無人飛行器近年來發展快速，而以導管風扇為推進動力之垂直/短場起降(Vertical/Short Take-off and Landing, V/STOL)無人飛行器因為其靈活的運用特性，近來引起航空工程師的關注。而一般固定幾何的導管風扇皆是以單一操作點做設計，在非操作點之效率低落，使整個飛行器性能受限，本研究採用可變幾何之導管風扇概念，其導管入口及噴嘴可依飛行速度做外型的調整，期望提升飛行器整體飛行操作性能。
本研究以計算流體力學方法來模擬SR3先進螺槳之流場，並與文獻之實驗數據相比較，以驗證數值方法準確度，接著研究導管風扇之導管有著不同導管長度、不同葉片位置以及不同入口及噴嘴角度在各前進比(Advance ratio)下的性能與流場，期望了解導管風扇之效率與推力，為未來無人飛行器之導管螺旋槳系統提供最佳化設計之選擇。
本研究所採用的計算理論與方法是架構在CFX計算流體力學軟體上，此軟體結合有限體積法與有限元素法來求解三維Navier-Stokes方程式，並加入紊流模型k-ε來模擬，網格則採用ICEM軟體產生的自適四面體非結構性網格。本研究結果顯示，在低前進比時，導管風扇採用入口角度+30°可比無導管之螺槳多出87.4%之推力，而在高前進比時採用噴嘴角度-5°可比無導管螺槳多出117.7%之推力。

關鍵字:導管風扇、可變導管、導管螺旋槳

Unmanned Aerial Vehicles (UAVs) advancement is very fast in recent years. The Vertical/Short Take-off and Landing (V/STOL) UAV with the ducted fan as propulsion system provides an attractive option for aeronautic engineers because of its ability to both hover and fly at high speed. In general, the ducted fan with fixed geometry has better performance at design point, and worse performance at off-design points. This study employed the concept of variable duct geometry at the inlet and outlet nozzle in order to enhance the UAV flight performance at different flight speeds.

This research simulated the SR3 advanced propeller flowfield and compared the performance with experimental data to verify the accuracy of numerical method. Then the flowfield and performance of a ducted fan based on SR3 configuration with different duct length, different propeller axial location, and different inlet and nozzle angles at various advanced ratios were simulated numerically. It was expected this research can provide an understanding to improve the efficiency and thrust of ducted fan and then an optimized choice for future UAV propulsion design.

The CFD tool used in this study is ANSYS CFX. This numerical method solved 3-D Navier-Stokes equations with combined finite volume method and finite element approach. The k-ε turbulence model was adopted to simulate the turbulent flowfield. The self-adjusted tetrahedral non-structural grid was constructed based on the mesh generation software ICEM. The result of this research has shown that the thrust of ducted fan with inlet angle +30° increases 87.4% than the propeller without duct at low advanced ratios. At high advanced ratios, the ducted fan with nozzle angle -5° improved 117.7% in thrust.

Keywords:Ducted-fan, Variable Nacelle, Ducted-Propeller

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