جستجوی مقالات مرتبط با کلیدواژه « توربین بادی » در نشریات گروه « مکانیک »

Converting electricity from wind to electric power by Small Wind Turbines (SWTs) a lot helps to produce electricity. They can be utilized to generate different networks, including independent, connected and integrated networks. Due to the size and installation location, SWTs are suitable for use in low Reynolds numbers (Re). With the aim of developing a marine Vertical Axis Wind Turbine (VAWT) with a porous blade in this research, simulations on different airfoils of NACA 4-digit, series 5-digit, and Selig profiles at different Re values of 60,000, 100,000, and 140,000, using the Double Multiple Stream Tube (DMST) with loss correction. In addition to blade specifications, turbine design parameters such as Aspect Ratio (AR) and solidity (σ) were also investigated by changing blade height and pitch. This paper presents an analysis for the design of a three-bladed VAWT to increase its aerodynamic performance in terms of power performance (Cp). The DMST approach, considering tip loss correction, is an effective lower-order accuracy performance prediction method for analyzing a wide range of turbine designs in a comparative manner with significantly lower computational cost. The study illustrated that the Selig S1046 airfoil to be suitable for wind tunnel tests at target chord Re in the specified Re range. The AR in different Re is more appropriate in the AR of 1.0 in lower and higher Re in a good range of TSR. Besides, the σ of 0.17 is suitable for increasing the turbine performance in the tested range.

The investment capacity in wind power generation is growing significantly. However, the increasing penetration of wind energy in the network may lead to instability of the system and this may have negative impacts on the power quality of the system. In recent years, the effects of wind turbines on the voltage stability of power systems have received much attention. In the past, wind turbines based on squirrel cage induction generator (SCIG) were usually used due to their low cost and simplicity. But in recent years, wind turbines based on doubly-fed induction generator (DFIG) are mostly used because they are more stable. Recent studies have shown that the performance of the grid-connected wind turbines can be improved by employing flexible ac transmission systems (FACTS) devices. In this paper, the performance of a 9 MW wind turbine based on SCIG and DFIG in the presence and absence of static synchronous series compensator (SSSC), at the point of common connection (PCC) is investigated, considering single-phase and two-phase short circuit faults. A voltage stability index (VSI) is used to evaluate the stability of the wind turbines. The simulation results show that in the case of a two-phase fault that the system variables experience some oscillations, SSSC helps to damp out the generated oscillations faster and improve system stability. In particular, in the presence of SSSC, oscillations for the wind turbine voltage, reactive power and active power are damped out about 0.3, 0.5 and 0.6 seconds faster, respectively. All simulations are performed in MATLAB/Simulink software.

Over the world, advancements in the design of wind turbines with augmentation are being made with the aim of producing electricity nearby users in built-up regions. By reducing the distance between the consumer and the power source, this is certain to aid in lowering the burden on the power generation system as well as the costs associated with the distribution and transmission network. By maximizing the upstream wind striking on the rotor blades, the major goals driving the development and progress of vertical-axis wind turbines (VAWTs) are raising the power coefficient and torque coefficient. VAWT produce both positive and negative torque while operating, in contrast to horizontal axis wind turbines (HAWTs). For VAWTs, the negative torque produced by the returning blade is a major problem that is counterproductive. When used to boost flow, porous blades lessen the negative torque generated by the return blades and also increase the torque by causing upstream airflow to be bent toward the leading blade. The studies conducted so far on the Darriues VAWT with porous blades are examined in this paper. Research results show that Darriues VAWT with porous blades has recorded more self-starting and turn than the Darriues VAWT base with straight blades. Moreover, the ability to self-starting torque, power, force less than the vertical axis of Darriues is required with straight blades.

