Prediction of blade trailing‐edge noise of an axial flow fan

2008 ◽  
Vol 123 (5) ◽  
pp. 3687-3687
Author(s):  
Alain Guedel ◽  
Arthur Finez ◽  
Gérald Perrin ◽  
Michel Roger
Keyword(s):  
Axial Flow ◽  
Axial Flow Fan ◽  
Trailing Edge ◽  
Trailing Edge Noise

scholarly journals The influence of axial-flow fan trailing edge structure on internal flow

2018 ◽  
Vol 10 (11) ◽  
pp. 168781401881174
Author(s):  
Weijie Zhang ◽  
Jianping Yuan ◽  
Banglun Zhou ◽  
Hao Li ◽  
Ye Yuan
Keyword(s):  
Numerical Simulation ◽  
Low Frequency ◽  
Axial Flow ◽  
Internal Flow ◽  
Axial Flow Fan ◽  
Trailing Edge ◽  
Edge Structure ◽  
Blade Loading ◽  
Wideband Noise ◽  
Fluctuation Amplitude

Axial-flow fan with advantages such as large air volume, high head pressure, and low noise is commonly used in the work of air-conditioner outdoor unit. In order to investigate the internal flow mechanism of the axial-flow fan with different trailing edge structures of impellers, four kinds of impellers were designed, and numerical simulation and experiment were deployed in this article. The pressure distribution on the blades surface and distribution of vorticity in impellers were obtained using numerical simulation. Distribution of blade loading and velocity at the circumference are discussed. The relationship between the wideband noise and the trailing edge was established based on the experiment results. The results show that after the optimization of the trailing edge structure, the distribution of vorticity near the trailing edge of the blade is more uniform, especially at the trailing edge of 80% of the chord length of the suction surface. From the blade height position of 70% to the impeller tip, the pressure on the surface rapidly increases due to the tip vortex and the vortex shedding on the blade edge occurred in the top region of impeller. The pressure fluctuation amplitude at the trailing edge structure of the tail-edge optimization structure is smaller. In the distribution of blade loading, the three tail-edge optimization structures have smaller pressure fluctuations and pressure differences at the trailing edge structure. It is extremely important to control the fluctuation amplitude at the trailing edge. The amplitude of low-frequency sound pressure level of optimizing the trailing edge structure decreases obviously in the range of 50–125 Hz, and the optimization structure of trailing edge has an obvious effect on low-frequency wideband noise.

121 Characteristics of Velocity Fluctuation near Trailing Edge of Rotor Blade of Axial Flow Fan

2014 ◽  
Vol 2014.67 (0) ◽  
pp. _121-1_-_121-2_
Author(s):  
Kazuki HOSOKAI ◽  
Naoki ANDO ◽  
Hiromitsu HAMAKAWA ◽  
Eru KURIHARA
Keyword(s):  
Velocity Fluctuation ◽  
Rotor Blade ◽  
Axial Flow ◽  
Axial Flow Fan ◽  
Trailing Edge

Rotating Stall Inception From Spike and Rotating Instability in a Variable-Pitch Axial-Flow Fan

2008 ◽  
Author(s):  
Takahiro Nishioka ◽  
Toshio Kanno ◽  
Hiroshi Hayami
Keyword(s):  
Three Dimensional ◽  
Axial Flow ◽  
Rotating Stall ◽  
Tip Leakage Flow ◽  
Axial Flow Fan ◽  
Trailing Edge ◽  
Stall Inception ◽  
Tip Leakage ◽  
Rotating Instability ◽  
Stagger Angle

End wall flow fields at the two stagger-angle settings for the rotor blades in the low-speed axial-flow fan are experimentally and numerically investigated to elucidate the mechanism of stall inception. Rotating instability is confirmed near the maximum pressure-rise point at both design and large stagger-angle settings. This instability is induced by the interaction between the incoming flow, tip leakage flow, and backflow from the trailing edge. The stall-inception pattern, however, differs at the two stagger-angle settings. The stall inception from a spike is observed at the design stagger-angle setting, and the stall inception without the spike and modal disturbance is observed at the large stagger-angle setting. The rotating instability seems to influence the formation of stall cell at the large stagger-angle setting. Tip-leakage vortex breakdown occurs at both design and large stagger angle settings. This breakdown induces the three-dimensional separation on the suction surface of the rotor blade at the tip. Three-dimensional separation at the design stagger-angle setting is stronger than that at the large stagger-angle setting. The strong separation grows into a three-dimensional separation vortex, which crosses the blade passage near the trailing edge. This separation vortex seems to be one of the conditions for spike initiation.

