scholarly journals Numerical Simulation and Wind Tunnel Investigation on Static Characteristics of VAWT Rotor Starter with Lift-Drag Combined Structure

Energies ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 6167
Author(s):  
Fang Feng ◽  
Guoqiang Tong ◽  
Yunfei Ma ◽  
Yan Li
Keyword(s):  
Numerical Simulation ◽  
Wind Speed ◽  
Wind Tunnel ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Speed Ratio ◽  
Static Characteristics ◽  
Torque Coefficient ◽  
Starting Characteristics ◽  
Static Torque

In order to get rid of the impact of the global financial crisis and actively respond to global climate change, it has become a common choice for global economic development to develop clean energy such as wind energy, improve energy efficiency and reduce greenhouse gas emissions. With the advantages of simple structure, unnecessary facing the wind direction, and unique appearance, the vertical axis wind turbine (VAWT) attracts extensive attention in the field of small and medium wind turbines. The lift-type VAWT exhibits outstanding aerodynamic characteristics at a high tip speed ratio, while the starting characteristics are generally undesirable at a low wind speed; thus, how to improve the starting characteristics of the lift-type VAWT has always been an important issue. In this paper, a lift-drag combined starter (LDCS) suitable for lift-type VAWT was proposed to optimize the starting characteristics of lift-type VAWT. With semi-elliptical drag blades and lift blades equipped on the middle and rear part outside the starter, the structure is characterized by lift-drag combination, weakening the adverse effect of the starter with semi-elliptical drag blades alone on the output performance of the original lift-type VAWT and improving the characteristics of the lift-drag combined VAWT. The static characteristic is one of the important starting characteristics of the wind turbine. The rapid development of computational fluid dynamics has laid a solid material foundation for VAWT. Thus the static characteristics of the LDCS with different numbers of blades were investigated by conducting numerical simulation and wind tunnel tests. The results demonstrated that the static torque coefficient of LDCS increased significantly with the increased incoming wind speed. The average value of the static torque coefficient also increased significantly. This study can provide guidelines for the research of lift-drag combined wind turbines.

Numerical Simulation of Dynamics of a Spar Type Floating Wind Turbine and Comparison With Laboratory Measurements

2016 ◽  
Author(s):  
Hyunseong Min ◽  
Cheng Peng ◽  
Fei Duan ◽  
Zhiqiang Hu ◽  
Jun Zhang
Keyword(s):  
Numerical Simulation ◽  
Wind Speed ◽  
Numerical Simulations ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Deep Water ◽  
Offshore Wind ◽  
Wind Loads ◽  
Floating Offshore Wind Turbines ◽  
The Cost

Wind turbines are popular for harnessing wind energy. Floating offshore wind turbines (FOWT) installed in relatively deep water may have advantages over their on-land or shallow-water cousins because winds over deep water are usually steadier and stronger. As the size of wind turbines becomes larger and larger for reducing the cost per kilowatt, it could bring installation and operation risks in the deep water due to the lack of track records. Thus, together with laboratory tests, numerical simulations of dynamics of FOWT are desirable to reduce the probability of failure. In this study, COUPLE-FAST was initially employed for the numerical simulations of the OC3-HYWIND, a spar type platform equipped with the 5-MW baseline wind turbine proposed by National Renewable Energy Laboratory (NREL). The model tests were conducted at the Deepwater Offshore Basin in Shanghai Jiao Tong University (SJTU) with a 1:50 Froude scaling [1]. In comparison of the simulation using COUPLE-FAST with the corresponding measurements, it was found that the predicted motions were in general significantly smaller than the related measurements. The main reason is that the wind loads predicted by FAST were well below the related measurements. Large discrepancies are expected because the prototype and laboratory wind loads do not follow Froude number similarity although the wind speed was increased (or decreased) in the tests such that the mean surge wind force matched that predicted by FAST at the nominal wind speed (Froude similarity) in the cases of a land wind turbine [1]. Therefore, an alternative numerical simulation was made by directly inputting the measured wind loads to COUPLE instead of the ones predicted by FAST. The related simulated results are much improved and in satisfactory agreement with the measurements.

