ECN publication
Aeroelastic Analysis of the LMH64-5 Blade
Published by: Publication date:
ECN Wind Energy 1-6-2003
ECN report number: Document type:
ECN-C--03-020 ECN publication
Number of pages: Full text:
51 Download PDF  

Within the DOWEC project, investigations were performed into the developmentof large size wind turbines for offshore applications. Many of the studies in this project were performed for a 6MW concept of which the turbine was designed by NEG-Micon Holland and the LMH64-5 blade by LM Glasfiber Holland. One of the tasks within this project was to investigate the aeroelastic stability problems for large size wind turbines which was performed for this 6MW concept. These analyses were done with the program BLADMODE. This document starts with a description of the modelling of the blade in basis of a set of 51 files with the cross sectional layout. For the first bending modes the direction of blade motion 'theta' was calculated for the rotating and non-rotating state, which can be used as input for hinge-spring-damper analysis tools. The operational conditions as function of wind speed for which the aeroelastic stability was investigated, were calculated with the program PHATAS. The aerodynamic damping was calculated for the original LMH64-5 blade concept, and also for some parameter variations on structural and aerodynamic modelling aspects and on the so-called 'Structural Pitch'. Finally a comparison was made of the aeroelastic damping calculated with the original LMH64-5 geometry and a tapered variant. It was concluded that for pitch-to-vane controlled wind turbines the flapwise blade vibrations have a positive aerodynamic damping. In general the aerodynamic damping for the edgewise modes is positive for most of the operational conditions. For the 6MW concept the aerodynamic damping of the edgewise blade motions can be improved with a small increase of the partial-load pitch angle, and with 'Structural Pitch' modifications of the blade structure. It was also concluded that increasing the torsional stiffness of the rotor shaft with a factor 1.7 avoids 6P resonance problems for the collective edgewise mode and reduces the negative contribution of the generator characterist.

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