風力發電機葉片負載計算及彈性耦合葉片之研究

A Method to Calculate the Loads of Wind Turbine Blades and Researches of Adaptive Blades

賴偉銘(Wei-Ming Lai)

指導教授 ： 林輝政

國立臺灣大學/工學院/工程科學及海洋工程學研究所/博士(2010年)

https://doi.org/10.6342/NTU.2010.01804

摘要

在風力發電機葉片的結構分析上，一般都採用有限元素法中的殼元素來進行分析，有限元素法計算量雖然大，但憑藉著現代計算機的發達，因此在計算上仍游刃有餘。但倘若需要瞭解流體與結構之間的耦合情況時，可能需要使用全域計算的有限元素法方式或是搭配CFD流體計算程式，同時網格點需要相互對應時，將會使得計算量遽增，導致計算耗時且無效率。因此，本文利用一個結合解析法與有限元素法的樑模型來計算風力發電機葉片受力負載，並可同時考慮流體與結構之間的耦合關係，除此之外，因為解析法的使用，此模型也可推得葉片各斷面之結構剛性，這些資訊對於設計者來說相當重要，此亦為使用殼元素之有限元素法無法達到的地方；另外，相對於殼元素來說，本文所提出之方法不僅在計算量上也可以大幅減少，在修改葉片參數上也更加方便。在本文的模型驗證中，計算結果與使用殼元素之有限元素法相比較，變形量差異大部分均保持在10%之內，顯示計算結果相當具有可靠度。綜合以上各點，本文所提出的計算方法將可作為風力機葉片設計時的參考工具。
本文亦利用此樑模型來分析彈性耦合葉片，討論其運用於風力機之可行性，所使用的標準葉片為NREL所開發之SERI-8；此外，並透過修改積層角度的方式來設計彈性耦合的葉片。本文試算兩種彈性耦合葉片模型，一種為彎扭耦合葉片，另一種為拉扭耦合葉片。彎扭耦合葉片是利用流體給予葉片之推力而產生扭轉變形，進而期望達到被動螺距控制的效果；而拉扭耦合葉片則是利用葉輪旋轉時的離心力來使得葉片各斷面螺距角改變，但根據計算結果顯示，本文所試算之兩種耦合葉片在一般風力機運轉條件下，耦合造成的扭轉量相當小，因此都達不到預期的效果。而在材料的受力上，由於本文內之彈性耦合葉片是利用標準葉片修改積層角度而成，因此彈性耦合葉片的材料應力如預期的是比標準葉片要高一些，但幅度並不大。

關鍵字

風力發電 ； 彈性耦合 ； 流固耦合 ； 葉片 ； 有限元素法

並列摘要

Typically, analyzations of wind turbine blades are completed by using the finite element method with shells. Despite huge processing time consumed, the finite element method is convenient in calculating blade structures based on the advance of modern calculators. When the coupling between fluid and the blade structures are considered, either the global finite element simulation or that together with the CFD simulation is often adopted; however, this kind of method accompanying increasing processing quantity tends to be time-consuming and inefficient. Thus, the article uses a combined analytical and finite element beam to not only solve the foregoing problem, but consider the interaction between fluid and the blade structures. Besides, the analytical method adopted in the article help find out the sectional properties of the blades, which are important information to blade designers yet is not able to acquire by using the finite element method with shells. In addition, the present method can also reduce processing time to a great extent comparing to the finite element method with shells. Further, the method allows easy means for modifying the parameters during simulations. In the verification models of the article, the errors between present method and pure finite element method with shells by ABAQUS are mostly less than 10%. Therefore, there is no doubt about the accuracy of the calculation results. With the advantages described above, the present method in the article is suitable to be a reference in the design of the wind turbine blades.
The article also analyzes the elastic coupling blades, of which discussions on the applicability are meanwhile elaborated. The baseline blade model adopted in the article is SERI-8 developed by NREL. Moreover, two elastic coupling blades—the bend-twist coupling blade and the extension-twist coupling blade—are tested by changing the fiber orientation angle to achieve the elastic coupling property. The bend-twist coupling blade is triggered by the thrust force generated by fluid, and is expected to twist the pitch angle like a passive controller. Considering the calculated results in the article, the twist angle of the bend-twist coupling blade is too small to be a fine passive controller of the wind turbines. On the other hand, the extension-twist coupling blade is triggered by the centrifugal force, but the results are worse than that of the bend-twist coupling blade. As for the mechanical behavior of materials, the stress of the coupling blades is a little higher as predicted than that of the baseline model.

並列關鍵字

wind turbine ； elastic coupling ； fluid-structure coupling ； blade ； FEM

參考文獻

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