Damping of Edgewise Vibration of Wind Turbine Blades by Smart Liquid Dampers

Andreasen, Rene Bundgaard

4. term

Structural and Civil Engineering, Master

2017

2017-06-08

Projektet undersøger, hvordan kantvise vibrationer i vindmøllevinger kan dæmpes. Vi bruger en numerisk, forenklet vingemodel med to frihedsgrader (to typer bevægelse), og sammenligner et passivt system med to semi-aktive tilgange. I udgangspunktet anvendes et passivt system med en åbning, der lader væsken i en torusformet kanal accelerere og decelerere og dermed dæmper bevægelserne. Herefter undersøges en semi-aktiv styring af åbningen samt brugen af smartvæsker, hvis egenskaber kan ændres med et magnetfelt, så væsken kan tilpasses situationen. Der udledes feedback-baserede kontrollove og testes i modellen. For en fast rotationshastighed viser resultaterne, at hverken semi-aktiv åbningstyring eller smartvæske giver en markant forbedring i forhold til passiv kontrol. Når rotationshastigheden derimod ændres, påvirkes centrifugalstivhed og dermed dæmpningen, og her kan semi-aktiv styring, der justerer åbning eller væskens viskositet, opretholde et mere optimalt dæmpningsforhold. Det gør den semi-aktive tilgang særligt relevant ved f.eks. opstart eller når vingerne pitches. Praktisk er der betydelige udfordringer: Smartvæsken kræver et magnetfelt (typisk fra en spole), som skal have plads, og væsken er omtrent tre gange tungere end vand, hvilket er problematisk, når dæmperen skal sidde langt ude i vingen. Åbningstyring kræver desuden meget hurtig responstid, fordi systemets tilstand kan ændre sig øjeblikkeligt, hvilket stiller store krav til udstyr og integration. Samlet peger studiet på, at semi-aktiv kontrol har potentiale under varierende driftsforhold, men at implementeringen er kompleks.

This project examines how to reduce edgewise vibrations in wind turbine blades. We use a numerical, simplified blade model with two degrees of freedom (two types of motion) and compare a passive system with two semi-active approaches. The baseline is a passive setup with an opening that lets fluid in a torus-shaped channel accelerate and decelerate, providing damping. We then study semi-active control of the opening and the use of smart fluids, whose properties can be changed by a magnetic field so the fluid can adapt to the situation. Feedback-based control laws are derived and tested in the model. At a fixed rotational speed, results show that neither semi-active opening control nor smart fluid delivers a clear improvement over passive control. When rotational speed varies, however, centrifugal stiffness changes and so does damping; in this case, semi-active control that adjusts the opening or the fluid’s viscosity can maintain a more optimal damping ratio. This makes the semi-active approach particularly relevant during start-up or blade pitching. In practice, there are significant challenges: smart fluids require a magnetic field (typically from a coil), which needs space, and the fluid is about three times heavier than water, which is problematic when a damper must be placed near the blade tip. Opening control also demands very fast response, because system changes can be instantaneous, imposing strict requirements on equipment and integration. Overall, the study indicates that semi-active control has potential under varying operating conditions, but implementation is complex.

[This abstract was generated with the help of AI]

Dynamik ; Dæmpning ; Vindmølle ; Vindmøllevinge ; Smart væsker ; Semi-aktiv

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