Aerodynamic behavior and acoustic signature of propellers fabricated by additive manufacturing

Abstract

This paper explores the effects of surface texture on noise response and propeller-media interaction for additively manufactured (AM) features of unmanned aerial vehicles (UAV) rotary propellers. The microgeometry nature of material extrusion (ME), molding in additively manufactured molds, and vat polymerization (VP) processes was captured with areal texture measurements, and further aerodynamic and acoustic tests allowed to differentiate among these AM technologies. Three layer thickness values of 50 µm, 125 µm and 254 µm were tested on fabricated rotary blades at eight different rotational speeds ranging from 4000 RPM to 7500 RPM by increments of 500 RPM; measuring their thrust, torque, vibration and sound pressure level (SPL). The experimental results showed the overall sound pressure level (OASPL) is mostly constant around the recording microphones. Surface roughness and RPM were the main factors that affect performance. AM propellers exhibited a thrust loss with an associated OASPL decrease; with blades fabricated via VP having the least form deviation and best surface quality, outperforming other specimens compared against the commercial off-the-shelf (COTS) baseline. Expected advantages of using VP over COTS include onsite production and customization.