Session: 8.4 - Turbomachinery

Paper Number: 158610

158610 - Optimization of Stator and Adoption of Bionic Rotor Blade on Noise Level of an Axial Flow Fan 

Abstract: 

The noise generated by the axial flow fan in the actual operation has a great impact on the physical and mental health of the operator, so it is of great significance to study the noise reduction design method of the fan that can meet the engineering needs.

Based on the design parameters of an axial flow fan, this paper used the isolated airfoil method to design the initial rotor of the fan by specifying a forced vortex with an exponent of 0.7. However, it was found that the chord length of the rotor at the hub of the fan was still too long. Therefore, the chords at three low sections of the rotor was reduced linearly, to reduce the axial dimension of the fan. Numerical simulations were carried out and we found that the modified rotor produced slightly reduced total pressure rise and total efficiency of the initial fan, with a considerably reduced axial dimension.

The common industrial axial flow fan usually adopts the plate guide vane, whose performance is inferior to the vane with the airfoil section. However, its flow fields is a key factor for fan noise. In this study, we fitted the profile (the camber line) of the vane using the third-order Bezier curve to optimize the guide vane and to study its impact on noise. The ANSYS Fluent software was used to conduct numerical simulation on the noise of the fan. The SST k-ω turbulence model was adopted for the steady-state calculation of the flow field, and the detached eddy simulation (DES) turbulence model was used for the transient calculation. Finally, the FW-H acoustic model was included to calculate the noise of the fan. The results showed that the noise of the fan with the optimized guide vanes was reduced by 2 dB. In addition, the computed flow field showed that the separated eddies inside the optimized guide vanes were greatly reduced, compared with those in the initial guide vane.

Then, the rotor blade was improved with the bionic configuration, to further reduce the noise of the fan. We designed the improved rotor with a wavily changed chord length distribution along the span of the blade, to imitate the wave leading or trailing edge of the bird. The numerical results showed that the total pressure and efficiency of the fan remain basically unchanged, but the overall sound pressure level was reduced by more than 2 dB, with a remarkable noise reduction effect. The main mechanism was that in the downstream of the rotor blades, the large-scale vortices at the trailing edge of the blades were broken into narrow and small vortices, and the low-frequency noise was significantly reduced while the high-frequency noise was slightly increased. In contrast, in the upstream area of the fan blades, due to the wave structure at the leading edge, many vortex structures are generated, and both the low-frequency and high-frequency noises were increased to a certain extent.

Overall, reasonable design of guide vanes and the adoption of the bionic blade have a good effect on reducing the noise of fans. The present method is a practical engineering routing for the design of a low noise axial flow fan and has certain reference significance for other researchers.

Presenting Author: Jingyin Li Xi’an Jiaotong University

Presenting Author Biography: