Analysis on the 2nd order blade passing frequency noise mechanism and research on optimization design method of axial fan based on the wavelet transform
In order to study the sources and suppression methods of second-order blade frequency noise in outdoor axial fans of air conditioning units,large eddy simulation was used in combination with energy spectrum analysis and wavelet analysis methods to identify typical flow field positions and flow structures that affect second-order blade frequency noise.The optimization design method of fan blade shape was studied and experimentally verified.Results show that the peak value of 2nd order blade passing frequency is influenced mostly by the clearance between blade and its surrounding component,as well as the outflow of the tip area.By increasing the gap between the fan and the separator by 9 mm,the 2nd order blade passing frequency noise can be reduced by 6 dB.The front loading blade can also reduce the peak value of 2nd order blade passing frequency.In addition,the 2nd order blade passing frequency phase difference can be controlled around π/3 by adjusting the circumferential stacking curve,thereby the amplitude superposition is suppressed,and the 2nd order blade passing frequency peak value is decreased by about 6.7dB.The results can provide technical reference for optimizing the 2nd order blade passing frequency noise of the axial fans.
axial fan2nd order blade passing frequency noisewavelet analysisoptimization design method
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