stability limits for a full wind turbine equipped with trailing edge systems

Stability limits for a full wind turbine equipped with trailing edge systems

by Thomas Buhl, Mac Gaunaa, Leonardo Bergami and Peter B. Andersen

17/04/2009EWEC 20092

Outline

• Motivation• 2D stability• 3D stability• Results• Conclusion

17/04/2009EWEC 20093

Motivation

Complex terrain CFD by Dr. Bechmann Risø

Siemens Wind power

17/04/2009EWEC 20094

Motivation

17/04/2009EWEC 20095

Adaptive trailing edges

From 2003 to today: three large research projectsinvolving more than 10

researchers,6 master thesis and 3 Ph.d’s

Inspiration Not applicable!

17/04/2009EWEC 20096

Typical turbine layout

17/04/2009EWEC 20097

Controller

”aerodynamic” controller part

”elastic” controller part

”pitch” controller part

”power” controller part

17/04/2009EWEC 20098

Motivation

Load reduction on Upwind turbine – by P. B. Andersen

17/04/2009EWEC 20099

Wind tunnel results

17/04/2009EWEC 200910

2D stability

2D stability results from L. Bergami and M. Gaunaa

17/04/2009EWEC 200911

Full turbine stability Results-Original turbine no flaps

17/04/2009EWEC 200912

Full turbine stability Results-Original turbine with and without flaps

17/04/2009EWEC 200913

Moving the center of gravity

Figures made by Li Na in ADAPWING2 project funded by Danish Research Council

17/04/2009EWEC 200914

Moving the center of gravity

17/04/2009EWEC 200915

2D Stability-Moving the center of gravity

From: Hansen, M.H., Aeroelastic instability problems for wind turbines.

Wind Energy (2007) 10 , 551-577

17/04/2009EWEC 200916

Moving the center of mass

17/04/2009EWEC 200917

Full turbine stability Results-Moving the center of gravity

17/04/2009EWEC 200918

Full turbine stability Results-Moving the center of gravity

17/04/2009EWEC 200919

Conclusions• Results from 2D studies show that adding flap control generally lowers

the stability limits• Results from 2D show that the effects of adding elastic trailing edges are

not trivial. Possibility of drastically lowered flutter velocities.

• The reference turbine is very stable.• The full turbine results show that the critical tip speed for which instability

occurs is lower for turbines equipped with trailing edge flaps compared to the turbine without.

• In most of the instability cases found an artificial propeller mode (large forward blade deflections) occurs.

17/04/2009EWEC 200920

Future work

• Emergency stop• future extensions to this work should focused also on the controller

parameters and the influence of these on the stability limits– Elastic flaps– Aggresivily tuned flap control – Less stable reference turbine

• This work is partially funded by

Acknowledgement