehicle with multiple electric machines is analyzed to…
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A Coupled Lattice Boltzmann-Finite Volume Method for the Thermal Transient Analysis of an Air-Cooled Li-Ion Battery Module for Electric Vehicles with Porous Media Insert Modeled at REV Scales

University of Rome Niccolò Cusano-Daniele Chiappini, Laura Tribioli
University of Rome Tor Vergata-Gino Bella
Published 2019-10-07 by SAE International in United States
Lithium ion batteries are the most promising candidates for electric and hybrid electric vehicles, owe to their ability to store higher electrical energy. As a matter of fact, in automotive applications, these batteries undergo frequent and fast charge and discharge processes, which are associated to internal heat generation, which in turns causes temperature increase. Thermal management is therefore crucial to keep temperature in an appropriate level for safe operation and battery wear prevention.In a recent work authors have already demonstrated the capabilities of a coupled lattice Boltzmann-Finite Volume Method to deal with thermal transient of a three-dimensional air-cooled Li-ion battery at different discharging rates and Reynolds numbers. Here, in order to improve discharge thermal capabilities and reduce temperature levels of the battery itself, a layer of porous medium is placed in contact with the battery so to replace a continuum solid aluminum layer. Many studies, which have already demonstrated how the porous media can improve thermal performance of heat exchange systems, are present in recent literature. There is a large number of models for representing…
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Assessment of Energy Consumption and Range in Electric Vehicles with High Efficiency HVAC Systems Based on the Tesla Expander

University of Rome Niccolò Cusano-Laura Tribioli
University of Brescia-Paolo Iora, Alberto Cassago, Costante Invernizzi, Alessandro Copeta, Gioele Di Marcoberardino, Stefano Uberti
Published 2019-10-07 by SAE International in United States
Battery electric vehicles (BEVs) are considered one of the most promising solution to improve the sustainability of the transportation sector aiming at a progressive reduction of the dependence on fossil fuels and the associated local pollutants and CO2 emissions.Presently, the major technological obstacle to a large scale diffusion of BEVs, is the fairly low range, typically less than 300 km, as compared to classical gasoline and diesel engines. This limit becomes even more critical if the electric vehicle is operated in severe weather conditions, due to the additional energy consumption required by the cabin heating, ventilating, and air-conditioning (HVAC).The adoption of vapor-compression cycle, either in heat pump or refrigerator configuration, represents the state-of-the-art technology for HVAC systems in vehicles. Such devices typically employ an expansion valve to abruptly reduce the pressure causing the flash evaporation of the working fluid. This component, although necessary to provide the cooling effect, is also responsible of a significant exergy loss, which reduces the efficiency of the thermodynamic cycle.In this paper we study the possible benefits in terms of energy…
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Multidimensional Modeling of SCR Systems via the Lattice Boltzmann Method

University of Rome Niccolò Cusano-Giovanni Di Ilio
University of Rome Tor Vergata-Vesselin Krastev, Gino Bella, Giacomo Falcucci
  • Technical Paper
  • 2019-24-0048
Published 2019-09-09 by SAE International in United States
In this paper, we deploy a novel, multidimensional approach to simulate SCR reactors across physical scales. For the first time, a full 3D Lattice Boltzmann (LB) solver is developed, able to accurately capture the fluid dynamic phenomena taking place inside SCR reactors, as well as the catalytic conversion of NOx. The influence of engine load on exhaust gas mass flow rate and catalytic converter activity is taken into account. The proposed approach is computationally light and the results prove the reliability and versatility of the LB Method for the simulation of the complex phenomena that take place inside the after-treatment devices.
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Effects of the LES-Mode SGS Viscosity Formulation on the Hybrid URANS/LES Modeling of Turbulent Fuel Sprays

University of Rome Niccolò Cusano-Giovanni Di Ilio
University of Rome Tor Vergata-Vesselin Krastev, Gino Bella
Published 2019-09-09 by SAE International in United States
The LES hybridization of standard two-equation turbulence closures is often achieved leaving formally unchanged the turbulent viscosity expression in the URANS and LES modes of operation. Although generally convenient in terms of ease of implementation, this choice leaves some theoretical consistency questions unanswered, the most obvious being the actual meaning of the two transported turbulent scalars and their exact role in the modeled viscosity build-up. A possible remedy to this is represented by the simultaneous modification of one or both the turbulent transport equations and of the turbulent viscosity formula, for which a standard LES behavior is enforced whenever needed. The present work compares a conventional DES-based hybrid model with a consistency-enforcing modified variant for turbulent fuel spray simulation. In our case, LES-mode consistency is accomplished by excluding the second turbulent scalar quantity from the viscosity calculation. In this way, the turbulent kinetic energy acts as SGS kinetic energy and the SGS viscosity is evaluated according to the well known one-equation LES implementation. The conventional and modified hybrid models are applied to the simulation of…
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Hybrid URANS/LES Turbulence Modeling for Spray Simulation: A Computational Study

University of Rome Niccolò Cusano-Giovanni Di Ilio
Politecnico di Milano-Federico Piscaglia
Published 2019-04-02 by SAE International in United States
Turbulence modeling for fuel spray simulation plays a prominent role in the understanding of the flow behavior in Internal Combustion Engines (ICEs). Currently, a lot of research work is actively spent on Large Eddy Simulation (LES) turbulence modeling as a replacement option of standard Reynolds averaged approaches in the Eulerian-Lagrangian spray modeling framework, due to its capability to accurately describe flow-induced spray variability and to the lower dependence of the results on the specific turbulence model and/or modeling coefficients. The introduction of LES poses, however, additional questions related to the implementation/adaptation of spray-related turbulence sources and to the rise of conflicting numerics and grid requirements between the Lagrangian and Eulerian parts of the simulated flow. About the latter, an efficient alternative might be found in hybrid URANS/LES formulations, which are still relatively unexplored for spray modeling applications and for ICE modeling in general. In this work, we conduct a systematic analysis aimed to assess the effects of several URANS, LES and hybrid turbulence modeling formulations on the spray dynamics. The hybrid form is based on…
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Influence of Fuel Type on the Pperformance of a Plug-In Fuel Cell/Battery Hybrid Vehicle with On-Board Fuel Processing

University of Rome Niccolò Cusano-Laura Tribioli, Raffaello Cozzolino, Daniele Chiappini
University of Brescia-Paolo Iora
Published 2017-09-04 by SAE International in United States
This paper describes the energy management controller design of a mid-sized vehicle driven by a fuel cell/battery plug-in hybrid powertrain, where an experimentally validated high temperature polymer electrolyte membrane fuel cell model is used. The power management strategy results from the application of the Pontryagin's Minimum Principle, where the optimal control parameter is derived in order to minimize fuel consumption under certain constraints. In particular, the vehicle is also equipped by an autothermal reformer and, in order to minimize the hydrogen buffer size, the control algorithm is subject to constraints on the maximum hydrogen buffer level. The effectiveness of the system is analyzed when feeding the autothermal reformer with different hydrocarbon fuels and over different driving conditions. The obtained solutions are compared in terms of hydrogen consumption, fossil fuel consumption, system efficiency, money saving and equivalent CO2 emissions.
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