Experimental Characterization of Surge Cycles in a Centrifugal Compressor

Abstract

Compressor operation under off-design conditions generates undesirable instabilities and detrimental effects both on system stability and machine reliability perspectives. The main objective is to provide a suitable approach and proper description of the flow and machine behaviour in the surge inception to reverse flow operating area, yielding valuable data for a deeper understanding of the underlying flow mechanisms, useful for tuning prediction models. A literature review, with a particular focus on the experimental method, test rig layout, and instrumentation when handling with reverse and pulsating flow, is presented. The need for a clear setting of test procedure and key parameters measurements to detect unsteady phenomena under transient conditions, with instrumentation available for field operation and separating compressor behaviour from system response, is specifically addressed. To perform this, the experimental technique is employed and described in detail in this paper, while performance modeling validation, object of parallel studies, will be presented in future publications. The test facility allows the required responsive dynamic measurements; tests cover a broad range of flow rates and two different rotational speeds. The aim is to specifically approach the instabilities sections and characterize the positive slope area, featuring rapid cycles between surge line and zero-flow. The results, presented as pressure and flow fluctuations, play a key role for the simulation of more complex dynamic scenarios. This wide collection of test data is of great value for a further understanding of the phenomenon, the development of reliable surge onset prediction models and control strategies.