Objective The objectives of the work are to clarify the importance of stall induced vibrations, to identify and provide a better understanding of the physical phenomena and set up the necessary restrictions concerning induced design parameters for the stall regulation principle when used on the forthcoming generation of larger, and possibly more flexible wind turbines The possiblity of stall induced vibrations as predicted by aeroelastic calculations has to some extent been hindering the developed of large stall regulated wind turbines. A continuous upscaling of smaller turbines has been going on, in general without serious vibrational problems showing up. However the behaviour in stall has not been based on a sufficient proper prediction method and the phenomena are not fully understood.Measurements from 3 of the 4 turbines involved in this project have been analyzed and all 4 turbines have been modelled. Different stall models are implemented in the aeroelastic codes, and the responses of the turbines are quite well predicted, though with less success for the WPX-20 rotor. This is the only one that has a high vibrational level in stall. Some of the causes for this are predictable, but for some reason not yet understood, 3-dimensional aerodynamic effects are not present for this rotor.Inclusion of the time delay stall model generally increases damping, but does not create absolute stability for a single blade section. However when integrated over the whole blade stability is obtained.The dynamic stall models have been tested with aerofoil section measurements. Some of the hysteresis characteristics are quite well modelled, but overall agreement is not obtained, which accordingly is reflected in the total response calculation. The uncertain aspects with respect to prediction of stall induced vibrations on design level are ways to account for 3-dimensional effects and dynamic stall (in combination) for specific aerofoils and blade shapes.The project consists of coordinated measurements and modelling of structural dynamics including aerodynamics in stall on four different stall regulated wind turbines. The turbines in question are two Danish and two Dutch, ranging in size from 20 to 500 kW. They are quite different in design ranging from the "Danish Standard Design" with a rather stiff three-bladed rotor to two-bladed machines with either teetering hub or hinged or stiff blades. All of these machines are instrumented to some degree. The intention of this project is not to make very detailed measurements on each of these machines but rather to have adequate data which will allow comparisons between the machines response to be made. For a reconciliation of the measurements with predictions of the interaction between the wind input, the aerodynamics and the structural response, codes for non-linear dynamic stall aerodynamics will be developed. Stall hysteresis may play an important role and will be included in the models. The underlying theory is a synthetics of Beddoes and Onera like models including stall delay and hysteresis. This is the foundation for the description of the aerodynamics in the aero-elastic programs. All the measurements made above will be complemented by equivalent theoretical predictions. The theoretical work will contain a complete description of the wind turbine system, the aerodynamics, the dynamics and the turbulent inputs. The programme of work is split into the following parts: 1) Measurements. 2) Data analysis. 3) Development of a suitable aero-elastic prediction code based on existing aerodynamic and structural dynamic packages incorporating the essential stall delay and stall hysteresis. 4) Reconciliation of theoretical and experimental data. 5) Formulation of scaling rules and guidelines for future designs. 6) Reporting. The results are intended to form a basis on which manufacturers can develop a new generation of large stall regulated wind turbines. Fields of science natural sciencescomputer and information sciencesdata scienceengineering and technologyenvironmental engineeringenergy and fuelsrenewable energywind powerengineering and technologymechanical engineeringvehicle engineeringaerospace engineeringaeronautical engineering Programme(s) FP2-JOULE 1 - Specific research and technological development programme (EEC) in the field of energy - non-nuclear energies and rational use of energy - (JOULE), 1989-1992 Topic(s) Data not available Call for proposal Data not available Funding Scheme CSC - Cost-sharing contracts Coordinator RISOE NATIONAL LABORATORY EU contribution No data Address Frederiksborgvej 399 ROSKILDE Denmark See on map Total cost No data Participants (2) Sort alphabetically Sort by EU Contribution Expand all Collapse all ENERGY RESEARCH CENTRE OF THE NETHERLANDS Netherlands EU contribution No data Address Westerduinweg 3 PETTEN See on map Links Website Opens in new window Total cost No data GARRAD HASSAN AND PARTNERS LTD United Kingdom EU contribution No data Address Saint Vincent Works, Silverthorne Lane BS2 0QD BRISTOL See on map Total cost No data
