Sharif Digital Repository

On account of the exhausting nature and increasing daily cost of the fossil fuels, it seems that replacing the fossil fuels by an alternative source of energy is inevitable. Moreover, in the remote areas that the electricity network is not accessible, the use of distributed sources (DSs) such as solar energy and wind energy is advantageous. Continuity of the supply and voltage control of the load in spite of the stochastic nature of the generated power of the renewable energy resources are the main concerns in the distributed generation (DG) systems. In this thesis, stand-alone operation of a DG unit comprising a solar unit and wind turbine as primary sources of energy is considered. A... 

One of the main drivers for the substantial growth in wind energy utilization in the world is the growing demand for renewable energy sources to reduce greenhouse gas emissions. At greater distances from the coastline, more and steadier potential energy resources are available. This has led the world offshore wind energy industry to grow at a faster rate than onshore in the past two decades. In deep waters, the wind turbine is mounted on a floating platform, whose movements increase the complexity of the turbine control system and enhance the mechanical loads on the various components of the turbine. Reducing these mechanical stresses is equivalent to increasing the lifetime of the turbine... 

The purpose of this project is designing a controller for a floating offshore wind turbine to exctract maximum power from wind energy in the first operating region of wind turbine. The NREL 5 MW OC3-Hywind floating wind turbine with BARGE platform will be used for this project. By using Turbsim software, proper wind profile for the first operating region of wind turbine will be produced. This profile will be excecuted for the FAST software that is simulates the mechanical part of wind turbine. By implementing the doubly fed induction generator in Simulink enviroment and designing the controller for doubly fed induction generator, the desired torque for maximizing the exctraction power of... 

This research investigates the use of baffles in sector jets for film cooling of turbine blades. The goal of this study is to compare the cooling performance in three conditions: sector jet without baffles (one 90-degree arc), with one baffle (two 45-degree arcs), and with two baffles (three 30-degree arcs). The effect of using this type of cooling is also compared to the crossflow jet, which is the simplest type of cooling jet. In all conditions, the mass flow ratio is constant and equal to 1. The problem is solved for a turbine blade with the “AGTB-B1” airfoil. The problem is first solved with the Transition SST turbulence model, and the results are used as the initial conditions for the... 

Advanced control techniques are required to achieve a cost-effective and reliable use of the wind power generation. The wind turbines are generally controlled based on two control objectives: the turbine protection and the generation of acceptable power for the utility grid. These objectives are achieved if the control inputs are applied based on appropriate control logics. In this work, a nonlinear multivariable model of the wind turbine with a DFIG generator is considered. The rotor speed and the d-axis rotor current (as the control outputs) are controlled via manipulation of the two generator voltages (as the control inputs) in low wind velocity condition. For high wind velocity, the... 

Wind turbines have been the subject of many researches in recent decades. Optimization and continuous improvement of these systems play a decisive role in the development and exploitation of wind farms. Wind turbines can be studied from several aspects such as structure, dynamics, aerodynamics, electricity and control. In this research, robust power control of the wind turbine has been studied with emphasis on accurate 2 DOF mechanical and aerodynamic modeling. Aerodynamic coefficients of the turbine have been calculated using the numerical methods and the effect of this numerical modeling has been studied in comparison with the analytical methods on the turbine power control. Several new... 

Nowadays, modern life needs energy resources. In the last few centuries, countries have focused on the use of fossil fuels. However, excessive use of fossil fuels, such as oil and coal, has resulted in enormous environmental hazards. Global warming and air pollution are the most visible manifestations of these hazards. In recent years, energy researchers have been looking for alternative sources. The result of this approach is to pay attention to clean and renewable resources such as wind energy.Wind turbines are used to generate electrical energy out of wind. Among the different types, floating offshore wind turbines have been mostly considered because of various benefits. However, they... 

Vibrations in HAWT reduce their efficiency and increase maintenance costs. In this paper, the blade edgewise vibrations are reduced by using several actuators in different parts of the wind turbine blade and optimization of the number and locations of actuators. The wind turbine blade dynamic behavior is investigated by using dynamic modeling. The actuators are trusses that are located inside each blade and apply control force to different parts of the blade. Active control force is applied to reduce edgewise vibrations. The designed controller is applied and simulated on NREL 5MW wind turbine. By applying the controller, the edgewise vibrations of wind turbine blades are significantly... 

Sustainable energy is an important and necessary subject. A significant number of studies address the increasing energy production ratio per its cost. To this end, first of all we should increase the energy production. Second, damage and costs of production, set up and maintenance must be reduced. Control is one of the most important and effective tools in the way of achieving these purposes. The problem of controlling a wind turbine is generally divided into two sections of controlling the power chain and yaw control. In this research, both subjects have been investigated.Since there are some problems in measuring the wind speed, controlling the power chain requires prediction of the wind... 

There is a growing potential for the use of micro-cogeneration systems in the residential sector because they have the ability to produce both useful thermal energy and electricity from a single source of fuel such as oil or natural gas. Benefits of cogeneration system will cover around 25% of internal electricity needs of ceramic, around 30 % saving in global fuel consumption, reduction of carbon dioxide. In tile factories, there is a system called a spray dryer. This system can use hot air to produce the soil needed to produce ceramic tiles. This hot air is supplied by a very large burner. In developed countries, instead of a burner, a gas turbine is used to produce hot air, with the... 