This paper introduces the schematic and new structure of a 115V AC multilevel inverter with an output frequency of 400Hz for use in the emergency power supply of aircraft and the electrical distribution system of aircraft. The input power of this converter is provided by connecting to the DC bus of the aircraft or by a pod equipped with a wind turbine and permanent magnet synchronous generator In order to stabilize the variable voltage produced by the wind turbine, an interleave boost converter has been used. In addition, the design of the desired converter has been made in such a way that compared to other conventional and novel converters, it has fewer parts. The proposed converter is able to produce a 25-level output voltage waveform with the ability to increase the input voltage. No need for a filter in the output of the converter due to the very low total harmonic distortion of this converter and its compliance with the IEEE 519-2022 standard are other noteworthy features of the converter. This feature causes a significant reduction in the weight and volume of the power supply of the aircraft compared to other available structures, which is especially important for air applications, both military and commercial types The efficiency and performance of the proposed structure under the conditions of load change and wind and aircraft speed change when connected to a wind turbine and permanent magnet synchronous generator have been checked and confirmed in MATLAB/SIMULINK simulation environment.

The nacelle cover and nose cones of most megawatt wind turbines are made of composite sheets. Due to the complex shapes, geometries, and large dimensions of these components, they are composed of several parts that must be assembled using non-permanent mechanical joints, such as bolts. Therefore, it is very important to consider all the effective parameters that affect composite joints. One of the most critical design parameters for bolt connections is the amount of bolt preload or tightening torque. However, increasing the preload without caution is not feasible due to the composite material present on both sides of the joint, as this can potentially damage the composite sheets. As a result, this paper aims to evaluate experimentally the effect of bolt preload or tightening torque on composite joints. To achieve this, identical specimens were fabricated, each with a different bolt tightening torque ranging from 2 Nm to 50 Nm. These specimens were then subjected to a tensile load. After determining the optimal preload force, four different types of arrangements were experimentally tested to find the best bolt arrangement. Finally, by examining various aspects, the best arrangement for connecting different parts of the nacelle cover and nose cone was determined.

Three airfoils NACA0015, NACA0018 and NACA0021 were selected and in the Q-Blade software, the coefficients of shear, post and the maximum ratio of the exponential coefficients were determined and, finally, the Airfoil Nakata 0015 at a speed of 5 and 10 meters per second, was selected and best. Fluent software was used to solve it, based on the finite volume method. For numerical analysis, the turbulence method K-ω SST was validated with experimental results. The wind turbine schematics was designed in Catia software and the height of the blades was 35 and 75 centimeters, the radius of the blade was 18.5 cm and the length of the airfoil 6.4 Cm is. The results show that in order to operate the turbine of porous blade windings at 35 cm height at speeds of 1, 2, 3, 4, 5, 7, 7.45, 8.25, 8.5 m / s 50% 50%, 33%, 50%, 50%, 60%, 57%, 55%, 50%, and for setting up a porous blade wind turbine at a height of 75 cm at a speed of one, two, three, four, Five, seven, 7.45, 8.25, 8.5, 9, 9.5 m / s 66.6%, 75%, 80%, 71.4%, 66.6%, 76.9%, 80%, 82%, 89%, 100% of the launching force Smooth wind turbine is required at the same height.

This paper presents a new method of energy management (EM). The proposed method was defined as a reinforcement learning problem for a system consisting of solar panels, wind turbines, gas engines and batteries. The best corresponding energy managements for all the possible system states were found by employing the Q-learning algorithm to solve the EM problem. These results were then used for managing the power supply of four residential buildings in Negin Island Bushehr located in the southwest of Iran. The simulation was performed for 8760 hours of a year. The proposed energy management method was compared with the load following energy management, which resulted in a 2.4% reduction in annual operational costs and a 3.7% reduction in CO2 emissions. With the same quality of the results, the new EM method took about 2.5 times less computational time compared to the optimum energy management performed by genetic algorithm. The effect of iteration number on the convergence of algorithm was also investigated.

Due to environmental considerations, the importance of using clean energy has been signified. In this regard, one of the proposed solutions is to generate energy from high- altitude winds or jet streams. On the other hand, in previous research, the issues of the jet stream, the formation of high-altitude winds, the effects of climate change on the jet stream, and wind power density in different parts of the world have been investigated separately. In this paper, while summarizing all topics related to this issue, the effects of climate change on these winds have been investigated by stating the layers of the atmosphere, the movement of air around the earth, and how the jet stream is formed. The results show that the presence of temperature changes caused by solar radiation and the creation of three temperature cells, Hadley, Ferrel, and Polar, simultaneously with the effect of the Coriolis force on moving air masses, causes the creation of a jet stream in the northern and southern hemispheres at latitudes of 30 degrees and 60 degrees. Climate change has increased the amplitude of the jet stream and its expansion to the north and south. Surveys show that Iran ranks 10th in the Middle East in terms of the energy density of high-altitude winds at a height of 500 meters above the ground. At an altitude of 1000 meters, in 50% of the time period, the west and center of Iran have a wind power density of 0.3 kW/m2, and at an altitude of 10000 meters and in the same time period, all areas of Iran have a wind power density of 3 kW/m2.

