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Träfflista för sökning "WFRF:(Andric Jelena 1979) "

Sökning: WFRF:(Andric Jelena 1979)

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1.
  • Andric, Jelena, 1979 (författare)
  • A computational parametric analysis of cavitating flows in injector nozzles
  • 2017
  • Ingår i: International Journal of Modelling and Simulation. - : Informa UK Limited. - 0228-6203 .- 1925-7082. ; 37:4, s. 220-226
  • Tidskriftsartikel (refereegranskat)abstract
    • The fuel injection system in diesel engines has crucial influence on the engine’s combustion process and emission formation. Cavitation in injector nozzles plays a critical role in primary spray break-up and atomization. Understanding the phenomenon of cavitation is hence important for accurate design of the injection process. This work presents a computational study of the characteristics of cavitating flows in the two-dimensional (2D) injector nozzle. The computations are performed by employing the multi-phase mixture approach with the k–ε realizable turbulence model and Schnerr–Sauer cavitation model. The results demonstrate the capability of the modeling framework to successfully predict the following experimentally observed cavitation regimes: no cavitation, developing cavitation, and super cavitation. A parametric study of the effects of the cavitation number σ and the Reynolds number Re verifies the experimental finding that cavitation strongly depends on σ, while the effect of Re is not large.
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2.
  • Andric, Jelena, 1979, et al. (författare)
  • A computational study of the impacts of driving aggressiveness on fuel consumption sensitivity in a parallel HEV
  • 2017
  • Ingår i: The 7th International Conference & Workshop REMOO–2017, 10-12 May 2017, Venice, Italy. - 9783981827552
  • Konferensbidrag (refereegranskat)abstract
    • Hybrid electric vehicles (HEVs) have an advantage over their conventional counterparts interms of reducing fuel consumption and meeting increasingly stringent emission reductioncriteria. Nonetheless, the variation in fuel consumption due to differences in driving style andbehaviour under real-world driving conditions is greater in HEVs than in the conventionalones. A reduction in variability of fuel consumption is hence of compelling relevance for designand optimization of HEVs. This work employs vehicle powertrain simulations to analyze theeffects of driving style on fuel consumption sensitivity in parallel HEVs for a range of trafficconditions. The driving aggressiveness is modeled using velocity-scaling and acceleration-scalingmethods, respectively, to account for various velocity characteristics and accelerationlevels. Hybrid powertrain simulations assess and quantify the impacts of the engineperformance, as well as the significance of the energy recovered by regenerative braking. Theresults presented in this paper provide valuable inputs for optimal control of HEVs to meetcustomer driving needs and expectations.
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3.
  • Andric, Jelena, 1979, et al. (författare)
  • A particle-level rigid fiber model for high-Reynolds number flow, implemented in a general-purpose CFD code
  • 2013
  • Ingår i: 8th International Conference on Multiphase Flow ICMF 2013, Korea.
  • Konferensbidrag (refereegranskat)abstract
    • A particle-level rigid fiber model has been integrated into a general-purpose, open source computational fluid dynamics code to carry out detailed studies of fiber–flow interactions in realistic flow fields. The fibers are modeled as chains of cylindrical segments, and their translational and rotational degrees of freedom are considered. The equations of motion contain the contributions from hydrodynamic forces and torques, and the segment inertia is taken into account. The model is validated for the rotational motion of isolated fibers in simple shear flow, and the computed period of rotation is in good agreement with the one computed using Jeffery’s equation for a prolate spheroid with an equivalent aspect ratio. The model is applied by suspending a number of fibers in the swirling flow of a conical diffuser, resembling one stage in the dry-forming of pulp mats. The Reynolds-averaged Navier–Stokes equations with an eddy-viscosity turbulence model are employed to describe the fluid motion, and a one-way coupling between the fibers and the fluid phase is included. The dependence of the fiber motion on initial position and density is analyzed.
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4.
  • Andric, Jelena, 1979, et al. (författare)
  • A study of a flexible fiber model and its behavior in DNS of turbulent channel flow
  • 2013
  • Ingår i: Acta Mechanica. - : Springer Science and Business Media LLC. - 0001-5970 .- 1619-6937. ; 224:10, s. 2359-2374
  • Tidskriftsartikel (refereegranskat)abstract
    • The dynamics of individual flexible fibers in a turbulent flow field have been analyzed, varying their initial position, density and length. A particlelevel fiber model has been integrated into a general-purpose, open source Computational Fluid Dynamics (CFD) code. The fibers are modeled as chains of cylindrical segments connected by ball and socket joints. The equations of motion of the fibers contain the inertia of the segments, the contributions from hydrodynamic forces and torques, and the connectivity forces at the joints. Direct Numerical Simulation (DNS) of the incompressible Navier–Stokes equations is used to describe the fluid flow in a plane channel and a one-way coupling is considered between the fibers and the fluid phase. We investigate the translational motion of fibers by considering the mean square displacement of their trajectories. We find that the fiber motion is primarily governed by velocity correlations of the flow fluctuations. In addition, we show that there is a clear tendency of the thread-like fibers to evolve into complex geometrical configurations in a turbulent flow field, in fashion similar to random conformations of polymer strands subjected to thermal fluctuations in a suspension. Finally, we show that fiber inertia has a significant impact on reorientation time-scales of fibers suspended in a turbulent flow field.
