Acoustic optimization of ducted fan designs

This study compares the aerodynamic and aeroacoustic performances of open rotors and ducted fans for small aircraft. The aim is to identify designs that maintain equal thrust conditions while minimizing noise. Ducted fans are known to offer improved aerodynamic efficiency and better safety over open rotors at a certain structural cost. It also presents the opportunity to utilize acoustic casing treatment, particularly desirable in urban mobility applications. In this study, multiple ducted fan configurations are developed and optimized using Computational Fluid Dynamics (CFD) simulations and noise predictions based on the Ffowcs Williams-Hawkings equation, validated through experimental measurements in an anechoic chamber. Acoustic casing treatments using porous materials and micro-perforated panels (MPPs) reduce tonal and broadband noise. Optimization minimizes the final noise radiation under the condition of equal aerodynamic performance. Factors influencing the aerodynamic performance, such as blade design and rotational speed, are investigated, together with optimal acoustic solutions for the casing with a length equal to the duct radius. The experiment is based on a scale model, but it is believed that the general approach will apply in real applications.