In order to discuss the major factor on the noise characteristics of a propeller fan, the influence of the number of blades on the periodical fan noise generated due to the tip vortex is analyzed. The influence of the tip vortex on the fan noise is argued by the measured internal flow. For the analysis of the structure on the mean flow in the blade passage, the phase of the unsteady signal of the wake is locked by the trigger signal synchronized with the rotation signal. The noise generated from the tip vortex became 200 Hz even if the number of blades was different. We clarified experimentally that the periodical noise due to the tip vortex became small according to the scale of the tip vortex.
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