成對垂直軸風機最佳間距的數值模擬分析

本文將兩座旋轉方向相反的垂直軸風力機並列成對，利用計算流體動力學(CFD)軟體作二維及三維的數值模擬，並以兩座相同且獨立運轉的單一垂直軸風機輸出為基準值，比較成對風機在不同間距下的輸出功率與轉矩，探討在高風速11m/s和低風速5m/s狀態下最佳輸出的風機間距。二維及三維結果皆顯示，間距逐漸縮短時，在高風速下的輸出功率、轉矩與翼尖速度比都有明顯的增加；在低風速下，翼尖速度比小於0.65時，間距縮小對輸出並無幫助，翼尖速度比大於0.65時，輸出功率及轉矩則會隨間距縮小而有提升。分析間距比縮小對功率增益與轉矩增益的影響，11m/s風速下的二維和三維模擬顯示兩種增益都有明顯提升；而5m/s風速下的二維模擬，功率增益當間距比小於0.2時才會增加，三維模擬的功率增益則是隨間距比縮小而降低；不管二維或三維模擬，轉矩增益都隨間距越小而下降。整體而言，在高風速和轉速較快的情況下，成對垂直軸風機的輸出效能確實比單一垂直軸風機有大幅提升。

關鍵字

計算流體動力學；成對垂直軸風機；單一垂直軸風機

並列摘要

To promote the output performance a system of two identical vertical axis wind turbines paired with opposite rotating directions was developed in this article. Outputs of two identical and independent operating vertical axis wind turbines are compared as the reference. We adopted two- and three-dimensional computational fluid dynamics simulations to investigate the optimized spacing between two rotors under wind speeds with 5m/s and 11m/s. Both two- and three-dimensional results show that the output power, output torque and tip speed ratio (TSR) all increase significantly as the spacing decreases for high wind speed of 11m/s. The output power and output torque for slow wind speed of 5m/s still increase but only as the TSR be larger than 0.65 when the spacing decreases. Gain analysis of output power and output torque show both gains are promoted obviously as the spacing ratio decreases for two- and three-dimensional simulations with wind speed of 11m/s. The gains of output power and output torque of two- and three-dimensional simulations however decrease under slow wind condition of 5m/s and only the power gains of two-dimensional ones will increase as spacing ratio is less than 0.2. It indicates the output performance of paired vertical axis wind turbines is overall much better than that of the single turbines under higher wind speed conditions.