Towards Active Flow Control on a Research Scale Wind Turbine Using PID controlled Trailing Edge Flaps

2018 ◽  
Author(s):  
Sirko Bartholomay ◽  
Grigoris Michos ◽  
Sebastian Perez-Becker ◽  
George Pechlivanoglou ◽  
Christian Nayeri ◽  
...  
Keyword(s):  
Flow Control ◽  
Wind Turbine ◽  
Active Flow Control ◽  
Trailing Edge ◽  
Trailing Edge Flaps ◽  
Active Flow

Dynamic Aeroelastic Response of Wind Turbine Rotors Under Active Flow Control

2019 ◽  
Author(s):  
Muraleekrishnan Menon ◽  
Fernando L. Ponta
Keyword(s):  
Flow Control ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Active Flow Control ◽  
Load Control ◽  
Aerodynamic Load ◽  
Trailing Edge ◽  
Trailing Edge Flaps ◽  
Utility Scale ◽  
Active Flow

Abstract The significance of wind power and the associated relevance of utility-scale wind turbines are becoming more prominent in tapping renewable sources for power. Operational wind turbines today rated at 8 MW have rotor diameters of 164 m. Economies-of-scale factor suggest a sustained growth in rotor size, forecasting the use of longer and heavier blades. This has led to an increased emphasis on studies related to improvements and innovations in aerodynamic load-control methodologies. Among several approaches to controlling the stochastic aerodynamics loads on wind turbine rotors, most popular is the pitch control. Widely used in operational wind turbines, conventional pitch control is an effective approach for long-term load variations. However, their application to mitigate short-term fluctuations have limitations that present a bottleneck for growth in rotor size. Sporadic changes occurring within short time scales near the turbine rotor have significant impact on the aeroelastic behavior of the blades, power generation, with long-term effects on the rotor life-span. Cyclic variations occurring within few seconds emphasize the need for swift response of control methods that counter the resulting adverse effects. Current study revolves around the need to evaluate innovative active load control techniques that can swiftly handle high frequency oscillations in dynamic loading of turbine rotors. This may result from sudden changes in wind conditions due to gusts, environmental effects like atmospheric boundary layer and uneven terrain, or from turbine design features and operating conditions such as tower shadow effects. The upward surge in rotor size is linked with a down-side for existing techniques in rotor control that now need to account for heavier blades and the associated inertia. For example, the pitching operation rotates the entire blade around its longitudinal axis to regulate angle of wind at specific blade sections, involving huge inertial loads associated with the entire blade. On the other hand, active flow-control devices (FCDs) have the potential to alleviate load variations through rapid aerodynamic trimming. Trailing-edge flaps are light weight attachments on blades that have gradually gained relevance in studies focused on wind turbine aerodynamics and active load control. This computational study presents an aeroelastic assessment of a benchmark wind turbine based on the NREL 5-MW Reference Wind Turbine (RWT), with added trailing-edge flaps for rapid load control. The standard blades used on the NREL 5-MW RWT rotor are aerodynamically modified to equip them with actively controllable fractional-chord trailing-edge flaps, along a selected span. The numerical code used in the study handles the complex multi-physics dynamics of a wind turbine based on a self-adaptive ODE algorithm that integrates the dynamics of the control system in to the coupled response of aerodynamics and structural deformations of the rotor. Using the 5-MW RWT as a reference, the blades are modified to add trailing-edge flaps with Clark Y profile and constant chord. Attached at chosen sections of the blade, these devices have a specific range of operational actuation angles. Numerical experiments cover scenarios relevant to the aeroelastic response of a rotor with such adapted blades under operating conditions observed in utility-scale wind turbines. These fractional-chord devices attached along short spans of the blades make them light weight devices that can be easily controlled using low power of actuation. This overcomes the bottleneck in active aerodynamic load control, giving flexibility to study a wider ranged of control strategies for utility-scale wind turbines of the future. Preliminary outcomes suggest that rapid active flow control has high potential in shaping the future of aerodynamic load control in wind turbines.

