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Magnetic equivalent circuit modelling of brushless doubly-fed induction generator
, Article IET Renewable Power Generation ; Vol. 8, Issue. 3 , 2014 , pp. 334-346 ; ISSN: 1752-1416 ; Jandaghi, B ; Oraee, H ; Abdi, E ; Sharif University of Technology
Abstract
The brushless doubly-fed induction generator (BDFIG) has substantial benefits, which make it an attractive alternative as a wind turbine generator. The aim of this work is to present a nodal-based magnetic equivalent circuit (MEC) model of the BDFIG which provides performance characteristics and flux density distributions. The model takes into account stator winding distributions, special configuration of rotor bars, slotting effects, teeth saturation, flux fringing and current displacement effects. The real flux tubes are considered for creating an MEC network and calculating its non-linear elements. A method for simplifying the rotor magnetic network has been applied and Gauss elimination...
Modeling of large deformation frictional contact in powder compaction processes
, Article Applied Mathematical Modelling ; Volume 32, Issue 5 , 2008 , Pages 775-801 ; 0307904X (ISSN) ; Keshavarz, Sh ; Khaloo, A. R ; Sharif University of Technology
2008
Abstract
In this paper, the computational aspects of large deformation frictional contact are presented in powder forming processes. The influence of powder-tool friction on the mechanical properties of the final product is investigated in pressing metal powders. A general formulation of continuum model is developed for frictional contact and the computational algorithm is presented for analyzing the phenomena. It is particularly concerned with the numerical modeling of frictional contact between a rigid tool and a deformable material. The finite element approach adopted is characterized by the use of penalty approach in which a plasticity theory of friction is incorporated to simulate sliding...
Finite Element Modeling of Particle Distribution in Al/Powder Composite Sheets Processed by ARB for Manufacturing Aluminium Foams
, M.Sc. Thesis Sharif University of Technology ; Akbarzade, Abbas (Supervisor)
Abstract
In this study closed cell aluminum foam was manufactured through accumulative roll bonding (ARB). In this method, aluminum AA1050 strip was used as the matrix and calcium carbonate was selected as blowing agent powder. The strips were roll-bonded with reduction of 50% during each pass. The produced composite was then subjected to different foaming conditions in order to achieve foams with maximum porosity. Subsequently, influences of content of the blowing agent, time, pressure, number of rolling passes and heating rate on the percentage of porosities were evaluated. In optimum condition quantity of the blowing agent, foaming temperature, holding time and number of ARB passes were equal to 1...
Heat transfer aspects of regenerative-cooling in methane-based propulsion systems
, Article Aerospace Science and Technology ; Volume 82-83 , 2018 , Pages 412-424 ; 12709638 (ISSN) ; Ebrahimi, A ; Sharif University of Technology
Abstract
In the present article, thermal behavior and heat transfer deterioration (HTD) of transcritical methane as well as the fluid state change in regenerative cooling with straight/curved rectangular channels are studied numerically. Simulations are conducted with a finite-volume based CFD solver utilizing reliable turbulence models and thermo-fluidic relations in transcritical conditions. The experimental and numerical results of hydrogen inside a heated tube in the literature are used for validation. The effects of mass flow rate, outlet pressure, wall temperature, surface roughness, and the channel geometry on the thermal behavior of the coolant fluid are studied in detail. According to the...
Chitosan interphase around nanodiamond: Insight from equilibrium molecular dynamics
, Article Diamond and Related Materials ; Volume 104 , 2020 ; Shojaei, A ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
In the context of nanodiamond/chitosan (ND/CS) nanocomposites and utilizing atomistic molecular dynamics, the interaction mechanism of adsorbed CS layer around a model ND has been investigated at three level of hydration: in bulk of water, water as a droplet, and completely dry condition. The effect of amination and carboxylation of ND has been studied. To ensure that the comparison of these model systems is meaningful (energetically and geometrically), the CS interphases around NDs were characterized through holistic concentration profiles and density distribution maps. Our results revealed that in a completely dry condition or hydrated by a molecularly small droplet, both of the...