Numerical Simulation for the Starting Characteristics of a Wind Turbine

2020 ◽  
Vol 38 ◽  
pp. 215-221
Author(s):  
Anna Kuwana ◽  
Xue Yan Bai ◽  
Dan Yao ◽  
Haruo Kobayashi
Keyword(s):  
Numerical Simulation ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Wind Farms ◽  
Vertical Axis ◽  
Offshore Wind ◽  
Optimum Shape ◽  
Blade Thickness ◽  
Basic Characteristics ◽  
Starting Characteristics

There are many types of wind turbine. Large propeller-type wind turbines are used mainly for large wind farms and offshore wind power generation. Small vertical-axis wind turbines (VAWTs) are often used in distributed energy systems. In previous studies on wind turbines, the basic characteristics such as torque coefficient have often been obtained during rotation, with the turbine rotating at a constant speed. Such studies are necessary for the proper design of wind turbines. However, it is also necessary to conduct research under conditions in which the wind direction and wind speed change over time. Numerical simulation of the starting characteristics is carried out in this study. Based on the flow field around the wind turbine, the force required to rotate the turbine is calculated. The force used to stop the turbine is modeled based on friction in relation to the bearing. Equations for the motion of the turbine are solved by their use as external force. Wind turbine operation from the stationary state to the start of rotation is simulated. Five parameters, namely, blade length, wind turbine radius, overlap, gap, and blade thickness, are changed and the optimum shape is obtained. The simulation results tend to qualitatively agree with the experimental results for steadily rotating wind turbines in terms of two aspects: (1) the optimal shape has an 20% overlap of the turbine radius, and (2) the larger the gap, the lower the efficiency.

Experimental Study of a Pinwheel-Type Wind Turbine

2003 ◽  
Vol 27 (3) ◽  
pp. 227-236 ◽  
Author(s):  
Yasuyuki Nemoto ◽  
Izumi Ushiyama
Keyword(s):  
Experimental Study ◽  
Wind Tunnel ◽  
Wind Turbine ◽  
Optimum Design ◽  
Architectural Design ◽  
Frontal Area ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Tip Speed Ratio ◽  
Torque Coefficient

Pinwheels have been familiar as toys for hundreds of years. Not only do they have an attractive appearance, they can also be fabricated from just one piece of plate. Application is possible, e.g. for education and architectural design. The purpose of this paper is to clarify the characteristics and to determine the optimum design configuration of pinwheel type wind turbines. The authors fabricated the test rotors with various shapes and carried out the experiment in a wind tunnel. As a result, the following facts were obtained: (1) Power coefficient with the traditional 4 blades has, CPmax = 0.17 at λ = 2. (2) High tip speed is obtained by cutting the frontal area of pinwheel. Tip speed ratio at no load can be easily changed from λ = 3 to 6 by changing the cutting area. Maximum power coefficient CPmax = 0.22 was obtained at tip speed ratio λ = 3.5. (3) Increased torque is obtained by cutting the edge area of the pinwheel. Tip speed ratio at no load can be easily changed from λ = 2 to 3, and torque coefficient can be easily changed from CQmax = 0.15 to 0.25, by changing the cut area.

Aerodynamic Design and Analysis of a Flanged Diffuser Augmented Wind Turbine

2013 ◽  
Author(s):  
A. Tourlidakis ◽  
K. Vafiadis ◽  
V. Andrianopoulos ◽  
I. Kalogeropoulos
Keyword(s):  
Wind Speed ◽  
Flow Field ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Research Work ◽  
Flow Analysis ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Computational Domain ◽  
Aerodynamic Design

