Effect of Gurney Flap on Performance and Aeroacoustics of Variable-Pitch Axial Fans

Abstract

For a variable-pitch axial fan with guide vanes, the effect of three series of Gurney flaps (GFs) configured at the trailing edge of blades on the performance and dynamics is numerically investigated; and the aerodynamic noise is predicted. Simulated results show that GFs increase the total pressure rise of the fan; the higher the GF height, the more notable the lifting capacity. The working point of the highest efficiency moves toward the large flow rate. GF0.5-100 extends the high-efficiency scope and increases efficiency by an average of 2.09%; and GF2-50R raises efficiency by an average of 1.12%. After implementing a GF, the dynamics in the impeller distinctly. Compared with the original fan, a secondary tip leakage vortex generated at the blade tip aggravates the leakage loss; a pair of shedding vortices generated in the downstream of the trailing edge promotes the pressure difference between the suction and pressure surfaces. The prediction with the large-eddy simulation method indicates that GFs heighten the aerodynamic noise of the fan, and GF0.5-100 and GF2-50R increase the sound pressure level by 12 and 13 dB, respectively. Although the GF0.5-100 and GF2-50R are preferred choices for such axial fans, some necessary measures should be taken to reduce the acoustic noise in practical applications.