scholarly journals Active flap control with the trailing edge flap hinge moment as a sensor: using it to estimate local blade inflow conditions and to reduce extreme blade loads and deflections

2021 ◽  
Vol 6 (3) ◽  
pp. 791-814
Author(s):  
Sebastian Perez-Becker ◽  
David Marten ◽  
Christian Oliver Paschereit
Keyword(s):  
Wind Turbine ◽  
Angle Of Attack ◽  
Bending Moment ◽  
Turbulent Wind ◽  
Extreme Loads ◽  
Out Of Plane ◽  
Blade Section ◽  
Inflow Conditions ◽  
Local Angle ◽  
Relative Wind

Abstract. Active trailing edge flaps are a promising technology that can potentially enable further increases in wind turbine sizes without the disproportionate increase in loads, thus reducing the cost of wind energy even further. Extreme loads and critical deflections of the blade are design-driving issues that can effectively be reduced by flaps. In this paper, we consider the flap hinge moment as a local input sensor for a simple flap controller that reduces extreme loads and critical deflections of the DTU 10 MW Reference Wind Turbine blade. We present a model to calculate the unsteady flap hinge moment that can be used in aeroelastic simulations in the time domain. This model is used to develop an observer that estimates the local angle of attack and relative wind velocity of a blade section based on local sensor information including the flap hinge moment of the blade section. For steady wind conditions that include yawed inflow and wind shear, the observer is able to estimate the local inflow conditions with errors in the mean angle of attack below 0.2∘ and mean relative wind speed errors below 0.4 %. For fully turbulent wind conditions, the observer is able to estimate the low-frequency content of the local angle of attack and relative velocity even when it is lacking information on the incoming turbulent wind. We include this observer as part of a simple flap controller to reduce extreme loads and critical deflections of the blade. The flap controller's performance is tested in load simulations of the reference turbine with active flaps according to the IEC 61400-1 power production with extreme turbulence group. We used the lifting line free vortex wake method to calculate the aerodynamic loads. Results show a reduction of the maximum out-of-plane and resulting blade root bending moments of 8 % and 7.6 %, respectively, when compared to a baseline case without flaps. The critical blade tip deflection is reduced by 7.1 %. Furthermore, a sector load analysis considering extreme loading in all load directions shows a reduction of the extreme resulting bending moment in an angular region covering 30∘ around the positive out-of-plane blade root bending moment. Further analysis reveals that a fast reaction time of the flap system proves to be critical for its performance. This is achieved with the use of local sensors as input for the flap controller. A larger reduction potential of the system is identified but not reached mainly because of a combination of challenging controller objectives and the simple controller architecture.

scholarly journals Active Flap Control with the Trailing Edge Flap Hinge Moment as a Sensor: Using it to Estimate Local Blade Inflow Conditions and to Reduce Extreme Blade Loads and Deflections

2021 ◽  
Author(s):  
Sebastian Perez-Becker ◽  
David Marten ◽  
Christian Oliver Paschereit
Keyword(s):  
Wind Turbine ◽  
Angle Of Attack ◽  
Bending Moment ◽  
Turbulent Wind ◽  
Extreme Loads ◽  
Out Of Plane ◽  
Blade Section ◽  
Inflow Conditions ◽  
Local Angle ◽  
Relative Wind