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5.
  • Andric, Jelena, 1979, et al. (författare)
  • Ballistic deflection of fibres in decelerating flow
  • 2016
  • Ingår i: International Journal of Multiphase Flow. - : Elsevier BV. - 0301-9322 .- 1879-3533. ; 85, s. 57-66
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigate the motion of inertial, rod-like fibres in the decelerating flow of a wedge-shaped channel with non-creeping fibre-flow interactions. We consider the trajectories of isolated fibres to identify the conditions for which these trajectories deflect from the streamlines of the flow as well as a rectilinear path. We carry out analytical and numerical studies under the assumption of an infinite fibre hydrodynamic resistance to transverse flow, and we expand the numerical study by taking into account a finite transverse hydrodynamic resistance. The analytical analysis identifies a longitudinal ballistic number Bℓ and a transverse ballistic number Bt as two dimensionless parameters that govern the fibre dynamics. It is found that Bℓ is the product of the Stokes number Stℓ in the longitudinal direction of the fibre and the channel opening angle β. As anticipated, a fibre moves along the streamlines in the viscosity-dominated regime (Bℓ « 1, Bt « 1), while it moves in a straight line without being rotated in the inertia-dominated regime (Bt » 1). The focus of the present study is on the intermediate regime (Bℓ » 1, Bt
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6.
  • Andric, Jelena, 1979, et al. (författare)
  • Calibration Procedure for Measurement-Based Fast Running Model for Hardware-in-the-Loop Powertrain Systems
  • 2020
  • Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. ; 2020- April:April
  • Tidskriftsartikel (refereegranskat)abstract
    • The requirements set for the next-generation powertrain systems (e.g. performance and emissions) are becoming increasingly stringent with ever-shortening time-to-markets at reduced costs. To remain competitive automotive companies are progressively relying on model-driven development and virtual testing. Virtual test benches, such as Hardware-in the-Loop simulators, are powerful tools to reduce the amount of physical testing and speed up engine software calibration process. The introduction of these technologies places new, often conflicting demands (such as higher predictability, faster simulation speed, and reduced calibration effort ) upon simulation models used at Hardware-in-the-Loop test benches. The new models are also expected to offer compliance to industry standards, performance and usability to further increase the usage of virtual tests in powertrain development. The present work describes a novel verification process for creating a fast running model for a heavy-duty diesel engine using FRM-d Builder in GT-SUITE simulation software. The approach uniquely applies the combination physical modelling and parameter estimation techniques, while relying solely on test cell measurements without data maps from the manufactures (e.g. for turbine and compressor). The procedure provides detailed description for subsystem calibration for turbocharger and intake path. The developed model is successfully employed at the VIRTEC system in Volvo Penta. The simulation results for engine performance and exhaust emissions provide favourable results for both steady-state and transient operating conditions.
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7.
  • Andric, Jelena, 1979, et al. (författare)
  • Description and validation of a flexible fiber model, implemented in a general-purpose CFD code
  • 2013
  • Ingår i: Proceedings of the 8th International Conference on Multiphase Flow ICMF 2013, Korea.
  • Konferensbidrag (refereegranskat)abstract
    • A flexible fiber model  has been implemented in a general purpose open-source computational fluid dynamics code. The fibers are modeled as chains of cylindrical segments. Each segment is tracked individually and  their equations of motion account for the hydrodynamic forces and torques from the interaction with the fluid, the elastic bending and twisting torques, and the connectivity forces and moments that ensure the fiber integrity. The segment inertia is taken into account and a one-way coupling with the fluid phase is considered. The model is applied to the rotational motion of an isolated fiber in a low segment Reynolds number  shear flow. In the case of a stiff fiber, the computed period of rotation is in good agreement with the one computed using Jeffery's equation for an equivalent spheroid aspect ratio. A qualitative comparison is made with experimental data for flexible fibers. These results show that the implemented model can reproduce the known dynamical behavior of rigid and flexible fibers successfully.
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8.
  • Andric, Jelena, 1979, et al. (författare)
  • Development and Calibration of One Dimensional Engine Model for Hardware-in-the-Loop Applications
  • 2018
  • Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. ; 2018-April
  • Tidskriftsartikel (refereegranskat)abstract
    • The present paper aims at developing an innovative procedure to create a one-dimensional (1D) real-time capable simulation model for a heavy-duty diesel engine. The novelty of this approach is the use of the top-level engine configuration, test cell measurement data, and manufacturer maps as opposite to common practice of utilizing a detailed 1D engine model. The objective is to facilitate effective model adjustments and hence further increase the application of Hardware-in-the-Loop (HiL) simulations in powertrain development. This work describes the development of Fast Running Model (FRM) in GT-SUITE simulation software. The cylinder and gas-path modeling and calibration are described in detail. The results for engine performance and exhaust emissions produced satisfactory agreement with both steady-state and transient experimental data. Therefore, the presented methodology shows a great potential for testing and validation of new control strategies in Engine Management System (EMS) and for optimizing engine performance using HiL systems. The model has been successfully used in powertrain testing and calibration in the VIRtual TEst Cell (VIRTEC) system at Volvo Penta.