Trailing edge noise reduction of wind turbine blades by active flow control

Wind Energy ◽  
2014 ◽  
Vol 18 (5) ◽  
pp. 909-923 ◽  
Author(s):  
Alexander Wolf ◽  
Thorsten Lutz ◽  
Werner Würz ◽  
Ewald Krämer ◽  
Oksana Stalnov ◽  
...  
Keyword(s):  
Flow Control ◽  
Wind Turbine ◽  
Noise Reduction ◽  
Active Flow Control ◽  
Turbine Blades ◽  
Wind Turbine Blades ◽  
Trailing Edge ◽  
Trailing Edge Noise ◽  
Active Flow

High Efficiency Wind Turbine Using Co-Flow Jet Active Flow Control

2021 ◽  
Author(s):  
Kewei Xu ◽  
Gecheng Zha
Keyword(s):  
Flow Control ◽  
Wind Turbine ◽  
Flow Separation ◽  
Power Output ◽  
Pitch Angle ◽  
Active Flow Control ◽  
Horizontal Axis Wind Turbine ◽  
Negative Power ◽  
Freestream Velocity ◽  
Active Flow

Abstract This paper applies Co-flow Jet (CFJ) active flow control airfoil to a NREL horizontal axis wind turbine for power output improvement. CFJ is a zero-net-mass-flux active flow control method that dramatically increases airfoil lift coefficient and suppresses flow separation at a low energy expenditure. The 3D Reynolds Averaged Navier-Stokes (RANS) equations with one-equation Spalart-Allmaras (SA) turbulence model are solved to simulate the 3D flows of the wind turbines. The baseline wind turbine is the NREL 10.06m diameter phase VI wind turbine and is modified to a CFJ blade by implementing CFJ along the span. The baseline wind turbine performance is validated with the experiment at three wind speeds, 7m/s, 15m/s, and 25m/s. The predicted blade surface pressure distributions and power output agree well with the experimental measurements. The study indicates that the CFJ can enhance the power output at the condition where angle of attack is increased to the level that conventional wind turbine is stalled. At the speed of 7m/s that the NREL turbine is designed to achieve the optimum efficiency at the pitch angle of 3°, the CFJ turbine does not increase the power output. When the pitch angle is reduced by 13° to −10°, the baseline wind turbine is stalled and generates negative power output at 7m/s. But the CFJ wind turbine increases the power output by 12.3% assuming CFJ fan efficiency of 80% at the same wind speed. This is an effective method to extract more power from the wind at all speeds. It is particularly useful at low speeds to decrease cut-in speed and increase power output without exceeding the structure limit. At the freestream velocity of 15m/s and the CFJ momentum coefficient Cμ of 0.23, the net power output is increased by 207.7% assuming the CFJ fan efficiency of 80%, compared to the baseline wind turbine due to the removal of flow separation. The CFJ wind turbine appears to open a door to a new area of wind turbine efficiency improvement and adaptive control for optimal loading.

Closed-Loop Active Flow Control of the Wake of a Compressor Blade by Trailing-Edge Blowing

2015 ◽  
Author(s):  
Matthias Kiesner ◽  
Rudibert King
Keyword(s):  
Flow Control ◽  
Mass Flow ◽  
Closed Loop ◽  
Active Flow Control ◽  
Hammerstein Model ◽  
Robust Controller ◽  
Trailing Edge ◽  
Velocity Deficit ◽  
Reference Velocity ◽  
Active Flow

This paper presents a closed-loop active flow control strategy to reduce the velocity deficit of the wake of a compressor stator blade. The unsteady stator-rotor interaction, caused by the incoming stator wakes, generates fast changes of the rotor blade loading, affecting the stability and the performance of the overall compressor. Negative effects will be seen likewise when unsteady combustion concepts, such as a pulsed detonation, produce upstream disturbances. Furthermore, the periodic unsteady flow leads to additional undesired effects such as noise and blade vibrations. A controlled reliable manipulation of the stator wake is a way to handle these issues. Therefore, investigations on wake manipulation with trailing-edge blowing were carried out on a new low-speed cascade test rig. Detailed information about the wake profile is obtained by five-hole probe measurements in a plane downstream of the cascade for the natural and the actuated flow at a Reynolds number of 6×105. These measurements show a significant reduction of the wake velocity deficit for the investigated actuator geometry with an injection mass flow of less than 1% of the passage mass flow. Based on these results a position in the wake was chosen which is representative for the actuation impact on the velocity deficit. There, a hot-wire-probe measurement serves as the controlled variable. A family of linear dynamic black-box models was identified from experimental data to account for nonlinear and unmodelled effects. Static nonlinearitiy was compensated for by a Hammerstein model to reduce the model uncertainty and get a higher controller performance. To handle off-design conditions, a robust controller working in a range of Reynolds numbers from 5×105 to 7×105 was synthesized. The task of the controller is to rapidly regulate the controlled variable to a reference velocity by changing the blowing amplitude. The synthesized robust controller was successfully tested in closed-loop experiments with good results in reference tracking for pulse series up to 20 Hz. This translates into a much higher frequency when scaled to the dimension of a real machine.

