風力發電機葉片之流固耦合分析與模流製程探討

Abstract

葉片為一細長複合材料構件，於旋轉運動時除了產生葉片長度方向的面外彎曲變形外，亦會伴隨葉片翼斷面之轉動現象，使得周圍流場改變，進而影響結構受力狀態，而葉片設計時多不考慮此氣動力與氣彈力效應，使得風力機運轉時無法達到最佳之發電狀態。此外葉片多以真空輔助樹脂灌注成型法製造，該製程的成功與否取決於適當的灌注管路安排，以及積層板滲透特性的充分掌握，而葉片的大型化使得纖維積層滲透行為更為複雜，亦增加灌注製程的困難度。 本研究首先藉由小型葉片彎扭實驗，確認纖維配向角與結構反應關係，接著利用葉片元素動量理論計算葉片入流攻角、二維流場分析翼斷面壓力分布，並結合有限元素處理結構計算，建立葉片於考慮氣動力作用下之流固疊代計算流程，藉由風力機發電效率之探討，說明葉片設計時考慮耦合效應之必要性，文中亦利用纖維配向角的安排，提升風力機之發電效率。模流製程研究著重於真空製程下之積層板滲透特性探討，葉片中夾芯積層的溝槽流動行為，藉由管元素及積層板組成之三維模型模擬之，如此可取代繁複的灌注實驗過程，而等效厚度概念的提出，有助於求得夾芯積層之滲透率，進而於灌注實驗基礎下，建立積層板之滲透率預估式，如此可迅速地求得不同積層板滲透率，並應用於大型構件真空灌注製程之數值解析。

Wind turbine blades are long, thin, composite structures and therefore will have bending deflection in the flapwise direction as well as foil-section twist during rotational motion. The twist phenomenon accompanies the change of flow filed around blades and then leads to the change of loading condition on blades. The blade design without considering the aerodynamic and aeroelastic effect makes a wind turbine could not performance the best power generation efficiency. Otherwise, blades are usually built by the vacuum assisted resin transfer molding method. The successful manufacture depends on the proper infusion strategy and well realization of permeated characteristics of various laminates. Large-scale blades make the complicated permeated behavior of laminates and increase the infusion difficulty. First, the study confirmed the relationship between fiber orientation angle and structural response by the bend-twist experiments of small wind turbine blades. Then the calculating procedure of fluid-structure interaction with considering the aerodynamic effect was established by calculating attack angles of a blade (BEM), pressure distribution on the foil sections (2D flow field analysis), and structural analyses (FEM). The fluid-structure coupling effect was specifically discussed by calculating the power efficiency of a wind turbine. The adjustment of fiber orientation angle in the blade laminates was also utilized to improve the operating efficiency of wind turbines. The mold-flow manufacturing analyses focused on discussing the permeating characteristics of composite laminates under the VARTM process. The operation of 3D model composed of 1D pipe elements and laminates simulated the groove-flowing behavior of sandwich laminates and then substituted for complicated infusion experiments. The idea of equivalent thickness contributed to derive the permeability of sandwich laminates. The permeability predictive equations that were derived on the basis of the infusion experiments produced permeability of various laminates conveniently and were beneficial for the numerical analyses of large structures manufactures under the VARTM process.