Abstract. Active trailing edge flaps are a promising technology that can potentially enable further increases in wind turbine sizes without the disproportionate increase in loads, thus reducing the cost of wind energy even further. Extreme loads and critical deflections of the blade are design driving issues that can effectively be reduced by flaps. In this paper, we consider the flap hinge moment as a local input sensor for a simple flap controller that reduces extreme loads and critical deflections of the DTU 10 MW Reference Wind Turbine blade. We present a model to calculate the unsteady flap hinge moment that can be used in aeroelastic simulations in the time domain. This model is used to develop an observer that estimates the local angle of attack and relative wind velocity of a blade section based on local sensor information including the flap hinge moment of the blade section. For steady wind conditions that include yawed inflow and wind shear, the observer is able to estimate the local inflow conditions with errors in the mean angle of attack below 0.2° and mean relative wind speed errors below 0.4 %. For fully turbulent wind conditions, the observer is able to estimate the low frequency content of the local angle of attack and relative velocity even when it is lacking information on the incoming turbulent wind. We include this observer as part of a simple flap controller to reduce extreme loads and critical deflections of the blade. The flap controller’s performance is tested in load simulations of the reference turbine with active flaps according to the IEC 61400-1 power production with extreme turbulence group. We used the lifting line free vortex wake method to calculate the aerodynamic loads. Results show a reduction of the maximum out-of-plane and resulting blade root bending moment of 8 % and 7.6 % respectively when compared to a baseline case without flaps. The critical blade tip deflection is reduced by 7.1 %. Furthermore, a sector load analysis considering extreme loading in all load directions shows a reduction of the extreme resulting bending moment in an angular region covering 30° around the positive out-of-plane blade root bending moment. Further analysis reveals that a fast reaction time of the flap system proves to be critical for its performance. This is achieved with the use of local sensors as input for the flap controller. A larger reduction potential of the system is identified but not reached mainly because of a combination of challenging controller objectives and the simple controller architecture.

Blade Element Momentum Study of Rotor Aerodynamic Performance and Loading for Active and Passive Microjet Systems

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Owen F. Hurley ◽  
Raymond Chow ◽  
Myra L. Blaylock ◽  
Aubryn M. Cooperman ◽  
C. P. van Dam
Keyword(s):  
Wind Turbine ◽  
Energy Input ◽  
Bending Moment ◽  
Load Reduction ◽  
Wind Condition ◽  
Flow Energy ◽  
Extreme Loads ◽  
Air Supply ◽  
Blade Section ◽  
Blade Element

This study investigates the performance of microjets for load reduction on the NREL-5 MW wind turbine and identifies optimal system parameters. Microjets provide blowing normal to the blade surface and can rapidly increase or decrease lift on a blade section, enabling a wind turbine to respond to local, short-term changes in wind condition. As wind turbine rotors become larger, control methods that act on a single blade or blade section are increasingly necessary to reduce critical fatigue and extreme loads. However, microjets require power to operate, and thus, it is crucial that the fatigue reduction justifies any energy input to the system. To examine the potential for fatigue reduction of a range of potential microjet system configurations, a blade element momentum (BEM) code and a flow energy solver were used to estimate the energy input and the change in primary fatigue metrics. A parametric analysis was conducted to identify the optimal spanwise position and length of the microjets over a range of air mass flow rates. Both active and passive air supply methods were considered. A passive microjet system applied to the NREL 5-MW rotor produced a 3.7% reduction in the maximum flapwise root bending moment (FRBM). The reduction in the peak bending moment increased to 6.0% with a 5 kPa blower that consumes approximately 0.1% of the turbine output power. The most effective configurations placed microjets between the blade midspan to three-quarters span. Load reduction was achieved for both active and passive modes of air supply to the microjet system.

scholarly journals Brief communication: Extraction of the wake induction and angle of attack on rotating wind turbine blades from PIV and CFD results

2017 ◽  
Author(s):  
Iván Herráez ◽  
Elia Daniele ◽  
J. Gerard Schepers
Keyword(s):  
New Mexico ◽  
Wind Turbine ◽  
Turbine Blades ◽  
Angle Of Attack ◽  
Accurate Information ◽  
Wind Turbine Blades ◽  
Cfd Simulations ◽  
Wind Turbine Aerodynamics ◽  
First Time ◽  
Local Angle

Abstract. The analysis of wind turbine aerodynamics requires accurate information about the axial and tangential wake induction as well as the local angle of attack along the blades. In this work, we present a new method for obtaining them conveniently from the velocity field. We apply the method to the New Mexico PIV-dataset and to CFD simulations of the same turbine. This allows comparing for the first time experimental and numerical results of the mentioned quantities on a rotating wind turbine. The presented results open up new possibilities for the validation of numerical rotor models.

scholarly journals Numerical Analysis of the Effect of Offshore Turbulent Wind Inflow on the Response of a Spar Wind Turbine

