Research Of Noise Analysis And Reduction Methods Of Cooling Fans

From the aviation equipment, engineering machinery industry, automobile enginesto the daily medium-and-small sized electronic equipment, cooling fans are necessaryfor their normal working. Due to the continuous development of electronic products, theproblem of cooling fan noise is receiving increasing attention. Especially, in recentyears, low noise has become a highly competitive factor in the purchase of fanequipment. The design of low-noise fans and the noise reduction methods are the urgentdemand of manufacturers as well as consumers. Take the DELTA AFB0712HHB as theresearch object, this paper mainly discuss the generation mechanism of its aerodynamicnoise and the noise reduction design. This paper finished the following work:(1) It summarizes the physical essence of the noise. Typically, it is caused by thetip leakage flow, non-uniform inlet flow, turbulence or separated flow condition on arotor, trailing edge noise as well as the rotor-stator interaction.(2) Based on UG and GAMBIT, the geometry model of cooling fan wasestablished and simplified further. GAMBIT is also used to build the grid of thecomputing domain which was divided into four different areas.(3) Two feasible boundary setting schemes are tested and compared. It proved thatthe first scheme converges faster and more accurate.(4) The steady and unsteady numerical calculation was simulated by FLUENT. Theinternal flow characteristics and aerodynamic noise of the fan was analyzed through thesimulation data.(5) The sound pressure level measurement is carried out for the noise of thecooling fan. The relative error is less than7%by comparing the measurement andsimulation results.(6) Analyzes how the airfoil parameters affect the aerodynamic noise of the coolingfan and proves that blades perforation and small hub ratio are feasible for noisereduction by CFD simulations.