Experimental Investigation of Propeller Noise from a 10% Scale Half-Model eVTOL Aircraft

A 10% scale, half-model eVTOL aircraft was built, and far-field noise measurements were performed in the National Aeroacoustic Wind Tunnels at the University of Bristol at various operating conditions. The half-model eVTOL aircraft consists of a PLA 3D-printed fuselage and wing with interchangeable flaps, pylons machined from stainless steel, and propellers machined from aluminium. There are two pylons: inboard and outboard of the fuselage and each pylon consists of a forward propeller mounted on an interchangeable part such that the forward propeller can be tilted from the hover to cruise condition, and an aft propeller that operates in the hover condition and is stationary and fixed in position in the cruise condition. The propellers are mounted on an electric motor such that it can be rotated to - RPM. Wind tunnel testing was performed for a forward and aft propeller installed on the inboard pylon of the 10% scale, half-model eVTOL aircraft for multiple forward propeller tilt angles, aircraft pitch angles, wind tunnel speeds, and multiple combinations of the forward and aft propeller rotational speeds. A microphone array consisting of 60 ¼-inch microphones encompassing a spherical quadrant of the anechoic wind tunnel was assembled to obtain far-field noise measurements. Preliminary experiments were performed to mitigate low-Reynolds number effects on the propeller and wings, and the effect of the wind tunnel nozzle size on the noise produced by the installed propeller was also investigated. Acoustic spectra and directivity plots will be presented showing the trends in the effect of the aircraft pitch angle and forward propeller tilt angle on the far-field noise.