Modelling the structural dynamics of chosen components of the horizontal axis wind turbine

As the horizontal axis wind turbines are getting larger, their dynamic behaviour is becoming more important. Dynamic analysis gives knowledge how to improve efficiency and safety also in small wind turbines. This article describes numerical models of chosen components of upwind, three-bladed wind turbine. Geometry of each component is generated separately and then assembled together by transformation matrices. Material of the blades is composite, the hub is assumed to be made of steel and material of the planet carrier is casted iron. These mentioned components are modelled by shell elements. The numerical model of the hub takes into account aerodynamic and gravity loads of blades, inertia forces due to rotation of the rotor and aerodynamic damping. The aerodynamic loads, calculated according to the modified Blade Element Momentum theory, are attached to aerodynamic centres. Wind conditions were assumed for I-class wind turbine according to Germanischer Lloyd. Stress Reserve Factors were calculated for DLC 6.1 load case according to Germanischer Lloyd, too. As a first step, numerical strength analysis with using AnSYS software was performed with maximum values of principal stresses as an output. Then, based on FEM analysis results, Stress Reserve Factors were calculated. SRF values show that analyzed hub and planet carrier have sufficient strength for extreme loads. Methodology of safety margin evaluation presented in this paper allows assessing if the object fulfils relevant standards demanding.