Sharif Digital Repository

The development of wind turbine blades model that accurately predict wind turbine thrust in a full range of applicable wind speed has provided a powerful and reliable source for simulation of horizontal axis wind turbine power and thrust force that serves as a valuable tool for wind turbine design and performance analysis. A single-element blade model that reduces the rotor blade characteristics to a lift and drag coefficient vs. angle-of-attack formulation was found to describe accurately the rotor characteristics over a wide operating range. Measurements of wind speed and altitude of wind turbine installation location, rotor speed, and provided thrust is within less than 2% over a wide... 

Gas turbines and centrifugal compressors are the preferred means of compressing the gas in pipeline systems. Both gas turbines and centrifugal compressors exhibit performance characteristics that depend on the operating point imposed on them by the pipeline operation. Simulation of gas turbine-driven centrifugal compressors is necessary for a variety of applications in the general area of pipeline simulation. This research focuses on modeling of twin shaft gas turbine dynamic and steady state performance. For this purpose, it was necessary to evaluate the thermodynamic working process of the gas turbine by using an in-house computer code. At design point, the calculations are solely based on... 

Nowadays, the structural health monitoring is considered as an essential element in improving the performance of the structures. The role and importance of the issues in this area have been reached to the point that different ideas and policies are developed for the safety margin over the useful life of the structures. To analyze more accurately, a real model of a turbine blade is required. This issue would be taken into more consideration when the scale of the turbine gets larger. Changing of the design philosophies over time results in effective changes in the design process and maintenance procedures. Any single of these inspections has different importance according to users' demands. In... 

This study develops an aerodynamic shape optimization code using parallel processing capability based on a gradient-based adjoint method. Calculation of the gradient of the objective function with respect to design variables is the most costly part of the gradient-based optimization algorithms. Applying adjoint methods, gradients can be calculated with solving some additional equations known as the "adjoint equations", instead of direct calculation. In this study, the blade shape optimization is performed by inverse design method and using steepest descent optimization algorithm. The objective function of inverse design problem is the desired blade surface pressure distribution. In each... 

In this research numerical and experimental study of a twin entry radial inflow gas turbine is performed. At first, various models of energy losses are investigated and compared and the most comprehensive combination of these models are selected. Using conservation equations, gas dynamics relations and energy loss models, the one dimensional model of radial inflow turbine is developed.One-dimensional modeling has lower computing cost in compare with two and three- dimensional models, while gives reliable results, Hence it would be the preferred option for turbine preliminary performance prediction. In this study the one dimensional model based on a step by step procedure, for each turbine... 

In this research, it is aimed to convert a turbojet engine to a turboshaft by replacing the exhaust nozzle with a new designed power turbine stage. The design procedure is backed up with parametric studies to increase efficiency. At first a program is written for one dimensional modelling of the stage of axial turbine. By the way, the three dimensional modelling of the stage of axial turbine with Ansys-cfx business software is done. These methods are validated by modelling the gas generator turbine and comparison of their results with experimental results. Then the power turbine including the blades and the geometry of flow walls on shaft and casing are designed. The performance of power... 

Prediction of axial flow turbine’s performance with different operating conditions due to the high costs and lack of reliable empirical data is always under developing. In this type of turbine, fluid flow is three-dimensional, viscous and highly turbulent. Nowadays, although a relatively detailed picture of the flow field can be obtained by the computational and numerical tools, but using of appropriate loss models in one-dimensional modeling for the performance prediction as well as optimization of the turbine in initial design phases, is a common trend.
In the current study, aerodynamic losses in the axial flow turbine are investigated. Several loss models for the axial flow turbines... 

As long as the wind power penetration is low, overall dynamic behavior of a power system is determined by the interactions of system synchronous generators, but introduction of large amounts of new wind generation can affect the power system behavior. In this research, the impact of large wind farms on the small signal stability of power systems is studied. Because constant wind turbines are not very conventional in today’s wind industry and the dynamics of full converter wind turbines are isolated from power system, in this study only the doubly fed wind turbines are considered. In this order, a novel index is introduced to analyze the impact of doubly fed wind farms on the damping of... 

Due to inherent dangerous on human and environment safety in the nuclear power plant has significant importance. In order to ensure the safety of the plant and proper functioning ofits various components,before its operational exploitation, a series of commissioning tests should be conducted according to international standards for nuclear power plants. In addition, safety of the plant can be guaranteed bymodeling of transient states and possible scenarios of accident in different situations.In this research,by gathering geometric data and information about the facilities installed in the plant, modeling of Commissioning test of Bushehr Nuclear Power Plant (BNPP) and its associated accident... 

Aiming to improve the extraction performance of wind energy has led to the noticeable increase of the structural dimensions in the modern wind turbines. The larger blade with more flexibility experiences large structural deformation even under nominal operational loading, so the nonlinear modeling and analysis of these structures have become as important subject of the recent wind turbine researches. In this dissertation, the geometrical exact model of the rotating wind turbine blade under the effects of the tower tip's motion, and also the operational loading comprising the aerodynamic and gravitational loadings is presented. In this way, the geometrical exact beam formulation is developed... 