Reliability assessment of renewable energy systems is a key step in evaluating the feasibility of renewable energy projects. The assessment can provide valuable information on the availability and reliability, operation and maintenance strategies, and operating costs of systems. In this regard, the present study analyzes the reliability parameters of a wind turbine system using a statistical / simulation approach. To this end, the Reliability block diagram has been used for modeling the problem which has the capability of analyzing complex systems with a high number of components while providing simplicity and transparency in the concept presentation. For the modeling and simulation, RAM Commander software developed by ALD software company was utilized. The block diagram model was developed considering a series arrangement (8 subsystems and 94 components) and taking into account the probability distributions of failure time, repair time, and other reliability data for each block. results were then obtained by implementing the Monte Carlo algorithm. The results of this study contain the values of reliability, availability, and failure rate for a turbine during its lifetime. According to the results, the average availability of a turbine over a 20-year life span was more than 0.999. At 25 points, the turbine needed repairs, and the mean time between failures was calculated to be 7008 hours. The mean time between system critical (catastrophic) failures is 77928 hours. Also, the sensitivity analysis of the model to changing input variables is presented.

Nowadays, the use of wind as one of the main sources of low carbon and renewable energy is expanding rapidly all around the world. Recently, with the development of wind farms and the consequent increase in the size of wind turbines, their maintenance has become more difficult. Therefore, researchers have deeply focused on the analysis and the control of their vibration. In this study, a wind turbine blade with a type of nonlinear absorber, called highly efficient nonlinear energy sink is analyzed, and the interaction between the heavy and long blade and the nonlinear energy sink (NES), under the influence of gravity in the vertical plane and wind force varying periodically due to height dependence is examined. For this purpose, the equations of motion for the blade connected to the NES are extracted using the energy method and solved numerically. Finally, the sensitivity of the parameters affecting the performance of the NES is analyzed and the performance of the system under rotation of the standalone blade and also the rotation of the blade in the presence of the optimal NES is studied.

The increasing consumption of non-renewable energy sources such as oil and gas and reducing their reserves make it more necessary to pay attention to clean and renewable resources. In this situation, wind energy is known as one of the safest options for generating electrical energy. In this study, with the aim of evaluating the impact of climate change on the economic and environmental characteristics of wind turbines, numerical modeling was developed in MATLAB software. In order to evaluate the effects of the mentioned parameters as a case study, this numerical modeling for the parameters expressed in 4 cities of Iran, including Rasht, Tehran, Abadan, and Sanandaj, as the representatives of the main climates of Iran has been analyzed. According to the results of the economic point of view, which represents the Levelized cost of the energy production unit, Abadan was recognized as the most economical case with a   Levelized cost of  1.04 $ per kilowatt-hour of energy. Also, the environmental aspect of the analysis, which is based on the life cycle assessment method, considering the amount of carbon dioxide produced during the system life cycle and its pricing based on penalty policies, Rasht with a mild climate and emissions of 156 kg. Carbon dioxide per year and the lowest fine cost (annual cost $ 2.26) showed the most suitable option among other cities.

In this paper, solar/wind/battery hybrid system for different prime movers including diesel engine, gas engine and gas turbine with hourly analysis during a year is modelled and optimized for Kerman city. Fuel ratio is defined for comparison of system fuel consumption than traditional system. Number of solar panels, wind turbines, batteries as well as nominal capacity of prime movers are considered as design parameters. Fuel ratio and total annual cost (TAC) are selected as two simultaneous objective functions and Fast and Elitism Non Dominated Sorting Genetic Algorithm (NSGA-II) is used to find the optimum value of design parameter. The optimum result showed that hybrid system with diesel engine as prime mover is the optimum system in large zones of Pareto front with lower TAC and higher fuel ratio compared with the other studied prime movers. Fuel ratio and total annual cost in final optimum point for diesel prime mover are obtained 0.735 and 185456.5 ($/year). The optimum number of solar panels, wind turbines and batteries for the diesel-powered hybrid system are determined 1266, 19 and 822, respectively. In addition, nominal power of diesel engine obtained 163 kW.