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9.
  • Andric, Jelena, 1979 (författare)
  • Implementation of a flexible fiber model in a general purpose CFD code
  • 2012
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • This work is related to the process of making pulp mats for use in hygienicproducts. One part of that process is the transportation of flexiblecellulose fibers suspended in flowing air. The fibers should be evenlydistributed on the substrate, and it is thus of high importance to avoidthe formation of fiber flocks during the transportation. The purposeof the present work is to implement a flexible fiber model in a generalpurpose Computational Fluid Dynamics (CFD) code, for detailed studiesof fiber-fiber and fiber-flow interaction in real flow situations. Thefibers are modeled as chains of cylindrical segments, and the translationaland rotational degrees of freedom of each segment are taken intoaccount. Each segment is tracked individually, using Lagrangian ParticleTracking (LPT), and the equations of fibermotion are derived fromthe conservation of momentum for each segment. The segment inertiais taken into account and the one-way coupling with the fluid phase isconsidered. The fiber integrity is ensured through connectivity forcesacting between the adjacent fiber segments. The implemented modelhas been applied both with imposed flow fields, and in a flow field simultaneouslypredicted by the CFD solver. The results show that thefibers are transported by the flow and are deformed due to flow gradients.Further, a generic test case is described and used to validate theenergy conservation and response time of the fiber model concept.This work is the foundation for further improvements of the fibermodelthrough the addition of bending and twisting forces, as well as the inclusionof interaction (e.g. collision) forces between individual fiber segments.These features, together with a two-way coupling with the flow,will lead to a more complete fiber model.
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10.
  • Andric, Jelena, 1979, et al. (författare)
  • Numerical investigation of fiber flocculation in the air flow of an asymmetric diffuser
  • 2014
  • Ingår i: Proceedings of the ASME 2014 4th Joint US-European Fluids Engineering Division Summer Meeting and 12th International Conference on Nanochannels, Microchannels and Minichannels, FEDSM 201, August 3-7, Chicago, Illinois, USA..
  • Konferensbidrag (refereegranskat)abstract
    • A particle-level rigid fiber model is used to studyflocculation in an asymmetric planar diffuser with a turbulent Newtonian fluid flow, resembling one stage in dry-forming process of pulp mats. The fibers are modeled as chains of rigid cylindrical segments. The equations of motion incorporatehydrodynamic forces and torques from the interaction with thefluid, and the fiber inertia is taken into account. The flow isgoverned by the Reynolds-averaged Navier ̶ Stokes equationswith the standard k-omega turbulence model. A one-waycoupling between the fibers and the flow is considered. Astochastic model is employed for the flow fluctuations tocapture the fiber dispersion. The fibers are assumed to interactthrough short-range attractive forces, causing them to interlockas the fiber-fiber contacts occur during the flow. It is found thatthe formation of fiber flocs is driven by both the turbulenceinduceddispersion and the gradient of the averaged flow field
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11.
  • Andric, Jelena, 1979 (författare)
  • Numerical modeling of air-fiber flows
  • 2014
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The dynamics of fiber suspensions are of great importance in applications such as the dry-forming process of pulp mats for use in hygiene products. In this forming process, fibers are transported in flowing air. The fibers interact with the fluid, and may interact with each other and interlock in flocs. The characteristics of the suspension structure are essential for the design and optimization of the forming process, and for improving the quality of the final products. Particularly, it is desired to achieve a uniform fiber distribution in the pulp mats. Thus, it is of high interest to develop tools, which can be used to perform comprehensive studies of the complex phenomenon of fiber suspension flows.This work is concerned with numerical analysis of fiber suspensions, related to the mat-forming process. For that purpose, a particle-level fiber model has been implemented into an open source computational fluid dynamics (CFD) code. A fiber is modeled as a chain of rigid cylindrical segments. The segments interact with the flow through hydrodynamic drag forces, and may interact with each other through short-range attractive forces. The segments are tracked individually using Lagrangian particle tracking (LPT). The implemented model comprises two alternatives, the flexible and the rigid fiber model, respectively. The equations of motion of a flexible fiber represent the application of Euler's second laws for rigid body motion for the fiber segments. The flexible fiber model takes into account all the degrees of freedom necessary to realistically reproduce the fiber dynamics. Connectivity forces act between the adjacent fiber segments to ensure the fiber integrity. The rigid fiber model keeps the relative orientation between the segments fixed. The equations of motion are formulated for the fiber as a whole, while the hydrodynamic contributions are taken into account from the individual segments. The fiber inertia is taken into account in both alternatives of the model. The fiber model has been coupled with imposed flow fields, or with flow fields computed by the CFD solvers.The behavior of the implemented model is compared with analytical and experimental results available in the literature. The simulation results show that the model correctly predicts the dynamics of isolated rigid and flexible fibers in creeping shear flow.The model is used to study the dynamics of flexible and rigid fibers in high Reynolds number flows and in geometries that are representative for the mat-forming process. The effects of fiber properties, such as fiber inertia and fiber length are analyzed.Simulations are carried out to investigate the rheology of suspensions of flexible and curved fibers in creeping shear flow of a Newtonian fluid. The effects of fiber flexibility and fiber curvature on the specific viscosity and the normal stress differences are examined.Finally, aggregation of rod-like fibers is investigated in a turbulent flow of an asymmetric planar diffuser. The influences of the average flow gradient, the fiber inertia and the turbulence dispersion on the aggregation rate are analyzed. The study identifies a darting fiber motion as a mechanism that significantly enhances fiber collisions and aggregation.
