Designing small propellers for optimum efficiency

Abstract

Unmanned aircraft systems (UAS) extend human potential and allow us to execute dangerous or difficult tasks safely and efficiently, saving time, saving money and, most importantly, saving lives. Recently, legislation was signed into law that will help safely and responsibly unlock the tremendous potential of UAS to keep the public safe, create lasting jobs, boost local economies, and further develop in technology and innovation. In the UAS community, one of the pillars is the design and performance of open propellers used in hand launched, small UASs. The performance of these small propellers directly influences the operational capabilities of the UAS. As such, the design and testing of these propellers is necessary to accurately predict UAS performance. This experimental investigation examined the relationship between diameter and pitch to aerodynamic efficiency. Thrust, torque, power, and propeller rotational speed (RPM) were tested for 8 different propeller configurations, 5 commercial propellers and 3 designed and printed locally. The commercial propellers had diameters ranging from 9 to 7 inches and pitches from 8 to 4. Each configuration was tested statically, so the advance ratio was not considered for our study. The larger diameter propeller performed the best and the 6 was the pitch that also had a better performance. Of the three built propellers, NACA 4415, ClarkY and ClarkYM15. ClarkY worked the best.