Many researchers proposed methods for improving the efficiency of small Horizontal Axis Wind Turbines (HAWTs). One of the methods developed to increase the efficiency of HAWTs and to overcome the theoretical Betz limit is the introduction of a converging – diverging casing around the turbine. To further improve the performance of the diffuser a flange is placed at its outlet, which smoothes the flow along the diffuser interior, allowing larger diffusion angles to be utilized. The purpose of this research work is the aerodynamic design and computational analysis of such an arrangement with the use of Computational Fluid Dynamics (CFD). First, a HAWT rotor rotating at 600 RPM was designed with the use of the Blade Element Momentum (BEM) method. The three rotor blades are constructed using the NREL airfoil sections family S833, S834 and S835. The power coefficient of the rotor was optimised in a wind speed range of 5 – 10 m/s, with a maximum value of 0.45 for a wind speed of 7m/s. A full three-dimensional CFD analysis was carried out for the modeling of the flow around the rotor and through the flanged diffuser. The computational domain consisted of two regions with different frames of reference (a stationary and a rotating). The rotating frame rotates at 600 RPM and includes the rotor with the blades. All the simulations were performed using the commercial CFD software package ANSYS CFX. The Shear Stress Transport turbulence model was used for the simulations. Detailed flow analysis results are presented, dealing with the various investigated test cases, a) isolated turbine rotor, b) diffuser without the presence of the turbine, and c) the full turbine – diffuser arrangement for different flange heights and wind speeds. By varying the height of the flange and the wind speed, the effects of the above on the flow field and the power coefficient of the turbine were studied. The CFD resulting power coefficients are also compared and good agreement with existing in the literature experimental data was obtained. The results showed that there is a significant improvement in the performance of the wind turbine (by a factor from 2 to 5 on power coefficient at high blade tip speed ratio) and the proposed modification is particularly attractive for small wind turbines. The particular characteristics of the flow field, that are responsible for this improvement are identified and analysed in detail offering a better understanding of the physical processes involved.

scholarly journals Wind Turbine Wake Characterization for Improvement of the Ainslie Eddy Viscosity Wake Model

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2823 ◽  
Author(s):  
Hyungyu Kim ◽  
Kwansu Kim ◽  
Carlo Bottasso ◽  
Filippo Campagnolo ◽  
Insu Paek
Keyword(s):  
Wind Speed ◽  
Wind Tunnel ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Eddy Viscosity ◽  
Wind Tunnel Test ◽  
Original Model ◽  
Test Results ◽  
Wake Model ◽  
Turbine Model

This paper presents a modified version of the Ainslie eddy viscosity wake model and its accuracy by comparing it with selected exiting wake models and wind tunnel test results. The wind tunnel test was performed using a 1.9 m rotor diameter wind turbine model operating at a tip speed ratio similar to that of modern megawatt wind turbines. The control algorithms for blade pitch and generator torque used for below and above rated wind speed regions similar to those for multi-MW wind turbines were applied to the scaled wind turbine model. In order to characterize the influence of the wind turbine operating conditions on the wake, the wind turbine model was tested in both below and above rated wind speed regions at which the thrust coefficients of the rotor varied. The correction of the Ainslie eddy viscosity wake model was made by modifying the empirical equation of the original model using the wind tunnel test results with the Nelder-Mead simplex method for function minimization. The wake prediction accuracy of the modified wake model in terms of wind speed deficit was found to be improved by up to 6% compared to that of the original model. Comparisons with other existing wake models are also made in detail.

scholarly journals Study on performance of a savonius wind turbines related with the blade angle

2019 ◽  
Vol 1 (2) ◽  
pp. 32-36
Author(s):  
Saowalak Thongdee ◽  
Churat Tararuk ◽  
Natthawud Dussadee ◽  
Rameshprabu Ramaraj ◽  
Tanate Chaichana
Keyword(s):  
Wind Speed ◽  
Wind Turbines ◽  
Vertical Axis ◽  
Speed Ratio ◽  
Blade Angle ◽  
Tip Speed Ratio ◽  
Vertical Axis Wind Turbines ◽  
Torque Coefficient ◽  
Savonius Wind Turbine ◽  
Positive Effect