A clustering fuzzification algorithm based on ALM
, Article Fuzzy Sets and Systems ; Volume 389 , 2020 , Pages 93-113 ; Malekzadeh, A ; Heydari, G ; Bagheri Shouraki, S ; Sharif University of Technology
Elsevier B.V
2020
Abstract
In this paper, we propose a fuzzification method for clusters produced from a clustering process, based on Active Learning Method (ALM). ALM is a soft computing methodology which is based on a hypothesis claiming that human brain interprets information in pattern-like images. The proposed fuzzification method is applicable to all non-fuzzy clustering algorithms as a post process. The most outstanding advantage of this method is the ability to determine the membership degrees of each data to all clusters based on the density and shape of the clusters. It is worth mentioning that for existing fuzzy clustering algorithms such as FCM the membership degree is usually determined as a function of...
The electron density distribution and field profile in underdense magnetized plasma
, Article Physics of Plasmas ; Volume 17, Issue 3 , 2010 ; 1070664X (ISSN) ; Etehadi-Abari, M ; Sharif University of Technology
2010
Abstract
In this work propagation of a high frequency electromagnetic wave in underdense plasma in presence of an external magnetic field is investigated. When a constant magnetic field perpendicular to the motion of electrons is applied, then the electrons rotate around the magnetic field lines and generate electromagnetic part in the wake with a nonzero group velocity. By using of the Maxwell equations and nonlinear differential equation for the electric field a direct one-dimensional (1D) procedure for calculating hydrodynamic equations are developed and the electric and magnetic field profiles in the plasma are investigated. It is shown that by using the external (dc) magnetic field in constant...
A novel modeling approach for design studies of brushless doubly fed induction generator based on magnetic equivalent circuit
, Article IEEE Transactions on Energy Conversion ; Volume 28, Issue 4 , 2013 , Pages 902-912 ; 08858969 (ISSN) ; Oraee, H ; McMahon, R. A ; Sharif University of Technology
2013
Abstract
Brushless doubly fed induction generator (BDFIG) has substantial benefits, which make it an attractive alternative as a wind turbine generator. However, it suffers from lower efficiency and larger dimensions in comparison to DFIG. Hence, optimizing the BDFIG structure is necessary for enhancing its situation commercially. In previous studies, a simple model has been used in BDFIG design procedure that is insufficiently accurate. Furthermore, magnetic saturation and iron loss are not considered because of difficulties in determination of flux density distributions. The aim of this paper is to establish an accurate yet computationally fast model suitable for BDFIG design studies. The proposed...
Modeling, design and fabrication of non-uniform catalyst layers for PEM fuel cells
, Article ASME 2010 8th International Conference on Fuel Cell Science, Engineering and Technology, FUELCELL 2010, 14 June 2010 through 16 June 2010 ; Volume 1 , 2010 , Pages 697-705 ; 9780791844045 (ISBN) ; Advanced Energy Systems Division ; Sharif University of Technology
Abstract
Catalyst layers are one of the most important parts of the PEM fuel cells and the cell performance is highly related to its structure. Catalyst layers are generally made by uniform distribution of catalyst on carbon cloth or carbon papers to form electrodes. In this paper, the idea of using non-uniform catalyst layer instead of common uniform catalyst layers is presented and simulated by a two-dimensional steady-state computational model. The model accounts for species transport, electrochemical kinetics, charge transport and current density distribution. A fuel cell test stand is designed and built to facilitate experimental validation of the model. Modeling results show that electrical...
Simulation and optimization of HEMTs
, Article 3rd International Conference on Advances in Computational Tools for Engineering Applications, 13 July 2016 through 15 July 2016 ; 2016 , Pages 1-6 ; 9781467385237 (ISBN) ; Ashrafi, R ; Khorasani, S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
Abstract
We have developed a simulation system for nanoscale high-electron mobility transistors, in which the self-consistent solution of Poisson and Schrödinger equations is obtained with the finite element method. We solve the exact set of nonlinear differential equations to obtain electron wave function, electric potential distribution, electron density, Fermi surface energy and current density distribution in the whole body of the device. For more precision, local dependence of carrier mobility on the electric field distribution is considered. We furthermore compare the simulation to a recent experimental measurement and observe perfect agreement. We also propose a novel graded channel design,...
