scholarly journals CFD-based curved tip shape design for wind turbine blades

2021 ◽  
Author(s):  
Mads Holst Aagaard Madsen ◽  
Frederik Zahle ◽  
Sergio González Horcas ◽  
Thanasis Barlas ◽  
Niels Nørmark Sørensen
Keyword(s):  
Wind Turbine ◽  
Turbine Blades ◽  
Bending Moment ◽  
Turbine Rotor ◽  
Wind Turbine Blades ◽  
Step Method ◽  
Design Iteration ◽  
Design Variables ◽  
Mesh Resolution ◽  
Computational Fluid Dynamics Cfd

Abstract. This work presents a high-fidelity shape optimization framework based on computational fluid dynamics (CFD). The presented work is the first comprehensive curved tip shape study of a wind turbine rotor to date using a direct CFD-based approach. Preceeding the study is a thorough literature survey particularly focused on wind turbine blade tips in order to place the present work in its context. Then follows a comprehensive analysis to quantify mesh dependency and to present needed mesh modifications ensuring a deep convergence of the flow field at each design iteration. The presented modifications allow the framework to produce up to 6 digit accurate finite difference gradients which are verified using the machine accurate Complex-Step method. The accurate gradients result in a tightly converged design optimization problem where the studied problem is to maximize power using 12 design variables while satisfying constraints on geometry as well as on the bending moment at 90 % blade length. The optimized shape has about 1 % r/R blade extension, 2 % r/R flapwise displacement, and slightly below 2 % r/R edgewise displacement resulting in a 1.12 % increase in power. Importantly, the inboard part of the tip is de-loaded using twist and chord design variables as the blade is extended ensuring that the baseline steady-state loads are not exceeded. For both analysis and optimization an industrial scale mesh resolution of above 14 · 106 cells is used which underlines the maturity of the framework.

scholarly journals Damage tolerance and structural monitoring for wind turbine blades

2015 ◽  
Vol 373 (2035) ◽  
pp. 20140077 ◽  
Author(s):  
M. McGugan ◽  
G. Pereira ◽  
B. F. Sørensen ◽  
H. Toftegaard ◽  
K. Branner
Keyword(s):  
Wind Turbine ◽  
Damage Tolerance ◽  
Turbine Blades ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Offshore Wind ◽  
Tolerance Index ◽  
Wind Turbine Blades ◽  
Efficient Operation ◽  
Reliable Design

The paper proposes a methodology for reliable design and maintenance of wind turbine rotor blades using a condition monitoring approach and a damage tolerance index coupling the material and structure. By improving the understanding of material properties that control damage propagation it will be possible to combine damage tolerant structural design, monitoring systems, inspection techniques and modelling to manage the life cycle of the structures. This will allow an efficient operation of the wind turbine in terms of load alleviation, limited maintenance and repair leading to a more effective exploitation of offshore wind.

Design and Evaluation of a Rooftop Wind Turbine Rotor With Untwisted Blades

2013 ◽  
Author(s):  
Sayem Zafar ◽  
Mohamed Gadalla
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Low Cost ◽  
Turbine Blades ◽  
Angle Of Attack ◽  
Turbine Rotor ◽  
Wind Turbine Blades ◽  
Wind Speeds ◽  
Small Wind Turbines ◽  
Wind Turbine Rotor

A small horizontal axis wind turbine rotor was designed and tested with aerodynamically efficient, economical and easy to manufacture blades. Basic blade aerodynamic analysis was conducted using commercially available software. The blade span was constrained such that the complete wind turbine can be rooftop mountable with the envisioned wind turbine height of around 8 m. The blade was designed without any taper or twist to comply with the low cost and ease of manufacturing requirements. The aerodynamic analysis suggested laminar flow airfoils to be the most efficient airfoils for such use. Using NACA 63-418 airfoil, a rectangular blade geometry was selected with chord length of 0.27[m] and span of 1.52[m]. Glass reinforced plastic was used as the blade material for low cost and favorable strength to weight ratio with a skin thickness of 1[mm]. Because of the resultant velocity changes with respect to the blade span, while the blade is rotating, an optimal installed angle of attack was to be determined. The installed angle of attack was required to produce the highest possible rotation under usual wind speeds while start at relatively low speed. Tests were conducted at multiple wind speeds with blades mounted on free rotating shaft. The turbine was tested for three different installed angles and rotational speeds were recorded. The result showed increase in rotational speed with the increase in blade angle away from the free-stream velocity direction while the start-up speeds were found to be within close range of each other. At the optimal angle was found to be 22° from the plane of rotation. The results seem very promising for a low cost small wind turbine with no twist and taper in the blade. The tests established that non-twisted wind turbine blades, when used for rooftop small wind turbines, can generate useable electrical power for domestic consumption. It also established that, for small wind turbines, non-twisted, non-tapered blades provide an economical yet productive alternative to the existing complex wind turbine blades.

