Rotor Vibration Analysis of Large-scale Centrifugal Compressor under the Flexible Support

doi:10.3901/JME.2019.19.121

Abstract

Abstract: The support stiffness is of significant influence on the dynamic characteristics of rotor system. The vibration caused by the support stiffness differences in high speed balancing and real operating conditions of large scale centrifugal compressor is studied. Due to the low stiffness of the swing of the high speed balance machine, the oil film stiffness of the bearing in some of the large scale centrifugal compressors is quite similar as the support stiffness which lead to the dramatic decrease of the second bending critical speed. Consequently, the rotor vibration is out of limits, and the high speed balancing could not meet the requirements of the standards. The rotordynamics analyses have been done respectively without considering the support stiffness and with the swing stiffness of the balance machine combined with real cases, and the FEA has been done on bearing pad, bearing pedestal, casing and baseplate to get the foundation stiffness of the compressor rotor. The results show that the second order critical speed of rotor taking the support stiffness into account decreased by 11.1%-18.3% while the first order critical speed decreased only by 3.6%-7.3% which fit the high speed balance results well. The real support stiffness should be higher than the bearing stiffness by 3.5 times, and the mechanical running test shows that the first order critical and the second order critical speeds do not decrease substantially and meet the requirements of API 617. The results are in consistent with the rotordynamic analysis results without considering the support stiffness.

Key words: flexible support, support stiffness, centrifugal compressor, rotordynamic coefficient, rotor vibration

CLC Number:

TG156

YANG Shuhua, HU Yong, XIAO Zhonghui, ZHANG Cheng, TAI Xingyu. Rotor Vibration Analysis of Large-scale Centrifugal Compressor under the Flexible Support[J]. Journal of Mechanical Engineering, 2019, 55(19): 121-127.

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