應用風洞試驗探討縮尺風力機於IEC風況下之風力特性

AERODYNAMIC CHARACTERISTICS OF SCALED-DOWN WIND TURBINE MODEL UNDER VARIOUS IEC-REGULATED WIND CONDITIONS

10.6652/JoCICHE.202309_35(5).0001

傅仲麟(Chung-Lin Fu)；羅元隆(Yuan-Lung Lo)；吳杰勳(Chieh-Hsun Wu)；陳立綱(Li-Gang Chen)

風力機 ； 風況條件 ； 風力係數 ； 風洞試驗 ； wind turbine ； wind conditions ； force coefficient ； wind tunnel test

中國土木水利工程學刊

35卷5期（2023 / 09 / 01）

437 - 449

繁體中文;英文

本研究之主要方向是以美國再生能源實驗室（NREL）所提供的5MW風力機資料為範例，在國際電工學會（IEC）所定義的不同風況條件下，採用風洞試驗方式，量測風力機縮尺模型在各種風況下的風力作用。IEC所定義的風況條件包含各種穩態流場風況及各種非穩態流場風況。各穩態風況的主要差異在於風速剖面及紊流強度；而非穩態風況的特性則是包含了風速隨時間改變及風速剖面隨時間改變此兩種非定常的設定。本研究風洞試驗的內容是在風洞中模擬出穩態及非穩態的各種風況條件，首先探討在各種穩態風況下，風力機模型在不同風攻角的風力係數特性。接著持續探討在非穩態風況條件下，風力係數隨著時間變化的情形。試驗結果顯示，若於各種流況條件下，輪毂高的風速皆相同時，均勻風速剖面的平均風力係數，通常最大，因為其風速在不同高度維持相同風速，因此在較低處的風速較其他風速剖面高，造成在該處有較大的風力。而指數較低的風速剖面條件下，因為不同高度風速變化較小，所以風機平均風力係數也會比高指數的風速剖面條件下的風力係數更大。若風速剖面相同情形下，低紊流風速所產生的平均風力係數也會高於高紊流風速所造成的平均風力係數。但是在高紊流風速的擾動風力係數則會明顯大於低紊流的擾動風力係數。而在非穩態流場，其風力係數變化與輪毂處風速變化特性相當一致。當風速剖面的指數變小時，有較大部分的受風面積承受風速增加的影響，造成風力係數會增加。而當風速剖面的指數上升，則代表大部分受風面積承受風速減少的影響，造成風力係數降低。另外，當風速高時，所造成的橫風向擾動風力會變大。

This research intends to conduct scaled-down wind tunnel tests to investigate the aerodynamic characteristics of the 5MW wind turbine, which was announced by National Renewable Energy Laboratory, under various IEC-regulated wind conditions. In IEC 61400-1, which was announced by the International Electrotechnical Society, various wind conditions are regulated for validating the safety of the wind turbines under stationary and non-stationary winds. The main differences between stationary wind conditions lie in the velocity profiles and turbulences, while those non-stationary wind conditions include the transient effects from wind speed changes or wind profiles changes. To investigate the aerodynamic characteristics of the 5MW wind turbine, stationary and non-stationary winds with specific parameters are first simulated in wind tunnels, including the utilizations of the conventional boundary layer wind tunnel and the multiple-fan wind tunnel. Then a scaled-down wind turbine model is manufactured with a high-frequency-force-balancer sensor for the measurements of base shears and overturning moments. Force coefficients under various wind conditions are calculated based on measured forces and projected tower area for comparisons. The test results indicate that if the wind speed at the height of the hub is the same for all wind conditions, the mean wind coefficient of NTM is the largest value because Wind speed remains constant with height, so the wind speed at the lower place is higher than other wind condition, resulting in larger wind force. Under the conditions of the wind speed profile with a low exponent (which means low roughness of terrain), because the wind speed changes at different heights are small, the mean wind coefficient of the fan will be larger than that under the wind speed profile with a high exponent. If the wind speed profile is the same, the mean wind force coefficient caused by low turbulent wind will be higher than that caused by high turbulent wind. However, the fluctuating wind coefficient at high turbulent wind speed is significantly greater than at low turbulence. In the non-stationary flow, the change of wind coefficient is consistent with the change characteristics of wind speed at the hub. When the exponent of the wind speed profile becomes smaller, a larger part of the wind-affected area is affected by the increase in wind speed, resulting in an increase in the wind coefficient. When the exponent of the wind speed profile rises, it means that most of the wind-affected area is affected by the reduction of wind speed, resulting in a decrease in the wind coefficient. In addition, when the wind speed is high, the resulting cross-wind fluctuating wind force will become larger.

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