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nili-ahmadabadi--ali
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Centrifugal compressor shape modification using a proposed inverse design method
, Article Journal of Mechanical Science and Technology ; Volume 27, Issue 3 , 2013 , Pages 713-720 ; 1738494X (ISSN) ; Poursadegh, F ; Sharif University of Technology
2013
Abstract
This paper is concerned with a quasi-3D design method for the radial and axial diffusers of a centrifugal compressor on the meridional plane. The method integrates a novel inverse design algorithm, called ball-spine algorithm (BSA), and a quasi-3D analysis code. The Euler equation is solved on the meridional plane for a numerical domain, of which unknown boundaries (hub and shroud) are iteratively modified under the BSA until a prescribed pressure distribution is reached. In BSA, unknown walls are composed of a set of virtual balls that move freely along specified directions called spines. The difference between target and current pressure distributions causes the flexible boundary to deform...
Innovation of Flexible String and Ball-Spine Inverse Design Methods for 2D and Axisymmentric Internal Flows
, Ph.D. Dissertation Sharif University of Technology ; Hajilouy Benisi, Ali (Supervisor) ; Dor Ali, Mohammad (Supervisor) ; Ghadak, Farhad (Supervisor)
Abstract
Duct Inverse design problems usually involve finding the wall shape associated with a prescribed distribution of wall pressure or velocity. In this investigation, a novel iterative inverse design method is presented and developed for internal flows. In the proposed method, the duct walls shape is changed under a novel algorithm based on the deformation of a virtual flexible string in flow. The deformation of the string due to the local flow conditions resulting from changes in wall geometry is observed until the target shape satisfying the prescribed wall’s pressure distribution is reached. The flow field at each step is analyzed to obtain the current pressure distribution along the wall....
A novel aerodynamic design method for centrifugal compressor impeller
, Article Journal of Applied Fluid Mechanics ; Vol. 7, issue. 2 , July , 2014 , p. 329-344 ; Durali, M ; Hajilouy, A ; Sharif University of Technology
2014
Abstract
This paper describes a new quasi-3D design method for centrifugal compressor impeller. The method links up a novel inverse design algorithm, called Ball-Spine Algorithm (BSA), and a quasi-3D analysis. Euler equation is solved on the impeller meridional plane. The unknown boundaries (hub and shroud) of numerical domain are iteratively modified by BSA until a target pressure distribution in flow passage is reached. To validate the quasi-3D analysis code, existing compressor impeller is investigated experimentally. Comparison between the quasi-3D analysis and the experimental results shows good agreement. Also, a full 3D Navier-Stokes code is used to analyze the existing and designed compressor...
Subsonic and transonic airfoil inverse design via Ball-Spine Algorithm
, Article Computers and Fluids ; Volume 84 , 2013 , Pages 87-96 ; 00457930 (ISSN) ; Ghadak, F ; Mohammadi, M ; Sharif University of Technology
2013
Abstract
Inverse design in external flow regimes usually involves finding the wall shape associated with a prescribed distribution of wall pressure or velocity. In this research, a novel iterative inverse design method is developed for inviscid subsonic and transonic external flow regimes. The method links up a novel inverse design algorithm, called Ball-Spine Algorithm (BSA), and a 2D inviscid analysis code. The Euler equations are solved for a physical domain of which some unknown boundaries are iteratively modified via BSA until a prescribed pressure distribution is reached. In BSA, the unknown walls are composed of a set of virtual balls that move freely along the specified directions called...
Experimental and numerical investigation of a centrifugal compressor
, Article ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, ESDA2010, 12 July 2010 through 14 July 2010, Istanbul ; Volume 3 , 2010 , Pages 447-458 ; 9780791849170 (ISBN) ; Hajilouy Benisi, A ; Nili Ahmadabadi, M ; Sharif University of Technology
2010
Abstract
In this research, centrifugal compressor of a gas turbine is investigated experimentally and numerically. Operation line of the compressor as a component of the gas turbine is obtained experimentally by measurements of impeller rotational speed, and flow parameters at the compressor inlet and outlet during the gas turbine operation. The flow field inside the impeller and diffusers are analyzed numerically using a full 3D Navier-Stokes program with SST turbulence model. Boundary conditions for the numerical simulation are specified from the experimental measurements. The operation line of the compressor is obtained numerically, which is compared with that of the experimental results, and...
