Passive Noise Reduction for a Contrarotating Fan

Abstract

There has been renewed interest in the contrarotating (CR) fan configuration in aviation and other applications where size and weight are important design factors. Contra-rotation recovers swirl energy compared with the single-rotor design, but this advantage is not fully harnessed due to, perhaps, the issue of noise. This study explores passive noise reduction for a small, axial-flow, CR fan with perforated trailing-edge for the upstream rotor and perforated leading-edge for the downstream rotor. The fan is designed with simple velocity triangle analyses, which are checked by 3D flow computations. The aerodynamic consequence and the acoustic benefit of such perforated blading are investigated experimentally. The results show that there is a reduction of total pressure compared with the baseline CR fan at the same rotating speeds, but this is easily compensated for by slightly raising the rotating speeds. A reduction of 6–7 dB in overall noise is achieved for the same aerodynamic output, although there is a moderate noise increase in the high frequency range of 12.5–15.0 kHz due to blade perforations. The effect of inter-rotor separation distance is also investigated for the baseline design. A clear critical distance exists below which the increased spacing shows clear acoustic benefits.

Experimental investigation on the effect of load distribution on the performances of a counter-rotating axial-flow fan

“…Counter-rotating axial turbomachines such as propellers, axial-flow pumps and low-speed fans are used in various industrial domains [1][2][3][4][5][6][7]. In a counter-rotating stage (CRS), the front rotor (FR) and the rear rotor (RR) rotate in opposite directions (see Fig.…”

Performance and Internal Flow of Contra-Rotating Small-Sized Cooling Fan

“…Further the fan noise becomes larger than the conventional rotor stator type fan because of the interaction between the front and rear rotors. Then, the passive noise reductions with the perforated blade were proposed for the contra-rotating fan [13]. It is important to clarify the influence of the wake from the front rotor to the rear rotor and the potential interaction between the front and rear rotors to increase the performance and to reduce the fan noise [14].…”

Investigation of Speed Matching Affecting Contrarotating Fan’s Performance Using Wireless Sensor Network including Big Data and Numerical Simulation

“…Development of high-performance turbomachinery is always an important orientation in the field of aeroengines. Thanks to unique advantages in structural and aerodynamic aspects, the contrarotating fan (CRF) technology is deemed as an important technology which can break through development limits in traditional rotor-stator blade row compressors and has drawn close attention from lots of scholars at present [1][2][3]. Basic ideas of the contrarotating fan technology are as follows: the stator component is canceled and the contrarotation of rotor is used to increase the power capability.…”