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    Effects of skewing on torque ripples for brushless doubly-fed machine

    , Article International Review of Electrical Engineering ; Volume 4, Issue 6 , 2009 , Pages 1283-1293 ; 18276660 (ISSN) Gorgin, H ; Sotoodeh, P ; Oraee, H ; Sharif University of Technology
    In this paper, analytical expressions are presented to describe the stator and rotor slotting effects on the distribution of Brushless Doubly-Fed Machine's quantities. The effects of rotor slot and loop skewing on the produced torque ripples are then investigated by means of an analytical model considering skew. Torque ripples have considerable effects in the machine operation especially on its starting process and avoid machine from successful starting in some instances. The cogging torque and distortion of the sinusoidal distribution of the magnetic flux density in the air gap, are two principle sources of torque ripples in Brushless Doubly-Fed Machine that are studied. © 2009 Praise... 

    Multi-point optimization of lean and sweep angles for stator and rotor blades of an axial turbine

    , Article Iranian Journal of Science and Technology - Transactions of Mechanical Engineering ; Volume 41, Issue 1 , 2017 , Pages 35-47 ; 22286187 (ISSN) Asgarshamsi, A ; Hajilouy Benisi, A ; Assempour, A ; Pourfarzaneh, H ; Sharif University of Technology
    In this research, numerical optimization of the rear part of a gas turbine, consisting of a single-stage axial turbine, is carried out. Automated aerodynamic shape optimization is performed by coupling a CFD flow simulationcode with the genetic algorithm. An effective multipointoptimization method to improve efficiency and/or pressure ratio of the axial turbine is performed. Some variations of optimization parameters such as lean and sweep angels of stator and rotor blades are accomplished. Furthermore, during the optimization process, three-dimensionaland turbulent flow field is numerically investigatedusing a compressible Navier-Stokes solver. The gas turbine experimental investigations... 

    Thermodynamic analysis of a hybrid gas turbine/thermoacoustic heat pump/refrigeration engine

    , Article International Journal of Exergy ; Volume 15, Issue 2 , 1 November , 2014 , Pages 152-170 ; ISSN: 17428297 Ghorbanian, K ; Karimi, M ; Sharif University of Technology
    Possible performance enhancement of small gas turbine power plants through the application of thermoacoustic systems is examined. The thermoacoustic subsystem is powered only by the waste heat of the gas turbine. Two different gas turbine configurations are considered: a Thermoacoustic refrigerator assisted gas turbine (TRG) and a Combined thermoacoustic heat pump and refrigeration assisted gas turbine (CTHRG). Exergy, rational efficiency and relative power gain (RPG) of these configurations are compared with those from the recuperated gas turbine engine. The results indicate that the integration of thermoacoustic system to a simple gas turbine cycle will not only enhance the energy/exergy... 

    Sensitivity analysis of gas turbine fuel consumption with respect to turbine stage efficiency

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) ; Volume 1 , 2012 , Pages 419-423 ; 9780791845172 (ISBN) Zeinalpour, M ; Mazaheri, K ; Irannejad, A ; Sharif University of Technology
    In this paper, the effect of turbine stage efficiency on fuel consumption of both gas turbines and aerial engines is assessed quantitatively. At the beginning of the gas generator optimization to decrease the fuel consumption, it is necessary to analyze the sensitivity of fuel consumption to its main components efficiencies. This will guide us which component is more important to be optimized. Here a zero-dimensional analysis has been done to determine the effect of turbine stage efficiency on the fuel consumption. Results of this analysis are evaluated in the context of thermodynamic cycle of a gas turbine generator and an aerial engine. As an example, it is shown that if the efficiency of... 

    Axial Turbine Performance Improvement Under Steam Injection

    , M.Sc. Thesis Sharif University of Technology Hooshyari, Taghi (Author) ; Ghorbanian, Kaveh (Supervisor)
    Steam Injection is one of the most effective methods to improve performance and emission reduction of a gas turbine engine. In this study, the effect of using steam injection on the performance of a mechanical drive gas turbine engine is simulated and power output, thermal efficiency, compressor surge margin, velocity field in axial turbine and turbine isentropic efficiency are examined. In the two-shaft configuration, turbine inlet temperature and gas generator spool speed are the two parameters limiting the output power. On the other hand, matching of compressor turbine and power turbine is an important task that affects the performance of engine under steam injection condition. Based on... 

