Parametric study of the noise of a propeller-driven fixed-wing unmanned aerial vehicle with a piston engine

The results of full-scale acoustic tests of a Ptero-G0 unmanned aerial vehicle (UAV) in an anechoic chamber are presented. The aim of the work is to determine the acoustic characteristics of a Ptero-G0 UAV and to assess the influence of various parameters on the noise level of the device. A unique aspect of the experiment is that a full-scale apparatus with a power plant including a single-cylinder 4-stroke piston engine and 2-bladed fixed-pitch propeller, was studied. Data on the spectral, energy and directivity characteristics of the UAV and its power plant were obtained. The tests assessed the effects of incoming flow velocity, power condition of the power plant, pitch angle of the UAV, propeller diameter, and vibrations of the bonnet on the UAV noise. In particular, increase in the power condition (engine speed) and incoming flow velocity led to an increase in spectral noise levels in the 1/3-octave frequencies bands ranging from 40 to 10,000 Hz. At the same time, background levels up to 40 Hz were determined by background noise. The influence of engine speed and incoming flow velocity on the directivity pattern has not been established. An increase in propeller diameter at a constant speed resulted in higher circumferential speed of the propeller and thrust, as well as increased load on the engine. As a result, intensity of the tonal components of propeller and engine noise increases. A slight decrease in diameter (by 6 %) led to a decrease in the overall noise level by 1.3 dB. Placing the engine in the bonnet without a vibration insulation system led to an increase in the overall sound pressure levels by up to 2.5 dB.