Papers by Vahid Esfahanian
International Symposium on Algorithms and Computation, May 14, 2013
Applied sciences, Apr 26, 2017
This study examines the implementation of a waste heat recovery system on an electric hybrid vehi... more This study examines the implementation of a waste heat recovery system on an electric hybrid vehicle. The selected waste heat recovery method operates on organic Rankine cycle principles to target the overall fuel consumption improvement of the internal combustion engine element of a hybrid powertrain. This study examines the operational principle of hybrid electric vehicles, in which the internal combustion engines operates with an electric powertrain layout (electric motors/generators and batteries) as an integral part of the powertrain architecture. A critical evaluation of the performance of the integrated powertrain is presented in this paper whereby vehicle performance is presented through three different driving cycle tests, offering a clear assessment of how this advanced powertrain configuration would benefit under several different, but relevant, driving scenarios. The driving cycles tested highlighted areas where the driver could exploit the full potential of the hybrid powertrain operational modes in order to further reduce fuel consumption.
Electrochimica Acta, 2018
Temperature rise is one of the main problems of battery applications. Thus, preventing the temper... more Temperature rise is one of the main problems of battery applications. Thus, preventing the temperature rise in lead-acid batteries is an important research topic. In the present study, the effect of Lewis number on temperature rise is investigated. Moreover, effects of the cell-length (CL), the maximum activated area (A max) and the newly defined parameter of maximum dimensionless volume (A max L) on Lewis number are studied. The governing energy equation is nondimensionalized due to saving cost and time. A typical lead-acid cell, taken from literature, is simulated using finite volume method. The results demonstrate that Lewis number has inverse relation with temperature rise. However, the parameters of CL, A max and A max L have direct impact on Lewis number. In this research, the aspect of battery design is presented in which the problem of temperature rise is overcome. In fact, the temperature rise can be restricted by changing some parameters due to modification of Lewis number.
Energy, 2019
A new approach to consider the influence of aging state on lithium-ion battery state of power est... more A new approach to consider the influence of aging state on lithium-ion battery state of power estimation for hybrid electric vehicle, Energy (2019), doi:
IEEE Transactions on Plasma Science, 2019
High thrust density per thruster area is the most desired achievement in current ion thruster des... more High thrust density per thruster area is the most desired achievement in current ion thruster designs. Dual-stage ion thruster concept is introduced to improve the ion beam focusing capability of single-stage thrusters in order to maximize the achievable thrust density for a fixed thruster area. In this paper, a two-grid ion thruster is converted to a dual-stage one by adding an extractor grid. Then, improvement of ion beam divergence characteristic is numerically investigated through the parametric study of extractor grid's geometrical and operational variables by a hybrid-particle-in-cell method. The sensitivity analysis shows that the beam divergence angle is very sensitive to acceleration-to-extraction voltage difference ratio. The effect of acceleration-to-extraction grid gap ratio is also significant. The initial dual-stage model is modified based on this result. The minimum divergence angle for the modified model is about 3.38°resulting in 70% and 60% improvement against the minimum divergence angle of the two-grid single-stage and the initial dual-stage numerical models, respectively.
Energy Conversion and Management, 2018
The spiral type one is more prominent of which the vertical type ground heat exchange (GHE) is th... more The spiral type one is more prominent of which the vertical type ground heat exchange (GHE) is the most common in ground source heat pumps (GSHP) and on the purpose of this study as well. The present paper provides numerical simulation for 1D-3D model of the ground source heat pumps in cooling mode by using COMSOL environment. In contrary to popular spiral models, this model is designed with a low depth and high diameter with special metal rods (Fins). The simulated spiral pipe has 10 m in depth and 1 m in diameter. In order to compensate the reduction in heat transfer due to the lower depth, the effect of different parameters such as velocity, pitch, thermal conductivity and specific heat capacity in backfill material and ground on the heat performance is investigated. Furthermore, different velocity range is recommended for several pitches. Also, as a novelty, an innovative design is modeled consisting of diverse type of horizontal aluminum rods (Fins) in the soil connected to the pipe completely (Finned pipe). The fins not only hold the pipe inside the ground firmly but also improve the heat transfer rate due to the area increase and the high thermal conductivity system up to 31%.