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12.
  • Andric, Jelena, 1979 (författare)
  • Numerical study of the effects of driving patterns on energy flow and fuel consumption in parallel hybrid electric vehicles
  • 2017
  • Ingår i: The 6th International Congress of Serbian Society of Mechanics, Tara, June 19-21, Serbia. - 9788690997367
  • Konferensbidrag (refereegranskat)abstract
    • Electrification and hybridization constitute an expanding paradigm shift in transportationindustry towards creation of more efficient alternative propulsion systems. The change isdriven by environmental and market objectives to minimize pollutant emissions and reducefossil fuel dependence. Nonetheless, the additional complexity of electrified powertrainsbrings a challenge to derive city and highway fuel consumption estimates. The present workanalyzes the role of different driving patterns on energy flow and fuel consumption in aparallel hybrid electric vehicle (HEV) by employing vehicle powertrain simulations. Thecomputational study considers five standard drive cycles representing various trafficconditions and driving styles. The investigation is performed to understand and quantify theeffect of drive cycle dynamics on vehicle energy use, fuel consumption, and kinetic energyrecuperation through regenerative braking. The results show that a parallel HEV is moreefficient in city driving conditions compared to the highway driving. Decreased fuelconsumption is due to the usage of the electric motor, which is more efficient in frequentstart-and-stop traffic conditions as the braking energy is recaptured and stored in the battery.The amount of energy recovered by regenerative braking correlates with vehicle inertiawheel work across drive cycles. The internal combustion engine (ICE) is clearly the mainparameter affecting vehicle fuel consumption. The impact of the engine operation ischaracterized by analyzing engine usage duration and engine energy losses. The observationsand assessments presented herein are useful inputs for further optimization studies onimproving the robustness of optimized vehicle design that is greatly influenced by drivecycle characteristics.
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13.
  • Andric, Jelena, 1979, et al. (författare)
  • Particle-level simulations of flocculation in a fiber suspension flowing through a diffuser
  • 2017
  • Ingår i: Thermal Science. - : VINCA INST NUCLEAR SCI. - 0354-9836 .- 2334-7163. ; 21, s. S573-S583
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigate flocculation in dilute suspensions of rigid, straight fibers in a decelerating flow field of a diffuser. We carry out numerical studies using a particle-level simulation technique that takes into account the fiber inertia and the non-creeping fiber-flow interactions. The fluid flow is governed by the Reynolds-averaged Navier-Stokes equations with the standard k-omega eddy-viscosity turbulence model. A one-way coupling between the fibers and the flow is considered with a stochastic model for the fiber dispersion due to turbulence. The fibers interact through short-range attractive forces that cause them to aggregate into flocs when fiber-fiber collisions occur. We show that ballistic deflection of fibers greatly increases the flocculation in the diffuser. The inlet fiber kinematics and the fiber inertia are the main parameters that affect fiber flocculation in the pre-diffuser region.
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14.
  • Andric, Jelena, 1979, et al. (författare)
  • Rheological properties of dilute suspensions of rigid and flexible fibers
  • 2014
  • Ingår i: Journal of Non-Newtonian Fluid Mechanics. - : Elsevier BV. - 0377-0257 .- 1873-2631. ; 212, s. 36-46
  • Tidskriftsartikel (refereegranskat)abstract
    • Particle-level simulations are used to study the rheology of monodispersed suspensions of rigid and flexible fibers in a creeping, simple shear flow of a Newtonian fluid. We also investigate the influence of different equilibrium shapes (straight and curved) of the fibers on the behavior of the suspension. A parametric study of the impacts of fiber flexural rigidity and morphology on rheology quantifies the effects of these realistic fiber features on the experimentally accessible rheological properties. A fiber is modeled as a chain of rigid cylindrical segments, interacting through a two-way coupling with the fluid described by the incompressible three-dimensional Navier--Stokes equations. The initial fiber configuration is in the flow--gradient plane. We show that, when the shear rate is increased, straight flexible fibers undergo a buckling transition, leading to the development of finite first and second normal stress differences and a reduction of the viscosity. These effects, triggered by shape fluctuations, are dissimilar to the effects induced by the curvature of stiff, curved fibers, for which the viscosity increases with the curvature of the fiber. An analysis of the orbital drift of fibers initially oriented at an angle to the flow--gradient plane provides an estimate for the time-scale within which the prediction of the rheological behavior is valid. The information obtained in this work can be used in the experimental characterization of fiber morphology and mechanics through rheology.
