The world’s energy demand is increasing, asking for new and cost-efficient ways to extract oil and gas. With traditional technologies, oil and gas production relies on a sufficiently high well head pressure for transportation to nearby process facilities. Utilization of subsea wet gas compression systems enables production at significantly lower pressures and is a favourable solution concerning production in remote regions.

Wet gas compressors are particularly useful when handling multiphase mixtures consisting of 95%–100% gas, on a volumetric basis. The remaining content is water and liquid condensate, which introduces flow mechanisms such as droplet deposition, liquid film formation and momentum transfer, which influence the fundamental flow behavior through the compressor. Previous tests have documented the occurrence of compressor hysteresis at low compressor flow rates. Recent findings have revealed the flow interaction between the diffuser and the volute is a governing factor concerning the documented hysteresis. This kind of behaviour induces challenges with regard to compressor performance prediction and securing stable operation.

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 test was performed by establishing the compressor characteristics while monitoring the diffuser/volute flow regime. Emphasis was put on the volute flow characteristics and the correlation with the compressor performance.

The investigation reveals that the volute flow characteristics and the interaction with the diffuser has a distinct impact on the compressor performance, particularly at lower gas mass fractions. Furthermore, the test reveals that the diffuser design is a key factor concerning the performance impact.

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