Investigating the Effect of Shaft-Bearing Clearance on Lateral Stability of a ۵-Stage Centrifugal Compressor

Centrifugal compressors are widespread turbomachineries in energy industry to either provide the driving pressure or compensate gas pressure loss. This type of compressors like any other rotary equipment is susceptible to several failure factors. Among all, dynamic damages resulted from vibrational loading is so frequent and costly. Dynamic studies consist of rotational and lateral analyses, as well as stability evaluations, which are vital subjects engaging many researchers and engineers in turbomachineries. Herein, stability analysis of a ۵-stage centrifugal compressor was numerically carried out to investigate the stability of the rotor including the effect of shaft-bearing clearance. The analysis was conducted as per API ۶۱۷ routine. Rotordynamic calculations also were performed and the results were applied to the current study as bearings stiffness and damping coefficient. The obtained results indicate that a limited increase of the clearance improves the logarithmic decrement; however, excessive rise is not allowed due to critical cross coupling consideration.

Keywords:

centrifugal compressor , stability , impeller , cross coupling , clearance.