Experimental and numerical study on the performance of an axial fan with a Gurney flap

Abstract

Gurney flap is a miniature lift-enhancement device installed at the airfoil trailing edge and has been successfully applied to fixed wing aircraft and low-speed horizontal wind turbines. In this article, Gurney flap is extended to increase pressure output of a diffusive cascade flow in rotating turbomachinery, which is complicated for its three dimensionalities and diffusive separation characteristics. Wind tunnel tests and computational fluid dynamic simulations were accomplished on an axial fan profiled with an NACA 65-(12)10 airfoil to investigate the effects of Gurney flap on the performance of a high solidity. We present the detailed flow features of the fan with and without Gurney flap after validating the simulation results with the experimental datum. The experimental results show positive Gurney flap effects on fan’s pressure rise and flow rate improvement. However, negative Gurney flap effects on fan’s efficiency are more evident than Gurney flap on isolated airfoils. Detailed flow field analysis from computational fluid dynamic computation reveals that the increased airfoil pressure loading along the fan blade chord strengthens the tip leakage flow, which induces more tip second flow losses than in the baseline fan. In addition to the positive lift enhancement, the net Gurney flap effect in diffusion cascade is influenced by the three-dimensional flow structure.