Mathematical-physical model of noise-absorbing volute of centrifugal fan and experimental validation

To reduce the aerodynamic noise of centrifugal fans, a mathematical-physical model was established to analyze the property of the sound-absorption volute of a centrifugal fan, which is composed of a perforated volute plate, an acoustic-absorbing liner, a micro-perforated plate and a cavity. The analysis with this model indicates that the absorbing liner of certain thickness would yield fine effect absorbing aerodynamic noise of about 1-8 kHz. The frequency range with higher coefficient values would be widened towards the direction of low frequency with the increase in liner thickness. Further application of cavity presents better effect absorbing tonal aerodynamic noise of a low frequency within a narrow range. The theoretical amount of noise reduction shows a similar tendency to that of sound-absorption coefficient, and increases with the increase in the number of wave reflections. The noise reduction rises gradually to a constant value of about 6 dB. Experimental results of multiple tests on the centrifugal fan with this sound-absorption volute for different operation conditions and geometry configurations are consistent with the predictions by the present model.