This research aimed to compare the performance of Savonius vertical axis wind turbines through blade numbers and different blade angles. In this study, applicable turbines having 4, 6, 8, 12, 16 and 18 numbers of blades with the angles of the blades of -15°, -5°, 0°, 5° and 15°, respectively. The rotor used was a semicircle shaped blade made from PVC material and has a blade diameter of 6 cm and 30 cm for both rotor diameter and height. The turbine was tested deadweight range of 0-0.49 kg at 4 m/s wind speed. The results showed that the blade angle has a positive effect on increasing the power and torque coefficient of Savonius wind turbine, specifically on blades less than 16. The highest power and torque coefficient was obtained from the turbine having16 blades at an angle of 5°. This configuration also found that the maximum power and torque coefficient in the tip speed ratio ranging from 0.3-0.4 are 0.2519 and 0.5858, respectively.

scholarly journals Dimensional Analysis in Power Predicting of a Real Scale Wind Turbine Based on Wind Tunnel Torque Measurement of Small Scaled Models

2018 ◽  
Author(s):  
Sutrisno Sutrisno ◽  
Sigit Iswahyudi ◽  
Setyawan Wibowo
Keyword(s):  
Wind Tunnel ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Large Scale ◽  
Correlation Equation ◽  
Field Size ◽  
Speed Ratio ◽  
Small Scale ◽  
Torque Measurement ◽  
Turbine Design

A preliminary study of a wind turbine design is carried out using a wind tunnel to obtain its aerodynamic characteristics. Utilization of data from the study to develop large-scale wind turbines requires further study. This paper aims to discuss the use of wind turbine data obtained from the wind tunnel measurements to estimate the characteristics of wind turbines that have field size. The torque of two small-scale turbines was measured inside the wind tunnel. The first small-scale turbine has a radius of 0.14 m and the second small turbine has a radius of 0.19 m. Torque measurement results from both turbines were analyzed using Buckingham π theorem to obtain a correlation between torsion and diameter variations. The obtained correlation equation is used to estimate the field measurement of turbine power with a radius of 1.2 m. The resulting correlation equation can be used to estimate the power generated by the turbine by the size of the field well in the operating area of the tip speed ratio of the turbine design.

Aerodynamic Rotor Performance of a 3300-kW Modern Commercial Large-Scale Wind Turbine Installed in a Wind Farm

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
Mehmet Bilgili ◽  
Mehmet Tontu ◽  
Besir Sahin
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Large Scale ◽  
Wind Farm ◽  
Thrust Force ◽  
Speed Ratio ◽  
Flow Angle ◽  
Onshore Wind ◽  
Turbine Performance

Abstract Wind turbine technology in the world has been developed by continuously improving turbine performance, design, and efficiency. Over the last 40 years, the rated capacity and dimension of the commercial wind turbines have increased dramatically, so the energy cost has declined significantly, and the industry has moved from an idealistic position to an acknowledged component of the power generation industry. For this reason, a thorough examination of the aerodynamic rotor performance of a modern large-scale wind turbine working on existing onshore wind farms is critically important to monitor and control the turbine performance and also for forecasting turbine power. This study focuses on the aerodynamic rotor performance of a 3300-kW modern commercial large-scale wind turbine operating on an existing onshore wind farm based on the measurement data. First, frequency distributions of wind speeds and directions were obtained using measurements over one year. Then, wind turbine parameters such as free-stream wind speed (U∞), far wake wind speed (UW), axial flow induction factor (a), wind turbine power coefficient (CP), tangential flow induction factor (a′), thrust force coefficient (CT), thrust force (T), tip-speed ratio (λ), and flow angle (ϕ) were calculated using the measured rotor disc wind speed (UD), atmospheric air temperature (Tatm), turbine rotational speed (Ω), and turbine power output (P) parameters. According to the results obtained, the maximum P, CP, CT, T, and Ω were calculated as approximately 3.3 MW, 0.45, 0.6, 330 kN, and 12.9 rpm, respectively, while the optimum λ, ϕ, U∞, and Ω for the maximum CP were determined as 7.5–8.5, 6–6.3°, 5–10 m/s, and 6–10 rpm, respectively. These calculated results can contribute to assessing the economic and technical feasibility of modern commercial large-scale wind turbines and supporting future developments in wind energy and turbine technology.

scholarly journals Effects of Inflow Shear on Wake Characteristics of Wind-Turbines over Flat Terrain

