並聯矩陣沙伯紐式風車效率改善數值研究

Abstract

本研究使用流體力學套裝軟體Fluent分析二葉式沙伯紐式風車周圍的流場與其對應的效能。效能的衡量標準為功率係數Cp(power coefficient)。本研究內容可分為三部分：其一為對單一風車的研究，其二為四風車並聯矩陣系統的研究，其三為十風車並聯矩陣系統的研究。三個系統將會與其分別對應的參數進行研究。在參數分析中，改變參數為風速與周速比，在此之後會探討風向對並聯矩陣系統的影響。最後，本研究將討論三種系統的差異比較。 由數值模擬結果顯示，單一風車之最大Cp值為0.191，發生在周速比0.8的情況下；四風車並聯矩陣系統之最大Cp值為0.402，發生在周速比0.9的情況下；而十風車並聯矩陣系統之最大Cp值為0.438，發生在周速比0.7的情況下。十風車並聯矩陣系統的平均Cp值是單一風車的2.25倍，四風車並聯矩陣系統的平均Cp值是單一風車的2.07倍，而十風車並聯矩陣系統的平均Cp值是四風車並聯矩陣系統的1.08倍。 三個系統的功率係數（Cp）分別在同一周速比的情況下，會隨風速提升而略微提高。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。當風向改變為0°時，其效能幾乎不會改變，甚至低於單一風車情況下的效能。

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. This research includes three cases: the first one is a study of a single Savonius wind rotor, the second is the parallel matrix system, consisting of four two-bladed Savonius wind rotors, and the last one is the parallel matrix system of ten two-bladed Savonius wind rotors. All of the cases are carried out by the corresponding parametric studies, whose parameters include the wind velocity and tip speed ratio. After that, the influence of wind direction change on the parallel system is also studied. Then, comparisons between the systems mentioned above are discussed. The simulation results show that the maximum Cp value of one single Savonius wind rotor is 0.191 at tip-speed ratio 0.8; the parallel matrix system with four Savonius wind rotors is 0.402 at tip-speed ratio 0.9; the parallel matrix system with ten Savonius wind rotors is 0.438 at tip-speed ratio 0.7. The average Cp of the parallel matrix system with ten Savonius wind rotors is 2.25 times higher than that in one single Savonius wind rotor and the average Cp of the parallel matrix system with four Savonius wind rotors is 2.07 times higher than that in one single Savonius wind rotor. However, the average Cp of the parallel matrix system with ten Savonius wind rotors is 1.08 times higher than that in the parallel matrix system with four Savonius wind rotors. The Cp of these three cases slightly increase with wind speeds at the same tip speed ratio. 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 0°, the Cp of the parallel matrix system becomes almost the same or even lower than that of a single one.