An Experimental Study on the Effects of Wake Interference on the Performances of Wind Turbines Over Complex Terrains

2012 ◽  
Author(s):  
Hui Hu ◽  
Ahmet Ozbay ◽  
Wei Tian ◽  
Zifeng Yang
Keyword(s):  
Experimental Study ◽  
Flow Field ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Flow Characteristics ◽  
Field Measurements ◽  
Wake Interference ◽  
Baseline Case ◽  
Power Yield ◽  
Power Outputs

An experimental study was conducted to investigate the interferences of wind turbines sited over hilly terrains in order to elucidate underlying physics to explore/optimize design paradigms of wind turbines sited over complex terrains for higher power yield and better durability. The experiments were conducted in a large wind tunnel with of wind turbine models sited over a flat terrain (baseline case) and a 2D-ridge with non-homogenous atmospheric boundary layer winds. In addition to measuring dynamic wind loads (both forces and moments) and the power outputs of the wind turbine models, a high-resolution digital Particle Image Velocimetry (PIV) system was used to conduct detailed flow field measurements to quantify the flow characteristics of the surface winds and wake interferences among multiple wind turbines over flat (baseline case) and complex terrains. The detailed flow field measurements were correlated with the wind load measurements and power outputs of the wind turbine models to elucidate the underlying physics associated with turbine power generation and fatigue loads acting on the wind turbines.

Numerical Shape Optimization of a Wind Turbine Blades Using Artificial Bee Colony Algorithm

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Shahram Derakhshan ◽  
Ali Tavaziani ◽  
Nemat Kasaeian
Keyword(s):  
Flow Field ◽  
Shape Optimization ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Artificial Bee Colony ◽  
Twist Angle ◽  
Turbine Blades ◽  
Flow Characteristics ◽  
Wind Turbine Blades ◽  
Bee Colony

Use of wind turbines is rapidly growing because of environmental impacts and daily increase in energy cost. Therefore, improving the wind turbines' characteristics is an important issue in this regard. This study has two objectives: one is investigating the aerodynamic performance of wind turbine blades and the other is developing an efficient approach for shape optimization of blades. The numerical solver of flow field was validated by phase VI rotor as a case study. First, flow field around the wind turbine blades was simulated using computational flow dynamics (CFD) and blade element momentum (BEM) methods, then obtained results were validated by available experimental data to show an appropriate conformity. Then for yielding the optimal answer, a shape optimization algorithm was used based on artificial bee colony (ABC) coupled by artificial neural networks (ANNs) as an approximate model. Effect of most important parameters in wind turbine, such as twist angle, chord line, and pitch angle, was changed till achieving the best performance. The flow characteristics of optimized and initial geometries were compared. The results of global optimization showed a value of 8.58% increase for output power. By using pitch power regulate, the maximum power was shifted to higher wind speed and results in a steady power for all work points.

Simulation of Flow Field on a Large Scale Wind Turbine

2008 ◽  
Author(s):  
I. Janajreh ◽  
C. Ghenai
Keyword(s):  
Flow Field ◽  
Wind Energy ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Cross Sections ◽  
Large Scale ◽  
Wind Farms ◽  
Operating Characteristics ◽  
Cross Sectional ◽  
Capital Costs

Large scale wind turbines and wind farms continue to evolve mounting 94.1GW of the electrical grid capacity in 2007 and expected to reach 160.0GW in 2010 according to World Wind Energy Association. They commence to play a vital role in the quest for renewable and sustainable energy. They are impressive structures of human responsiveness to, and awareness of, the depleting fossil fuel resources. Early generation wind turbines (windmills) were used as kinetic energy transformers and today generate 1/5 of the Denmark’s electricity and planned to double the current German grid capacity by reaching 12.5% by year 2010. Wind energy is plentiful (72 TW is estimated to be commercially viable) and clean while their intensive capital costs and maintenance fees still bar their widespread deployment in the developing world. Additionally, there are technological challenges in the rotor operating characteristics, fatigue load, and noise in meeting reliability and safety standards. Newer inventions, e.g., downstream wind turbines and flapping rotor blades, are sought to absorb a larger portion of the cost attributable to unrestrained lower cost yaw mechanisms, reduction in the moving parts, and noise reduction thereby reducing maintenance. In this work, numerical analysis of the downstream wind turbine blade is conducted. In particular, the interaction between the tower and the rotor passage is investigated. Circular cross sectional tower and aerofoil shapes are considered in a staggered configuration and under cross-stream motion. The resulting blade static pressure and aerodynamic forces are investigated at different incident wind angles and wind speeds. Comparison of the flow field results against the conventional upstream wind turbine is also conducted. The wind flow is considered to be transient, incompressible, viscous Navier-Stokes and turbulent. The k-ε model is utilized as the turbulence closure. The passage of the rotor blade is governed by ALE and is represented numerically as a sliding mesh against the upstream fixed tower domain. Both the blade and tower cross sections are padded with a boundary layer mesh to accurately capture the viscous forces while several levels of refinement were implemented throughout the domain to assess and avoid the mesh dependence.