A novel QUASI-3D design method for centrifugal compressor meridional plane
, Article Proceedings of the ASME Turbo Expo, 14 June 2010 through 18 June 2010 ; Volume 7, Issue PARTS A, B, AND C , 2010 , Pages 919-931 ; 9780791844021 (ISBN) ; Durali, M ; Hajilouy Benisi, A ; Sharif University of Technology
2010
Abstract
This paper is concerned with a quasi-3D design method for centrifugal compressor impeller in the meridional plane. The method links up a novel inverse design algorithm, called Ball-Spine Algorithm (BSA), and a quasi-3D analysis code. The Euler equation is solved on the meridional plane for a numerical domain of which some unknown boundaries (hub and shroud) are iteratively modified under the BSA until a prescribed pressure distribution is reached. In BSA, the unknown walls are composed of a set of virtual balls that move freely along the specified directions called spines. The difference between target and current pressure distribution causes to deform flexible boundary at each modification...
Natural Vibrations of Nanostructures Using a Developed 3D Model Based on Nonlocal Theory of Elasticity
,
M.Sc. Thesis
Sharif University of Technology
;
Dehghani Firoozabadi, Rouhollah
(Supervisor)
Abstract
The goal of this thesis is to survey natural frequencis of nanostructures such as nanobeams and nanoplates using nonlocal theory of elasticity by finite element method. In nonlocal theory of elasticity,the constitutive relation appears as an integral form so that the stress of a point is a function of the strain of all points in the field such that by getting away from the assumed point, the effect of strains on the stress of that point decreases. In fact, the stress on a point is an average of stress in the field and the effect of stress of other points in determined by a function called the kernel function. In order to achieve natural frequencies and shape modes of a structure, we need to...
Duct design in subsonic and supersonic flow regimes with and without normal shock waves using Flexible String Algorithm
, Article Scientia Iranica ; Volume 17, Issue 3 B , MAY-JUNE , 2010 , Pages 179-193 ; 10263098 (ISSN) ; Durali, M ; Hajilouy Benisi, A ; Ghadak, F ; Sharif University of Technology
2010
Abstract
In this investigation, the Flexible String Algorithm (FSA) used before for the inverse design of 2D subsonic ducts is developed and applied for the inverse design of subsonic and supersonic ducts with and without normal shock waves. In this method, the duct wall shape is changed under a novel algorithm based on the deformation of a virtual flexible string in a flow. Deformation of the string due to the local fl.ow conditions resulting from changes in the wall geometry is performed until the target shape satisfying the. prescribed walls pressure distribution is achieved. The flow field at each shape modification step is analyzed using an Euler equation solution by the. A USM method. Some...
A novel 2D incompressible viscous inverse design method for internal flows using flexible string algorithm
, Article Journal of Fluids Engineering, Transactions of the ASME ; Volume 132, Issue 3 , 2010 , Pages 0314011-03140110 ; 00982202 (ISSN) ; Hajilouy Benisi, A ; Ghadak, F ; Durali, M ; Sharif University of Technology
2010
Abstract
In this investigation, the flexible string algorithm (FSA), used before for inverse design of subsonic and supersonic ducts in compressible flows with and without normal shock, is developed and applied for inverse design of 2D incompressible viscous internal flow with and without separation. In the proposed method, the duct wall shape is changed under an algorithm based on deformation of a virtual flexible string in flow. At each modification step, the difference between current and target wall pressure distributions is applied to the string. The method is an iterative inverse design method and utilizes the analysis code for the flow field solution as a black-box. Some validation test cases...
Inverse design of 2-D subsonic ducts using flexible string algorithm
, Article Inverse Problems in Science and Engineering ; Volume 17, Issue 8 , 2009 , Pages 1037-1057 ; 17415977 (ISSN) ; Dural, M ; Hajilouy Benisi, A ; Ghadak, F ; Sharif University of Technology
2009
Abstract
The duct inverse design in fluid flow problems usually involves finding the wall shape associated with a prescribed distribution of wall pressure or velocity. In this investigation, an iterative inverse design method for 2-D subsonic ducts is presented. In the proposed method, the duct walls shape is changed under a novel algorithm based on the deformation of a virtual flexible string in flow. The deformation of the string due to the local flow conditions resulting from changes in wall geometry is observed until the target shape satisfying the prescribed wall's pressure distribution is reached. The flow field at each step is analysed using Euler equations and the advection upstream splitting...