Evaluation of dual-axis fatigue testing of large wind turbine blades

2011 ◽  
Vol 226 (7) ◽  
pp. 1693-1704 ◽  
Author(s):  
Peter R Greaves ◽  
Robert G Dominy ◽  
Grant L Ingram ◽  
Hui Long ◽  
Richard Court
Keyword(s):  
Service Life ◽  
Wind Turbine ◽  
Fatigue Testing ◽  
Turbine Blades ◽  
Bending Moment ◽  
Fatigue Tests ◽  
Simulation Software ◽  
Wind Turbine Blades ◽  
Moment Distribution ◽  
Large Wind

Full-scale fatigue testing is part of the certification process for large wind turbine blades. That testing is usually performed about the flapwise and edgewise axes independently but a new method for resonant fatigue testing has been developed in which the flapwise and edgewise directions are tested simultaneously, thus also allowing the interactions between the two mutually perpendicular loads to be investigated. The method has been evaluated by comparing the Palmgren–Miner damage sum around the cross-section at selected points along the blade length that results from a simulated service life, as specified in the design standards, and testing. Bending moments at each point were generated using wind turbine simulation software and the test loads were designed to cause the same amount of damage as the true service life. The mode shape of the blade was tuned by optimising the position of the excitation equipment, so that the bending moment distribution was as close as possible to the target loads. The loads were converted to strain–time histories using strength of materials approach, and fatigue analysis was performed. The results show that if the bending moment distribution is correct along the length of the blade, then dual-axis resonant testing tests the blade much more thoroughly than sequential tests in the flapwise and edgewise directions. This approach is shown to be more representative of the loading seen in service and can thus contribute to a potential reduction in the weight of wind turbine blades and the duration of fatigue tests leading to reduced cost.

Optimal Design of Horizontal Axis Wind Turbine Blades

2008 ◽  
Author(s):  
Ohad Gur ◽  
Aviv Rosen
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Design Method ◽  
Turbine Blades ◽  
Horizontal Axis ◽  
Optimization Strategy ◽  
Wind Turbine Blades ◽  
Horizontal Axis Wind Turbine ◽  
Wind Speeds ◽  
Design Variables

The optimal aerodynamic design of Horizontal Axis Wind Turbine (HAWT) is investigated. The Blade-element/Momentum model is used for the aerodynamic analysis. In the first part of the paper a simple design method is derived, where the turbine blade is optimized for operation at a specific wind speed. Results of this simple optimization are presented and discussed. Besides being optimized for operation at a specific wind speed, without considering operation at other wind speeds, the simple model is also limited in the choice of design goals (cost functions), design variables and constraints. In the second part of the paper a comprehensive design method that is based on a mixed numerical optimization strategy, is presented. This method can handle almost any combination of: design goal, design variables, and constraints. Results of this method are presented, compared with the results of the simple optimization, and discussed.

scholarly journals Experimental Investigation of Finite Aspect Ratio Cylindrical Bodies for Accelerated Wind Applications

Fluids ◽  
2020 ◽  
Vol 5 (1) ◽  
pp. 25 ◽  
Author(s):  
Michael Parker ◽  
Douglas Bohl
Keyword(s):  
Aspect Ratio ◽  
Wind Turbine ◽  
Turbine Blades ◽  
Cylindrical Body ◽  
Turbine Rotor ◽  
Flow Speed ◽  
The Body ◽  
Rotor Blades ◽  
Wind Turbine Blades ◽  
Smooth Cylinder

