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Delegates are invited to meet and discuss with the poster presenters in this topic directly after the session 'Advanced rotor technologies' taking place on Tuesday, 11 March 2014 at 11:15-12:45. The meet-the-authors will take place in the poster area.

Jaione Ortega Gomez Leibniz Universität Hannover, Germany
Co-authors:
Jaione Ortega Gomez (1) F P Claudio Balzani (1) Andreas Reuter (1)
(1) Leibniz Universität Hannover, Hannover, Germany

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Abstract

Evaluation of the possibility of replacing pitch control by active trailing edge flaps in wind turbines

Introduction

In the last years, wind turbines with large rotor diameters have been built in order to make wind energy more competitive. However, a problem arises according to the well-known square-cube scaling law: the aerodynamic and gravitational loads increase substantially. As a consequence, the investment in materials and/or operation and maintenance increases and the profit made out of the produced energy decreases.

Approach

Research in the field of so-called smart blades has a main goal: the reduction of loads in the wind turbine in order to increase the profitability and competitiveness of turbines with large rotor blades. Two concepts rule the development of this new technology in the research field: passive control and active control.

Main body of abstract

The work proposed in this contribution deals with the concept of active trailing edge flaps and as a first step performs a 2D aerodynamic analysis on a DU (1) profile containing a rigid flap.As a similar study to the one made by Troldborg (2) in a Risø-B1-18 airfoil, this paper uses the numerical code XFOIL to analyze how the flap angle and the position of the hinge point affect the lift and drag coefficients. For negative flap angles (flap up), the influence of the flap on the lift coefficient decreases with increasing angles of attack, and, for a given hinge point position, the change in lift when modifying the flap angle increases with decreasing angles of attack. A deep analysis on the hinge moment coefficient, and the effect of flap control on the blade root bending moments is also performed.




References:
(1) Airfoil developed by Delft University
(2) Troldborg, Computational Study oft the Risø-B1-18 Airfoil Equipped with Actively Controlled Trailing Edge Flaps, Technical University of Denmark (DTU), September 2004


Conclusion

Out of these analyses one configuration is chosen. A rotor composed of three blades equipped with flaps is modeled and simulations are performed at rated rotational speed and various over-rated wind speeds. The flap angles are adjusted to keep the rotor at rated power. Following from this feasibility study conclusions are drawn about the bandwidth of wind speeds for which the trailing edge flaps can replace a pitch system.



Learning objectives
Generally the trailing edge flaps are though to reduce the root bending moments. The main objective of this contribution is to show if the flaps are also a possibility to replace the pitch control.