| dc.description.abstract | Aero Energy, in conjunction with the North-West University and Stellenbosch University, is supplying small-scale wind turbines with power capacities of 1kW, 3kW and 10kW. The design of a 50kW blade is intended to serve as the next logical step in the process ladder to design even larger wind turbines, and at the end, reach the goal to design and manufacture wind turbines in the megawatt range. The design of the 50kW blade is thought to be rational as it lies near the boundary in distinguishing between small- and large-scale wind turbines. This project therefore covers the structural design, hence the design of the thickness distribution and topology of the structural subcomponents of the blade.
The structural design is performed by applying the loads from IEC 61400-2 to the aerodynamic shape obtained from a previous design. The loads are calculated according to IEC 61400-2’s simplified load calculation method. The blade is divided into 10 sections and the loads are applied to the blade similar to the BEM method. A preliminary design is performed to determine the thickness distribution and topology of the structural subcomponents of the blade. These subcomponents consist of the blade’s outer skin, spar caps and shear webs. The maximum stress criterion is used in the preliminary design due to the simplicity in its calculation and to validate the FEA model. The load-carrying spar caps’ topology is optimised by determining the smallest cross-section area at each section of the blade that satisfies the design-required safety factor. This optimisation is performed to minimise the weight of the blade.
The thickness distribution and topology of the blade’s subcomponents as obtained from the preliminary design are used to validate the FEA model performed with the commercially available software package Patran. Safety factor distribution results from performing an FEA on the blade, with the preliminary design thickness distribution and topology compared well with the design calculations. Thus, the application of the material properties, loads, layup sequence, layup orientation and meshing on the FEA model was validated.
The detailed structural design is performed by adjusting the thickness and topology of each of the subcomponents at each section of the blade to satisfy the design requirements. Safety factor and tip deflection are set as the design requirements for the blade. The detailed structural design is performed through several FEAs from which the results are analysed to perform the necessary adjustments. The results presented a relatively lightweight blade compared to those currently available in the market. The structural design process is verified by comparing the results obtained from performing the same analysis procedure on an existing composite propeller blade to that obtained from full-scale tests. The results from this FEA compared well with the full-scale test results, therefore the structural design and analysis of the 50kW wind turbine blade are assumed to be adequate | en_US |