scholarly journals CFD for Helical Type Vertical Axis Wind Turbine

2019 ◽  
Vol 9 (2S4) ◽  
pp. 474-476
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Computer Aided Design ◽  
Flow Characteristics ◽  
Vertical Axis ◽  
Urban Environments ◽  
Vertical Axis Wind Turbine ◽  
Wind Turbine System ◽  
Twisted Blade ◽  
Aided Design

Vertical axis wind turbines are most effective for home energy generation especially in urban environments. Wind energy creates a stand-alone energy source that is relied on any place. The main criteria for this work is the design of micro wind turbines for all kinds of applications. Design of Twisted Blade Micro-Wind Turbine system is accomplished using computer aided design with Computational Fluid Dynamics (CFD). The flow characteristics in the wind turbine blade were analyzed by varying its twist ratio. The wind turbines with vertical axis utilize the wind from any direction with no yaw mechanism. The risk of blade ejection besides catching wind from all the directions is avoided by using the helical tye vertical axis wind turbine.

scholarly journals An experimental study of the optimal design parameters of a wind power tower used to improve the performance of vertical axis wind turbines

2018 ◽  
Vol 10 (9) ◽  
pp. 168781401879954
Author(s):  
Soo-Yong Cho ◽  
Sang-Kyu Choi ◽  
Jin-Gyun Kim ◽  
Chong-Hyun Cho
Keyword(s):  
Experimental Study ◽  
Optimal Design ◽  
Wind Turbine ◽  
Wind Power ◽  
Wind Turbines ◽  
Vertical Axis ◽  
Power Coefficient ◽  
Design Parameters ◽  
Vertical Axis Wind Turbine ◽  
Vertical Axis Wind Turbines

In order to augment the performance of vertical axis wind turbines, wind power towers have been used because they increase the frontal area. Typically, the wind power tower is installed as a circular column around a vertical axis wind turbine because the vertical axis wind turbine should be operated in an omnidirectional wind. As a result, the performance of the vertical axis wind turbine depends on the design parameters of the wind power tower. An experimental study was conducted in a wind tunnel to investigate the optimal design parameters of the wind power tower. Three different sizes of guide walls were applied to test with various wind power tower design parameters. The tested vertical axis wind turbine consisted of three blades of the NACA0018 profile and its solidity was 0.5. In order to simulate the operation in omnidirectional winds, the wind power tower was fabricated to be rotated. The performance of the vertical axis wind turbine was severely varied depending on the azimuthal location of the wind power tower. Comparison of the performance of the vertical axis wind turbine was performed based on the power coefficient obtained by averaging for the one periodic azimuth angle. The optimal design parameters were estimated using the results obtained under equal experimental conditions. When the non-dimensional inner gap was 0.3, the performance of the vertical axis wind turbine was better than any other gaps.

Performance Characterization of a Wind Turbine Simulator for Grid Connected and Islanded Wind Turbine Operation

2007 ◽  
Author(s):  
Dan Zimmerle ◽  
Oliver Pacific ◽  
Nathan Howard
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Field Measurements ◽  
State University ◽  
Electrical Networks ◽  
Transmission Grid ◽  
Colorado State University ◽  
Grid Simulation ◽  
Field Information ◽  
The Individual

To better understand the effect of significant wind power production on distributed electrical networks, a Wind Turbine Simulator (WTS) was incorporated into the Grid Simulation Laboratory (GSL) at Colorado State University. This paper discusses the development of the engine controls, gain tuning and response matching to field measurements of wind turbines. Response was characterized while connected to the transmission grid, similar to the field information, using a series of transient events gleaned from field information. Transients caused by breaker events, which emulate connecting or disconnecting the individual wind turbines, were also considered. While overall correlation between commanded and actual power output was strong, several limitations were identified and are described.

An Experiment Study of Wall Slot Jets Pertinent to Trailing Edge Cooling of Turbine Blades

2010 ◽  
Author(s):  
Zifeng Yang ◽  
Anand Gopa Kumar ◽  
Hirofumi Igarashi ◽  
Hui Hu
Keyword(s):  
Flow Field ◽  
Turbine Blades ◽  
Flow Characteristics ◽  
Field Measurements ◽  
Main Stream ◽  
Wall Jet ◽  
Ambient Conditions ◽  
Trailing Edge ◽  
Jet Streams ◽  
Cooling Effectiveness

An experimental study was conducted to quantify the flow characteristics of wall jets pertinent to trailing edge cooling of turbine blades. A high-resolution stereoscopic PIV system was used to conduct detailed flow field measurements to quantitatively visualize the evolution of the unsteady vortex and turbulent flow structures in cooling wall jet streams and to quantify the dynamic mixing process between the cooling wall jet streams and the main stream flows. The detailed flow field measurements are correlated with the adiabatic cooling effectiveness maps measured by using pressure sensitive paint (PSP) technique to elucidate underlying physics in order to improve cooling effectiveness to protect the critical portions of turbine blades from the harsh ambient conditions.

