Research on noise reduction of annular axial cooling fan blade with perforated structure

The aerodynamic noise produced by the annular axial cooling fan significantly impacts the NVH performance of automobiles. In response to this challenge, the paper proposes a low-noise annular axial cooling fan design, which based on the principle of small-hole jet flow. To balance the aerodynamic performance and the benefits of noise reduction, an L16 orthogonal array was utilized to optimize the perforated blade parameters at the fan rated operating condition (rotational speed of 2400 rpm and a static pressure rise of ΔPs =120 Pa). Numerical simulations reveal that micro-jets ejected from the perforations effectively optimize the blade surface pressure distribution, diminishing negative pressure backflow zones and significantly reducing vorticity at the guide ring and blade trailing edge. The comprehensive optimal configuration was identified as: radial spacing divided into 15 equal segments, 1 circumferential locating line, 3 radial locating lines, and a 2 mm perforation diameter. Under the identical 120 Pa aerodynamic loading, the optimized model successfully maintained the required mass flow rate while achieving a 1.92 dBA experimental reduction in the A-weighted Total Sound Pressure Level (TSPL) compared to the original model. While discrete tonal noise is significantly suppressed at high speeds, an inherent acoustic tradeoff was observed, characterized by a slight increase in broadband high-frequency noise at lower speeds. The results confirm that this perforation-based method is a viable noise reduction strategy. It provided new insights and references for the low-noise design of annular axial cooling fans.