T. Nazghelichi, F. Torabi, V. esfahanian, Optimization of geometrical parameters in a lead-acid b... more T. Nazghelichi, F. Torabi, V. esfahanian, Optimization of geometrical parameters in a lead-acid battery using response surface method to access of maximum capacity, minimum charge-time and minimum temperature rise, Modares Mechanical Engineering, Vol. 18, No. 04, pp. 1-10, 2018 (in Persian) هنیهب برس یرتاب یسدنه یاهریغتم یزاس هب دیسا تسد یارب خساپ هحفص شور هب یبای امد شیازفا نیرتمک و ژراش نامز نیرتمک ،تیفرظ نیرتشیب
Electrical Engineering (ICEE), Iranian Conference on
Hardware-in-the-Loop (HiL) simulation is recognized as a reliable approach for testing and verifi... more Hardware-in-the-Loop (HiL) simulation is recognized as a reliable approach for testing and verification of the control systems of hybrid vehicles. To perform the HiL simulation, a real-time vehicle simulator is needed which can virtually emulate the real vehicle in communication with the control unit. This paper presents the design and implementation of a low-cost single PC based HiL simulation platform for testing of the Central Control Unit (CCU) in a series hybrid electric bus. For HiL simulation purposes, the generation and flow of the signals should be the same as those of the real system. Therefore, based on the Controller Area Network (CAN) messages and dynamic behaviour of each component, a comprehensive real-time simulator is designed in LabVIEW environment. The designed simulator together with the control unit and the necessary interfaces makes a functional low-cost HiL test bench. Due to modular simulation, subsystems of the designed simulator can be replaced by the real prototypes and this in turn leads to a more flexible HiL simulation test bench. With this system, the user can act like a real driver and experience driving regimes which may happen in reality without being involved with difficulties of testing on an actual vehicle. The designed simulation model has been validated using real test results. Using the designed test bench, the results show that all control functions in the CCU can be tested and verified.
Journal of Energy Storage, 2021
Abstract Long charging time is one of the main disadvantages of lead–acid batteries. Although the... more Abstract Long charging time is one of the main disadvantages of lead–acid batteries. Although the higher charging voltage can shorten the charging time, it is limited in order to avoid thermal instability. In the present research, the charging time has shortened using a higher charging voltage while the stability of the system has remained the same through thermal stability analysis. The method of linear stability analysis is applied to derive governing equations of perturbations. The set of derived equations are rearranged to obtain the desired form of the eigenvalue problem. The obtained eigenvalue problem is solved numerically, which has resulted in a neutral curve separating the stable zone from the unstable one, and the critical point. In addition, the effects of some geometrical parameters on the position of the neutral curve are investigated. All charging processes are simulated using the computational battery dynamic method. The results show that on the one hand, the stable zone increases by increasing the maximum dimensionless volume. On the other hand, the stable zone decreases by increasing the charging voltage. In conclusion, an eight percent reduction in the charging time is observed through increasing both of the charging voltage and the maximum dimensionless volume at the same time.
ECS Meeting Abstracts, 2016
Thermal management of lithium-ion battery pack in hybrid electric vehicles (HEVs) and electric ve... more Thermal management of lithium-ion battery pack in hybrid electric vehicles (HEVs) and electric vehicles (EVs) have become a research focus in recent years because performance, safety and life time of battery have significant dependency on temperature distribution throughout the cell. As the first step in designing a reliable thermal strategy, heat generation of battery must be computed accurately. But the most effective physical properties involved in heat source may not be exactly known, possibly because of intrinsic variability which cannot be measured directly in practice. In any simulation process, some uncertainties appear whose understanding and quantification is critical to assess the differences between the numerical predictions and actual system behavior. For this purpose, these uncertainties must be quantified and propagated through energy equation and heat flux to roll up the uncertainties of interest in order to determine range of temperature distribution, and consequent...