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15.
  • Astaneh, Majid, 1990, et al. (författare)
  • Calibration Optimization Methodology for Lithium-Ion Battery Pack Model for Electric Vehicles in Mining Applications
  • 2020
  • Ingår i: Energies. - : MDPI AG. - 1996-1073 .- 1996-1073. ; 13:14
  • Tidskriftsartikel (refereegranskat)abstract
    • Large-scale introduction of electric vehicles (EVs) to the market sets outstanding requirements for battery performance to extend vehicle driving range, prolong battery service life, and reduce battery costs. There is a growing need to accurately and robustly model the performance of both individual cells and their aggregated behavior when integrated into battery packs. This paper presents a novel methodology for Lithium-ion (Li-ion) battery pack simulations under actual operating conditions of an electric mining vehicle. The validated electrochemical-thermal models of Li-ion battery cells are scaled up into battery modules to emulate cell-to-cell variations within the battery pack while considering the random variability of battery cells, as well as electrical topology and thermal management of the pack. The performance of the battery pack model is evaluated using transient experimental data for the pack operating conditions within the mining environment. The simulation results show that the relative root mean square error for the voltage prediction is 0.7–1.7% and for the battery pack temperature 2–12%. The proposed methodology is general and it can be applied to other battery chemistries and electric vehicle types to perform multi-objective optimization to predict the performance of large battery packs.
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16.
  • Astaneh, Majid, 1990, et al. (författare)
  • Lithium-ion Battery Pack Design for Electric Vehicles Using GT-AutoLion: Multi-Physics Simulation and Multi-Criteria Optimization Approach
  • 2021
  • Ingår i: Global Gamma Technologies Virtual Conference.
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • High specific energy battery systems with improved thermal performance are required for large-scale introduction of electric vehicles (EVs) into the market. This study presents a comprehensive multi-physics simulation and multi-criteria optimization framework for Lithium-ion (Li-ion) battery pack design for EV applications. The battery cells are modeled by electrochemical thermally coupled approach using GT-AutoLion. Multi-objective optimization using genetic algorithm is employed to explore energy and thermally efficient cell design alternatives. The performances of the optimally designed cells are then evaluated under pack environment to account for inhomogeneities in large traction battery packs under realistic working scenarios. It is observed that considering the thermal efficiency of battery cells is crucial for obtaining improved battery pack performance. The integrated framework developed in this work provides systematic pack-aware guidelines for manufacturers already at the initial cell design stage. Moreover, the proposed design optimization methodology is generic, handing over valuable knowledge for future cell and pack designs for various applications.
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17.
  • Astaneh, Majid, 1990, et al. (författare)
  • Lithium-Ion Battery Pack Modelling for Electric Vehicles in Mining Applications Using GT-AutoLion
  • 2020
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Large traction battery packs play a pivotal role in electric vehicles (EVs) to fulfill the system demand for high voltage and capacity. Therefore, accurate and robust modeling of both individual battery cells and their aggregated behavior in battery packs is of crucial importance. This presentation proposes a novel approach to integrate the validated electrochemical-thermal models of the Lithium-ion (Li-ion) cells into battery pack simulations for electric vehicle applications. The approach employs the calibration optimization methodology that utilizes experimental measurements for battery cells and for the battery pack under realistic operating conditions in mining applications. The random variability of battery cells, as well as electrical topology and thermal management of the pack have been considered in the present study to mimic the actual behavior of the battery pack under consideration. The simulations were carried out in GT-AutoLion and the optimizations were performed using GT-SUITE direct optimizer. The experimental data were provided by Northvolt AB, a leading European manufacturer of the next-generation Li-ion battery cells and complete battery systems. The proposed methodology is general and can be applied to other battery chemistries and electric vehicle types to perform multi-objective optimization to predict the performance of large battery packs.
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18.
