Experimental Studies on Twelve Bladed Fan Vibration Considering Flexibility of Shaft

A fan rotor system can generate a large amplitude blade-passing frequency (BPF) component if the gap between rotating fans and stationary diffusers is not equal. A series of experiments was conducted in this study using Spectra Quest’s Machinery Fault Simulator (MFS) to observe the behavioral changes of the BPF and its harmonics before and after installing an obstruction nearby an axial fan. In order to incorporate the flexibility of the shaft a modification in the existing setup (MFS-LITE) has been designed and fabricated. The whole study is divided into two parts: in the first part readings were taken without considering the effect of flexibility of shaft and for performing this, the shaft of smaller length is taken; and in the second part readings were taken with a longer shaft in order to incorporate the effect of flexibility during experimentation. The result shows that the obstruction had an obvious and consistent effect on the 1BPF and 2BPF components for the axial fan rotor system.