An aerodynamic performance test stand has been developed for validation of the performance of a 105,000 rpm compressor-expander which is intended for subsurface natural gas reinjection. The turbomachine consists of a two-stage centrifugal compressor, which is driven by a single-stage expansion turbine. The rotor is supported by foil gas journal bearings and a spiral-groove gas thrust bearing. The test stand is configured for open-loop testing of the overall compressor and turbine performance with air as the working fluid and atmospheric pressure at the compressor suction and turbine discharge locations. Several performance curves were generated for each component ranging from 73,500–115,500 rpm (70–110% of design speed). In general, measured compressor head was slightly lower than predictions, while measured efficiencies were close to predicted values. The turbine had higher flow than predicted, due in part to a larger flow area in the turbine. The turbomachine has shown acceptable performance on the open-loop test stand, and further testing at higher-pressure closed-loop conditions are planned.

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