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Environmental Analysis Based on Life Cycle Assessment: An Empirical Investigation on the Conventional and Hybrid Powertrain

University of Naples, Parthenope-Antonio Forcina
University of Rome, Niccolò Cusano-Luca Silvestri, Gabriella Arcese
Published 2019-10-07 by SAE International in United States
The Life Cycle Sustainability Assessment (LCA) methodology is today considered as a crucial paradigm with multiple levels of analysis, including the economic, social and environmental aspects. In this scenario, the purpose of the present research is to carry out an accurate and extensive LCA based analysis to compare the environmental impact, between conventional gasoline and hybrid vehicle powertrains. Two different powertrain scenarios were considered maintaining the same vehicle chassis. The performed analysis concerned resources and energy consumption as well as pollutant emission of each process, evaluating the impact of powertrain production, the vehicle use phase, and powertrain end of life scenarios. A large set of indicators - including human toxicity, eutrophication, and acidification - was considered. The study indicates that the potential of electrified vehicles basically depends on efficient production and recycling of the battery. We found that the conventional powertrain determines a higher Global Warming Potential (GWP) than hybrid powertrain (by almost 30%). Conversely, the water-related impact is higher in hybrid powertrain, and this is associated to the extraction and processing of the metal…
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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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A Coupled Lattice Boltzmann-Finite Volume Method for the Thermal Transient Modeling of an Air-Cooled Li-Ion Battery Cell for Electric Vehicles

Univ. Tor Vergata-Gino Bella
Univ. di Roma Niccolo Cusano-Daniele Chiappini, Laura Tribioli
Published 2019-09-09 by SAE International in United States
Due to their ability to store higher electrical energy, lithium ion batteries are the most promising candidates for electric and hybrid electric vehicles, whose market share is growing fast. Heat generation during charge and discharge processes, frequently undergone by these batteries, causes temperature increase and thermal management is indispensable to keep temperature in an appropriate level. In this paper, a coupled Lattice Boltzmann-Finite Volume model for the three-dimensional transient thermal analysis of an air-cooled Li-ion battery module is presented. As it has already been successfully used to deal with several fluid-dynamics problems, the Lattice Boltzmann method is selected for its simpler boundary condition implementation and complete parallel computing, which make this approach promising for such applications. The standard Lattice Boltzmann method, here used only for the fluid-dynamic evolution, is coupled with a Finite Volume approach for solving the energy equation and recovering the temperature field throughout the whole domain (air, aluminum and battery). This coupled approach allows having a fully reliable control of the transients in conjugate heat transfer problems without introducing any simplification on…
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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

Politecnico di Milano-Federico Piscaglia
University of Rome Niccolò Cusano-Giovanni Di Ilio
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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Effects of Turbulence Modeling and Grid Quality on the Zonal URANS/LES Simulation of Static and Reciprocating Engine-Like Geometries

SAE International Journal of Engines

University of Rome Tor Vergata-Luca Silvestri, Gino Bella
University of Tuscia-Vesselin Krassimirov Krastev
  • Journal Article
  • 2018-01-0173
Published 2018-04-03 by SAE International in United States
The interest in Unsteady Reynolds-Averaged Navier-Stokes (URANS)/Large Eddy Simulation (LES) hybrids, for the simulation of turbulent flows in Internal Combustion Engines (ICE), is consistently growing. An increasing number of applications can be found in the specialized literature for the past few years, including both seamless and zonal hybrid formulations. Following this trend, we have already developed a Detached Eddy Simulation (DES)-based zonal modeling technique, which was found to have adequate scale-resolving capabilities in several engine-like reference tests. In the present article we further extend our study by evaluating the effects of the underlying turbulence model and of the grid quality/morphology on the scale-resolved part of the flow. For that purpose, we consider DES formulations based on an enhanced version of the k-g URANS model and on the URANS form of the popular RNG k-ε model. The simulated test cases include a static intake valve geometry and a reference reciprocating piston/cylinder assembly. All the numerical predictions are assessed against the available experimental datasets and with previous computational studies made by other research groups.
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A Zonal-LES Study of Steady and Reciprocating Engine-Like Flows Using a Modified Two-Equation DES Turbulence Model

