並聯矩陣整合型發電風車動力效率數值分析

Abstract

本研究使用流體力學套裝軟體Fluent分析二葉式Savonius風車周圍的流場與效能，研究主題分為單一風車與並聯矩陣系統，改變參數為風速、周速比及相位角差，此外探討風向對並聯矩陣系統的影響，最後討論兩個主題的差異，並與其他文獻之提升效能方法進行比較。 從模擬結果可得知，單一風車在同一周速比的情況下，功率係數（cp）會隨風速提升而略微提高，另外比較單一風車在大氣與風洞中的情境後發現，由於風洞中邊界的影響，使得風車在大氣中的效能會低於在風洞中的情境。二維模擬結果顯示，在並聯矩陣系統中，相位角差90°可得到最好的cp，為單一風車情況下的2.05倍。並聯矩陣系統的效能提升主要歸因於風車間的正向干擾情形，而流場的波動現象在此效應中扮演主要角色，但此種正向干擾效應受風向改變的影響極大。當風向改變45°時，其效能會趨近於甚至低於單一風車情況下的效能。在三維模擬中，並聯矩陣系統的最大效能會達到單一風車的1.45倍，另外比較二維與三維cp的差異，在單一風車條件下其比值為1.28，而在並聯矩陣系統中為1.83。

This study employs a computational fluid dynamics (CFD) software, Fluent, to analyze the flow fields around two-bladed Savonius wind rotors and their corresponding performances. It is divided into two topics: one is a study of a single Savonius wind rotor, and the other is of a parallel matrix system. Both are carried out by the related parametric studies. The parameters for the single wind rotor are wind velocity and tip speed ratio. The ones for the parallel matrix system are wind velocity, tip speed ratio, phase angle difference and wind direction change. Then, comparison between the two systems is discussed. Besides, comparisons with other studies are also given. The simulation results show that the cp (power coefficient) of a single wind rotor slightly increases with wind speeds at the same tip speed ratio, and the performance of the one in atmosphere is lower than that inside the wind tunnel due to the influence of walls. In the 2-D simulation results of parallel matrix system, phase angle difference 90° can obtain the best cp that is 2.05 times of that by a single wind rotor. The higher performance of parallel matrix system is resulted from the positive interaction between these Savonius wind rotors, and the flow fluctuation plays the major role in contributing to this effect, but this effect is strongly influenced by the change of wind direction. When wind direction is 45°, the cp of the parallel matrix system becomes almost the same or even lower than that of a single one. The maximal cp in the parallel matrix system by 3-D simulation is about 1.45 times of that by a single Savonius wind rotor. The ratio of 2-D cp to 3-D one is 1.28 in the single Savonius wind rotor condition and 1.83 in the parallel matrix system.