  • Astaneh, Majid, 1990, et al. (författare)
  • Multiphysics simulation optimization framework for lithium-ion battery pack design for electric vehicle applications
  • 2022
  • Ingår i: Energy. - : Elsevier BV. - 0360-5442. ; 239
  • Tidskriftsartikel (refereegranskat)abstract
    • Large-scale commercialization of electric vehicles (EVs) seeks to develop battery systems with higher energy efficiency and improved thermal performance. Integrating simulation-based design optimization in battery development process expands the possibilities for novel design exploration. This study presents a dual-stage multiphysics simulation optimization methodology for comprehensive concept design of Lithium-ion (Li-ion) battery packs for EV applications. At the first stage, multi-objective optimization of electrochemical thermally coupled cells is performed using genetic algorithm considering the specific energy and the maximum temperature of the cells as design objectives. At the second stage, the energy efficiency and the thermal performances of each optimally designed cell are evaluated under pack operation to account for cell-to-pack interactions under realistic working scenarios. When operating at 1.5 C discharge current, the battery pack comprising optimally designed cells for which the specific energy and the maximum temperature are equally weighted delivers the highest specific energy with enhanced thermal performance. The most favorable pack design shows 8% reduction in maximum pack temperature and 16.1% reduction in module-to-module temperature variations compared to commercially available pack. The methodology for design optimization presented in this work is generic, providing valuable knowledge for future cell and pack designs that employ different chemistries and configurations.
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19.
  • Faghani, Ethan, et al. (författare)
  • Toward an Effective Virtual Powertrain Calibration System
  • 2018
  • Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. ; 2018-April
  • Tidskriftsartikel (refereegranskat)abstract
    • Due to stricter emission regulations and more environmental awareness, the powertrain systems are moving toward higher fuel efficiency and lower emissions. In response to these pressing needs, new technologies have been designed and implemented by manufacturers. As a result of increasing complexity of the powertrain systems, their control and optimization become more and more challenging. Virtual powertrain calibration, also known as model-based calibration, has been introduced to transfer a part of test bench testing into a virtual environment, and hence considerably reduce time and cost of product development process while increasing the product quality. Nevertheless, virtual calibration has not yet reached its full potential in industrial applications. Volvo Penta has recently developed a virtual test cell named VIRTEC, which is used in an ongoing pilot project to meet the Stage V emission standards. The integrated powertrain system includes engine, Exhaust Aftertreatment System (EATS), and Engine Management System (EMS). The objective of this paper is to describe the essential aspects required to increase the contribution of virtual testing in powertrain calibration activities. These aspects comprise the following: Hardware-in-the-Loop (HiL) system, simulation models, and working process for joint virtual and physical testing to facilitate efficient powertrain development process. The current paper describes the design, test and verification of a calibration platform based on the requirements of the project. The future phases in the current project (Virtual Calibration at Volvo Penta) will cover validation of the platform by performing calibrations in industrial scales on the virtual system.
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20.
  • Mamikoglu, Mehmet Sarp, 1984, et al. (författare)
  • Impact of Conventional and Electrified Powertrains on Fuel Economy in Various Driving Cycles
  • 2017
  • Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. ; 2017-March:March
  • Tidskriftsartikel (refereegranskat)abstract
    • Many technological developments in automobile powertrains have been implemented in order to increase efficiency and comply with emission regulations. Although most of these technologies show promising results in official fuel economy tests, their benefits in real driving conditions and real driving emissions can vary significantly, since driving profiles of many drivers are different than the official driving cycles. Therefore, it is important to assess these technologies under different driving conditions and this paper aims to offer an overall perspective, with a numerical study in simulations. The simulations are carried out on a compact passenger car model with eight powertrain configurations including: a naturally aspirated spark ignition engine, a start-stop system, a downsized engine with a turbocharger, a Miller cycle engine, cylinder deactivation, turbocharged downsized Miller engine, a parallel hybrid electric vehicle powertrain and an electric vehicle powertrain. These are tested in seven driving cycles including the NYCC, FTP75, NEDC, WLTC, US06, HWFET and CADC. The impacts of different technologies on fuel economy and CO₂ emissions are analyzed, with respect to different operating conditions. Results reveal that a combination of certain driving cycles and vehicle configurations have a large influence on fuel consumption and CO₂ emissions. In general, Miller and downsized engines offer some improvements in all cycles while the start-stop system has benefits in city cycles with frequent stops. The HEV and EV configurations offer a substantial improvement compared to conventional technologies in lower speed conditions like city cycles, but their benefits are reduced at cycles including higher speeds.
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21.
