Sharif Digital Repository

One of the most important problems in using wind energy is the estimation of wind energy potential of a region with acceptable accuracy. To use wind energy and convert it to electrical energy it is necessary to study the economical aspects of wind farm installation, and to choose an appropriate wind turbine to be installed in a region. To do such a study and to choose approperiate wind turbine, annual energy output of different wind turbines should be estimated in that region. The porpuse of this thesis is to develop new methods to estimate annual energy production of a wind turbine by using some of the parameters of wind speed pattern of a region such as wind speed average, wind speed... 

Application of wind energy and specially wind turbines as a green source of energy is getting more popular and as a result, the knowledge of wind energy has been improved dramatically. The purpose of this research is to determine the flow characteristics in the boundary layer profile over an airfoil which is used in a wind turbine blade. The model is sinusoidally oscillated in pitch. For the present study, the critical cross section of the wind turbine blade has been selected and the boundary layer velocity profiles over its airfoil have been investigated experimentally. Dynamic motion is produced with sinusoidal oscillator and the reduced frequency is varied in the range of 0.054 to 0.1.... 

World environmental concerns sharp increase in necessity of using energy in comparison with permanent progress in the field of renewal energy technologies causes modern forms of energy sources which can be used by public. This project studies the increasing influence of the wind power in power systems and also designing and exploiting techniques of local saving energy systems. For this purpose, models and possibilities in order to anticipate the operation of wind farm which is connected to grid by saving energy is described. In this project, the operation of compound system components which is totally a combination of three systems is being studied. The considered compound systems consist of... 

An improvement of thermal efficiency of modern gas turbines is achieved by increasing turbine inlet temperatures. One of the methods of turbine cooling is to form a film layer on the external surfaces of the blades, so that they can work at high temperatures. Most of the studies concentrate on flat plate geometries with injection through slots or rows of holes. Turbine blade surfaces usually have curvatures which seem to alter the flow field significantly on the film-cooled surfaces. However, there are few reports which investigate the effect of curvature on three-dimensional jet flow injected into the turbulent boundary layer over a curved surface. The surface curvature and the blowing... 

Nowadays, the use of gas turbines with low capacity have acceptance in large quantity. This type of gas turbines with a capacity of approximately 5-200kW are known as microturbines. This type of turbines due to the existence of limitations on increasing of turbine inlet temperature and compressor pressure ratio has low efficiency compared to the turbine with high capacity. Therefore the use of a recuperator in the cycle is necessary. Optimum design of heat recuperator has important effect on improving of gas turbine cycle efficiency. In this project for optimum design of heat recuperator, the effect of recuperator on gas turbine cycle efficiency is studied. By determining geometric... 

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... 

Material selection is one of the most important works should be done prior to the designing of any part of the mechanical and/or nonmechanical structures. Various material selection methods, such as digital logic, modified digital logic, z-transformation and fuzzy logic, have been introduced and used in recent years. All these methods have some advantages and disadvantages in selection of appropriate materials. Since, all these methods exhibit some disadvantages, the main objective of thesis is to introduce the new method to reduce or eliminate the other method’s disadvantages with less complexity. The fuzzy logic method which is mostly used in this thesis will result in some problems due to... 

Considerable attention has been given in recent years to renewable energy sources due to concerns about dwindling fuel reserves and the potential impact of conventional energy systems on the environment. Wind power is one form of renewable energy resources and also considered as Dispersed Generation (DG). Widespread utilization of wind power imposes many effects on planning and operation of power system. In other side, reliability evaluation and enhancement is an important factor in modern power system planning and operation. So, reliability assessment of wind turbines is of great importance and will receive more attention in the future according to increase of WT utilization. The... 

The interactions between jets and cross flows appear in many engineering applications (such as film cooling) and thus their study is of great importance. In film cooling, the coolant fluid is transferred from the compressor to the surface of the turbine blades via small holes. An increase of about 170⁰C of the engine working temperature increases the engine efficiency about 5%. To reach higher temperatures of the inlet air flow, one tries to have the least amount of interactions between the film cooling jets and the the cross flow. In this work, we computationally studied turbulent film cooling of a flat plate, in which we used the combined triple jet and investigated the effects of density...