Vibrations in centrifugal fans due to v-belt excitation

For satisfactory prediction and reduction of the vibrations in centrifugal fans, it is necessary to consider the forced vibration with not only unbalance due to rotary machinery but also V-belt excitation. The object of this paper is to show the mechanism of the vibration caused by the V-belt and present an analysis method that is applicable to predict this vibration. The fluctuation of the belt tension takes place when the belt seams pass through the pulleys during operation. While operating, it is considered that the excitation force due to the fluctuation of the belt tension should be a periodic pulse. Hence, the amplitudes of the higher harmonics are predicted by Fourier series and the amplitudes of the frequency response are calculated by using the modal analysis result. As a result, it was concluded that the analyzed data were consistent with the measured data. In addition, it was shown that there is a higher harmonic resonance between the fourth order component of the belt rotation and the natural frequency of the tested fan.