Print Email Facebook Twitter Aero-elastic Stability Analysis for Large-Scale Wind Turbines Title Aero-elastic Stability Analysis for Large-Scale Wind Turbines Author Meng, F. Contributor Van Tooren, M.J.L. (promotor) Faculty Aerospace Engineering Department Aerospace Design, Integration & Operations Date 2011-01-24 Abstract Nowadays, many modern countries are relying heavily on non-renewable resources. One common example of non-renewable resources is fossil fuel. Non-renewable resources are ?nite resources that will eventually dwindle, becoming too expensive or too environmentally damaging to retrieve. In contrast, renewable energy resources, like wind energy, are constantly replenished and are important because of the bene?ts it provides for us as well as for our environment. However, getting the energy from wind must be further investigated in order to make the usage of wind energy more economically. During the past thirty years, the trend in wind energy is to increase the size of wind turbines for producing more electricity power with lower cost. The increase in size is bene?cial in terms of reduction of manufacturing costs per kW hours and reduction of the ground surface occupied by the wind farms. Further increases in size are not easily achievable because designers are expected to face more unknown technical problems such as aero-elastic stability problems. Therefore, it is important to investigate the aero-elastic stability problem of each new design concept in order to prevent the damage happen. In practice the larger blades have a lower edge-wise frequency that is closer to the ?ap-wise frequency than the case for the smaller blades. This could result in bigger edge-wise vibrations and unexpected aero-elastic problems. Larger blades will also result in large deformations even when the wind turbines are running at the design condition. Furthermore, designing pitch-regulated wind turbines will often result in lightweight and very ?exible blades. The effects of large and ?exible blade are mainly reducing diameter of the rotor during operation and coupling between edge-wise and torsional forces and motion. Most aero-elastic codes for wind turbines do not consider the e?ects of large de?ections in their simulation of the loads and responses. The reduced effective rotor area leads to lower power production than predicted by linear calculations and the coupling between edge-wise and torsional forces and motion will increases pitch moment at the blade pitch system. The problems mentioned above are the current research problems needed to be investigated and solved due to upscaling of the wind turbines. In this research work, nonlinear ?exible multi-body dynamics has been chosen to couple with nonlinear aerodynamics to investigate the current research problems mentioned before. An aero-elastic simulation tool called MBDyn-AeroDyn is developed by integration of two existing code named MBDyn [1] and AeroDyn [2]. MBDyn is a nonlinear ?exible multi-body dynamic code, which can simulate the effect of large de?ections and large rotations. The aerodynamic forces acting on wind turbine blades are calculated using AeroDyn which is based on the blade element-momentum theory. Improvement of aerodynamic calculation has been made by adding a modi?ed Pitt-Peters dynamic in?ow model in AeroDyn. Afterwards, both a linear time invariant system identi?cation method and a linear time periodic system identi?cation method have been used and implemented to investigate the aero-elastic stability of multi-MW wind turbine blades. Finally wind tunnel measurements have been performed in order to validate the aero-elastic simulation tool developed in this work. The validation of this aero-elastic simulation code has been carried out in this thesis. The time domain simulation results show that this aero-elastic simulation tool has good agreement with wind tunnel experiment results at the design operation condition. For the offdesign cases, the differences become larger gradually. Further more, an aero-elastic simulation has been applied on a 5MW wind turbine. Comparison has been made between FAST and BLADMODE in time domain. The results show that MBDyn-AeroDyn and FAST have a good agreement for an uniform wind ?eld. Finally, ?ap-torsion ?utter analysis on the 5MW wind turbine has been performed. The main feature of this aero-elastic simulation tool for multi-MW large horizontal axis wind turbines developed in this work is that kinematically large displacements and rotations are included, and that loads are applied on the deformed geometry. This allows the designers to simulate large wind turbines with more ?exible blades to capture the effect of large displacements and rotations more accurately. Another feature is that both a linear time invariant system identi?cation method and a linear time periodic system identi?cation method have been implemented. It allows the designers to analyse stability from the time domain simulation data. From the result of ?ap-torsion ?utter analysis on the 5MW wind turbine, it is shown that ?ap-torsion ?utter is not likely to occur on this 5MW wind turbine with the current blade structural properties and intended operating conditions. Considering with the current Ph.D works which have been done so far, ?rstly, another wind tunnel experiment maybe necessary by using the same blades. Future measurement should be made at a higher rotation speed and combined with higher wind speed in order to ?nd the stability boundary of this model wind turbine. Secondly, this aero-elastic simulation tool should be integrated into a knowledge based engineering(KBE) wind turbine blades design environment in order to take advantage of this aero-elastic simulation tool. Further research work should be carried out to simulate wind turbine blades with smart control devices, for example, ?aps on the blades. Last but not the least, an user friendly graphical interface for this tool should be made in order to make it more convenient to use for a wider group of users. Subject wind turbine simulationaero-elasticstability To reference this document use: http://resolver.tudelft.nl/uuid:c0cb51f7-dc9f-418e-b80d-a312e9f3b6b5 ISBN 9789090259581 Part of collection Institutional Repository Document type doctoral thesis Rights (c) 2011 Meng, F. Files PDF FanzhongMeng-thesis-ready ... oprint.pdf 208.14 MB Close viewer /islandora/object/uuid:c0cb51f7-dc9f-418e-b80d-a312e9f3b6b5/datastream/OBJ/view