Evaluating static and modal responses of a small scale conventional and bio-inspired wind turbine blade

Abstract

Wind turbine blade is considered as one of the most vital component of the wind turbine system meant to produce energy from the power of the wind. A finite element model of a three bladed small-scale Kestrel e230i horizontal axis wind turbine will be used in this study. Firstly, the three-dimensional solid geometry of the conventional wind turbine was generated using a customized aerofoil measurement technique in the laboratory. The generated geometry was then cleaned to remove all abrupt changes in surface profile. Then the actual conventional wind turbine blade was statically tested and resulting strains measured in different positions along its blade length. The blade was rigidly fixed at its root by bolting it into a laboratory test bench. The three-dimensional model was subsequently loaded and supported at its root in a similar manner. Finite element analysis and model updating was performed in ANSYS v 19.0 by iteratively correlating stress values between the finite element model and the test. A bio-inspired version of the updated finite element model was generated by adding undulations/corrugations to the bottom surface of the conventional blade in a longitudinal direction. Modal analyses were then performed for the two models to compare their natural frequencies in first two bending and first twist modes. These two modes are reported to be the most important modes in wind turbine dynamic response and may also be very influential in energy production of wind turbines. The numeral results show that the inclusion of undulations/corrugations increases the natural frequencies, which typically means that for low-speed inland applications, the risk of wind turbine blade structural failure due to resonant or near-resonant excitations is heavily averted due to increased potential operating frequency ranges.