DYNAMIC BEHAVIOR ANALYSIS OF ENCLOSURES EFFECT ON AXIAL FAN SYSTEM

The main purpose of this study is to simulate and analyze the fan system assembly design considering enclosures as space constraints. The enclosures which disturb flow cause high value of vibration amplitude in fan systems. In this study, behavioral changes of an axial fan system with and without obstruction or shroud attached as enclosures considering Blade Passing Frequency (BPF) and its harmonics are experimentally studied. During the fan system operation, the BPF can force the fan to vibrate at its natural frequencies. Since large amplitude values of the BPF are generated due to enclosures, the effort is to investigate the feasible fan enclosures assembly in order to minimize vibration sources. Evenly spaced a 12-blade axial fan for eight different shaft speeds is tested for five different cases; no obstruction and no shroud on the fan, an obstruction on side left of the fan (the air exiting), an obstruction on right side of the fan (the air entering), an obstruction on both side of the fan and only a shroud on the fan. Taking the first and the second maximum vibration amplitude peaks in account, results showed that the fan generates higher amplitude when the inlet of the air to the fan is obstructed.