Load Alleviation on Wind Turbines using Camber Morphing Blade Tip

2018 ◽  
Author(s):  
Etana Ferede ◽  
Farhan Gandhi
Keyword(s):  
Wind Turbines ◽  
Blade Tip

scholarly journals Numerical Simulations of Novel Conning Designs for Future Super-Large Wind Turbines

2020 ◽  
Vol 11 (1) ◽  
pp. 147
Author(s):  
Zhenye Sun ◽  
Weijun Zhu ◽  
Wenzhong Shen ◽  
Qiuhan Tao ◽  
Jiufa Cao ◽  
...  
Keyword(s):  
Wind Turbines ◽  
Cone Angle ◽  
Angle Of Attack ◽  
Normal Direction ◽  
Velocity Decomposition ◽  
New Concepts ◽  
Blade Tip ◽  
Tip Position ◽  
Large Wind ◽  
Lower Angle

In order to develop super-large wind turbines, new concepts, such as downwind load-alignment, are required. Additionally, segmented blade concepts are under investigation. As a simple example, the coned rotor needs be investigated. In this paper, different conning configurations, including special cones with three segments, are simulated and analyzed based on the DTU-10 MW reference rotor. It was found that the different force distributions of upwind and downwind coned configurations agreed well with the distributions of angle of attack, which were affected by the blade tip position and the cone angle. With the upstream coning of the blade tip, the blade sections suffered from stronger axial induction and a lower angle of attack. The downstream coning of the blade tip led to reverse variations. The cone angle determined the velocity and force projecting process from the axial to the normal direction, which also influenced the angle of attack and force, provided that correct inflow velocity decomposition occurred.

scholarly journals Active control of wind turbines through varying blade tip sweep

2019 ◽  
Vol 131 ◽  
pp. 25-36 ◽  
Author(s):  
Achilles M. Boulamatsis ◽  
Thanasis K. Barlas ◽  
Herricos Stapountzis
Keyword(s):  
Active Control ◽  
Wind Turbines ◽  
Blade Tip

Implementation of Computational Methods to Obtain Accurate Induction Factors for Offshore Wind Turbines

2014 ◽  
Author(s):  
Anand Bahuguni ◽  
Krishnamoorthi Sivalingam ◽  
Peter Davies ◽  
Johan Gullman-Strand ◽  
Vinh Tan Nguyen
Keyword(s):  
Wind Turbines ◽  
Lift Coefficient ◽  
Offshore Wind ◽  
Cfd Simulations ◽  
Sea State ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines ◽  
Blade Tip ◽  
Computational Fluid Dynamics Cfd ◽  
Blade Element

Most of the wind turbine analysis softwares widely being used in the market are based on the Blade Element Momentum method (BEM). The two important parameters that the BEM codes calculate are the axial and the tangential induction factors. These factors are calculated based on the empirical blade lift coefficient Cl and drag coefficient Cd along with some loss/correction functions to account for the losses near the blade tip and the hub. The current study focusses on verifying the values of induction factors using Computational Fluid Dynamics (CFD) simulations for floating offshore wind turbines at a selected sea state. The study includes steady state calculations as well as transient calculations for pitching motions of the turbine due to waves. The NREL FAST software is used to set the simulation scenarios according to OC3 Phase IV cases. The blades are divided a number of elements in CFD calculations and the data are extracted at individual elements to have an exact comparison with the BEM based calculations.

scholarly journals Land-based wind turbines with flexible rail-transportable blades – Part 1: Conceptual design and aeroservoelastic performance

2021 ◽  
Vol 6 (5) ◽  
pp. 1277-1290
Author(s):  
Pietro Bortolotti ◽  
Nick Johnson ◽  
Nikhar J. Abbas ◽  
Evan Anderson ◽  
Ernesto Camarena ◽  
...  
Keyword(s):  
Carbon Fiber ◽  
Wind Turbine ◽  
Conceptual Design ◽  
Wind Turbines ◽  
State Of The Art ◽  
Levelized Cost ◽  
Cost Of Energy ◽  
Blade Tip ◽  
Turbine Rotors ◽  
Future Work

Abstract. This work investigates the conceptual design and the aeroservoelastic performance of land-based wind turbines whose blades can be transported on rail via controlled bending. The turbines have a nameplate power of 5 MW and a rotor diameter of 206 m, and they aim to represent the next generation of land-based machines. Three upwind designs and two downwind designs are presented, combining different design goals together with conventional glass and pultruded carbon fiber laminates in the spar caps. One of the five blade designs is segmented and serves as a benchmark to the state of the art in industry. The results show that controlled flexing requires a reduction in the flapwise stiffness of the blades, but it represents a promising pathway for increasing the size of land-based wind turbine rotors. Given the required stiffness, the rotor can be designed either downwind with standard rotor preconing and nacelle uptilt angles or upwind with higher-than-usual angles. A downwind-specific controller is also presented, featuring a cut-out wind speed reduced to 19 m s−1 and a pitch-to-stall shutdown strategy to minimize blade tip deflections toward the tower. The flexible upwind and downwind rotor designs equipped with pultruded carbon fiber spar caps are found to generate the lowest levelized cost of energy, 2.9 % and 1.3 %, respectively, less than the segmented design. The paper concludes with several recommendations for future work in the area of large flexible wind turbine rotors.

scholarly journals Active control of wind turbines through varying blade tip sweep

