| Summary: | 碩士 === 國立成功大學 === 航空太空工程學系碩博士班 === 101 === 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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