Energies ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2506
Author(s):  
Rieska Mawarni Putri ◽  
Charlotte Obhrai ◽  
Jasna Bogunovic Jakobsen ◽  
Muk Chen Ong
Keyword(s):  
Wind Turbine ◽  
Energy Content ◽  
Atmospheric Stability ◽  
Bending Moment ◽  
Turbulent Energy ◽  
Offshore Wind ◽  
Stability Conditions ◽  
Turbulent Wind ◽  
Base Side ◽  
Side Bending

Turbulent wind at offshore sites is known as the main cause for fatigue on offshore wind turbine components. Numerical simulations are commonly used to predict the loads and motions of floating offshore wind turbines; however, the definition of representative wind input conditions is necessary. In this study, the load and motion responses of a spar-type Offshore Code Comparison Collaboration (OC3) wind turbine under different turbulent wind conditions is studied and investigated by using SIMO-Riflex in Simulation Workbench for Marine Applications (SIMA) workbench. Using the two spectral models given in the International Electrotechnical Commission (IEC) standards, it is found that a lower wind lateral coherence under neutral atmospheric stability conditions results in an up to 27% higher tower base side–side bending moment and a 20% higher tower top torsional moment. Comparing different atmospheric stability conditions simulated using a spectral model based on FINO1 wind data measurement, the highest turbulent energy content under very unstable conditions yields a 26% higher tower base side–side bending moment and a 27% higher tower top torsional moment than neutral conditions, which have the lowest turbulent energy content and turbulent intensity. The yaw-mode of the OC3 wind turbine is found to be the most influenced component by assessing variations in both the lateral coherence and the atmospheric stability conditions.

scholarly journals Evaluation of different methods of determining the angle of attack on wind turbine blades under yawed inflow conditions

2018 ◽  
Vol 1037 ◽  
pp. 022028 ◽  
Author(s):  
K. Vimalakanthan ◽  
J.G Schepers ◽  
W.Z Shen ◽  
H. Rahimi ◽  
D. Micallef ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Turbine Blades ◽  
Angle Of Attack ◽  
Wind Turbine Blades ◽  
Inflow Conditions

scholarly journals Predicting the Extreme Loads in Power Production of Large Wind Turbines Using an Improved PSO Algorithm

2019 ◽  
Vol 9 (3) ◽  
pp. 521 ◽  
Author(s):  
Caicai Liao ◽  
Kezhong Shi ◽  
XiaoLu Zhao
Keyword(s):  
Control System ◽  
Wind Turbine ◽  
Pitch Angle ◽  
Bending Moment ◽  
Pso Algorithm ◽  
Power Production ◽  
Bending Moments ◽  
Rotor Speed ◽  
Blade Root ◽  
Extreme Loads

Predicting the extreme loads in power production for the preliminary-design of large-scale wind turbine blade is both important and time consuming. In this paper, a simplified method, called Particle Swarm Optimization-Extreme Load Prediction Model (PSO-ELPM), is developed to quickly assess the extreme loads. This method considers the extreme loads solution as an optimal problem. The rotor speed, wind speed, pitch angle, yaw angle, and azimuth angle are selected as design variables. The constraint conditions are obtained by considering the influence of the aeroelastic property and control system of the wind turbine. An improved PSO algorithm is applied. A 1.5 MW and a 2.0 MW wind turbine are chosen to validate the method. The results show that the extreme root load errors between PSO-ELPM and FOCUS are less than 10%, while PSO-ELPM needs much less computational cost than FOCUS. The distribution of flapwise bending moments are close to the results of FOCUS. By analyzing the loads, we find that the extreme flapwise bending moment of the blade root in chord coordinate (CMF_ROOT) is largely reduced because of the control system, with the extreme edgewise bending moment of the blade root in chord coordinate (CME_ROOT) almost unchanged. Furthermore, higher rotor speed and smaller pitch angle will generate larger extreme bending moments at the blade root.

scholarly journals Evaluation of different methods for determining the angle of attack on wind turbine blades with CFD results under axial inflow conditions

