When the inlet guide vane operating under the off-design conditions

strong unsteady interaction may occur between the inlet guide vane and the impeller blades of a centrifugal blowers with adjustable inlet guide vane.Interaction between the inlet guide vane and the impeller blades will cause a vibration response at the support points of the rotor and its frequency equals the passing frequency of the impeller blades.The frequency of the vibration response at the support points of the rotor caused by interaction between the inlet guide vane and the impeller blades is close to some of the characteristic frequency of a fault in rolling bearings

but there are significant differences in both the time domain and frequency domain waveform.