Flow Control for Wind Turbine Airfoil

2011 ◽  
Author(s):  
Andreas Gross ◽  
Hermann F. Fasel
Keyword(s):  
Flow Control ◽  
Wind Turbine ◽  
Active Flow Control ◽  
Turbine Blades ◽  
Vortex Generator ◽  
Suction Side ◽  
Boundary Layer Separation ◽  
Plasma Actuators ◽  
Flip Flop ◽  
Wind Turbine Airfoil

The flow over a NREL S822 wind turbine airfoil was simulated for a chord Reynolds number of 100,000 and an angle of attack of 5deg. These conditions approximately match the blade element conditions at 80% radius of a 2m diameter turbine operating at 300rpm. A simulation of the uncontrolled flow with steady approach flow conditions shows boundary layer separation on the suction side which is consistent with University of Illinois at Urbana-Champaign experimental data. Active flow control has the potential to locally (and on demand) reduce the unsteady loads on individual turbine blades during non-nominal operation, thereby increasing turbine life. In addition, flow control may help lower the cut-in wind speed. Unsteady flow control for reducing the suction side separation using pulsed vortex generator jets, flip-flop jets, and plasma actuators were evaluated. It was found that very low actuation amplitudes were already sufficient for eliminating the suction side separation. The high effectiveness and efficiency is traced back to hydrodynamic instabilities that lead to a downstream growth of the forced disturbances. Too high actuator amplitudes resulted in early disturbance saturation which made the control inefficient.

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

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.

Numerical Investigations of the Efficiency of Circulation Control in a Compressor Stator

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
Arne Vorreiter ◽  
Susanne Fischer ◽  
Horst Saathoff ◽  
Rolf Radespiel ◽  
Joerg R. Seume
Keyword(s):  
Flow Control ◽  
High Speed ◽  
Design Method ◽  
Active Flow Control ◽  
Suction Side ◽  
Boundary Layer Separation ◽  
Circulation Control ◽  
Compressor Cascade ◽  
First Results ◽  
Active Flow

Airfoil active flow control has been attempted in the past in order to increase the permissible loading of boundary layers in gas turbine components. The present paper presents a stator with active flow control for a high-speed compressor using a Coanda surface near the trailing edge in order to inhibit boundary layer separation. The design intent is to reduce the number of vanes while—in order to ensure a good matching with the downstream rotor—the flow turning angle is kept constant. In a first step, numerical simulations of a linear compressor cascade with circulation control are conducted. The Coanda surface is located behind an injection slot on the airfoil suction side. Small blowing rates lead to a gain in efficiency associated with a rise in static pressure. In a second step, this result is transferred to a four-stage high-speed research compressor, where the circulation control is applied in the first stator. The design method and the first results are based on steady numerical calculations. The analysis of these results shows performance benefits of the concept. For both the cascade and the research compressor, the pressure gain and efficiency are shown as a function of blowing rate and jet power ratio. The comparison is performed based on a dimensionless efficiency, which takes into account the change in power loss.

scholarly journals Numerical Analysis of Wind Turbine Airfoil Aerodynamic Performance with Leading Edge Bump

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Majid Asli ◽  
Behnam Mashhadi Gholamali ◽  
Abolghasem Mesgarpour Tousi
Keyword(s):  
Wind Turbine ◽  
Control Method ◽  
Flow Behavior ◽  
Renewable Energy Sources ◽  
Lift Coefficient ◽  
Turbine Blades ◽  
Vortex Generator ◽  
Leading Edge ◽  
Suction Side ◽  
Aerodynamic Performance

Aerodynamic performance improvement of wind turbine blade is the key process to improve wind turbine performance in electricity generated and energy conversion in renewable energy sources concept. The flow behavior on wind turbine blades profile and the relevant phenomena like stall can be improved by some modifications. In the present paper, Humpback Whales flippers leading edge protuberances model as a novel passive stall control method was investigated on S809 as a thick airfoil. The airfoil was numerically analyzed by CFD method in Reynolds number of 106and aerodynamic coefficients in static angle of attacks were validated with the experimental data reported by Somers in NREL. Therefore, computational results for modified airfoil with sinusoidal wavy leading edge were presented. The results revealed that, at low angles of attacks before the stall region, lift coefficient decreases slightly rather than baseline model. However, the modified airfoil has a smooth stall trend while baseline airfoil lift coefficient decreases sharply due to the separation which occurred on suction side. According to the flow physics over the airfoils, leading edge bumps act as vortex generator so vortices containing high level of momentum make the flow remain attached to the surface of the airfoil at high angle of attack and prevent it from having a deep stall.

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

Numerical Investigations of the Efficiency of Circulation Control in a Compressor Stator

2010 ◽  
Author(s):  
A. Vorreiter ◽  
S. Fischer ◽  
H. Saathoff ◽  
R. Radespiel ◽  
J. R. Seume
Keyword(s):  
Flow Control ◽  
High Speed ◽  
Design Method ◽  
Active Flow Control ◽  
Suction Side ◽  
Boundary Layer Separation ◽  
Circulation Control ◽  
Compressor Cascade ◽  
First Results ◽  
Active Flow

Airfoil active flow control has been attempted in the past in order to increase the permissible loading of boundary layers in gas turbine components. The present paper presents a stator with active flow control for a high speed compressor using a Coanda surface near the trailing edge in order to inhibit boundary layer separation. The design intent is to reduce the number of vanes while — in order to ensure a good matching with the downstream rotor — the flow turning angle is kept constant. In a first step, numerical simulations of a linear compressor cascade with circulation control are conducted. The Coanda surface is located behind an injection slot on the airfoil suction side. Small blowing rates lead to a gain in efficiency associated with a rise in static pressure. In a second step, this result is transferred to a 4-stage high speed research compressor, where the circulation control is applied in the first stator. The design method and the first results are based on steady numerical calculations. The analysis of these results shows performance benefits of the concept. For both, the cascade and the research compressor, the pressure gain and efficiency are shown as a function of blowing rate and jet power ratio. The comparison is performed based on a dimensionless efficiency which takes into account the change of power loss.

Design of a Low Solidity Flow-Controlled Stator With Coanda Surface in a High Speed Compressor

2008 ◽  
Author(s):  
Y. Guendogdu ◽  
A. Vorreiter ◽  
J. R. Seume
Keyword(s):  
Boundary Layer ◽  
Flow Control ◽  
High Speed ◽  
Design Method ◽  
Active Flow Control ◽  
Suction Side ◽  
Boundary Layer Separation ◽  
Synthetic Jets ◽  
Layer Separation ◽  
Active Flow

Aerofoil active flow control has been attempted to increase the permissible loading of boundary layers in gas turbine components. Steady suction and blowing, pulsing and synthetic jets are all means to remove low energy flow, replace momentum deficits, or promote mixing to inhibit boundary layer separation. A curved surface near the trailing edge (“Coanda surface”) is another technique used to control aerofoil boundary layer separation. This paper presents the design of a stator with active flow control for a high speed compressor using a Coanda surface. The Coanda surface is located behind an injection slot on the aerofoil suction side of the first stage of a four-stage high speed research compressor. The design method and the present results are based on steady numerical calculations. The design intent is to reduce the number of vanes. This active flow control is used to maintain the flow exit angle of the reference stator despite the resulting increase in stator loading. It is shown that the solidity of the flow-controlled stator can be decreased by 25% with a blowing rate of 0.5% of the main mass flow.

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