On the Transient Interaction of Centrifugal Compressors and Their Piping Systems

Abstract

The problems of surge and other low-frequency pulsation phenomena in centrifugal compressors are described in terms of both machine (head curve) characteristics and the flow impedance characteristics of its attached piping. Flow stability criteria are presented in terms of net modal damping, as the combination of piping acoustic damping and equivalent negative damping of the compressor in the surge region of its performance curve. Surge and instability frequencies are related to acoustic reactance of the piping system. Finally, theoretical concepts are verified both by electrical analog models and by field and laboratory data on real compressors. This paper provides some new and significant findings on the dynamic interaction of centrifugal compressors with piping systems and describes the basic phenomena underlying these interactions. Good agreement is shown between predicted and measured surge frequencies, and for those termed “piping resonance surge” produced by high flow offsets or flat spots in the head curve.