The Effect of Sweep and Taper on Static Performance for Small Propellers
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These past few years have been the years of the UAV. UAVs, also called drones, now have the friendly tasks of filming sports or movie scenes, civilian surveillance, and simple general aviation. Some companies see a future where UAVs are delivering pizza or packages. All of this shows a demand for civilian UAVs, typically in the form of quadcopters, but can also be small R/C planes. These aircraft are usually powered by small propellers and the design for propellers has not changed much despite the recent wave of UAV popularity. Two universities have made serious progress in the tabulation of small and micro propeller performance, but the realm of small and micro propeller geometry has not been pursued. Most propellers today are only classified by diameter and pitch, a measure of how far a propeller would “screw” into a solid object but other geometries of the propeller may lead to enhanced performance as well. In this study, seventeen 9 in. propellers were fabricated and tested. Thrust and torque coefficients were plotted against RPM since the tests were conducted statically. Forward sweep has adverse effects on both thrust and torque with only a hint that a higher sweep magnitude might yield significant performance improvements. Aft sweep yields substantial increases in thrust and torque, at the expense of higher power, and should qualify as a viable parameter for propeller manufactures to include in designs. A taper ratio greater than 1 has negligible increases in both thrust and torque while a taper ratio less than 1 has adverse effects on both. Varying taper ratio, at least solely from root to tip, is therefore not an effective strategy for thrust or torque augmentation, however small taper does reduce the induced power for a given thrust.