1. The School of Mechanical Engineering
Current Trends in the Application of
Atmospheric Plasma for the Improvement
of Wind Turbine Efficiency through
Separation Control
Authors: Mei Cheong
Dr. Maziar Arjomandi
Presenter: Amelia Greig
21st July 2011

2. The School of Mechanical Engineering
Wind Energy
• Clean alternative source of power
• Currently competitive with fossil power
• Major limitation comes from adverse aerodynamic
loadings shortening lifespans
Wind turbine on Rottnest Island
Courtesy of Caniluna Pty Ltd
Price comparison between wind and traditional power.
Courtesy of UTS
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3. The School of Mechanical Engineering
Loads on Wind Turbines
• Inertial forces due to dead weight of rotor blades
which are periodic and unsteady
• Aerodynamic loads
– Uniform, steady airflows generate time-independent steady-
state loads
– Steady but spatially non-uniform airflows cause cyclic
loadings
– Turbulent airflows cause non-periodic stochastic loads
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4. The School of Mechanical Engineering
Aerodynamic Blade Loading
• Two velocity components – wind and blade motion
• Resultant gives optimal angle of attack
– Generally between 12o-15o
• Wind gusts up to 25%, alter required angle of attack
Turbine velocity components and resulting angle of attack
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5. The School of Mechanical Engineering
Blade Separation and Stall
• Lift coefficient varies with angle of attack. Should be as
high as possible for efficient turbine operation
• Wind gusts cause separation and stall to occur if angle
of attack increases past maximum levels
Lift coefficient of turbine blade with angle of attack Change in airflow with angle of attack
Adapted from http://www.sportpilot.org
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6. The School of Mechanical Engineering
Separation Control
• Wind turbines designed to operate in specific ranges of
wind speeds
• Outside this range, adverse aerodynamic loads occur
predominantly due to separation control
• Turbine blade loads controlled through:
– Flow velocity through variable speed rotor
– Blade length
– Blade incidence angle through variation of blade pitch
– Blade section aerodynamics
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7. The School of Mechanical Engineering
Load Reduction - Blade Section Aerodynamics
• Minimize fatigue life of system due to changes
in wind direction and speed
• Passive control
– Control through adaptation of aero-elastic
responses of blades and stall regulation
• Active control
– Control through adjustment of aerodynamic
properties and pitch angles of blades
Photos from http://www.lmwindpower.com and http://en.wikipedia.org
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8. The School of Mechanical Engineering
Plasma Actuators
• Standard Dielectric Barrier Discharge (DBD) Actuator
configuration
Schematic configuration for DBD actuator
• Plasma generated by applying an electric field to sustain
electron-ion pairs
Electron movement: a) negative half-cycle, b) positive half-cycle
8 Adapted from Cheong et al. 2010

9. The School of Mechanical Engineering
DBD Actuator Physics
• Dielectric material retains more electrons than the
electrode material resulting in an asymmetric flow pattern
• Induced airflow, called ‘Ionic Wind’ results
Plasma induced airflow and response force Plasma discharge
Adapted from Cheong et al. 2010
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10. The School of Mechanical Engineering
Massless Wall Jets
• DBD actuators modify fluid flow characteristics by
generating massless wall jets in the boundary layer of the
flow
• Introduction of these jets injects momentum into retarded
boundary layers to delay separation or even reattaching
separated flow
Lift coefficient with and without actuator
1
Adapted from Nelson et al., 2008
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11. The School of Mechanical Engineering
DBD Actuators for Flow Separation
• DBD actuators were shown to
– energize flow near locations of separation (Huang et al. 2006)
– increase stall angle and delaying leading-edge separation (Orlov et
al. 2007, Post & Corke 2004)
– improve lift cycle by controlling dynamic stall vortices (Post & Corke
2006)
Adapted from Post & Corke, 2006
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12. The School of Mechanical Engineering
Summary
• DBD actuators are an effective means of separation and
stall control
• Feasible method of load control for wind turbine blades
• Advantages over conventional methods of load control:
High frequency response
Do not introduce parasitic drag
Low power consumption
• Further investigations to implement DBD actuators on wind
turbines highly valuable
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13. The School of Mechanical Engineering
Acknowledgements
• Electrical and Mechanical Engineering Workshop at the University
of Adelaide
• The Sir Ross and Sir Keith Smith Fund
Disclaimer
Research undertaken for this report has been assisted with a grant from the Smith Fund (www.smithfund.org.au). The support is acknowledged
and greatly appreciated. The Smith Fund by providing for this project does not verify the accuracy of any findings or any representation contained
in it. Any reliance in any written report or information provided to you should be based solely on your own assessment and conclusions. The Smith
Fund does not accept any responsibility or liability from any persons, company or entity that may have relied on any written report or
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