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DYNAMIC AND AEROELASTIC RESPONSE OF WIND ENERGY CONVERTER TO AERODYNAMIC

Obiettivo

THE MAIN PURPOSE OF THIS PROJECT IS TO DEVELOP AN ANALYTICAL TECHNIQUE TO PERMIT RELIABLE AND ECONOMIC DESIGN OF MONO- AND MULTIPLE- BLADED WIND ENERGY CONVERTERS BY NEW TIME- DEPENDANT SIMULATION PROGRAMMES.
A general computer code for horizontal axis wind turbines was developed. The simulation started with design rotor speed. The wind velocity was 12 metres per second and the blade pitch angle was set to a value at which flow separates over approximately 35% of the blades. By treating rotor speed as a degree of freedom, it is possible to investigate unsteady operating conditions, like start up and shut down, which can produce much stronger loads than normal speed operation. Stall effects can be investigated by considering the real profile characteristics using an interpolation routine for the measured data or using an improved version of the semiempirical theory of Leiss and Wagner, which was also developed.
TO ACHIEVE THIS GOAL, A HYBRID COMPUTER MODEL CALCULATES THE DYNAMIC AND AEROELASTIC RESPONSE OF HORIZONTAL AXIS WIND TURBINES TO AERODYNAMIC LOADS. THE MOST IMPORTANT CHARACTERISTICS, DIFFERENCES AND IMPROVEMENTS COMPARED TO OTHER COMPUTER MODELS ARE LISTED BELOW:
THE DYNAMIC EQUATIONS CONSIDER ELASTIC DEFORMATIONS OF TOWER AND THE BLADES AND RIGID BODIES LIKE NACELLE AND HUB. THE BLADES CAN BE MOUNTED AT THE HUB WITH ADDITIONAL HINGES.
AS ROTOR SPEED IS TREATED AS A NONLINEAR DEGREE OF FREEDOM AND THE BLADE PITCH ANGLE CAN BE VARIED DURING SIMULATION, IT BECOMES POSSIBLE TO INVESTIGATE UNSTEADY OPERATING CONDITIONS LIKE START-UP AND SHUT-DOWN. THESE WORKING CONDITIONS RESULT IN MUCH HIGHER STRESS LOADING THAN CONSTANT SPEED OPERATION.
AERODYNAMIC FORCES ARE COMPUTED BY A 3-DIMENSIONAL, NONLINEAR AND UNSTEADY THEORY. (UP TO NOW, THIS IS FRICTIONLESS POTENTIAL THEORY.)
THE WAKE GEOMETRY IS PRECALCULATED BY A VORTEX-LATTICE-METHOD (ORIGINALLY DEVELOPED BY BEHR & WAGNER FOR THE INVESTIGATION OF VORTEX INTERACTIONS OF DELTA-WING-CONFIGURATIONS). THE CORRESPONDING SOFTWARE HAS BEEN MODIFIED FOR AN APPLICATION AT VARIOUS ROTOR FLOWS.
THE DISTRIBUTION OF WIND SPEED IS ALMOST ARBITRARY IN TIME AND SPACE.

THE THREE FIGURES IN THE LOWER PART OF THE FLOW CHART DISPLAY EXAMPLES OF THE DIFFERENT TYPES OF COMPUTED RESULTS. THEY CAN BE EMPLOYED WITHIN THE DESIGN PROCESS AS FOLLOWS :
TIME HISTORIES OF UP TO TWENTY DEGREES OF FREEDOM (AND/OR ROOT BENDING AND DRIVING MOMENTS) AS WELL AS AERODYNAMIC LOAD DISTRIBUTIONS ARE THE PRIMARY OUTPUT OF THE MAIN PROGRAMME. (THESE RESULTS CAN BE UTILIZED WITHIN EXTERNAL PROGRAMMES - NOT DEVELOPED WITHIN THIS PROJECT - , TO PREDICT PEAK AND MEAN STRESS LOADING.)
FREQUENCY SPECTRA ARE CALCULATED IN A SECONDARY PROGRAMME BY A FOURIER-TRANSFORMATION. THEY CAN BE USED AS INPUT DATA FOR LIFE-TIME PREDICTIONS.
THE STABILITY CHARTS DISPLAY THE TIME HISTORIES OF THE SIGNIFICANT PEAKS OF THE FREQUENCY SPECTRA.
AS THERE ARE NO STABILITY THEORIES KNOWN FOR THIS TYPE OF NON-LINEAR DIFFERENTIAL EQUATIONS, THIS NEW TECHNIQUE HAS BEEN DEVELOPED TO OBTAIN AN INDICATION, WHETHER A CERTAIN MOTION IS DAMPED OR EXCITED. THESE CHARTS COULD BE A HELPFUL TOOL TO SEARCH FOR AND TO DETECT DYNAMIC INSTABILITIES.

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Meccanismo di finanziamento

CSC - Cost-sharing contracts

Coordinatore

WIRTSCHAFT UND INFRASTRUKTUR GMBH & CO PLANUNGS KG
Contributo UE
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Indirizzo
SYLVENSTEINSTRASSE 2
MUENCHEN
Germania

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