Aeroacoustic Experimental Investigation of a Distributed Electrical Propulsion 1:1 Scale Model

A 1:1 scale experimental setup has been developed to study the arrangement of propellers in Distributed Electrical Propulsion systems. A wing from a Pipistrel Taurus Electro airplane is placed downstream of 3 propellers designed and manufactured for this experimental campaign. The relative positioning of components and the change of the wing angle of attack are made possible. The test rig has load cells to compute the wing lift and the propeller's thrust. The radiated sound is measured with an array of 16 microphones mounted on ground boards. Results show that the proper placing of the propellers relative to the wing can increase the lift of the DEP system, mainly when propellers are located on the suction side of the wing. Up to 5 dB noise reduction is observed in the mid-frequency range when the wing angle of attack is increased due to a change in the wake interaction noise mechanism. At frequencies lower than the first BPF, the wing is probably acting as a reflective surface. The research also highlighted the difficulties of performing measurements in uncontrolled environments, as a difference in wind conditions can hide the effect of small geometrical effects on aerodynamic and acoustic performances.