University of Rome "Tor Vergata"-Luca Silvestri, Giacomo Falcucci, Gino Bella
University of Tuscia-Vesselin Krassimirov Krastev
Published 2017-09-04 by SAE International in United States
A two-equation Zonal-DES (ZDES) approach has been recently proposed by the authors as a suitable hybrid URANS/LES turbulence modeling alternative for Internal Combustion Engine flows. This approach is conceptually simple, as it is all based on a single URANS-like framework and the user is only required to explicitly mark which parts of the domain will be simulated in URANS, DES or LES mode. The ZDES rationale was initially developed for external aerodynamics applications, where the flow is statistically steady and the transition between zones of different types usually happens in the URANS-to-DES or URANS-to-LES direction. The same “one-way” transition process has been found to be fairly efficient also in steady-state internal flows with engine-like characteristics, such as abrupt expansions or intake ports with fixed valve position. However, assuming that a pure LES treatment is applied on the in-cylinder region, the reciprocating nature of a real engine flow implies a “two-way” URANS-LES-URANS transition during the engine cycle. In the present work, we further validate the Zonal-LES mode (i. e. with only pure URANS and pure LES…
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A Zonal Turbulence Modeling Approach for ICE Flow Simulation

SAE International Journal of Engines

University of Rome "Tor Vergata"-Gino Bella
University of Tuscia-Vesselin Krassimirov Krastev
  • Journal Article
  • 2016-01-0584
Published 2016-04-05 by SAE International in United States
Turbulence modeling is a key aspect for the accurate simulation of ICE related fluid flow phenomena. RANS-based turbulence closures are still the preferred modeling framework among industrial users, mainly because they are robust, not much demanding in terms of computational resources and capable to extract ensemble-averaged information on a complete engine cycle without the need for multiple cycles simulation. On the other hand, LES-like approaches are gaining popularity in recent years due to their inherent scale-resolving nature, which allows the detailed modeling of unsteady flow features such as cycle-to-cycle variations in a DI engine. An LES requires however a large number of simulated engine cycles to extract reliable flow statistics, which coupled to the higher spatial and temporal resolution compared to RANS still poses some limits to a wider application of such methodology on realistic engine geometries. In this paper a hybrid zonal RANS/LES simulation methodology is proposed, based on a Detached Eddy Simulation (DES) technique previously developed by the authors. The aim is to preserve the turbulence scale-resolving capabilities wherever actually needed, reducing at…
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Some Developments in DES Modeling for Engine Flow Simulation

University of Rome "Tor Vergata"-Gino Bella
University of Tuscia-Vesselin Krassimirov Krastev
Published 2015-09-06 by SAE International in United States
Scale-resolving turbulence modeling for engine flow simulation has constantly increased its popularity in the last decade. In contrast to classical RANS modeling, LES-like approaches are able to resolve a larger number of unsteady flow features. In principle, this capability allows to accurately predict some of the key parameters involved in the development and optimization of modern engines such as cycle-to-cycle variations in a DI engine. However, since multiple simulated engine cycles are required to extract reliable flow statistics, the spatial and temporal resolution requirements of pure LES still represent a severe limit for its wider application on realistic engine geometries. In this context, Hybrid URANS-LES methodologies can therefore become a potentially attractive option. In fact, their task is to preserve the turbulence scale-resolving in the flow core regions but at a significantly lower computational cost compared to standard LES. In this paper, we present our achievements in the development of an original hybrid simulation method which relies on the Detached Eddy Simulation (DES) concept applied to a reformulated two-equation turbulence model. The resulting method has…
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