| Abstract |
This research combines aerodynamics and finite element analysis software packages to perform multi-objective optimal blade shape designs for a 3 MW horizontal-axis wind turbine. First, a wind field simulation program, TurbSim, was used to create the time-varying load acting on the turbine. A wind turbine simulation code, FAST, was utilized to calculate the turbineˇ¦s rotor speed, generated power and applied aerodynamic forces and moments, with an input file modified from the FASTˇ¦s sample file no. 12. Some of the simulation outcomes were then fed into a finite element parametric model as the applied loads. Meanwhile, an aerodynamics software program, XFoil, was employed to compute the lift and drag coefficients of various airfoil shapes, which were then used to analyze the best chord lengths and twist angles for the turbine bladesˇ¦ airfoil-shaped cross sections. Finally, the optimal material distribution of the hollow blades made of composite materials was achieved by optimizing the finite element parametric model under the ANSYS environment. The blade cross sections are based on NREL airfoils S818, S825 and S826, and connected by B-spline surfaces. Also, the rotor blades are reinforced by box-spar to improve their strength. To design minimum-weight blades with stress constraints satisfied and their natural frequencies well separated from the turbine rotorˇ¦s operating speed, material thicknesses for various blade segments were chosen as the design variables during the optimization process. Two cases were studied in this research. For the first case, the final optimized mass was 16,668 kg. The second case increased the numbers of the divided blade segments and the design variables. As a result, the total mass of the blade was further reduced to 11,642 kg with both stress and frequency constraints satisfied. |
