팁 간격이 덕티드 팬의 공력 및 소음 성능에 미치는 영향에 관한 전산해석

Abstract

A ducted fan offers improved safety by preventing object collisions and shielding the rotating blades. The tip clearance is an important parameter that can control the strong vortex generated at the rotating blade tips and impacts the performance. This study conducted computational analysis to investigate the effect of tip clearance on the aerodynamic performance and noise level of a ducted fan in hover condition using lattice-Boltzmann method (LBM) simulations. The tip clearance was defined as s/R = 1%, 2%, 4% using propeller radius(R), and computational analysis was conducted, including an propeller without duct. The thrust contribution of duct system was confirmed through the axial velocity field and surface pressure contour on ducted fan. Duct Shielding effect and aerodynamic noise level were investigated by comparing the overall sound pressure level (OASPL). Moreover, the directionality of noise propagation was observed using the instantaneous sound pressure field with various tip clearances. As a result, the strength of blade tip vortex increased as the tip clearance increased, thus leading to increase in tonal and broadband noise. It was concluded that a reduced tip clearance demonstrated enhanced noise reduction performance for the ducted fan.