Computation of armature reaction field and full-load characteristics of an axial flux surface mounted pm machine using a new analytical approach
, Article 26th Iranian Conference on Electrical Engineering, ICEE 2018, 8 May 2018 through 10 May 2018 ; 2018 , Pages 1027-1031 ; 9781538649169 (ISBN) ; Sharifi, A. H ; Abedini Mohammadi, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
In recent years axial flux permanent magnet (AFPM) machines have found industrial applications because of such characteristics as high power density, compact structure and disc-like shape. Like other electrical machines, prediction of flux density distribution in the air gap of AFPM is essential. In this paper, an analytical method for calculation of air gap flux density caused by armature reaction is presented. The solution is based on Maxwell's equations. Separation of variables method is applied to field equations and 2D distribution of magnetic flux density in the air gap calculated in term of Fourier series. The 2-D distribution of three-phase armature winding is modeled exactly....
An integrated process configuration of solid oxide fuel/electrolyzer cells (SOFC-SOEC) and solar organic Rankine cycle (ORC) for cogeneration applications
, Article International Journal of Energy Research ; Volume 45, Issue 7 , 2021 , Pages 11018-11040 ; 0363907X (ISSN) ; Karimian Bahnamiri, F ; Mehrpooya, M ; Sharif University of Technology
John Wiley and Sons Ltd
2021
Abstract
This research work presents a novel integrated structure for the cogeneration of electricity and renewable syngas. The base structure of the process is developed by solid oxide cells in which electricity is generated by the natural gas-fueled fuel cell unit, and renewable syngas is produced by the electrolyzer cell unit. Direct integration between fuel cell and electrolyzer cell units is established for optimal use of fuel cell off-gases. To improve system's sustainability, a solar power cycle, including solar collectors coupled with an organic Rankine cycle (ORC), is designed to provide renewable electricity for steam and CO2 co-electrolysis operation. 1D mathematical approaches are...
3D dynamic modeling of powder forming processes via a simple and efficient node-to-surface contact algorithm
, Article Applied Mathematical Modelling ; Volume 37, Issue 1-2 , 2013 , Pages 443-462 ; 0307904X (ISSN) ; Biabanaki, S. O. R ; Parvaneh, S. M ; Sharif University of Technology
2013
Abstract
In this paper, a simple and efficient contact algorithm is presented for the evaluation of density distribution in three-dimensional dynamic modeling of powder compaction processes. The contact node-to-surface algorithm is employed to impose the contact constraints in large deformation frictional contact, and the contact frictional slip is modified by the Coulomb friction law to simulate the frictional behavior between the rigid punch and the work-piece. The 3D nonlinear contact friction algorithm is employed together with a double-surface cap plasticity model within the framework of large finite element deformation in order to predict the non-uniform relative density distribution during the...
Startup of "cANDLE" burnup in a Gas-cooled Fast Reactor using Monte Carlo method
, Article Annals of Nuclear Energy ; Volume 50 , December , 2012 , Pages 44-49 ; 03064549 (ISSN) ; Abbaspour, A ; Pazirandeh, A ; Sharif University of Technology
2012
Abstract
During the past decade, the CANDLE burnup strategy has been proposed as an innovative fuel cycle and reactor design for complete utilization of uranium resources. In this strategy the shapes of neutron flux, nuclide densities and power density distribution remain constant but the burning region moves in axial direction. The feasibility of this strategy has been demonstrated widely by using the diffusion technique in conjunction with nuclide transmutation equations. On the other hand since the Monte Carlo method provides the exact solution to the neutron transport, the Monte Carlo technique is becoming more widely used in routine burnup calculations. The main objective of this work is startup...
Prediction of shape and internal structure of the proximal femur using a modified level set method for structural topology optimisation
, Article Computer Methods in Biomechanics and Biomedical Engineering ; Volume 15, Issue 8 , 2012 , Pages 835-844 ; 10255842 (ISSN) ; Farahmand, F ; Rouhi, G ; Movahhedy, M. R ; Sharif University of Technology
Abstract
A computational framework was developed to simulate the bone remodelling process as a structural topology optimisation problem. The mathematical formulation of the Level Set technique was extended and then implemented into a coronal plane model of the proximal femur to simulate the remodelling of internal structure and external geometry of bone into the optimal state. Results indicated that the proposed approach could reasonably mimic the major geometrical and material features of the natural bone. Simulation of the internal bone remodelling on the typical gross shape of the proximal femur, resulted in a density distribution pattern with good consistency with that of the natural bone. When...