The placement of a cylindrical body in a flow alters the velocity and pressure fields resulting in a local increase in the flow speed near the body. This interaction is of interest as wind turbine rotor blades could be placed in the area of increased wind speed to enhance energy harvesting. In this work the aerodynamic performance of two short aspect ratio (AR = 0.93) cylindrical bodies was evaluated for potential use in “accelerated wind” applications. The first cylinder was smooth with a constant diameter. The diameter of the second cylinder varied periodically along the span forming channels, or corrugations, where wind turbine blades could be placed. Experiments were performed for Reynolds numbers ranging from 1 × 105 to 9 × 105. Pressure distributions showed that the smooth cylinder had lower minimum pressure coefficients and delayed separation compared to the corrugated cylinder. Velocity profiles showed that the corrugated cylinder had lower peak speeds, a less uniform profile, and lower kinetic energy flux when compared to the smooth cylinder. It was concluded that the smooth cylinder had significantly better potential performance in accelerated wind applications than the corrugated cylinder.

Design of Experimental Procedure and Analysis Methods of Small Scale Wind Turbine Blades With Different Geometries

2014 ◽  
Author(s):  
Abdulrahman Alsultan ◽  
Andrew Ryan Block ◽  
Trevor James Burg ◽  
Joshua Neal Vriesman ◽  
R. S. Amano
Keyword(s):  
Wind Turbine ◽  
Turbine Blades ◽  
Energy Output ◽  
Design Parameters ◽  
Small Scale ◽  
Wind Turbine Blades ◽  
Experimental Procedure ◽  
Torque Generation ◽  
Computational Fluid Dynamics Cfd ◽  
To Come

The renewable energy is a promising field, which shows a lot of potential for future energy solutions. The design of the blade shows a lot effects on the efficiency of the wind turbine, and the design parameters governs the performance characteristics. This paper addresses a number of innovative blade designs that was developed by alterations made to the existing conventional straight blade. These blades were extensively studied using computational fluid dynamics (CFD) software, and showed promising results, which was the motive behind this study. We are designing an experiment to study small scale wind turbines, which will enable us to gather data that will explain some differences in power and torque output. These steps will help us to come to a better understanding of some aerodynamic aspects that will impact the performance of each individual blade design. The comparing criteria for this study was the torque generation at the axes of rotation, which can be translated to several parameters, such as energy output, using some theoretical basis equations.

Basalt Carbon Hybrid Composite for Wind Turbine Rotor Blades: A Short Review

2014 ◽  
Vol 970 ◽  
pp. 67-73 ◽  
Author(s):  
Ali Nawaz Mengal ◽  
Saravanan Karuppanan ◽  
Azmi Abdul Wahab
Keyword(s):  
Composite Material ◽  
Carbon Fiber ◽  
Wind Turbine ◽  
Hybrid Composite ◽  
Turbine Blades ◽  
Basalt Fiber ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Wind Turbine Blades ◽  
Wind Turbine Rotor

Wind turbine blades are the major structural element and highest cost component in the wind power system. Modern wind turbine blade sizes are increasing, and the driving motivation behind this is to increase the efficiency and energy output per unit rotor area, and to reduce the cost per kilowatt hour. However due to the increase in size the material selection for wind turbine has become critical and complex. To achieve the desired materials to improve the design of wind turbine blades several factors such as high fatigue strength, less weight, less cost and potential of recycling must be focused. Basalt fiber is a relative newcomer to fiber reinforced polymers and structural composites. Basalt fiber with their excellent mechanical properties represents an interesting alternative composite material for modern wind turbine blades. Some manufacturers claim that basalt fiber has similar or better properties than S-2 glass fiber and its cheaper than carbon fiber. Basalt fiber together with carbon fiber are the most advanced and interesting area of hybrid technologies. This paper reviews extra ordinary properties of basalt fiber over other fiber reinforced composites and highlight how the basalt special properties together with carbon fiber will reduce the weight and cost of wind turbine blades while improving their performance. This paper also demonstrates why the basalt carbon hybrid composite material will be an ideal alternative for the wind turbine rotor blades.

scholarly journals Development of High Performance Airfoils for Application in Small Wind Turbine Power Generation

