Effects of Hub Geometry on the Aerodynamic and Acoustic Performance of Axial Flow Fans

Axial flow fans are widely used in high-speed train cooling and ventilation systems, where both static efficiency and noise reduction are critical performance requirements. In this study, the effects of hub geometry variation on the aerodynamic and acoustic characteristics of an axial flow fan are numerically investigated through three-dimensional simulations. Five fan configurations with different hub angles are analyzed under identical operating conditions. Steady aerodynamic performance is first evaluated using the Reynolds-averaged Navier–Stokes (RANS) approach with the k-ω shear stress transport (SST) turbulence model. The unsteady flow field is then resolved using large eddy simulation (LES) to capture the vortex structures and blade surface pressure fluctuations responsible for noise generation. The far-field aerodynamic noise is predicted based on the Ffowcs Williams–Hawkings (FW–H) acoustic analogy, and both tonal and broadband noise characteristics are analyzed using multiple virtual microphones. The results show that reducing the hub angle leads to improved aerodynamic performance at lower volumetric flow rates. Meanwhile, a reduction in tonal noise at the blade-passing frequency (BPF) and broadband noise at higher frequencies is observed. The findings demonstrate that appropriate hub angle design provides an effective approach for the simultaneous improvement of static efficiency and the reduction of aerodynamic noise of axial-flow fans used in high-speed train applications.