Interactional Aerodynamics between a Rotor and a Blade-Tip-Propeller through Wind Tunnel and Hover Stand Testing

A blade-tip-propeller driven rotor consists of small electric motors and propellers attached to the rotor blade tip to spin the main rotor. This study address a propeller driven shortcoming that was identified in previous research: a high required power to spin the main rotor. To investigate this, a series of wind tunnel and hover stand test campaigns were conducted to experimentally characterize the 6 ft diameter propeller driven rotor performance. A streamlined tip nacelle was designed to house the blade tip motor, and featured an embedded load cell to measure the tip propeller's aerodynamic forces and moments. A propeller aerodynamic model was developed from propeller hover tests and then validated through wind tunnel testing of the propeller in axial flow. Next, the interactional aerodynamics between the stationary rotor blade and tip mounted propeller were investigated through wind tunnel testing. These tests were performed between 0 and 12 degrees wing angle of attack, and at airspeeds of 15 and 20 m/s. Finally, the shaft driven isolated rotor, the shaft driven rotor with tip nacelle, and the propeller driven rotor were tested in hover, and their figures of merit and power loading were compared.