Synchrophasing as a Noise Reduction Tool in Distributed Electric Propulsion Systems during Flight

Abstract

This paper presents an extension of an active control strategy, synchrophasing, to mitigate noise levels caused by Distributed Electric Propulsion. By dynamically computing specific phase differences between rotating propellers, destructive interference is sought at certain longitudinal locations on the fuselage, reducing noise exposure for passengers. To effectively implement synchrophasing, an Extremum-Seeking Controller strategy has been previously demonstrated to be able to minimize the noise perceived by external, on-ground microphones in an overflight case. This work focuses on the noise perceived by microphones on the aircraft fuselage. Upon setting the measured Sound Pressure Level at particular microphone locations as a cost function, a minimization thereof is pursued using the relative phases as manipulated variables. This paper evaluates the utility of ESC for a preliminary in-flight model considering an arbitrary number of propellers on one side of the wing and a longitudinal array of microphones on the fuselage skin. The objective is that, on running the control algorithm, ESC should reduce the SPL at certain microphone locations. This reduction, added to the structure-based sound reduction, enables a quiet flight experience in electrified aircraft.