Duct design in subsonic & supersonic flow regimes with and without normal shock wave using flexible string algorithm
, Article Proceedings of the ASME Turbo Expo, 8 June 2009 through 12 June 2009, Orlando, FL ; Volume 7, Issue PART A , 2009 , Pages 513-523 ; 9780791848883 (ISBN) ; Hajilouy Benisi, A ; Durali, M ; Ghadak, F ; Sharif University of Technology
2009
Abstract
In this investigation, the Flexible String Algorithm (FSA), used before for 2D subsonic ducts inverse design, is developed and applied to inverse design of supersonic ducts with and without normal shock wave. In this method, the duct wall shape is changed under an algorithm based on deformation of a virtual flexible string in a flow. The deformation of the string due to the local flow conditions resulting from changes in wall geometry is performed until the target shape satisfying the prescribed walls pressure distribution is achieved. The flow field at each step is analyzed using Euler equations solutions by the AUSM method. Some validation test cases and design examples in subsonic and...
Investigation of a centrifugal compressor and study of the area ratio and TIP clearance effects on performance
, Article Journal of Thermal Science ; Volume 17, Issue 4 , December , 2008 , Pages 314-323 ; 10032169 (ISSN) ; Hajilouy Benisi, A ; Durali, M ; Ghadak, F ; Sharif University of Technology
2008
Abstract
In this research, the centrifugal compressor of a turbocharger is investigated experimentally and numerically. Performance characteristics of the compressor were obtained experimentally by measurements of rotor speed and flow parameters at the inlet and outlet of the compressor. Three dimensional flow field in the impeller and diffuser was analyzed numerically using a full Navier-Stokes program with SST turbulence model. The performance characteristics of the compressor were obtained numerically, which were then compared with the experimental results. The comparison shows good agreement. Furthermore, the effect of area ratio and tip clearance on the performance parameters and flow field was...
Experimental & numerical investigation of a centrifugal compressor and numerical study of the area ratio and tip clearance effects on the performance characteristic
, Article 2008 ASME Turbo Expo, Berlin, 9 June 2008 through 13 June 2008 ; Volume 6, Issue PART B , 2008 ; 9780791843161 (ISBN) ; Hajilouy Benisi, A ; Durali, M ; Motavalli, S. M ; Sharif University of Technology
American Society of Mechanical Engineers(ASME)
2008
Abstract
In this research, the centrifugal compressor of a turbocharger is investigated experimentally and numerically. Performance characteristics of the compressor were obtained experimentally by measurements of rotor speed and flow parameters at the inlet and outlet of the compressor. Three dimensional flow field in the impeller and diffuser was analyzed numerically using a full Navier-Stokes program with SST turbulence model. The performance characteristics of the compressor were obtained numerically, which were then compared with the experimental results. The comparison shows good agreement. Furthermore, the effect of area ratio and tip clearance on the performance parameters and flow field was...
Rolling Contact Mechanics of Graded Coatings Involving Frictional Heating
, Ph.D. Dissertation Sharif University of Technology ; Adibnazari, Saeed (Supervisor) ; Karimzadeh, Ardavan (Co-Supervisor)
Abstract
In this Thesis ,the two-dimensional thermoelastic tractive rolling contact problem for an FGM coated half-plane under the plane strain deformation is investigated. A rigid cylinder rolls on the surface of an FGM coated half-plane with constant translational velocity, generating frictional heat in the slip zones of the contact area. Thermo-mechanical properties of the FGM vary exponentially along the thickness. It is assumed that the contact area consists of a central stick zone and two slip zones of the same sign. The transfer matrix method and Fourier integral transform technique are used to achieve a system of two Cauchy singular integral equations. The associated governing equations are...