Prediction of the Blade Trailing-Edge Noise of an Axial Flow Fan

2011 ◽  
Author(s):  
Alain Guedel ◽  
Mirela Robitu ◽  
Nicolas Descharmes ◽  
Didier Amor ◽  
Je´rome Guillard
Keyword(s):  
Input Data ◽  
Pressure Fluctuations ◽  
Axial Flow ◽  
Suction Side ◽  
Axial Fan ◽  
Trailing Edge ◽  
Frequency Spectra ◽  
Pressure Transducers ◽  
Trailing Edge Noise ◽  
Wall Pressure Fluctuations

The objective of this work is to predict the trailing-edge noise of axial fans with an analytical model deduced from an extension of Amiet’s formulation. The input data of the acoustic model are the frequency spectra and the spanwise correlation length scales of the wall-pressure fluctuations on the blade suction side close to the trailing edge. This model was successfully validated in former studies on single steady airfoils in anechoic wind tunnels and, to a lesser extent, on an axial fan equipped with small unsteady pressure transducers flush mounted on the blade suction side. The present research is carried out on a 6-blade axial fan no longer equipped with embedded pressure transducers. The input data of the prediction are then deduced from non-dimensional spectra and correlation lengths of the pressure fluctuations measured in the previous study and RANS simulations performed on the test fan. A validation of the prediction method is made by comparing the predicted and measured sound power spectra of the fan for two blade pitch angles and different operating points.

Computation of trailing-edge noise due to turbulent flow over an airfoil

AIAA Journal ◽  
2002 ◽  
Vol 40 ◽  
pp. 2206-2216 ◽  
Author(s):  
A. Oberai ◽  
F. Roknaldin ◽  
T. J. R. Hughes
Keyword(s):  
Turbulent Flow ◽  
Trailing Edge ◽  
Trailing Edge Noise

Noise source location and scaling of subsonic upper-surface blowing

2020 ◽  
Vol 19 (3-5) ◽  
pp. 191-206
Author(s):  
Trae L Jennette ◽  
Krish K Ahuja
Keyword(s):  
Strouhal Number ◽  
Noise Source ◽  
Low Frequency ◽  
Directivity Pattern ◽  
Source Location ◽  
Dipole Source ◽  
Frequency Noise ◽  
Noise Sources ◽  
Trailing Edge ◽  
Trailing Edge Noise

This paper deals with the topic of upper surface blowing noise. Using a model-scale rectangular nozzle of an aspect ratio of 10 and a sharp trailing edge, detailed noise contours were acquired with and without a subsonic jet blowing over a flat surface to determine the noise source location as a function of frequency. Additionally, velocity scaling of the upper surface blowing noise was carried out. It was found that the upper surface blowing increases the noise significantly. This is a result of both the trailing edge noise and turbulence downstream of the trailing edge, referred to as wake noise in the paper. It was found that low-frequency noise with a peak Strouhal number of 0.02 originates from the trailing edge whereas the high-frequency noise with the peak in the vicinity of Strouhal number of 0.2 originates near the nozzle exit. Low frequency (low Strouhal number) follows a velocity scaling corresponding to a dipole source where as the high Strouhal numbers as quadrupole sources. The culmination of these two effects is a cardioid-shaped directivity pattern. On the shielded side, the most dominant noise sources were at the trailing edge and in the near wake. The trailing edge mounting geometry also created anomalous acoustic diffraction indicating that not only is the geometry of the edge itself important, but also all geometry near the trailing edge.

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