設計風車考慮要點之系列教具

A Series of Teaching Aids that Expose the Considerations for Designing Wind Turbines

周鑑恆(Chien-Heng Chou)

《物理教育學刊》 23卷1期 (2022/07) Pp. 25-36

https://doi.org/10.6212/CPE.202207_23(1).0003

摘要

設計風車的目的，在於利用風車從風中獲得最大比例的風能，到目前為止，絕大多數現代專業風車獲取風能的比例，都遠比貝茲極限59.3%少。設計風車首先要考慮：風車要裝幾片葉片以及葉片速度比風速要大多少倍，以便使風車各葉片不互相干擾，也就是說，後方的葉片不會受到前方葉片造成的慢速風影響，另一方面，也要避免白白流失風能。所以，風車葉片的數目，風車葉片尖端的速度與風速的最佳比例，是同時被決定的。一旦確定了風車葉片尖端速度與風速的最佳比例之後，風車葉片在此最佳比例轉動時，就不會受到其它葉片的干擾。接下來要詳細考慮葉片各區段的安裝角、翼型、以及葉片本身的形狀等等，以便能夠充分利用風對葉片造成的升力來轉動風車，獲得風能。本文介紹的系列教具，一一說明設計風車的各步驟中所考慮的要點，包括：顯示「經過風車葉片附近而被風車葉片取出動能的風，分布在空間中哪些地方」的教具；第二個教具是兩具葉片數目相差懸殊的風車，突顯風車葉片會互相干擾的現象。第三個教具由兩項教具構成，共同說明：風車葉片各區段的安裝角必須依序合理調整，才能發揮最佳的性能。第四個教具顯示翼型對於風車運轉的重要性。

關鍵字

風力發電 ； 升力 ； 貝茲極限 ； 最佳周速比 ； 攻角 ； 失速 ； 翼型 ； 相對風速

並列摘要

The purpose of designing wind turbines is to use wind turbines to harness the largest proportion of wind energy from the wind. So far, the proportion of wind energy obtained by most modern professional wind turbines is far less than the Betz limit of 59.3%. The first issue to consider when designing a wind turbine is how many blades should be installed in the wind turbine and how many times the speed of the blades is higher than the wind speed in order that the blades of the windmill do not interfere with each other. Therefore the rear blades will not be affected by the slow wind caused by the front blades, On the other hand, it is also necessary to avoid the loss of wind energy in vain. Therefore, the number of wind turbine blades and the optimum ratio of the tip speed of the wind turbine blades to the wind speed are determined together. Once the optimal ratio of the tip speed of the wind turbine blade to the wind speed is determined, the wind turbine blade will not be disturbed by other blades when it rotates. Consequently, the installation angle of each section of the blade, the airfoil, and the blade itself must be considered in detail. All the design characteristics of the wind turbine can make full use of the lift caused by the wind which rotates the wind turbine to obtain wind energy. The series of teaching aids introduced in this article illustrate the key points considered in each step of designing a wind turbine, including four types of instruments with different teaching purposes. The first teaching aids show the location of the wind which passes near the wind turbine blades and whose kinetic energy is taken out by the wind turbine blades. The second teaching aids are two wind turbines with 12 blades and 2 blades respectively which highlight the phenomenon that the blades of the windmill will interfere with each other. The third teaching aid consists of two teaching aids, which together indicate that the installation angles of each section of the wind turbine blade must be adjusted in a reasonable order so that the wind turbine blade can exert the best performance. The fourth teaching aid shows the importance of airfoils to the operation of wind turbines.

並列關鍵字

wind power generation ； lift ； Betz limit ； optimal tip speed ratio ； angle of attack ； stall ； airfoil ； relative wind speed

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