2020 ◽  
Vol 2020 ◽  
pp. 1-9 ◽  
Author(s):  
Emmanuel Yeboah Osei ◽  
Richard Opoku ◽  
Albert K. Sunnu ◽  
Muyiwa S. Adaramola
Keyword(s):  
Power Generation ◽  
Wind Turbine ◽  
High Performance ◽  
Turbine Blades ◽  
Turbine Rotor ◽  
Wind Turbine Blades ◽  
Small Wind Turbine ◽  
Stall Angle ◽  
Power Generation Systems ◽  
Drag Ratio

Small wind turbine power generation systems have the potential to meet the electricity demand of the residential sector in developing countries. However, due to their exposure to low Reynolds number (Re) flow conditions and associated problems, specific airfoils are required for the design of their blades. In this research, XFOIL was used to develop and test three high performance airfoils (EYO7-8, EYO8-8, and EYO9-8) for small wind turbine application. The airfoils were subsequently used in conjunction with Blade Element Momentum Theory to develop and test 3-bladed 6 m diameter wind turbine rotors. The aerodynamic performance parameters of the airfoils tested were lift, drag, lift-to-drag ratio, and stall angle. At Re=300,000, EYO7-8, EYO8-8, and EYO9-8 had maximum lift-to-drag ratios of 134, 131, and 127, respectively, and maximum lift coefficients of 1.77, 1.81, and 1.81, respectively. The stall angles were 12° for EYO7-8, 14° for EYO8-8, and 15° for EYO9-8. Together, the new airfoils compared favourably with other existing low Re airfoils and are suitable for the design of small wind turbine blades. Analysis of the results showed that the performance improvement of the EYO-Series airfoils is as a result of the design optimization that employed an optimal thickness-to-camber ratio (t/c) in the range of 0.85–1.50. Preliminary wind turbine rotor analysis also showed that the EYO7-8, EYO8-8, and EYO9-8 rotors had maximum power coefficients of 0.371, 0.366, and 0.358, respectively.

Performance Effects of Leading Edge Tubercles on the NREL Phase VI Wind Turbine Blade

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Giada Abate ◽  
Dimitri N. Mavris ◽  
Lakshmi N. Sankar
Keyword(s):  
Wind Turbine ◽  
Turbine Blades ◽  
Leading Edge ◽  
Wind Turbine Blades ◽  
Wind Speeds ◽  
Variable Nature ◽  
Performance Effects ◽  
Computational Fluid Dynamics Cfd ◽  
Nrel Phase Vi ◽  
Positive Effect

Several studies on wind energy have been conducted to find possible solutions to power issues related to the variable nature of the wind. One of the most promising seems to be the application of sinusoidal modifications (tubercles) on the leading edge of wind turbine blades. In the present work, a systematic study on the effects of different tubercle configurations on NREL phase VI wind turbine performance is conducted. A design of experiments is used to generate blades with different tubercle amplitude and wavelength that are then simulated by a computational fluid dynamics (CFD) analysis. The resulting power and annual energy production (AEP) are compared with the baseline values noticing a positive effect of tubercles on the power at high wind speeds.

PERFORMANCE EVALUATION AND WAKE STUDY OF A MICRO WIND TURBINE

2011 ◽  
Vol 35 (1) ◽  
pp. 101-117 ◽  
Author(s):  
Graeme I. Comyn ◽  
David S. Nobes ◽  
Brian A. Fleck
Keyword(s):  
Wind Tunnel ◽  
Wind Turbine ◽  
Power Output ◽  
Turbine Blades ◽  
Turbine Rotor ◽  
Published Data ◽  
Wind Turbine Blades ◽  
Axial Thrust ◽  
Cross Sectional ◽  
Output Performance

In preparation for a study on icing of wind turbine blades, we tested a horizontal axis micro wind turbine in a low speed wind tunnel. The ratio of wind turbine rotor area to wind tunnel cross-sectional area resulted in highly blocked experimental configuration. The turbine was instrumented to measure rotational speed of the rotor, axial thrust and power output. Performance characteristics were calculated and compared with the manufacturer’s published data. In addition, the near wake of the turbine was measured with a Kiel probe. One dimensional axial momentum theory, including a modification that includes channel walls, was applied to determine power extracted from the wind by the rotor. The results were compared to actual power output and show that though the assumptions of the model over-predict power by 50 % the basic trend is followed.

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