  • Minovski, Blago, 1986, et al. (författare)
  • A Coupled 1D–3D Numerical Method for Buoyancy-Driven Heat Transfer in a Generic Engine Bay
  • 2019
  • Ingår i: Energies. - : MDPI AG. - 1996-1073 .- 1996-1073. ; 12:21, s. 4156-
  • Tidskriftsartikel (refereegranskat)abstract
    • Energy efficient vehicles are essential for a sustainable society and all car manufacturers are working on improved energy efficiency in their fleets. In this process, an optimization of aerodynamics and thermal management is most essential. The objective of this work is to improve the energy efficiency using encapsulated heat generating units by focusing on predicting temperature distribution inside an engine bay. The overall objective is to make an estimate of the generated heat inside an encapsulation and consecutively use this heat for climatization purposes. The study presents a detailed numerical procedure for predicting buoyancy-driven flow and resulting natural convection inside a simplified vehicle underhood during thermal soak and cool-down events. The procedure employs a direct coupling of one-dimensional and three-dimensional methods to carry out transient one-dimensional thermal analysis in the engine solids synchronized with sequences of steady-state three-dimensional simulations of the fluid flow. The boundary heat transfer coefficients and averaged fluid temperatures in the boundary cells, computed in the three-dimensional fluid flow model, are provided as input data to the one-dimensional analysis to compute the resulting surface temperatures which are then fed back as updated boundary conditions in the flow simulation. The computed temperatures of the simplified engine and the exhaust manifolds during the thermal soak and cool-down period are in favorable agreement with experimental measurements. The present study illustrates the capabilities of the coupled thermal-flow methodology to conduct accurate and fast computations of buoyancy-driven heat transfer. The methodology can be potentially applied to design and analysis of multiple demand vehicle thermal management systems in hybrid and electrical vehicles.
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22.
  • Minovski, Blago, 1986, et al. (författare)
  • A numerical investigation of thermal engine encapsulation concept for a passenger vehicle and its effect on fuel consumption
  • 2019
  • Ingår i: Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering. - : SAGE Publications. - 2041-2991 .- 0954-4070. ; 233:3, s. 557-571
  • Tidskriftsartikel (refereegranskat)abstract
    • Increasingly tough regulations for emission levels and a growing demand for an environmentally clean motor industry impose high requirements in modern automotive development. During recent decades, carmakers have been utilizing various strategies to minimize energy losses in the powertrain to meet legislative and market demands. A great part of research efforts has been focused on improving engine performance during cold starts characterized by increased friction losses. Thermal engine encapsulation is an effective design choice to reduce engine friction in applications with frequent cold starts. In the present work, a coupled 1-D–3-D system-level approach is used to investigate the effects of a novel engine-mounted encapsulation concept featuring air shutters on fuel consumption in a Volvo S80 passenger vehicle. Simulations are performed for sequences of the Worldwide harmonized light vehicles test cycle (WLTC) drive cycle, which include different time intervals of engine inactivity when the car is parked in air of an quiescent ambient temperature. The results show that engine encapsulation with high area coverage (97%) can retain engine oil temperature above 19°C for up to 16 h after engine shutdown at an ambient temperature of 5°C, leading to 2.5% fuel saving during engine warm-up when cold starts occur between 2 and 8 h after key-off. Encapsulations with a lower area coverage (90%) have proven to be less effective, with fuel saving of 1.25% as the temperatures of the oil and engine structures decrease more quickly after key-off compared to the fully enclosed encapsulation.
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23.
  • Norouzi, MohammadJavad, et al. (författare)
  • Shape evolution of long flexible fibers in viscous flows
  • 2022
  • Ingår i: Acta Mechanica. - : Springer Science and Business Media LLC. - 1619-6937 .- 0001-5970. ; 233, s. 2077-2091
  • Tidskriftsartikel (refereegranskat)abstract
    • The present work studies numerically the dynamics and shape evolution of long flexible fibers suspended in a Newtonian viscous cellular flow using a particle-level fiber simulation technique. The fiber is modeled as a chain of massless rigid cylindrical segments connected by ball and socket joints; one-way coupling between the fibers and the flow is considered while Brownian motion is neglected. The effect of stiffness, equilibrium shape, and aspect ratio of the fibers on the shape evolution of the fibers are analyzed. Moreover, the influence of fiber stiffness and their initial positions and orientations on fiber transport is investigated. For the conditions considered, the results show that the fiber curvature field resembles that of the flow streamline. It is found that the stiffer fibers experience not only a quicker relaxation phase, in which they transient from their initial shape to their "steady-state shape," but they also regain their equilibrium shape to a larger extent. The findings also demonstrate that even a small deviation of fiber shape from perfectly straight impacts significantly the early-stage evolution of the fiber shape and their bending behavior. Increasing the fiber aspect ratio, when other parameters are kept fixed, leads the fiber to behave more flexible, and it consequently deforms to a larger extent to adjust to the shape of the flow streamlines. In agreement with the available experimental results, the fiber transport studies show that either the fiber becomes trapped within the vortices of the cellular array or it moves across the vortical arrays while exhibiting various complex shapes.
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24.
  • Ramesh Babu, Anandh, 1996, et al. (författare)
  • System-level modeling and thermal simulations of large battery packs for electric trucks
  • 2021
  • Ingår i: Energies. - : MDPI AG. - 1996-1073 .- 1996-1073. ; 14:16
  • Tidskriftsartikel (refereegranskat)abstract
    • Electromobility has gained significance over recent years and the requirements on the performance and efficiency of electric vehicles are growing. Lithium-ion batteries are the primary source of energy in electric vehicles and their performance is highly dependent on the operating temperature. There is a compelling need to create a robust modeling framework to drive the design of vehicle batteries in the ever-competitive market. This paper presents a system-level modeling methodology for thermal simulations of large battery packs for electric trucks under real-world operating conditions. The battery pack was developed in GT-SUITE, where module-to-module discretization was performed to study the thermal behavior and temperature distribution within the pack. The heat generated from each module was estimated using Bernardi’s expression and the pack model was calibrated for thermal interface material properties under a heat-up test. The model evaluation was performed for four charging/discharging and cooling scenarios typical for truck operations. The results show that the model accurately predicts the average pack temperature, the outlet coolant temperature and the state of charge of the battery pack. The methodology developed can be integrated with the powertrain and passenger cabin cooling systems to study complete vehicle thermal management and/or analyze different battery design choices.
