Impact of inlet guide vane on performance and internal flow field of a supercritical CO₂ centrifugal compressor

In this study, an unsteady numerical simulation of supercritical carbon dioxide (SCO₂) centrifugal compressors with inlet guide vanes (IGV) was conducted. First, using a condensable fluid model, the study validates the accuracy of property lookup tables generated by the FEK model against Lettieri's SCO₂ Laval nozzle experimental data. Then, the internal flow fields under different IGV pre-swirl angles are analyzed. The results indicate that the IGV with zero pre-swirl angle induces minimal unsteady disturbances within the impeller, whereas the rotation of the impeller generates significant unsteady disturbances in the IGV. At a negative 30° pre-swirl angle, the compressor's peak efficiency decreases by approximately 5 %, accompanied by intense pressure pulsations and widespread phase transitions. Moreover, at a negative 30° pre-swirl angle, high-intensity pressure pulsations occur on the suction side of the IGV, triggering extensive phase transitions on both the suction side and at the outlet, covering the entire passage.