Numerical investigation of the benefits of serrated Gurney flaps on an axial flow fan

Abstract

A novel serrated Gurney flap (SGF) is proposed, and a large eddy simulation is employed to simulate a two-stage variable-pitch axial fan with SGFs. The influence of the novel blades on the aerodynamic performance, sound characteristics and internal dynamics of the fan was examined, and the possible mechanism for noise reduction and vortex structure were investigated. Results indicate that the peak efficiency of the fan shifts toward the large flowrate side, and the high-efficiency region is widened when using SGFs. SGFs with an appropriate serration height reduce high-frequency noise, and the noise reduction gradually improves with decreasing serration height. The use of SGFs decreases the turbulence pulsation intensity, improves the size and distribution of wake vortices, and abates the leading-edge separation vortex and turbulence intensity. Mechanism studies indicate that two counter-rotating vortex pairs in the vertical and horizontal directions interact strongly, which alleviates the aerodynamic acoustics of the fan. A fan with an SGF with a serration height of 0.8% chord achieves the optimal overall performance, including improved efficiency, total pressure rise, and reduced noise.