Measurement of Static and Dynamic Performance Characteristics of Electric Propulsion Systems

Today’s unmanned aerial vehicles are being utilized by numerous groups around the world for various missions. Most of the smaller vehicles that have been developed use commercially-off-the-shelf parts, and little information about the performance characteristics of the propulsion systems is available in the archival literature. In light of this, the aim of the present research was to determine the performance of various small-scale propellers in the 4.0 to 6.0 inch diameter range driven by an electric motor. An experimental test stand was designed and constructed in which the propeller/electric motor was mounted in a wind tunnel for both static and dynamic testing. Both static and dynamic results from the present experiment were compared to those from previous studies. For static testing, the coefficient of thrust, the coefficient of propeller power, and the overall efficiency, defined as the ratio of the propeller output power to the electrical input power, were plotted versus the propeller rotational speed. For dynamic testing, the rotational speed of the propeller was held constant at regular intervals while the freestream airspeed was increased from zero to the windmill state. The coefficient of thrust, the coefficient of power, the propeller efficiency and the overall efficiency were plotted versus the advance ratio for various rotational speeds. The thrust and torque were found to increase with rotational speed, propeller pitch and diameter, and decrease with airspeed. Using the present data and data from the archival and non-archival sources, it was found that the coefficient of thrust increases with propeller diameter for square propellers where D = P. The coefficient of thrust for a family of propellers (same manufacturer and application) was found to have a good correlation from static conditions to the windmill state. While the propeller efficiency was well correlated for this family of propellers, the goodness of fit parameter was improved by modifying the propeller efficiency with D/P.