此研究主要是利用眼鏡蛇探針(Cobra probe)針對本實驗室所設計的三葉小型風力發電機擺設在開放式風洞內，在不同的葉尖速度比下的的狀態進行尾流的逐點量測(在輪鼓高度的來流風速為6.1ms-1,紊流強度5%)。使用Cobra探針風速計測量風機後方尾流的三個瞬時速度分量，在藉由此三個速度分量來做後續的紊流統計值分析。實驗當中，藉由改變小型風機的負載電阻，使葉片在定量的風速下改變轉速，並且利用雷射轉速計用於測量風機葉片的轉速。由國家儀器公司的USB-6001資料擷取器控制頻率轉換器，進而用於控制風洞的風扇轉速，可變動風洞吸取的風速快慢，從而固定風洞的入流風速。風速量測的範圍是量測從風機後方一個葉片直徑的距離到八倍的葉片直徑距離以及無擺放風機情況的入流狀況，每條量測線有五十七個量測點，且有六種不同的葉尖速度比，而每點量測的時間為兩分鐘。
在實驗中，紀錄每個葉尖速度比小型風機的負載電阻，以及量測葉片運轉產生的電流，算出其他物理量(例如：電壓、功率、發電效率係數)。比較在不同的葉尖速度比時產生的發電多寡，並且找出在哪個葉尖速度比會產生相對較大的發電效率，之後拿發電的效率資料與結論的紊流統計值(包括時間平均主流方向速度、紊流強度、紊流動能、動量通量和能量頻譜圖)來做進一步的探討與比較。隨時間平均的主流方向速度表明速度的分佈在小型機風機的下游會有下降的現象；隨時間平均的垂直方向速度的分布圖可以明顯地看得出，風經過小型風力發電機，輪鼓上方和下方會有反方向的垂直速度分布；紊流強度在近尾流區域的葉片尖端處具有強烈增強；紊流動能是與湍流中的渦流相關的每單位質量的平均動能；動量通量的分布圖說明流體的動能被傳遞到後方尾流，恢復了尾流中的速度不足；能量頻譜圖的分佈非常接近-5/3的斜率，這增加了使用Cobra探測器收集的風數據的可靠性。

An experiment was carried out to study the power generation efficiency of a 3-blade miniature wind turbine and observe turbulence characteristics of wakes under different tip speed ratios (TSRs) with the same freestream inflow velocity of 6.1 ms-1 in an open type wind tunnel. A calibration-free Cobra Probe was used to measure three instantaneous velocity components (streamwise, spanwise, and vertical) in the turbine wakes. By changing the loading resistance of the miniature wind turbine, the blade angular velocity is changing at a constant wind speed. The adjustment of resistors in the electrical circuit is used to effect immediately the TSRs to 0.9, 1.5, 3.0, 4.1, 5.2, and 5.9 in the prescribed total circuit resistances of 9.5, 10.5, 10.9, 14.4, 31.2, and 88.8 ohms, respectively. In the experiment, we recorded the load resistance of miniature wind turbine under each tip speed ratio, and measured the generated current, and calculated other physical quantities (e.g., voltage, power, and power coefficient of the wind turbine). Establish the power coefficient (CP) distribution, which is similar to a parabola with a maximum CP of 0.21 at the TSR of 4.1. The relationship of the generator torque constant versus the blade angular velocity, which can be used for the estimation of the electromagnetic torque of a given blade angular velocity.
The turbulence statistics including time-averaged streamwise velocity, turbulence intensity, turbulence kinetic energy, momentum flux, and power spectrum are presented. The key results show that the turbine wakes at the TSRs of 3.0 and 4.1 have the greater velocity reduction, the stronger turbulence intensity enhancement, and the larger increment of the lateral momentum flux magnitude, with a coincidence that the turbine blades at these two TSR conditions generate similar torque but different power outputs. This behavior demonstrates clearly the significance of the blade-rotation control system to power generation efficiency. The time-averaged streamwise velocity shows that the distribution of the velocity declines immediately downstream of the turbine models. The turbulence intensity has a strong enhancement at the top tip level in the near-wake region. Turbulence kinetic energy is the mean kinetic energy per unit mass associated with eddies in turbulent flow. Momentum flux demonstrates that the kinetic energy of the flow is transported recover the velocity deficit in the wakes. The distribution of power spectrum is quite close to a slope of -5/3, which increases the reliability of the wind data collected using the Cobra probe.

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