Effect of serrated trailing-edge blades on aerodynamic noise of an axial fan

A bionic geometric modification inspired by the trailing-edge serrations of owl wings provides a new approach for controlling the aerodynamic noise of rotary fluid machinery. The effect of different serrated trailing-edges (STEs) on aerodynamic performance and noise of a single-stage variable-pitch axial fan was numerically investigated using steady Reynolds averaged Navier-Stokes and large eddy simulation model, respectively. Results show that STEs could improve fan efficiency at the design and low flow rates, and significantly reduce the noise in the middle- and low-frequency as well as suppress the pressure pulsation of airflow. STEs split large-scale vortices into small ones by intensifying the turbulent flow mixing. STEs with appropriate serration parameters improve the spanwise distribution of the vortex, reduce the span dimension of wake vortices, and induce wake vortices distribution to be more uniform. The innovation of this paper is that a novel blade with partial serrations is presented for the realization of the apparent noise reduction and more preferred aerodynamic performance of the axial fan by improving serration parameters and rearranging the region of the serration.