    Wind tunnel study of the effect zigzag tape on aerodynamics performance of a wind turbine airfoil

    , Article Journal of Advanced Research in Fluid Mechanics and Thermal Sciences ; Volume 41, Issue 1 , 2018 , Pages 1-9 ; 22897879 (ISSN) Jafari Gahraz, R ; Lazim, T.M ; Darbandi, M ; Sharif University of Technology
    Penerbit Akademia Baru  2018
    A wind tunnel study was performed on the FFA-W-3-270 airfoil, which form a segment of a 1.25 MW wind turbine blade, to examine the effect of fixed roughness height and position using a zigzag tape boundary layer trip strip. Tests were conducted at a Reynolds number of 1×106 over a wide range of angles of attack. The zigzag tape, as an artificial roughness device, not only triggers a premature transition in the flow whereby laminar flow regimes change to turbulent, but also increases the momentum thickness of the turbulent boundary layer and change the airfoil camber. The 60° zigzag tape of 0.5 mm and 1 mm height was placed on the suction side of the airfoil at different chord wise locations.... 

    Numerical Study on Improvement of Performance of Savonius Wind Turbine with Curtaining

    , M.Sc. Thesis Sharif University of Technology Emdad, Amir Hossein (Author) ; Shamloo, Amir (Supervisor) ; Sadrhosseini, Hani (Supervisor)
    In this study, the performance of an existing Savonius turbine has been improved through designing a curved curtain, the curtain has been placed in front of the rotor. To do so, the main purpose is to increase the net static torque of wind rotor via a newly designed curtain. A new guide vane is designed to prevent negative torque produced by convex surface of wind rotor and increasing wind velocity which is impacted concave side of wind turbine rotor blade. The numerical modeling of flow field is verified by experimental result for wind rotor without straightener. The numerical code verification accomplished at three different angle of rotation which the biggest difference between... 

    Empirical assessment of the performance characteristics in turbocharger turbine and compressor

    , Article Experimental Techniques ; Volume 34, Issue 3 , July , 2010 , Pages 54-67 ; 07328818 (ISSN) Hajilouy Benisi, A ; Rad, M ; Shahhosseini, M. R ; Sharif University of Technology
    The performance parameter uncertainties of turbomachines at different rotational speed were determined by experimental and analytical consideration. The instruments/sensors were located and installed according to the standards for evaluating the performance characteristics of turbine and compressor in a turbocharger laboratory in a wide range of rotational speeds. The comparison of turbine and compressor sensitivity shows that the sensitivity of compressor to 1% shift in the pressure is higher than that for the turbine. Results also show that the sensitivities of efficiency and power of turbine reduce as rotational speed increases. The total uncertainty of turbine and compressor are obtained... 

    Design and implementation of extended predictive functional control for boiler-turbine unit of power plant

    , Article 24th Mediterranean Conference on Control and Automation, 21 June 2016 through 24 June 2016 ; 2016 , Pages 131-134 ; 9781467383455 (ISBN) Amirabadi Farahani, M ; Haeri, M ; MCA ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc 
    In this paper, a new model predictive controller is introduced to control a power unit process with three inputs and three outputs. This method is proposed to reduce the complexity of the required computation. In fact, the presented controller ensures achieving an acceptable performance in the presence of noise and disturbances and reduces the volume of calculations to control a complex and nonlinear boilerturbine process. The simulation results indicate that the implementation of the proposed controller requires less computing time while the performance degradation is not more than five percent  

    Evaluation of imperial performance characteristic of turbocharger turbine and compressor

    , Article 9th AIAA/ASME Joint Thermophysics and Heat Transfer Conference Proceedings, San Francisco, CA, 5 June 2006 through 8 June 2006 ; Volume 2 , 2006 , Pages 1019-1028 ; 1563478153 (ISBN); 9781563478154 (ISBN) Rad, M ; Hajilouy, A ; Shahhosseini, M. R ; Sharif University of Technology
    Performance characteristics of turbocharger turbine and compressor such as efficiency, mass parameter and power are determined experimentally at turbocharger laboratory. Accurate determination of the performance map is significant for manufacturers as well as end users. To this end accurate measurement of test parameters such as temperature, pressure, and speed are required. In this paper an analytic method to predict the measurement uncertainties in turbocharger laboratory, is described. Furthermore the effect of each test parameter on the performance uncertainty is considered. Test parameters that have the most significant influence on the performance uncertainties are identified.... 

