Embedded Micro Electric Ducted Fan Propulsion for Small Fixed-Wing UAVs

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Abstract
Small fixed-wing unmanned aerial vehicles are almost always driven by exposed propellers, whose slipstream washes the airframe. This paper discloses an alternative in which a multi-bladed micro electric ducted fan is embedded in the centreline body of a delta wing, with a row of guide vanes behind the rotor and the exhaust discharged behind the airframe, so that no rotating component is exposed to the external flow. Two variants with 13-bladed, high-solidity rotors of 68 mm and 46 mm tip diameter, driven at 30,000 revolutions per minute by a 6300 KV motor, are defined and assessed by computational fluid dynamics against the same airframe fitted with an APC 10x7 puller propeller, after independent validation of the airframe and propeller models. At 10 degrees angle of attack both embedded variants produce a net propulsive force at their design speeds of 30 m/s and 10 m/s, and velocity vectors confirm that the guide vanes remove the rotor swirl. The 46 mm variant retains the lift coefficient of the clean wing, 0.574 against 0.570, while the larger 68 mm duct reduces it to 0.427 but raises the lift-to-drag ratio from 9.8 with the puller propeller to 10.4. A 3D-printed prototype of the engine was built and run, and its rotor was tested on a thrust stand.

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