2017 ◽  
Author(s):  
Αχιλλεύς Μπουλαμάτσης
Keyword(s):  
Active Control ◽  
Wind Turbines ◽  
Blade Tip ◽  
Lifting Line ◽  
Blade Element

Σε αυτή την ερευνητική εργασία παρουσιάζεται ένας πρωτότυπος τρόπος ελέγχου των ανεμογεννητριών οριζόντιου άξονα. Η ιδέα αυτή, αναφέρεται σε πτερύγια ανεμογεννήτριας μεταβλητής γωνίας οπισθόκλισης των ακροπτερύγιων τους, τα οποία έχουν την ικανότητα να περιστρέφονται συλλογικά (κίνηση εντός επιπέδου περιστροφής του ρότορα) γύρω από έναν άξονα που βρίσκεται επάνω στα πτερυγία. Το οπισθοκλινές ακροπτερύγιο μπορεί να είναι τμήμα του υπάρχοντος πτερυγίου με ενσωματωμένο μηχανισμό ή προέκταση αυτού. Η ιδέα αυτού του πρωτότυπου τρόπου ενεργού ελέγχου, έχει ως σκοπό την αύξηση της παραγώμενης ενέργειας σε συγκεκριμένες περιοχές λειτουργίας, τη μείωση των φορτίων κόπωσης των πτερυγίων καθώς και των υψηλών φορτίων κατά τη διάρκεια μίας ριπής ανέμου που διέρχεται από την ανεμογεννήτρια, μέσω της μεταβολής της γωνίας οπισθόκλισης των ακροπτερυγίων του ρότορα. Η έρευνα διεξάγεται με ένα κατάλληλα τροποποιημένο μοντέλο βασισμένο στη θεωρία Blade Element Momentum (BEM) ώστε να λαμβάνεται υπόψη η επίδραση του οπισθοκλινούς ακροπτερυγίου και η τροποποίηση αυτή βασίστηκε στα αποτελέσματα που προκύπτουν από ένα αντίστοιχο μοντέλο βασισμένο στη θεωρία Lifting Line. Τα αποτελέσματα από το τελευταίο μοντέλο συγκρίθηκαν επίσης με αποτελέσματα που προέκυψαν από αντίστοιχα μοντέλα υπολογιστικής ρευστομηχανικής (CFD) και επιπλέον έγινε προσπάθεια επιτάχυνσης των υπολογισμών (με χρήση CUDA platform) που εκτελούνται εντός του μοντέλου (Lifting Line) πριν αυτό χρησιμοποιηθεί ως σημείο αναφοράς για την τροποποίηση του μοντέλου BEM. Οι προσομοιώσεις αφορούν την 5MW NREL ανεμογεννήτρια αναφοράς που ενσωματώνει ένα κατάλληλο ελεγκτή και τα πρώτα αποτελέσματα δείχνουν ωφέλιμη συμπεριφορά σε όλες τους τομείς που μελετήθηκε η επίδρασή του.

Calculation of the Water Droplets Local Collection Efficiency on the Wind Turbines Blade

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Liangquan Hu ◽  
Xiaocheng Zhu ◽  
Chenxing Hu ◽  
Jinge Chen ◽  
Zhaohui Du
Keyword(s):  
Wind Turbines ◽  
Collection Efficiency ◽  
Three Dimensional ◽  
Lower Surface ◽  
Cold Climate ◽  
Test Cases ◽  
Water Droplets ◽  
Blade Tip ◽  
Air Flow Velocity ◽  
3D Effect

Wind turbines operating in cold climate are susceptible to icing events. In order to gain a better understanding of the blade icing, the water droplets local collection efficiency affected by different factors was investigated. First, the water droplets conservation equations which are based on the fluent user-defined scalar (UDS) were introduced. Second, the Eulerian method was validated. Two test cases indicate that the developed method is effective. Then, the local collection efficiency on the S809 airfoil was studied. Results show that as the angle of attack (AOA) increases, the water droplets impingement region moves toward the airfoil lower surface and the maximum local collection efficiency decreases. The local collection efficiency and the impingement region increase with the water droplets diameter and the air flow velocity but decrease with the airfoil chord length. Finally, the local collection efficiency affected by the three-dimensional (3D) effect was studied. Results show that the maximum local collection efficiency in the blade tip region decreases up to 96.29% due to the 3D effect.

On the Design of Horizontal Axis Two-Bladed Hinged Wind Turbines

1984 ◽  
Vol 106 (2) ◽  
pp. 171-176 ◽  
Author(s):  
K. H. Hohenemser ◽  
A. H. P. Swift
Keyword(s):  
Angular Velocity ◽  
Wind Turbines ◽  
Horizontal Axis ◽  
Dynamic Loads ◽  
Helicopter Rotors ◽  
Blade Tip ◽  
Velocity Variations ◽  
Large Wind

Hinged two-bladed wind turbines are not necessarily free of disturbing vibrations. The combination of elastic or built-in blade coning with blade flapping about a conventional teeter hinge produces periodic blade angular velocity variations in the blade tip path plane with associated vibrations and dynamic loads. The paper discusses and evaluates various hinge configurations for two-bladed rotors and shows why the conventional teeter hinge leads to nonuniform blade angular velocity in the blade tip path plane. The solution to this problem adopted for two-bladed helicopter rotors, though complex, could be of interest for large wind turbines. A much simpler solution, calling for the suppression of blade flapping by passive blade cyclic pitch variation produced by a strong negative pitch-flap coupling, was found to be practical for upwind tail vane stabilized two-bladed wind turbines.

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