    A coupled adjoint formulation for non-cooled and internally cooled turbine blade optimization

    , Article Applied Thermal Engineering ; Volume 105 , 2016 , Pages 327-335 ; 13594311 (ISSN) Zeinalpour, M ; Mazaheri, K ; Chaharlang Kiani, K ; Sharif University of Technology
    Elsevier Ltd  2016
    Most researches on the application of the adjoint method in turbine blade design are concentrated on the aerodynamic shape optimization without considering the heat transfer to/from the blade material. In this study, the adjoint method is extended to the conjugate heat transfer problems in which the viscous flow field is coupled to heat transfer in the solid region. Introducing a new adjoint variable in the solid domain, a heat adjoint equation is derived which is coupled with the energy adjoint equation in the fluid zone at the fluid/solid interface. The detailed mathematical description associated with the derivation of the heat adjoint equation with corresponding boundary conditions are... 

    Simulation of startup operation of an industrial twin-shaft gas turbine based on geometry and control logic

    , Article Energy ; Volume 183 , 2019 , Pages 1295-1313 ; 03605442 (ISSN) Keshavarz Mohammadian, P ; Saidi, M. H ; Sharif University of Technology
    Elsevier Ltd  2019
    In this paper, a transient model is developed to simulate the start-up operation of an industrial twin-shaft gas turbine based on real geometry and control logic. The components’ characteristic curves of the studied gas turbine were generated with the aid of CFD simulation tools and according to the real geometry of each component. The control logic of the studied gas turbine was simplified and coupled with the developed engine performance model. Also, the gas turbine actuators including variable inlet guide vanes, compressor bleed valves, and fuel valves were simulated so that their concurrent effects on the gas turbine transient behavior can be captured precisely. Moreover, the air-cooled... 

    Control oriented modeling of a radial turbine for a turbocharged gasoline engine

    , Article Proceedings of the American Control Conference ; Article number 6580648 , 2013 , Pages 5207-5212 ; ISSN: 07431619 ; ISBN: 9781479901777 Salehi, R ; Shahbakhti, M ; Alasty, A ; Vossoughi, G. R ; Sharif University of Technology
    This paper presents a control oriented model for predicting turbine major variables in a turbocharged spark ignition engine. The turbine is simulated as a two-nozzle chamber where the pressure ratio over the two nozzles is not the same. A convex nonlinear estimation algorithm is formulated to determine the relation between these pressure ratios. The new model is experimentally validated with transient and steady state data collected from a 1.7 liter gasoline engine. The results show the new model can predict the turbine mass flow with an average error of 1.4%. In addition, the application of the turbine model is illustrated for the design of a nonlinear observer to estimate the turbocharger... 

    A numerical investigation on effects of the gap between plates of Savonius vertical axis wind turbines with different shapes on their performance

    , Article ASME 2012 Gas Turbine India Conference, GTINDIA 2012, 1 December 2012 through 1 December 2012 ; December , 2012 , Pages 259-264 ; 9780791845165 (ISBN) Abbaszadeh, M ; Doroodian, F ; Sharif University of Technology
    Present study introduces the vertical gap between the blades of a Savonius rotor's blades as a parameter that can enhance performance of the rotor. To provide comprehensive concept about application of gap between blades, two different models were tested in different working conditions and working regimes. The study completed by using R.S.M. turbulence model through ANSYS Fluent commercial software package. Utilization of the method was validated by comparing results of a conventional model with experimental data from one of the references. Results of the study proved that application of a proper gap between blades can improve rotor's moment coefficient by 20 percent; however, the amount of... 

    Improvement of grain structure and mechanical properties of a land based gas turbine blade directionally solidified with liquid metal cooling process

    , Article Materials Science and Technology ; Volume 24, Issue 1 , 2008 , Pages 100-106 ; 02670836 (ISSN) Kermanpur, A ; Mehrara, M ; Varahram, N ; Davami, P ; Sharif University of Technology
    The manufacturing process of a directionally solidified (DS) IN738LC turbine blade, produced with the liquid metal cooling (LMC) process was improved based on process modelling. The improvement involved varying the system dimensions in the baffle area and optimising the mould thickness, design and the withdrawal parameters. The grain structure of the DS blades produced exhibits a well defined <001> texture with a few stray grains near the blade top compared to the previous design. Some blades were given to a two stage heat treatment followed by tension tests at 25 and 650°C as well as creep tests at 152 MPa/982°C and 340 MPa/850°C. The yield and tensile strength of improved DS blades were... 