Energies ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3745 ◽  
Author(s):  
Takanori Uchida
Keyword(s):  
Wind Tunnel ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Turbine Rotor ◽  
Wind Tunnel Experiment ◽  
Scale Model ◽  
Speed Ratio ◽  
Flat Terrain ◽  
Wind Turbine Rotor ◽  
Wake Characteristics

The scope of the present study was to understand the wake characteristics of wind-turbines under various inflow shears. First, in order to verify the prediction accuracy of the in-house large-eddy simulation (LES) solver, called RIAM-COMPACT, based on a Cartesian staggered grid, we conducted a wind-tunnel experiment using a wind-turbine scale model and compared the numerical and experimental results. The total number of grid points in the computational domain was about 235 million. Parallel computation based on a hybrid LES/actuator line (AL) model approach was performed with a new SX-Aurora TSUBASA vector supercomputer. The comparison between wind-tunnel experiment and high-resolution LES results showed that the AL model implemented in the in-house LES solver in this study could accurately reproduce both performances of the wind-turbine scale model and flow characteristics in the wake region. Next, with the LES solver developed in-house, flow past the entire wind-turbine, including the nacelle and the tower, was simulated for a tip-speed ratio (TSR) of 4, the optimal TSR. Three types of inflow shear, N = 4, N = 10, and uniform flow, were set at the inflow boundary. In these calculations, the calculation domain in the streamwise direction was very long, 30.0 D (D being the wind-turbine rotor diameter) from the center of the wind-turbine hub. Long-term integration of t = 0 to 400 R/Uin was performed. Various turbulence statistics were calculated at t = 200 to 400 R/Uin. Here, R is the wind-turbine rotor radius, and Uin is the wind speed at the hub-center height. On the basis of the obtained results, we numerically investigated the effects of inflow shear on the wake characteristics of wind-turbines over a flat terrain. Focusing on the center of the wind-turbine hub, all results showed almost the same behavior regardless of the difference in the three types of inflow shear.

Design and Performance Analysis of Distributed Equal Angle Spiral Vertical Axis Wind Turbine

2020 ◽  
Vol 14 (1) ◽  
pp. 120-132
Author(s):  
Li Zheng ◽  
Zhang Wenda ◽  
Han Ruihua ◽  
Tian Yongsheng
Keyword(s):  
Wind Speed ◽  
Wind Energy ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Vertical Axis ◽  
Energy Utilization ◽  
Normal Operation ◽  
Utilization Rate ◽  
Speed Ratio ◽  
Vertical Axis Wind Turbine

Background: The wind turbine is divided into a horizontal axis and a vertical axis depending on the relative positions of the rotating shaft and the ground. The advantage of the choke wind turbine is that the starting torque is large and the starting performance is good. The disadvantage is that the rotation resistance is large, the rotation speed is low, the asymmetric flow occurs when the wind wheel rotates, the lateral thrust is generated, and the wind energy utilization rate is lowered. How to improve the wind energy utilization rate of the resistance wind turbine is an important issue to be solved by the wind power technology. Objective: The nautilus isometric spiral wind turbines studied in this paper have been introduced and analyzed in detail, preparing for the further flow analysis and layout of wind turbines, improving the wind energy utilization rate of wind turbines, introducing patents of other structures and output characteristics of its generator set. Methods: Combined with the flow field analysis of ANSYS CFX software, the numerical simulation of the new wind turbine was carried out, and the aerodynamic performance of the new vertical axis wind turbine was analyzed. The mathematical model and control model of the generator were established by the maximum power control method, and the accuracy of the simulation results was verified by the measured data. Results: The basic parameters of the new wind turbine tip speed ratio, torque coefficient and wind energy utilization coefficient are analyzed. Changes in wind speed, pressure and eddy viscosity were investigated. Three-dimensional distribution results of wake parameters such as wind speed and pressure are obtained. By simulating the natural wind speed, the speed and output current of the generator during normal operation are obtained. Conclusion: By analyzing the wind performance and power generation characteristics of the new wind turbine, the feasibility of the new wind turbine is determined, which provides reference and reference for the optimal design and development of the wind turbine structure.

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