- 學位論文
阻力型垂直軸風機流場之數值模擬
Numerical Simulation of the Flow Field of Drag Type Vertical-Axis Wind Turbines
摘要
本研究利用FLUENT計算流力軟體來模擬阻力型垂直軸風車之流場，求解二維非穩態不可壓縮紊流的Navier-Stokes方程式，並與實驗數據進行比對。 先利用Gambit繪製外型以及建構非結構網格且給定邊界條件，從圓柱的模擬開始，了解FLUENT對於此種外型的計算能力何在，接者透過使用不同紊流模式流經單一C型葉片，驗證何種模式為此幾何外型最適用的紊流模式，最後進行兩組阻力型垂直軸風車之模擬，第一組為兩葉片C型轉子加上分別為四片、六片以及八片所組成的導風罩，第二組則為六葉片C型轉子加上以四片、六片組成的導風罩進行模擬，計算風機的流場以及平均力矩。 得到之結果為，不同的紊流模式對於得出之結果影響甚鉅，因此在紊流的使用上仍有許多不足且需要探討的地方。而與實驗數據的比對，整體趨勢大致與實驗相符，流場向量圖符合物理現象，於低轉速高力矩時得到的值誤差大約10％~20％，尚在接受範圍，然而高轉速低力矩時則與實驗值大相逕庭，可能是由於數值結果並未包含風車系統的摩擦阻抗。
並列摘要
This study used the commercial CFD software, FLUENT, to simulate the flow field of drag type VAWTs and compare the numerical results with the experimental data. The governing equations are the two-dimensional, unsteady, incompressible, turbulent Navier-Stokes equations. This work were divided into three parts. Part 1 simulated the flow passing a circular cylinder with various Reynolds numbers to understand the predicting capability of FLUENT. Part 2 simulated the flow passing a single c-type blade subject to different turbulent models to find the applicability of turbulent model for such flows. Part 3 simulated the flow field of drag type VAWTs to obtain the average torque and power. The results show that different turbulence models affect the numerical results significantly. The applicability of turbulence models in VAWTs need to be investigated extensively. The trends of the performance curves predicted numerically match that obtained experimentally. The discrepancy between experimental and numerical results is about 10-20% when the rotational speed of turbines is lower and the torque is higher. The discrepancy is much larger when the rotational speed is high and the torque is low. This may be due to the resistance from the wind turbine system, which was not included in the numerical results.