Prediction of Aerodynamic Noise Radiated From a Vertical-Axis Wind Turbine

2003 ◽  
Author(s):  
Akiyoshi Iida ◽  
Akisato Mizuno ◽  
Kyoji Kamemoto
Keyword(s):  
Flow Field ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Sound Source ◽  
Vertical Axis ◽  
Aerodynamic Performance ◽  
Low Noise ◽  
Aerodynamic Noise ◽  
Speed Ratio ◽  
Vertical Axis Wind Turbine

Unsteady flow field and flow induced noise of vertical axis wind turbine are numerically investigated. The flow field is numerically calculated by the vortex method with core-spreading model. This simulation obtains aerodynamic performance and aerodynamic forces. Aerodynamic noise is also simulated by using Ffowcs Williams-Hawkings equation with compact body and low-Mach number assumptions. Tip speed of rotor blades are not so high, then the contribution of the moving sound source is smaller than that of the dipole sound source. Since the maximum power coefficient of VAWT can be obtained at lower tip-speed ratio compared to the conventional, horizontal axis wind turbines, the aerodynamic noise from vertical axis wind turbine is smaller than that of the conventional wind turbines at the same aerodynamic performance. This result indicates that the vertical axis wind turbines are useful to develop low-noise wind turbines.

Aerodynamic Measurements on a Vertical Axis Wind Turbine in a Large Scale Wind Tunnel

2010 ◽  
Author(s):  
L. Battisti ◽  
L. Zanne ◽  
S. Dell’Anna ◽  
V. Dossena ◽  
B. Paradiso ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Flow Field ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Large Scale ◽  
Fluid Dynamic ◽  
Vertical Axis ◽  
Vertical Axis Wind Turbine ◽  
Aerodynamic Optimization ◽  
Vertical Axis Wind Turbines

This paper presents the first results of a wide experimental investigation on the aerodynamics of a vertical axis wind turbine. Vertical axis wind turbines have recently received particular attention, as interesting alternative for small and micro generation applications. However, the complex fluid dynamic mechanisms occurring in these machines make the aerodynamic optimization of the rotors still an open issue and detailed experimental analyses are now highly recommended to convert improved flow field comprehensions into novel design techniques. The experiments were performed in the large-scale wind tunnel of the Politecnico di Milano (Italy), where real-scale wind turbines for micro generation can be tested in full similarity conditions. Open and closed wind tunnel configurations are considered in such a way to quantify the influence of model blockage for several operational conditions. Integral torque and thrust measurements, as well as detailed aerodynamic measurements were applied to characterize the 3D flow field downstream of the turbine. The local unsteady flow field and the streamwise turbulent component, both resolved in phase with the rotor position, were derived by hot wire measurements. The paper critically analyses the models and the correlations usually applied to correct the wind tunnel blockage effects. Results evidence that the presently available theoretical correction models does not provide accurate estimates of the blockage effect in the case of vertical axis wind turbines. The tip aerodynamic phenomena, in particular, seem to play a key role for the prediction of the turbine performance; large-scale unsteadiness is observed in that region and a simple flow model is used to explain the different flow features with respect to horizontal axis wind turbines.

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.

On the Influence of the Diffuser Inlet Shape on the Performance of a Centrifugal Compressor Stage

1983 ◽  
Author(s):  
K. Bammert ◽  
M. Jansen ◽  
M. Rautenberg
Keyword(s):  
Experimental Study ◽  
Flow Field ◽  
Centrifugal Compressor ◽  
Field Measurements ◽  
Single Stage ◽  
Compressor Stage ◽  
Vaned Diffuser ◽  
Centrifugal Compressor Stage ◽  
Essential Components

Results from an experimental study of the influence of the diffuser inlet shape on the performance of the diffuser and the whole compressor stage are presented. The investigations were carried out using a single stage centrifugal compressor. Three different vaned diffusers were tested. From detailed flow field measurements the influence of the diffuser inlet shape on the performance of the essential components of the compressor stage, i.e. the impeller, the diffuser, and the collecting chamber was analyzed. It is shown that the reaction of the vaned diffuser on the efficiency of the impeller is only weak but the losses in the collecting chamber are considerably affected by the used diffuser types.

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