2018 ◽  
Vol 125 ◽  
pp. 866-876 ◽  
Author(s):  
H. Rahimi ◽  
J.G. Schepers ◽  
W.Z. Shen ◽  
N. Ramos García ◽  
M.S. Schneider ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Turbine Blades ◽  
Angle Of Attack ◽  
Wind Turbine Blades ◽  
Inflow Conditions

scholarly journals Is the Blade Element Momentum theory overestimating wind turbine loads? – An aeroelastic comparison between OpenFAST's AeroDyn and QBlade's Lifting-Line Free Vortex Wake method

2020 ◽  
Vol 5 (2) ◽  
pp. 721-743
Author(s):  
Sebastian Perez-Becker ◽  
Francesco Papi ◽  
Joseph Saverin ◽  
David Marten ◽  
Alessandro Bianchini ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Bending Moment ◽  
Vortex Wake ◽  
Free Vortex ◽  
Aerodynamic Loads ◽  
Blade Root ◽  
Out Of Plane ◽  
Design Loads ◽  
Lifting Line ◽  
Blade Element

Abstract. Load calculations play a key role in determining the design loads of different wind turbine components. To obtain the aerodynamic loads for these calculations, the industry relies heavily on the Blade Element Momentum (BEM) theory. BEM methods use several engineering correction models to capture the aerodynamic phenomena present in Design Load Cases (DLCs) with turbulent wind. Because of this, BEM methods can overestimate aerodynamic loads under challenging conditions when compared to higher-order aerodynamic methods – such as the Lifting-Line Free Vortex Wake (LLFVW) method – leading to unnecessarily high design loads and component costs. In this paper, we give a quantitative answer to the question of load overestimation of a particular BEM implementation by comparing the results of aeroelastic load calculations done with the BEM-based OpenFAST code and the QBlade code, which uses a particular implementation of the LLFVW method. We compare extreme and fatigue load predictions from both codes using sixty-six 10 min load simulations of the Danish Technical University (DTU) 10 MW Reference Wind Turbine according to the IEC 61400-1 power production DLC group. Results from both codes show differences in fatigue and extreme load estimations for the considered sensors of the turbine. LLFVW simulations predict 9 % lower lifetime damage equivalent loads (DELs) for the out-of-plane blade root and the tower base fore–aft bending moments compared to BEM simulations. The results also show that lifetime DELs for the yaw-bearing tilt and yaw moments are 3 % and 4 % lower when calculated with the LLFVW code. An ultimate state analysis shows that extreme loads of the blade root out-of-plane bending moment predicted by the LLFVW simulations are 3 % lower than the moments predicted by BEM simulations. For the maximum tower base fore–aft bending moment, the LLFVW simulations predict an increase of 2 %. Further analysis reveals that there are two main contributors to these load differences. The first is the different way both codes treat the effect of the nonuniform wind field on the local blade aerodynamics. The second is the higher average aerodynamic torque in the LLFVW simulations. It influences the transition between operating modes of the controller and changes the aeroelastic behavior of the turbine, thus affecting the loads.

scholarly journals Wind inflow observation from load harmonics

2017 ◽  
Author(s):  
Marta Bertelè ◽  
Carlo L. Bottasso ◽  
Stefano Cacciola ◽  
Fabiano Daher Adegas ◽  
Sara Delport
Keyword(s):  
Numerical Simulations ◽  
Wind Turbine ◽  
Wind Field ◽  
Wind Farm ◽  
High Fidelity ◽  
Bending Moments ◽  
Turbulent Wind ◽  
Out Of Plane ◽  
Wind Characteristics ◽  
Blade Loads

Abstract. The wind field leaves its fingerprint on the rotor response. This fact can be exploited to use the rotor as a sensor: by looking at the rotor response, in the present case in terms of blade loads, one may infer the wind characteristics. This paper describes a wind state observer that estimates four wind parameters, namely the vertical and horizontal shears and the yaw and upflow misalignment angles, from out-of-plane and in-plane blade bending moments. The resulting observer provides on-rotor wind inflow characteristics that can be exploited for wind turbine and wind farm control. The proposed formulation is evaluated by extensive numerical simulations in turbulent and non-turbulent wind conditions using a high-fidelity aeroservoelastic model of a multi-MW wind turbine.

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