프로세스 고속 경량 원심 압축기의 로터다이나믹 안정성 강화를 위한 설계해석 - Part II: 로터다이나믹 안정성 개선

Abstract

In this Part II study, rotordynamic stability analyses were carried out to confirm improvements to the stability of a process high-speed lightweight centrifugal compressor, depending on the effects of tilting pad journal bearing designs. The bearing design variables considered were the clearances, LBPs, LOPs, and preloads. The results showed that the rotordynamic stability of the subject compressor rotor-bearing system improves exactly in accordance with the effects of the bearing design variables, which were determined in the preceding Part I study, owing to reduced bearing stiffnesses. Specifically, it was confirmed that the stability of the rotor system can be greatly improved by increasing both the machined and assembled bearing clearances, but there were no stability improvements by simply changing from an LBP to an LOP design. In addition, it was confirmed that for given fixed machined bearing clearances, the stability can be additionally improved by decreasing the preloads, i.e., by increasing the assembled clearances. In conclusion, it may be necessary to improve the designs of the original tilting pad bearings to obtain a sufficient margin of rotordynamic stability against a possible aerodynamic cross-coupled stiffness in a process high-speed centrifugal compressor. Thus, increasing the machined and assembled bearing clearances and decreasing the preload could be effective solutions.