A way to increase the generated power of an available wind turbine blade without changing its base shape is to add proper add-on to the blade tip. In this paper, seven tip add-ons are added to the blade tip of the NREL Phase VI wind turbine, and their effect on generated power is studied using computational fluid dynamics. Reynolds averaged Navier-Stokes equations are used with k-ω SST turbulence model to simulate the flow over the blade. Results show that the tapered tip add-on does not have a notable effect on generated power, while the shark-tip add-on increases the output power by about 4%, which is a minor increase comparing to the other add-ons. The suction surface and pressure surface winglets (without sweepback) increase the power generated by 5.23% and 9.6% respectively, which shows the superiority of pressure surface winglet over suction counterpart. Afterwards, sweepback is added to winglets, showing 11.87% and 13.25% power increase for suction surface and pressure surface winglets respectively, which shows the positive effect of sweepback angle in generated power increase. This is obtained by only a 28 cm add-on to the base blade with a radius of 553 cm.

New generation of wind turbines, in comparison to the old versions, have been designed with colossal blades to produce larger amount of power output. However, this has led into some unpredictable challenges including their construction procedure and expenses and particularly blades’ transportation. To overcome these issues, multi-rotor wind turbines have been suggested. Aerodynamic performances of such turbines have been previously assessed by other investigators. However, the wake characteristics of these turbines have been less studied. The focus of the present research is on the assessment of these characteristics, which are crucial in the process of any wind farm design. For this purpose, wake flow of a small three-rotor wind turbine is numerically simulated using computational fluid dynamics. A numerical simulation has been conducted for a single-rotor wind turbine and three-rotor small horizontal axis wind turbine with the angle of 180⸰ arrangement. The results of single rotor wind turbine indicated that far downstream wake extended up to 8D, with Jensen-Gaussian model can be better predicted. The comparison between three bladed wind turbine and the results of wake models for the equivalent turbine showed that because of wake interactions in the downstream of the rotor, the loss of turbulent kinetic energy and recovery of the stream speed will be faster. As a result, in the wind farms, the turbines in closer distances around 4D of the equivalent signle-rotor wind turbine can be installed.

In this paper, a designate of a small scale solar-wind power plant, integrated with battery storage was performed in order to supply the energy demand of a suburb region of Ahvaz, Iran. The aim of this work was to minimize the expenses by help of Homer software with consideration of the amount of the consumed electricity, solar irradiation and wind velocity for the considered region. To optimize the system, Particle Swarm Optimization (PSO) method was used. The simulation results indicates that in the proposed plan, almost 45% of the costs are spent for purchasing, maintaining and replacing the batteries, while, the portion of solar and wind equipment are 15% and 20%, respectively.

In the present work, the numerical investigation of a wind turbine airfoil with suction flow control is initially performed to find the relative improvement in its erodynamic efficiency. Consequently the study of turbine performance is accomplished using 2D simulation results as extending the flow control to wind turbine blades. The latter is incorporated via definition of new input data file in Q-blade code including complete set of section aerodynamic coefficients for both with and without suction control against variety of angles of attack and velocities. The benchmark turbine in this study is NREL 5 MW. It is shown that using suction in 1/3 of chord length would lead in better enhancement. Simulation of the airflow with and without suction control has been presented in three different locations in the chord-wise direction (26%C, 33.5%C and 50%C) and for several intensities or suction speed ratios (0.022, 0.045, 0.11, and 0.155). The turbulence model is transitional 4-equation SST model. The aerodynamic improvement in section is dominant and this method could tolerate stall behavior. Wind turbine power and thrust coefficients were analyzed via Q-blade versus tip speed ratio and flow control parameter. The range of tip speed ratio studied here is 3.5 to 15. The results depicted that applying suction in certain part of the blades could increase output power at low tip speed ratio. Applying suction at 33.5% of chord length improves the average power coefficient by 4.1%.