Experimental and theoretical investigation of centrifugal compressor performance characteristics
, Article Proceedings of the ASME Turbo Expo, 9 June 2008 through 13 June 2008, Berlin ; Volume 6, Issue PART B , 2008 ; 9780791843161 (ISBN) ; Hajilouy Benisi, A ; Nili Ahmadabadi, M ; International Gas Turbine Institute ; Sharif University of Technology
2008
Abstract
Prediction of compressor performance is a basic step in design of this turbomachine, while designer can optimize plan by considering various conditions and calculating machine performance. Flow field in centrifugal compressor is threedimensional and intricate. Since 2-D and 3-D methods are very costly, consequently the mean line method usually is used for predicting compressor performance. The energy loss coefficients are used for this method. Because of the intricacy in flow and analysis of losses, most energy loss coefficients are attained by experimental procedures, however just some of them are determined according to theory and nature of the flow field. The purpose of this work is...
Coarse Grained-Atomistic Concurrent Multi-Scale Modeling for Numerical Simulation of Mechanical Behavior of Heterogeneous Materials in Nano-cale
, M.Sc. Thesis Sharif University of Technology ; Khoei, Amir Reza (Supervisor)
Abstract
In this thesis, a method has been exploited to couple the atomistic domain with the coarse-grained domain. Since molecular dynamics has a high computational cost when a large number of atoms exist, coarse-grained molecular dynamics was used in which a number of atoms are assumed as a bigger bid and interatomic potential is modified for bids so that the material’s mechanical properties remain constant. This method not only reduces the computational cost of calculating forces in molecular dynamics simulation but also, the time step used in Coarse-Grained Methods can be more than atomistic simulations as the frequency of occurring phenomena in CG scale is less than atomistic scale.The advantage...
Role of Oil in Financial Development-economic Growth Volatility Nexus
, M.Sc. Thesis Sharif University of Technology ; Nili, Masoud (Supervisor) ; Madanizadeh, Ali (Supervisor)
Abstract
In this research, we investigate the role of oil and degree of dependence to it on nexus between financial development and growth volatility. The link between financial development and growthvolatility has been the focus of extensive literature, but no empirical study has been investigated the role of oilin relationship between financial development and growth fluctuations. By using information of 78 developing countries (11 oil exporting and 67 non-oil countries) during 1983-2008, we construct a dynamic model. Difference GMM technique is used to estimate the model. Our findings show that negative impact of financial development on volatility of GDP, Investment and Consumptiongrowth is...
Measuring Core Inflation by Using the VAR Approach
, M.Sc. Thesis Sharif University of Technology ; Nili, Masoud (Supervisor) ; Madanizadeh, Ali (Supervisor)
Abstract
The present study aims to calculate the core inflation percentage using a SVAR model. Core inflation which is defined in policy-making, includes that component of measured inflation that has no (medium- to) long-run impact on real output but rather includes monetary and demand shocks. To this end, the VAR model is defined with 4 endogenous variables, namely production, inflation, money supply and exchange rate in addition to 2 exogenous variables, which are dummy (due to attracting the uneven behavior of exchange rate) and energy prices. Core inflation is produced using the results of the model estimation and the monetary and demand shocks. The results show that the core inflation usually...
Study and Comparison the Incidence of Dutch Disease in Iranian Economy in Two Periods of Oil Shock
, M.Sc. Thesis Sharif University of Technology ; nili, Masoud (Supervisor) ; Madanizadeh, Ali (Supervisor)
Abstract
This paper studies and compares the effect of "Dutch disease" in Iranian economy in two periods of rising oil price (1973-1978) and (2004-2010). The study presents a DSGE model to analysis the behavior of economic variable in both periods and to address this question that whether or not policy maker has learning behavior. The model consists of households, final goods producers who divided in tradable goods and non-tradable goods sector and the government. I use calibration methods to estimate models parameters.Comparison of simulated results and the actual macroeconomic variables in Iran during 1338-1390 indicates that, first of all Dutch disease effect occur in both periods of oil shock so...
The Effect of Political Systems on Economic Performance in Resource-Rich Countries
, M.Sc. Thesis Sharif University of Technology ; Nili, Farhad (Supervisor) ; Nili, Masoud (Co-Advisor)
Abstract
In this research, the effect of political system on economic performance of resource abundant countries is studied. We use political economy litreture to develop a theoritical model in this issue. Here, the politcal systems are divided to democracy and dictatory and in each of them other institutional variable will be introduced. Policy indicator is based on the difference between social welfare in each situation and its optimal amount when maximized. We show that if democracy does not come with high accountability it reduces social welfare more than dictatory. Also, if politician are myopic, democracy aggravates economic performance in those countries. In addition, easy access to income...