    An analytical method for the reliability evaluation of wind energy systems

    , Article TENCON 2005 - 2005 IEEE Region 10 Conference, Melbourne, 21 November 2005 through 24 November 2005 ; Volume 2007 , 2005 ; 21593442 (ISSN); 0780393112 (ISBN); 9780780393110 (ISBN) Ehsani, A ; Fotuhi, M ; Abbaspour, A ; Ranjbar, A. M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2005
    Wind generation is one of the most successful sources of renewable energy for the production of electrical energy. The technical characteristics of wind generation make existing conventional generation models not directly applicable. This paper presents an analytical method for the reliability assessment of the flat-rated wind turbine generation systems. An example of flat rating is that of the MOD-2, a second-generation class of wind turbines. The power-velocity characteristic of the flat-rated wind turbines is employed in this paper to model the operating behavior of the installed wind turbine generators. For wind-power potential estimation, the Weibull distribution model is used. The... 

    Design, Manufacture & Test a Small Sample of Type Darrieus Vertical Axis Wind Turbine

    , M.Sc. Thesis Sharif University of Technology Khojasteh, Hassan Ali (Author) ; Saboohi, Yadollah (Supervisor) ; Boroushaki, Mehrdad (Supervisor)
    Recently wind turbines with vertical axis attract attention of world’s scientific society to itself because of many reasons such as: ability to work in areas with high turbulency, structural simplicity, independency from wind direction, easy maintenance and low capital cost. So that major part of recent researches in context of wind turbines are about these turbines. In this project a small sample of wind turbine from darrieus type have been designed, manufactured and finally important parameters such as Pitch Angle, Blade numbers and Aspect Ratio have been investigated. Darrieus turbine with 4 Blades and Pitch Angle of +15° was the most appropriate sample between the test samples. In the... 

    Unsteady Aerodynamic Simulation of Horizontal Axis Wind Turbine (HAWT)

    , M.Sc. Thesis Sharif University of Technology Radmanesh, Amirreza (Author) ; Abbaspour, Madjid (Supervisor) ; Soltani, Mohamad Reza (Co-Advisor)
    The ultimate aim of this research is optimizing high- performance Horizontal Axis Wind Turbine (HAWT) associated with using Computational fluid dynamics (CFD) to predict the flow behavior over wind turbine blades. Computational prediction of the flow over wind turbines is a challenging numerical problem because of the complicated aerodynamics and large variation in length scales. Phenomena such as; the unsteady flow, vortex shedding of the blade tips, flow separation, complicated blade geometry due to variable twist and chord and changes in angle of attack, and highly turbulent flow over blade sections makes CFD prediction challenging, as well as interesting. The goal is to gain an in depth... 

    Analytical modeling of performance characteristics of axial flow two-stage turbine engine using pressure losses models and comparing with experimental results

    , Article World Applied Sciences Journal ; Volume 21, Issue 9 , February , 2013 , Pages 1250-1259 ; 18184952 (ISSN) Jouybari, J ; Eftari, M ; Kaliji, H. D ; Ghadak, F ; Rad, M ; Sharif University of Technology
    The main objective of this paper is to make a detailed systematic analysis of two-stage, axial flow turbine by using of different losses models and a new suggested algorithm based on one-dimensional simulation. The suggested method is found to be effective, fast and stable, in obtaining performance characteristics of multi-stage axial flow turbines. In one-dimensional modeling, mass flow rate, pressure ratio and efficiency are unknown, with define turbine geometry, inlet total pressure and temperature the turbine performance characteristics can be modeled. This modeling is based on common thermodynamics and aerodynamics principles in a mean stream line analysis under steady state condition.... 

    Energy and exergy assessments of modified Organic Rankine Cycles (ORCs)

    , Article Energy Reports ; Volume 1 , November , 2015 , Pages 1-7 ; 23524847 (ISSN) Safarian, S ; Aramoun, F ; Sharif University of Technology
    Elsevier Ltd  2015
    This paper presents a theoretical framework for the energy and exergy evaluation of a basic as well as three modified Organic Rankine Cycles (ORCs). The modified ORCs considered incorporating turbine bleeding, regeneration and both of them. The results demonstrate that evaporator has major contribution in the exergy destruction which is improved by increase in its pressure. The results confirm that the integrated ORC with turbine bleeding and regeneration has the highest thermal and exergy efficiencies (22.8% and 35.5%) and the lowest exergy loss (42.2 kW) due to decrease in cold utility demand and high power generation