An Experimental Investigation on Hysteresis in a Wet Gas Compressor

Performance monitoring of wet gas compressors is challenging due to the liquid phase impact on performance. Introduction of a liquid phase alters both the thermodynamics as well as the fluid dynamics of the compression process. Hence, understanding the flow interaction between the impeller, diffuser and volute is pivotal. Previous investigations have detected occurrence of compressor hysteresis at certain wet gas operating conditions, resulting in temporary deviations from the steady state compressor characteristics. This kind of behavior influences both the compressor stability and performance. Thus, being able to understand the onset of hysteresis and its impact on the compressor is paramount. An experimental test campaign has been performed at the Norwegian University of Science and Technology (NTNU). The test facility is an open loop configuration consisting of a shrouded centrifugal impeller, a vaneless diffuser and a circular volute. The current investigation document the compressor performance shift and the occurrence of compressor hysteresis when gradually increasing the liquid load on a centrifugal compressor. Emphasis was put on the compressor performance and its correlation to the diffuser multiphase flow regime. The investigation revealed that there is a clear dependence between the diffuser multiphase flow characteristics and the compressor performance.