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... 

Nowadays, gas turbines are from the most widely used devices in terms of power generation. According to their vital role in suppling electrical power required for daily life and their widespread application in power plants, tremendous efforts have been made to improve the efficiency of gas turbine working cycle. One of the most applicable methods to optimize a gas turbine is to cool the compressor inlet air. Applying an absorption chiller is a wisely technique especially when it comes to hot and humid weather condition. In this thesis, effects of applying an absorption chiller with specified technical facts on the performance of gas turbines, which are now functional in Kish Island power... 

In recent years, renewable energy equipments such as wind turbines has become more common for electric power generation. Due to the complexity of the aerodynamics of wind turbines,experimental studies in this field are very important. The purpose of this study is to investigate the aerodynamic performance of a new wind turbine airfoil in static mode and pitching motion.The airfoil is a section of 2 MW wind turbine blade, pitching around its quarter-chord axis .All experiments are carried out in a subsonic wind tunnel. In these experiments, the reynolds number is 140,000 and the reduced frequency varies from 0.034 to 0.126. Pressure transducers have been used to determine the pressure... 

The present research deals with the effect of steam injection to gas turbine engines. First, a comparison is made across the possible positions in the gas turbine for steam injection. Commercial software is used to investigate the pros and cons. Second, the investigation is focused on an industrial 4 MW gas turbine engine. Classical cycle and sensitivity analysis are performed and the operating envelope of the gas turbine engine with steam injection at various operating states as well as different environmental conditions is determined. Finally, a simulator based on Matlab Simulink is developed to examine the impact of different design and thermodynamic conditions of steam injection to the... 

The issues relevant to lubricants in industry, construction and production processes such as machining and grinding have been recently taken into serious consideration. Unlike the positive effects of applying lubricants on machining forces, chip formation, thermal defects which lead to force reduction, lower power consumption and surface quality improvement, its conventional usage has adverse effects such as environmental problems, high cost of high volume lubricant application as well as recycling problems. Therefore, attention was drawn toward chip removal under dry or near dry conditions and as thermal defects such as surface burning is important particularly in grinding, grinding under... 

In this research, an attempt is made to obtain the geometrical and performance matching between a centrifugal compressor and a pre-designed radial inflow turbine. In this regard, constraints such as the same outer diameters, stagnation pressure, rotational speed, and power are considered. The impeller of the centrifugal compressor is designed by employing one-dimensional design method. The aerodynamic performance of the centrifugal compressor is 3-dimensionally evaluated by the commercial CFX software. A comparison of the 1D and 3D results reveals a maximum deviation of 7% indicating relatively good agreement. A sensitivity analysis on the flow coefficient and tip clearance shows a change of... 

Increasing the efficiency of gas turbines is directly related to the increase in the inlet gas temperature. There exist, however, limitations on increasing the temperature of the inlet gas, such as materials and metallurgy restrictions. There have been numerous methods to overcome and lessen these restrictions. In fact, two conventional ways proposed so far, are film cooling and effusion cooling. In fact, film cooling is used in many applications to reduce convective heat transfer to a turbine blade surface. In addition, Effusion-cooling is the next logical step in gas turbine blade cooling in which the flow through effusion-cooling holes is, due to their small size and the lesser amount of... 

Environmental issues and energy crisis have led the world attention to the renewable energies; especially wind power, since they have low cost and high reliability. One of the most challenging areas of studying for wind power is to increase the capacity of wind turbines. As a result, over the years, wind turbines have got progressively larger. Vibration is one of the problems that reduces the life and efficiency of wind turbines; and the growing size of the blades has worsen this problem due to the importance of nonlinear effects in large scale wind turbines. Researchers have been constantly working on this issue in order to make the wind turbines more efficient. In this research, a... 

Aerodynamical design of backward swept for a horizontal axis wind turbine blade has been carried out to produce more power. Computational Fluid Dynamics (CFD) calculations were used for solving the conservation equations in one outer stationary reference frame and one inner rotating reference frame, where the blades and grids were fixed in reference to the rotating frame. The Reynolds Averaged Navier-Stokes (RANS) solver was validated in a test case, the National Renewable Energy Laboratory (NREL) VI blades. Simulation results show considerable agreement with the measurements. Three different turbulence models have been compared: Spalart-Allmaras, the Standard K-ε, and Shear Stress Transport... 

The most important challenge and the most time consuming part of the gradient based optimization algorithms in the aerodynamic shape optimization problems is the evaluation of the sensitivity of the objective function with respect to the design variables. The adjoint method which has been the subject of many research in the recent three decades, is capable of computing the complete gradient information needed for optimization by solving the governing flow equations and their corresponding adjoint equations only once, regardless of the number of design parameters. In this study, the continues adjoint equations for compressible inviscid and viscous flows are derived and the formulation of...