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25.
  • Sediako, Anton D., et al. (författare)
  • Heavy Duty Diesel Engine Modeling with Layered Artificial Neural Network Structures
  • 2018
  • Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. ; 2018-April
  • Tidskriftsartikel (refereegranskat)abstract
    • In order to meet emissions and power requirements, modern engine design has evolved in complexity and control. The cost and time restraints of calibration and testing of various control strategies have made virtual testing environments increasingly popular. Using Hardware-in-the-Loop (HiL), Volvo Penta has built a virtual test rig named VIRTEC for efficient engine testing, using a model simulating a fully instrumented engine. This paper presents an innovative Artificial Neural Network (ANN) based model for engine simulations in HiL environment. The engine model, herein called Artificial Neural Network Engine (ANN-E), was built for D8-600 hp Volvo Penta engine, and directly implemented in the VIRTEC system. ANN-E uses a combination of feedforward and recursive ANNs, processing 7 actuator signals from the engine management system (EMS) to provide 30 output signals. To improve the accuracy in predicting exhaust emissions, the ANNs were arranged into two layers, such that engine temperature and pressure output signals and their average rate of change act as extra inputs for exhaust emission signals. The simulation results show that the ANN-E model accurately predicts engine performance, engine temperatures and pressures along the flow path, as well as exhaust emissions. In addition, the modular nature of ANN-E makes it possible for fast rebuild of the model if engine components are changed. Therefore, the layered modular ANN modeling approach represents a powerful tool for virtual engine testing and calibration optimization.
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26.
  • Sjöblom, Jonas, 1968, et al. (författare)
  • Intrinsic Design of Experiments for Modeling of Internal Combustion Engines
  • 2018
  • Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. ; 2018-April
  • Tidskriftsartikel (refereegranskat)abstract
    • In engine research and development there are often different engine parameters that produce similar effects on the end-point results. When calibrating modern engines, a huge number of parameters needs to be set, which also includes compensation parameters for model imperfections. In this context, simpler, more robust, and physically based models should be beneficial both for calibration work load and powertrain performance. In this study, we present an experimental methodology that uses intermediate ("intrinsic") variables instead of engine parameters. By using simple thermodynamic models, the engine parameters EGR, IVC, and P Boost could be translated into oxygen concentration, temperature and gas density at the start of injection. The reason for this transformation of data is to "move" the Design of Experiment (DoE) closer to the situation of interest (i.e. the combustion) and to be able to construct simpler and more physically based models. In this example, the system was a diesel engine. However, the method can be applied to any experimental system that shares the non-intrinsic nature (e.g. the internal combustion engine), which makes this methodology general. The approach was demonstrated for a heavy-duty diesel engine and five design variables were investigated. Regression models were made using either the engine variables or the intrinsic variables and the resulting regression coefficients were compared and contrasted. By using exactly the same experiments but described in a different way (using the intrinsic variables), the optimization task becomes facilitated. Furthermore, by using physical properties instead of engine settings, these models should be more general and more robust during powertrain optimization.
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27.
  • Yang, Ying, et al. (författare)
  • Data-driven rolling eco-speed optimization for autonomous vehicles
  • 2024
  • Ingår i: Frontiers of Engineering Management. - 2096-0255 .- 2095-7513. ; In Press
  • Tidskriftsartikel (refereegranskat)abstract
    • In urban settings, fluctuating traffic conditions and closely spaced signalized intersections lead to frequent emergency acceleration, deceleration, and idling in vehicles. These maneuvers contribute to elevated energy use and emissions. Advances in vehicle-to-vehicle and vehicle-to-infrastructure communication technologies allow autonomous vehicles (AVs) to perceive signals over long distances and coordinate with other vehicles, thereby mitigating environmentally harmful maneuvers. This paper introduces a data-driven algorithm for rolling eco-speed optimization in AVs aimed at enhancing vehicle operation. The algorithm integrates a deep belief network with a back propagation neural network to formulate a traffic state perception mechanism for predicting feasible speed ranges. Fuel consumption data from the Argonne National Laboratory in the United States serves as the basis for establishing the quantitative correlation between the fuel consumption rate and speed. A spatiotemporal network is subsequently developed to achieve eco-speed optimization for AVs within the projected speed limits. The proposed algorithm results in a 12.2% reduction in energy consumption relative to standard driving practices, without a significant extension in travel time.
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