利用力平衡儀風洞試驗探討風力機整體氣動力行為

羅元隆(2020)曾經提及我國目前積極發展替代能源，風力發電更是其中最重要的一環，並且因為風機技術掌握於外國風機設計公司等受限原因，因此目前國內僅能間接獲取風力機基底的反力歷時並進行下部結構的設計。基於以上考量，本研究利用淡江大學風工程研究中心第一號大氣邊界層風洞實驗室進行風機縮尺模型的氣動力實驗，利用縮尺模型量測風機基底風力係數變化。離岸風機主要分布範圍靠近沿海一帶。當風吹過海平面時，水面會因不穩定現象而產生小的波紋和漣漪，成為風前進的粗糙表面。根據海氣象研究，海洋地況風速剖面較符合指數律α = 0.1 ～ 0.14的大氣紊流流場。因此，本研究藉由風洞試驗模擬海上流場，並對風速剖面進行分析。以日本規範AIJ 2015建議的參考值模擬D地況，接著以建築物風洞模擬中常見的C地況(α = 0.15)，平坦開闊地面或草原地況，與D地況進行平均風速、紊流強度及紊流積分尺度等剖面的比較。並繪製參考度(輪鼓高)的風速頻譜，以確認本研究模擬之流場可靠性。　　接著本研究以常見之實場風機進行縮尺相似性的探討，得出所需之縮尺比例後，進行風機模型之製作與氣動力風洞試驗。試驗過程中，本研究利用高靈敏度的六力平衡儀進行風力量測(Fx, Fy, Fz, Mx, My, Mz)。六力平衡儀的主要功能為將各軸之力與彎矩同時且連續以高精度品質輸出，採樣頻率可達 8000 Hz，並增置一數位訊號處理器以解決當訊號高速輸出時，產生之軸間偏移與雜訊等問題。本研究實驗中，採樣頻率為1000 Hz，採樣時間為5分鐘，採樣長度為300,000個資料點。分析時採用每段分成8,192點，接著針對“風力機風攻角”與“葉片轉角”兩項參數去做改變，藉此來研究各種組合下的風力係數變化特性。藉由六力平衡儀量測到的基底剪力及彎矩，進行實場的一秒移動平均，接著計算平均風力係數、擾動風力係數及風力頻譜等重要風場參數。以“葉片轉角”跟“風攻角”分類繪製出各曲線圖，同時比對兩個地況的差異性，並加以探討每個係數值其主要受到的影響原因。另外，本研究亦參考J. Jonkman(2009)針對5MW Reference Wind Turbine此海上機型的定義及設計，其中，本研究亦與OpenFAST軟體所輸出之風力歷時進行比較，探討以風洞實驗為主以及以目前國際社會常用之風場模擬軟體為主的差異性。

關鍵字

風洞試驗；力平衡儀；風力係數； FAST ； TurbSim

並列摘要

Wind power generation is an alternative energy source in future development. It comes from the fact that the wind turbine technology is mastered by the foreign wind turbine design companies. Therefore, we can only obtain the time series of the reaction from the wind turbine foundation from and carry out the structural design. Based on the above considerations, this study uses the wind tunnel of Tamkang University to do the aerodynamic experiment of the wind turbine model, and uses the model to measure the changes in the basic force coefficients of the wind turbine. 　　The main distribution of the offshore wind turbines is close to the coastal area. When the wind blows over the sea level, the water surface will produce small ripples and ripples due to instability, then become a rough surface for the wind to move forward. According to marine meteorological research, the wind profile of the ocean terrain is more consistent with the atmospheric turbulence flow field with the power law profile α = 0.1 ~ 0.14. Therefore, this study simulates the offshore flow through wind tunnel tests and analyzes the wind profile. 　　In the first stage, use the reference value recommended by the Japanese standard AIJ 2015 to simulate the D terrain, and compare it with the average wind speed, turbulence intensity and integral scale of the common C terrain (α = 0.15) profile in the wind tunnel simulation, and afterward confirm the reliability of the flow simulated in this study with the wind speed spectrum of the reference degree (high of the wheel drum). 　　In the second stage, using the model of the wind turbine to do the aerodynamic experiment of the wind tunnel. During the experiment, this study uses a high-sensitivity six-force balancer to measure the force reaction. Then, the study changes the two parameters which are "the wind attack angle of wind turbine " and "blade rotation angle" to study the characteristics of force coefficient under various combinations, and compare the differences between the two terrain conditions, and then discuss the reason for mainly affected for every factor value. 　　After the two stages, this study also compares the wind time serious output by the OpenFAST software, and explores the difference between the wind tunnel experiment and the wind flow simulated in software commonly used in the international community.