Physics of Fluids, 2019
Dynamic Mode Decomposition (DMD) is a data-driven reduced order method, which is known for its po... more Dynamic Mode Decomposition (DMD) is a data-driven reduced order method, which is known for its power to capture the basic features of dynamical systems. In fluid dynamics, modal analysis of unsteady fluid flows over moving structures is significant in terms of state estimation and control. However, the underlying algorithm of the DMD requires a fixed spatial domain, which is an obstacle for applying the DMD on the numerically investigated problems using dynamic meshes. In this study, a hybrid method called Hybrid Dynamic Mode Decomposition (HDMD) is presented for analysis of unsteady fluid flows over moving structures based on the DMD and machine learning. According to the assessment of several data interpolation methods, the K-nearest neighbor algorithm is employed for the interpolation of the numerical data from dynamic meshes at each time step to a single stationary grid. Three different case studies (rotating cylinder, oscillating airfoil, and Savonius wind turbine) are assessed...
Journal of Energy Storage, 2019
Accurate estimation of the State of Power (SoP) can ensure safe and efficient operation of Lithiu... more Accurate estimation of the State of Power (SoP) can ensure safe and efficient operation of Lithium-ion batteries in Electric Vehicles (EVs) and Hybrid Electric Vehicles (HEVs). The cell-to-cell variation within a battery pack is a major challenge towards accurate estimation of the SoP, particularly when the cells get aged. This paper presents a hybrid model predictive and fuzzy logic based control system to accurately estimate the SoP for seriesconnected Lithium-ion cells. The estimation strategy consists of two steps; the power capability for a single new cell is first reckoned under the light of the model predictive control algorithm. The second step is devoted to designation of a model-less fuzzy logic based control system to compensate for the concurrent aging state and State of Charge (SoC) differences among the cells. Accordingly, the present approach only utilizes the actual values of current and cell voltages together with the Electric Circuit Model (ECM) parameters of the new cell, which are identified off-line. Moreover, it benefits from a closed-loop framework which ends in an accurate and reliable SoP estimation. An experimental setup consisting of fresh and aged LiFePO 4 cell samples is designed and the extracted data are utilized to verify the proposed estimation method in a feed-forward simulation model for a HEV. The results indicate that the proposed method can estimate the pack SoP accurately while the safe operation for the cells is guaranteed.
Energy, 2018
The increasing number of passenger cars worldwide and the consequent increasing rate of global oi... more The increasing number of passenger cars worldwide and the consequent increasing rate of global oil consumption have raised the attention on fuel prices and have caused serious problems to the environment. Nowadays, the demand for reducing fuel consumption and pollutant emissions has paved the way to the development of more efficient power generation systems for the transportation sector. The lower fuel burning and pollutant emissions of hybrid electric vehicles give a strong motivation and encourage further investigations in this field. This research aims to investigate novel configurations, which could achieve further performance benefits for vehicle powertrain. Automakers claim that the employment of a gas turbine operating as range extender in a series hybrid configuration is the most efficiency solution in the coming years. In particular, a Micro Gas Turbine (MGT) can be considered as an alternative to the internal combustion engine (ICE) as a range extender for electric vehicles. The MGT produces less raw exhaust gaseous emissions such as HC and CO and static applications compared to the ICE. In addition, the MGT weight is lower than an equivalent ICE and potentially can reduce the level of CO 2 especially in a vehicle application. This study presents a parametric study of MGT applications for Range-Extended Electric Vehicle (REEV). The main objective is to examine the MGT performance to meet the requirements for a REEV that could become competitive, in terms of fuel consumption and pollutant emissions, to equivalent diesel or gasoline hybrid propulsion units or to conventional diesel vehicle.
