ROTOR DESIGN CONSIDERATIONS TO PREVENT IMPELLER AND PREMATURE BEARING FAILURES IN CENTRIFUGAL FANS

摘要

Centrifugal Fans are subjected to blade-pass pulsation and mass imbalance forces as part of normal operation. Fan impellers have several n-nodal diameter modes of natural frequency that can be sensitive to blade-pass pulsation forces. Excitation of these modes can lead to catastrophic failure. The principal flexural mode of a fan rotor is sensitive to mass imbalance force, and if excited, can result in amplified stresses in the shaft and amplified force transmission to the bearings. In the case of SWSI fan rotors, where the 1-nodal diameter mode of the impeller couples with the flexural mode of the shaft, excitation of the rotor mode can lead to catastrophic failure of the impeller.