Impact of Design and Operation of Distributed Electric Propulsors to Aircraft Noise

This paper develops a methodology to design propulsor architectures for a distributed electric propulsion (DEP) vehicle and model its noise at various operating states and propulsor geometries. The methodology is used in a parametric study to demonstrate how variables, such as tip speed, blade count, and blade radius affect the source noise of a single propulsor with fixed thrust and flight speed. Lower tip speeds, larger blade diameters, and higher blade counts were found to decrease propulsor noise. Such designs were found to have a higher solidity ratio, however, and require more power for the same performance. The DEP architecture design capabilities of the methodology were used to assess the noise impacts of propulsor count on a representative blown-flap Short Takeoff and Landing (STOL) vehicle. Increasing propulsor count was found to reduce total thrust and noise of a representative STOL vehicle. These effects diminish at higher propulsor counts and incur higher power requirements to achieve comparable takeoff performance. The results of these studies indicate that propulsor noise can be significantly affected though propulsor geometry, its operation, and its overall arrangement when part of a multi-propulsor DEP arrangement.