Active Flow Control of Wind Turbine Blades

This paper presents the continuation of the research efforts of the authors in the direction of the development of “smart blades” for the wind turbines of the future. Results from previous research work is further in combination with a newly developed simulation code in order to assess the performance of Active Flow Control (AFC) elements implemented on modern wind turbine blade structures. Parametric investigations have been conducted in order to identify the optimal configuration of various AFC elements. These are tested under identical boundary conditions to define an overall optimal solution. The results of the research project show that the Active Gurney Flap is the element with a highest probability for the fastest implementation on wind turbine blades for load alleviation purposes. The most promising however overall solution is the Flexible Trailing Edge Flap. With its high control authority and relatively high regulation speed is able to significantly vary the aerodynamic performance of wind turbines.

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Load Control for Turbine Blades: A Non-Traditional Microtab Approach

ASME 2002 Wind Energy Symposium ◽

10.1115/wind2002-54 ◽

2002 ◽

Author(s):

D. T. Yen Nakafuji ◽

C. P. van Dam ◽

J. Michel ◽

P. Morrison

Keyword(s):

Flow Control ◽

Wind Turbine ◽

Active Flow Control ◽

Turbine Blades ◽

Suction Side ◽

Turbine Rotor ◽

Load Control ◽

Drag Forces ◽

Macro Scale ◽

Active Flow

Active flow control and load mitigation concepts developed for traditional aeronautical applications have potential to decrease torque, bending and fatigue loads on wind turbine blades and to help increase turbine life. Much of the early work in flow control focused on steady aerodynamic benefits. More recent technologies have focused on unsteady flow control techniques which require a deeper understanding of the underlying flow physics as well as sensors to record the various time-dependent aerodynamic phenomena and fast actuators for control. This paper identifies some developmental control concepts for load mitigation along with a new translational microfabricated tab concept available for active flow and load control on lifting surfaces and explores their applicability for wind turbine rotor blades. Specifically, this paper focuses on experimental results based on an innovative microtab approach for unsteady, active load control. Previous papers on this effort by Yen et al. focused on the multi-disciplinary design methodology and the significant lift enhancement achieved using these micro-scale devices. The current research extends the effort to include dynamic results with discontinuous tab effects, effects on drag, and lower (pressure side) and upper surface (suction side) tab deployment effects for the prototype airfoil as well as for the S809, a representative wind turbine airfoil. Results show that the microtab concept can provide macro-scale load changes and is capable of offering active control of lift and drag forces for load alleviation.

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

10.1115/gt2021-59664 ◽

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.

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

Wind Engineering ◽

10.1177/0309524x20961394 ◽

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.

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