Energy, 2017
One major drawback about premixed charge compression ignition (PCCI) engines is incomplete combus... more One major drawback about premixed charge compression ignition (PCCI) engines is incomplete combustion and producing high levels of carbon monoxide (CO) emission in lean operating conditions. This issue becomes even more serious when fuels with high octane number, e.g. natural gas, are used. In the present work, the combustion process of premixed charge natural gas engines is studied by means of numerical tools. The studied engine concepts are: conventional homogenous charge compression ignition (HCCI), HCCI with a pre-chamber and PCCI with a pre-chamber. The numerical model is validated against the experimental data and then, combustion characteristics and engine emissions in various operating regions, are discussed and compared. The results reveal that the PCCI case has the earliest start of combustion. It is also shown that in the ultra lean operating conditions (fuel equivalence ratio of 0.1) decreasing the intake temperature from 450 K results in an efficiency increment for the PCCI engine, while for the HCCI case this causes misfiring and more CO emission. Nevertheless, the PCCI engine has higher levels of NO emission compared to the HCCI cases and only in the ultra lean condition this level reaches amounts less than the acceptable limits set by Euro 6 emission regulations.
International Journal of Energy Research, 2016
Electric energy storage systems are used considerably in industries and daily applications. The d... more Electric energy storage systems are used considerably in industries and daily applications. The demand for batteries with high energy content has increased because of their use in hybrid vehicles. Lead-acid batteries have wide applications because of their advantages such as high safety factor and low cost of production. The major shortcoming of lead-acid batteries is low energy content and high dimension and weight. Nowadays, a common method to increase the energy content of lead-acid battery is the experimental method with trial and error, which is time consuming and expensive. In this paper, non-isothermal one-dimensional numerical simulation of lead-acid battery with finite volume method is performed. In addition, a cell with higher energy content and lower thickness is designed by using particle swarm optimization algorithm based on developed simulation code. The results of single objective optimization show that an optimal battery that has 27.6% higher energy can be made with the same cell dimension. The results also show that an optimum cell battery can be obtained with a decrease of 24% in thickness while keeping the energy the same. Moreover, a multi-objective optimization algorithm is utilized to find Pareto optimal solutions while considering the energy content and thickness objectives simultaneously.
Aim of this paper is to investigate mechanism of NO and soot reduction by using multiple injectio... more Aim of this paper is to investigate mechanism of NO and soot reduction by using multiple injection as useful strategy for reducing DI diesel engines emissions. In this paper, we first studied the mechanism of NO and soot reduction by using double injection. Then after investigating different modes of injection, at last we introduce optimum mode of fuel injection for a DI diesel engine manufactured in our country. Experiments were induced at Motorsazan Tabriz to validate results of CFD simulation. Amount of fuel in each pulse and dwell time between injection pulses are essential parameters. Results showed that by using double injection soot and NO will reduce by 33% and 11% respectively.
Journal of Computational Medicine, 2014
Background. In order to reduce the mortality risk of aneurysm rupture, a timely diagnosis and tre... more Background. In order to reduce the mortality risk of aneurysm rupture, a timely diagnosis and treatment are vital. There are different reasons for aneurysm, such as hypertension, arteriosclerosis, and heredity. An efficient and cost-effective method to study the generation, development, and rupture of aneurysm and also analysis of treatment methods can accelerate progress. The Computational Fluid Dynamics is a well-known tool to simulate various phenomena. A reliable virtual modeling in biology depends on our knowledge about variety of characteristics, that is, biological features, structural properties, and flow conditions. Objective. Because of the vast research about the related subjects, an organized review is required. The aim of current review article is classification of the required foundations for a reliable virtual modeling of cerebral aneurysm, especially in the Circle of Willis.
Fluids, Jul 10, 2020
The conceptual changes wrought by modern physics are radical, important, and fascinating, yet the... more The conceptual changes wrought by modern physics are radical, important, and fascinating, yet they are only vaguely understood by people working outside the field. Exploring the four pillars of modern physics-relativity, quantum mechanics, elementary particles, and cosmology-this clear and lively account, that will interest anyone who has wondered what Einstein, Schrödinger, Feynman, Hubble, and others were really talking about. The book discusses quarks and leptons, antiparticles and Feynman diagrams, curved spacetime, the Big Bang and the expanding Universe. Suitable for undergraduate students on nonscience majors as well as science majors, it uses problems and worked examples to help readers develop an understanding of what recent advances in physics actually mean.
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Papers by Vahid Esfahanian