Periodic stability assessment of a flexible hub connection for load reduction on two-bladed wind turbines

The Science of Making Torque from Wind

Luhmann, Birger^1 ; Cheng, Po Wen^1

Stuttgart Wind Energy, University of Stuttgart, Allmandring 5b, Stuttgart

70569, Germany^1

关键词: Aerodynamic excitations;    Asymmetric rotors;    Floquet multiplier;    Gyroscopic Effects;    Linearized systems;    Periodic coefficients;    Resonance phenomena;    Stability assessment;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/753/8/082013/pdf
DOI  :  10.1088/1742-6596/753/8/082013

来源: IOP

【 摘 要 】

The periodic stability of an innovative load reduction system for two-bladed wind turbines is investigated using Floquet theory. The load reduction system introduces an additional cardanic degree of freedom between the hub mount and the nacelle carrier flange. A reduced rotor model is considered to analyze the time-variant behavior as a function of rotor shapes and design parameters. Aerodynamic excitation of the rotor is neglected in this study. The linearized system equations of motion of this system indicate a dependance of the rotor shape and the periodic system stability. Due to the time-variance of the asymmetric rotor the Floquet multipliers are derived to determine system stability and the dominant periodic coefficients. It can be shown that the rotor shape has a significant impact on the stability of gimbal-hinged rotors. Gyroscopic effects are the reason for a stabilization of disc-like rotors, whereas a cylindrical, two-bladed rotor assembly is in general unstable. The introduction of an additional spring-damper coupling is a possibility to stabilize such configurations, but results show that resonance phenomena have to be accounted for.