One of the main concerns in renewable energy technologies, such as wind turbines, is the economic cost and cost savings associated with its construction. Reducing the vibrations of a turbine structure can attenuate the fatigue damage caused by wind loads led to reduction in material consumption and cost. Besides, if the force and flexural moment at the base of the structure is reduced, a smaller foundation can be used to install the wind turbine. All of these factors have a positive impact on lowering the cost of a wind turbine. In this study, application of gyroscopic stabilization to decrease the wind-induced vibrations in 5 mega Watt wind turbine is studied. A valid FAST model is employed for this purpose. Moreover, two versions of the gyroscopic actuator including a passive stabilizer and an active gyroscopic actuator has been proposed. Furthermore, a PID controller has been designed to control the active system. The effect of gyroscope actuator on vibration, shear force and bending moment caused by wind loads is studied via extensive simulations. It was shown that the proposed system can reduce the decease the tip vibration, base shear and base moment by 32 percent in active mode and 14 percent in passive mode. As a result enclosing circle of foundation reduces 5 meter.

Nowadays, as the wind turbines become widespread, it is important to study the turbine behavior in real conditions which may be oscillatory or unsteady. Identifying the characteristics of airfoils used in HAWT blades in different operating conditions can predict the turbine’s aerodynamic performance with acceptable accuracy. In this research, NACA 4412 airfoil has been studied and its performance characteristics such as lift coefficients drag coefficient, surface pressure distributions in subsonic flow field at different angles of attack and Reynolds numbers have been investigated. For this purpose, RANS & URANS governing equations are employed for analysis of static & oscillating conditions respectively using two different turbulence models (Spallart- Almaras and "K-ω" ) have been used. Numerical solution results show acceptable agreement with experimental results. Furthermore, the aerodynamic characteristics with oscillating flow field and the effect of Reynolds number and reduced domain variation has been investigated. The results show that as the value of the reduced domain parameter increases, the lift coefficient increases, but drag coefficient, especially at low angles of attack, does not change significantly.

In the present study, an energy production system using two types of renewable solar and wind energy with climatic conditions and close to areas with high potential for the system under study, with suitable conditions in terms of wind speed and solar radiation as energy sources, We act. To use the heat from the solar system with a parabolic-linear collector, a steam cycle is designed to which heat is transferred through an evaporator and generated electrical energy by a steam turbine. The heat remaining after the evaporator was used to generate a single-effect absorption refrigeration system to generate a cooling load. The main components of the system consist of an organic Rankine cycle, steam Rankine cycle, thermoelectric, absorption refrigeration system, reverse osmosis, wind turbine and a parabolic-linear solar collector. EES software has been used as an engineering tool to model the system and obtain thermodynamic results. The results showed that due to the increase in solar radiation intensity and wind energy on the total exergy, the freshwater production output of the multiple production system is effective and increases the system output. According to the results, solar energy with the central receiver has the highest amount of exergy destruction. Also, the results of exergy degradation showed that the solar system with 60% and wind turbine with 17% have the highest amount of exergy degradation in the system components.

In the present study, the instantaneous velocity profile behind an airfoil at two different Reynolds numbers has been measured experimentally. Data are used to study the wake profile and the corresponding drag coefficient force of the airfoil in different conditions. In the conventional and common methods for calculation of the drag force coefficient through the velocity measurement behind an airfoil, turbulence velocity terms of the momentum equation are ignored. However at moderate to high angles of attack where the flow becomes turbulent and separation occurs, the nature of the flow becomes three dimensional and disregarding the components of the fluctuation of velocity (in three dimensions) in calculation of the drag coefficient of airfoil may result in erroneous information. In the present study, in order to increase the accuracy of the experimental drag coefficient of the airfoil for moderate to high angles of attack, turbulence velocity terms in experimental drag coefficient calculation are considered and this causes an acceptable compatibility between experimental and numerical results whereas for low angles of attack, disregarding the effects of turbulence velocity terms in experimental drag coefficient calculation will improve the accuracy of the experimental drag coefficient and a desired compatibility between experimental and numerical data will be established.