Jet-Wake Axial and Swirling Flow Characteristics of Ducted and Unducted Propulsors

The current program considers the swirl produced by three different propulsive devices, a ducted fan device with standard stators, a ducted fan device with swirling stators, and an open propeller. These devices permit an isolated comparison of the influences of jet axial velocity, tangential (swirl) velocity, and wake vortex features on wing/body integration considerations. An off-the-shelf electric ducted fan was analyzed using precision 3D scanning of the fan blade in conjunction with open-source ducted fan design codes. The resulting aerodynamic performance was used to match thrust and wake advection of a geometrically similar propeller. Thrust and torque data were collected over a range of RPM, as well as during steroscopic particle image velocimetry to verify consistency in design thrust production of all propulsive devices. Using the integrated axial thrust across the same radial volume it was found that peak axial velocity across the each propulsive device was within ten percent of the reference velocity using momentum theory of an equivalent actuator disk, thus each propulsive device could be determined to have nominally dimensional equivalent thrust with wakes advecting at the same bulk velocity. An empirical model for viscous vortex cores was used to estimate the concentrated circulation strength produced by each propulsive device. It was found that compared to the baseline EDF, the EDF Swirl and the propeller produced five times higher vorticity at the same wake pitch normalized axial location. It was however found that the empirical model of the swirl velocity did not well match the experimental data outside the core region. This work was supported by the US Office of Naval Research under grant number N00014-22-1-2191. The authors would like to thank David Gonzalez and Ashish Bagai for their support of this work. Undergraduate researcher Marty Bathgate is also gratefully acknowledged for their help in the lab.