Numerical investigation of active flow control with co-flowing jet in a horizontal axis wind turbine

2020 ◽  
pp. 0309524X2096139
Author(s):  
Fangrui Shi ◽  
Yingqiao Xu ◽  
Xiaojing Sun
Keyword(s):  
Flow Control ◽  
Wind Turbine ◽  
Performance Enhancement ◽  
Active Flow Control ◽  
Three Dimensional ◽  
Horizontal Axis ◽  
Suction Surface ◽  
Horizontal Axis Wind Turbine ◽  
Momentum Coefficient ◽  
Active Flow

In this paper, a three-dimensional numerical simulation of the aerodynamic performance of a horizontal axis wind turbine (HAWT) whose blades are equipped with a new active flow control concept called Co-Flowing Jet (CFJ) is carried out. Numerical results show that the use of CFJ over the blade suction surface can effectively delay flow separation, thus improving the net torque and power output of HAWT. Besides, this increment in the net power produced by the turbine is considerably higher than the power consumed by the CFJ. Thus, the overall efficiency of the HAWT can be greatly increased. Furthermore, influences of different CFJ operating parameters including location of injection port, jet momentum coefficient and slot length on the performance enhancement of a HAWT are also systematically studied and the optimal combination of these parameters to obtain the best possible turbine efficiency throughout a range of different wind speeds has been identified.

scholarly journals Performance Optimization of Wind Turbine Rotors with Active Flow Control (Part 1)

2012 ◽  
Vol 134 (04) ◽  
pp. 51-51 ◽  
Author(s):  
G. Pechlivanoglou ◽  
C.N. Nayeri ◽  
C.O. Paschereit
Keyword(s):  
Neural Network ◽  
Flow Control ◽  
Wind Turbine ◽  
Performance Optimization ◽  
Active Flow Control ◽  
Fine Tuning ◽  
Dynamic Force ◽  
Empirical Parameter ◽  
Turbine Rotors ◽  
Active Flow

This article describes the performance optimization of wind turbine rotors with active flow control. The active Gurney flap concept was tested in the wind tunnel under dynamic AoA variations to simulate unsteady inflow conditions. A high-deflection micro flap was actuated by four digital electric servos with a maximum deflection rate of 360°/sec. A custom code was created to allow dynamic AoA variations of the test wing with simultaneous dynamic force measurements. During the dynamic investigations, various control strategies were tested, starting from standard PID controllers with semi-empirical parameter tuning models to Direct Inverse Controllers with neural network tuning strategies and pure self-learning neural network controllers. The results of the closed-loop measurements using the manually tuned PID controller showed a reduction potential for the dynamic lift loads in the range of 70% as well as a stable controller behavior. The Direct Inverse Controller not only showed a load reduction of 36.8%, but also significant improvement potential with respect to its fine-tuning.

scholarly journals Performance Optimization of Wind Turbine Rotors with Active Flow Control (Part 2)

2012 ◽  
Vol 134 (08) ◽  
pp. 55-55 ◽  
Author(s):  
G. Pechlivanoglou ◽  
C.N. Nayeri ◽  
C.O. Paschereit
Keyword(s):  
Flow Control ◽  
Wind Turbine ◽  
Performance Optimization ◽  
System Integration ◽  
Large Scale ◽  
Active Flow Control ◽  
Lightning Strike ◽  
Scale Production ◽  
Turbine Rotors ◽  
Active Flow

This article discusses the performance optimization of wind turbine rotors with active flow control. An extensive multi-parameter investigation with a thorough matrix-grading system was performed to identify the most suitable solution for industrial quality, short/mid-term implementation on actual utility scale wind turbines. A very wide selection of aerodynamic flow control solutions was analyzed based on extensive multi-disciplinary literature review and through aerodynamic and aeroelastic simulations. It is suggested that the trailing edge devices have the most favorable performance in the field of system integration and mechanical design performance. Compliant structures like the flexible flap keep the number of moving parts to a minimum while maintaining high performance and manufacturing simplicity. The use of flexible and elastic materials based on polymers or rubber material improves the lightning strike resistance of these solutions and allows for low-cost large-scale production. The actuator principle, sensitivity, and reliability are decisive parameters, and pneumatic actuators seem to strike a good balance between performance, cost, and reliability.

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