Experimental Characterization of Surge Cycles in a Centrifugal Compressor Under Wet Gas Operation

Abstract

Abstract This investigation focuses on instabilities in turbomachinery operation due to variations in fluid properties and composition, as with the injection of water droplets. The main objective of this study is to experimentally document compressor behaviour and characteristics under off-design condition in the unstable area between surge inception point to zero flow; flow visualization is used at this scope. The test rig is a single stage compressor operating with air and water. The compressor is full-sized, and the design is based on a traditional dry gas design optimized for wet gas compression. It is equipped with visualization slots enabling detection of unsteady and reversible flow. A suitable description of the positive slope area requires unsteady mass flow measurement: gas fractions accurate measuring and control still play a key role in a proper description of the flow phenomena involved, with reverse flow detection being the major challenge to be properly identified. The results quantify the liquid impact on performance and instability of system characteristics and flow composition, and show the development of unsteady flow regimes. This proves valuable for future system modeling tuning and validation and further understanding of the phenomenon, the development of reliable surge onset prediction models and control strategies. In addition, useful guidelines focused on compressor system design and its behaviour, rather than machine design.