Experimental and numerical investigation of the surface-modified treatment and aerodynamic performance of a ducted-fan impeller

A ducted fan is a potential solution to improve the dynamic performance of
an Unmanned Aerial Vehicle (UAV). The impeller of the ducted fan is the
most critical plastic part. Compared with the injection molding process,
the Fused Deposition Modeling (FDM) process has a lower cost and shorter
cycle time, but its roughness and lift performance are undesirable. Based
on the hydrophobic surface treatment and the related performance research
of the ducted fan impeller, this research aimed to improve the
anti-impedance properties. Then, the modified surface of the impeller was
built based on mussel-inspired mechanisms and the chemical surface-coating
process of fan products. Experiments were conducted using a scanning
electron microscope with an ener-gy-dispersive x-ray spectroscopy system
(SEM-EDS), laser scanning confocal microscopy (LSCM), and a UAV dynamic
test platform. The experimental results show that the coating resulted in
reduced surface roughness for injection molding and FDM molding, and the
maximum lift of the impellers manufactured by the injection molding and
FDM methods was increased by 3.3% and 12%, respectively. Moreover, the
effect on the integrity of this coating process on FDM was significantly
better than on the injection molding. The numerical analysis of the
aerodynamic performance of the impeller with different roughness reveals
the mechanism by which the surface treatment affects the blade
effectiveness. The CFD results show that reducing the roughness led to
less low-energy fluid in the flow channel and reduced the turbulent
pulsation dissipation. In addition, the reduction in the blade’s surface
roughness decreased the boundary layer thickness and the boundary layer
velocity. Thus, the aerodynamic performance of the impeller was optimized.