臺灣博碩士論文加值系統

同軸雙旋翼與其他旋翼型直升機相比，具有升力較大、機動性高、機身體積較小之優點，適合在地形起伏較大的環境下執行任務，為了研究雙旋翼間的氣動效應及氣動噪音特性，本研究除進行數值模擬外，並將模擬結果與實驗量測之噪音值比對。首先分析單旋翼、雙旋翼、及雙旋翼含機身的氣動特性，模擬結果發現雙旋翼的升力較佳，而機身會降低升力。而當俯仰角增加時，升力會線性增加至定值停止。間距增大時，上旋翼升力會緩慢上升，下旋翼則至最大值後急速下降，導致升力整體下降。從渦度流場中可以發現，源於旋翼交互作用生成之渦度較強時，噪音值相對較高，因此當轉速增大時，噪音值會呈現線性增加，升力則是曲線增加。在相同的條件下，比較對稱翼與非對稱翼，升力與噪音前者皆較後者為低，而非對稱翼若增加後掠角時，噪音值會隨之降低，升力則略微下降後再上升。此外，適度施以導圓角時，噪音值會有所改善，且升力並沒有太大的差異。因此，若同軸雙旋翼機在需要高負載及低噪音的考量下，建議使用非對稱後掠導圓角翼型較為合適。

Compared with another type of helicopters, the coaxial rotor has the advantages of greater lift capacity, higher maneuverability and more compact. Thus, it is allowed to operate in places where others cannot. Consequently, this study conducts numerical analysis to learn the aerodynamic and aeroacoustics characteristics of the coaxial rotor in more detail and then the simulated results are validated with the experimental acoustic data. In this research, the aerodynamics characteristics of a single rotor, coaxial rotor and coaxial rotor with fuselage are analyzed and the simulated results show that the coaxial rotor performs the higher lift and the existence of fuselage causes some reduction of lift. It was found that the lift increases linearly to a saturated value with increasing pitch angle. As the spacing increases, the lift of the upper rotor increases gradually, and the lower rotor also increases to a peak value and then drops rapidly which lowers the total lift. By observing the vorticity field, it can be found that the stronger vortices resulting from the rotor interactions, higher level noise to be produced. Consequently, as the rotational speed increases, the noise level increases linearly while the lift increases curvilinearly. Under the same conditions, the rotor blades with symmetric section perform higher lift and lower noise level than the asymmetric one. The noise level can be further reduced to have the tip of rotor blade swept back while still keeping the lift. In addition, adding a fillet to the above-mentioned swept rotor blade can alleviate the noise further. According to the analysis, asymmetric rotor blade with sweep angle and fillet is recommended for the coaxial rotor of heavy-payload and low-noise requirement.

誌謝 I
摘要 II
Abstract III
目錄 IV
表目錄 VI
圖目錄 VII
符號 XII
第一章 緒論 1
1.1 前言 1
1.2 文獻回顧 3
1.3 研究目的 6
第二章 數值模擬與實驗方法 7
2.1 數學模式 7
2.2 物理模型 10
2.3 數值模擬方法與條件 11
2.4 實驗設備與方法 13
第三章 結果與討論 16
3.1 數值模擬與實驗結果比較分析 16
3.2 雙旋翼、單旋翼與機身氣動特性分析 18
3.3 雙旋翼間距與俯仰角氣動特性分析 20
3.4 雙旋翼氣動與噪音特性分析 22
第四章 結論與建議 25
4.1 結論 25
4.2 建議 26
參考文獻 75

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