The present research proposes a new method to establish a practical framework for extension of gas turbine life time. This method is based on an nine-step operational algorithm which is capable for different types of gas turbine. The essential inputs for this algorithm includes documents of inspection and knowledge of repair and maitenance experts. In this algorithm is used the Bayesian network probabilistic method. Therefore, based on the observations and the knowledge of experts, gas turbine Bayesian network is produced. According to this Bayesian network consequenses are created. Furthermore, making the steps of the algorithem more explicit, FTA and FMEA methods are used to creat the... 

Gas turbine engine control is a demanding task that requires the regulation of the thrust as well as the satisfaction of the limitations such as engine aerodynamic instability, over temperature and over speed. Fuzzy logic is an attractive technique for the control of poor understood unmodeled, or complex systems especially where the experience of human operators is available to provide qualitative rules. In such cases, it has been found that control decisions can be made on the basis of linguistic measures or fuzzy algorithms. The controller that is designed on the basis of this theory is called fuzzy logic controller. The main objective of this thesis is hardware implementation of fuzzy... 

As a matter of fact, power systems are always faced with a variety of uncertainties. These uncertainties change system parameters in an unwanted manner which may deteriorate the system security and reliability. For instance, a transmission line which is designed for a certain capacity may be suffered as a result of load increment and consequently may influence the normal operation of other network elements. In recent years, as a result of environmental considerations and especially after the oil shock at 1973 which caused the the energy prices to increase unprecedentedly, the human has taken more attention to renewable energies exploitation. Theses energies have a fluctuating nature and are... 

Over the last decades the attention of the most modern countries about usage of wind has grown due to the recent crisis of energy. This renewable energy source offers a cost effective solution for electricity production. Wind energy is the best candidate among other sources due to wind turbines technology reliability. In order to gain maximum power from wind turbines, their size becomes relatively large, which creates more complexity in their repair and maintenance, furthermore Wind turbine downtime is outside the expectations, which is more costly than corrective maintenance, therefore in order to minimize sudden downtimes and related huge maintenance, a reliable monitoring technique must... 

Rotary equipment are being used in many industries over a wide range of applications, such as gas turbine. Due to the nature of the operating conditions, gas turbines are subjected to variety of damages especially crack propagation of a blade. The Cracks propagation may lead to catastrophic failure during operation. Therefore, detection of the crack presence and its propagation is very important and may reduce possible significant cost of the whole system failure. The thesis aims to investigate the cracks presence and their propagation effects on vibration of a turbine blade which is located at the National Iranian South Oilfields. First, theoretical study is calculated to validate an... 

Nowadays because of population growth and limitation of fossil fuels for power generation purpose, utilization of renewable energy sources has become highlighted. According to the geographical situation for use of wind energy, since some areas of Iran are in suitable conditions the manufacture of wind turbines and installation in wind farms has been under development recently. Monitoring the performance and operation of turbines and wind farms is an inevitable matter. Because of the suitable geographical location of Iran and pursuant to fair wind potential sites widespread this country, this phenomenon requires some backgrounds in many aspects to be achieved. One of the most important... 

This project has been carried out to investigate the feasibility of using thermoplastic materials in constructing large wind turbine blades made of composite materials. By proving the similarity of the mechanical behavior of blades made of thermoplastic and thermosetting composite materials, the possibility of using these materials with better recycling capabilities has been studied. By studying different thermosetting and thermoplastic resins and checking the Processing methods and mechanical properties of thermoplastic resins, the materials for blades have been selected. The suitable manufacturing method for producing large blades with dimensions above 30 meters is the vacuum-assisted... 

In recent years, much attention has been paid to wind energy and the expansion of wind farms to replace fossil fuels with this energy source. Wind turbine blades are currently made of composite materials using thermoset matrices. These materials are not recyclable, and it is impossible to return their resins or fibers to the production cycle. In this research, an attempt has been made to replace thermoset resins with thermoplastic materials that can be recycled. In the following, manufacturing and performance aspects of thermoplastic resins have been examined, and the optimal material has been selected using the modified fuzzy logic method (MFLM). In this study, reactive processing of... 

MILD combustion under high preheating and high dilution condition illustrates some interesting characteristics. Very low oxygen concentration in the reaction zone and reduced chemical reaction rates compared to conventional combustion are some of these features which make MILD combustion to be an unique type of combustion. In this work numerical investigation of a gas turbine model combustor (GTMC) was aimed to done using model of the EDC as turbulence-chemistry interaction combustion model. Modeling was performed by solving RANS equations and RSM equations for a 2D axisymmetric computational domain. The combustion chamber was investigated for both reacting and non-reacting conditions. A... 

Well worn gas turbine blade made of Nickel based superalloy, IN738LC was remelted due to remove inclusion and use it in casting process of new blade after microstrucrure investigation in neutral atmosphere and vacuum. The composition of slags for removing inclusions used for this practice were 70CaF2-20CaO-10Al2O3 and 55CaO-45Al2O3. The microstructural characterization involved use both optical as well as electron microscope including application of EDS technique for denoted the type of carbides and inclusion investigation. Chemical composition was determined by despersive spectroscopy method. The changing in main elements were reported too low. Number of inclusions were decreased in the...