| Summary: | 碩士 === 長庚大學 === 機械工程學系 === 101 === When a blade was designed without the consideration of the axial induction factor, the blade has a problem of excessive twist angle, which reduces the performance of the blade. Therefore, the purpose of this study is to find the optimized twist angle for the blade of a micro horizontal axis wind turbine and to fabricate the blade for performance verification. Firstly, we estimate the blade size based on the rated parameters. Secondly, we choose the airfoil type, chord length, and twist angle without considering the axial induction factor for each section of the blade. Then, the twist angle of the blade is characterized with a factor, p, which represents the degree of twist. The blades with varying p are analyzed with the Blade Element Momentum theory for their performance. After that, the power of coefficient CP of each section with independently varied twist angle is calculated and the combination of the twist angles with the highest CP is recorded. Finally, the blade with the optimal combination of twist angles is modeled with a 3D computer aided design software and fabricated. The model blades are installed on a vehicle mounted test-bench for performance tests. The results show that, the optimal design blade has a CP of 0.45 under a TSR (tip speed ratio) of 6.2. This CP is 0.05 higher than that of a non-optimal blade. More over, the maximum TSR becomes 10 from a previous value of 8, which shows a much stable output from the rotor can be expected. However, the optimal twisted blade has a higher start-up speed than that of the non-optimal bladed. This suggests that a pitch-adjustment mechanism is needed for the optimal blades so that the high performance would not be overlooked.
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