Vibrations of a Three-Bladed Wind Turbine Rotor Due to Classical Flutter

2002 ◽  
Author(s):  
M. H. Hansen
Keyword(s):  
Wind Turbine ◽  
Critical Frequency ◽  
Turbine Blades ◽  
Turbine Rotor ◽  
Normal Operation ◽  
Aerodynamic Damping ◽  
Operation Conditions ◽  
Torsional Frequency ◽  
Classical Flutter ◽  
Wind Turbine Rotor

The aeroelastic stability of a three-bladed wind turbine is considered with respect to classical flutter. Previous studies have shown that the risk of stall-induced vibrations of turbine blades is related to the dynamics of the complete turbine, for example does the aerodynamic damping of a rotor whirling mode depend highly on the tower stiffness. The results of this paper indicate that the turbine dynamics also affect the risk of flutter. The study is based on an eigenvalue analysis of a linear aeroelastic turbine model. In an example of a MW sized turbine, the critical frequency of the first torsional blade mode is determined for which flutter can occur under normal operation conditions. It is shown that this critical torsional frequency is higher when the blades are interacting through the hub with the remaining turbine, than when all blades are rigidly clamped at the root. Thus, the dynamics of the turbine has increased the risk of flutter.

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.

scholarly journals Design Studies for Twist-Coupled Wind Turbine Blades

2003 ◽  
Author(s):  
James Locke ◽  
Ulyses Valencia ◽  
Kosuke Ishikawa
Keyword(s):  
Wind Turbine ◽  
Rotor Blade ◽  
Turbine Blades ◽  
Load Condition ◽  
Turbine Rotor ◽  
Unit Load ◽  
Baseline Design ◽  
Turbine Rotor Blade ◽  
Extreme Wind ◽  
Wind Turbine Rotor

This study presents results obtained for three designs of the Northern Power Systems (NPS) 9.2-meter version of the ERS-100 wind turbine rotor blade. The ERS-100 wind turbine rotor blade was designed and developed by TPI composites. The baseline design uses e-glass unidirectional fibers in combination with ±45-degree and random mat layers for the skin and spar cap. This project involves developing structural finite element models of the baseline design and carbon hybrid designs with twist-bend coupling. All designs were evaluated for a unit load condition and two extreme wind conditions. The unit load condition was used to evaluate the static deflection, twist and twist-coupling parameter. Maximum deflections and strains were determined for the extreme wind conditions. Buckling eigenvalues were determined for a tip load condition. The results indicate that carbon fibers can be used to produce twist-coupled designs with comparable deflections, strains and buckling loads.

scholarly journals Optimum Power Output Control of a Wind Turbine Rotor

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
S. Wijewardana ◽  
M. H. Shaheed ◽  
R. Vepa
Keyword(s):  
Equilibrium Point ◽  
Wind Turbine ◽  
Power Output ◽  
Turbine Blades ◽  
Turbine Rotor ◽  
Power Coefficient ◽  
Output Control ◽  
The Stability ◽  
Lift And Drag ◽  
Wind Turbine Rotor

An active and optimum controller is applied to regulate the power output from a wind turbine rotor. The controller is synthesized in two steps. The first step defines the equilibrium operation point and ensures that the desired equilibrium point is stable. The stability of the equilibrium point is guaranteed by a control law that is synthesized by applying the methodology of model predictive control (MPC). The method of controlling the turbine involves pitching the turbine blades. In the second step the blade pitch angle demand is defined. This involves minimizing the mean square error between the actual and desired power coefficient. The actual power coefficient of the wind turbine rotor is evaluated assuming that the blade is capable of stalling, using blade element momentum theory. This ensures that the power output of the rotor can be reduced to any desired value which is generally not possible unless a nonlinear stall model is introduced to evaluate the blade profile coefficients of lift and drag. The relatively simple and systematic nonlinear modelling and MPC controller synthesis approach adopted in this paper clearly highlights the main features on the controller that is capable of regulating the power output of the wind turbine rotor.

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.

Statistical extrapolation methods for estimating extreme loads on wind turbine blades under turbulent wind conditions and stochastic material properties

2020 ◽  
pp. 0309524X2093620
Author(s):  
Panagiotis N Schinas ◽  
Dimitris I Manolas ◽  
Vasilis A Riziotis ◽  
Theodore P Philippidis ◽  
Spyros G Voutsinas
Keyword(s):  
Wind Turbine ◽  
Material Properties ◽  
Ultimate Load ◽  
Turbine Blades ◽  
Turbine Rotor ◽  
Wind Turbine Blades ◽  
Extreme Loads ◽  
Certification Procedure ◽  
Peak Over Threshold ◽  
Wind Turbine Rotor

According to the IEC Standard 61400-1, designers of wind turbines are required to apply statistical extrapolation techniques to estimate the extreme (ultimate) load. In the present article, the certification procedure is assessed under the uncertainty of the material properties using a simulated load time series of the National Renewable Energy Laboratory 5MW reference wind turbine rotor. The uncertainty of the material properties is introduced in the elastic properties of the composite materials based on the OptiDAT composite material database. The assessment relies on the comparison of the estimated blade extreme loads and deflections, obtained for the reference and the stochastically varied material properties. It is found that the variability of the material properties does not affect the estimated ultimate moments (differences < 1.5%) but affects the maximum flapwise deflection (differences ~8%). It is concluded that the peak over threshold peak extraction technique and the three-parameter Weibull fitting functions outperform among those considered in the article.

Computation of Modal Aerodynamic Damping Using CFD

2003 ◽  
Author(s):  
F. Bertagnolio ◽  
M. Gaunaa ◽  
N. N. So̸rensen ◽  
M. Hansen ◽  
F. Rasmussen
Keyword(s):  
Wind Turbine ◽  
Structural Model ◽  
Turbine Rotor ◽  
Dynamic Stall ◽  
Navier Stokes ◽  
Test Cases ◽  
Flow Solver ◽  
Aerodynamic Damping ◽  
Semi Empirical ◽  
Wind Turbine Rotor

This work focuses on the numerical evaluation of aerodynamic damping for a wind turbine rotor. A finite beam element code is used to describe the structure. Two types of aerodynamic models are compared. Firstly, two engineering semi-empirical dynamic stall models implemented in the structural code for modelling the aerodynamic forces are applied. Secondly, a Navier-Stokes flow solver has been coupled to the structural model. Test cases involving a two-bladed wind turbine rotor are computed. The aerodynamic damping is determined for the two first eigenmodes of the structure. A comparison study of the results highlights the discrepancies between the different models.

Harmonization of new wind turbine rotor blades development process: A review

2014 ◽  
Vol 39 ◽  
pp. 874-882 ◽  
Author(s):  
B. Rašuo ◽  
M. Dinulović ◽  
A. Veg ◽  
A. Grbović ◽  
A. Bengin
Keyword(s):  
Wind Turbine ◽  
Development Process ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Wind Turbine Rotor
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