The centrifugal compressor is the key component to improve the SCO2 cycle efficiency. In this paper, according to 150kW class supercritical carbon dioxide (SCO2) simple Brayton cycle, a centrifugal compressor with rotating speed 60000r/min is designed. For the small-scale SCO2 centrifugal compressor, the impeller tip clearance loss accounts for most of the aerodynamic loss. Therefore, the designed compressor performance is numerically studied by the three-dimensional Reynolds-Averaged Navier-Stokes (RANS) and k-ε (Extended Wall Function) turbulence model. The large variations in physical properties for SCO2 near the critical make simulation be difficult to convergence. To keep the numerical stability and accuracy, 400 × 400 resolution physical properties tables are adopted by the physical properties tables verification. The designed SCO2 centrifugal compressor is with the isentropic efficiency of 73.2% and the pressure ratio of 2.207 under the design flow condition, and good off-design conditions performance are obtained. Compared to the flow condition without the impeller tip clearance, the isentropic efficiency of designed compressor decreases by 14%. For the impeller tip clearance leakage flow, the flow can be divided into three regions, the separation flow region which is along the mainstream flow direction, the back flow region which occupies the top of the impeller tip clearance and the downstream flow region which occupies the bottom of the impeller tip clearance. These flow phenomena and their causes are analyzed. The obtained results reveal that the designed centrifugal compressor meets the requirement of the aerodynamic performance for the 150kW class simple Brayton cycle. The detailed flow pattern of the designed SCO2 centrifugal compressor with consideration of the impeller tip leakage flow is also illustrated.

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The hub cavity leakage has large effect on the aerodynamic performance on the Supercritical carbon dioxide (SCO2) centrifugal compressor. In this paper, the aerodynamic performance and strength characteristics of the 150 kW SCO2 centrifugal compressor with the hub cavity were numerically investigated using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) and [Formula: see text] turbulence model. The high precision physical properties tables of SCO2 were used to calculate the SCO2 property parameters across the centrifugal compressor flow passages. The aerodynamic performance of the 150 kW SCO2 centrifugal compressor without and with the hub cavity and the labyrinth seal at different mass flow coefficients was compared. The equivalent (von-Mises) stress and the deformation on the SCO2 centrifugal impeller were obtained by the combination of the aerodynamic pressure and centrifugal force calculation. The results show that the isentropic efficiency of the SCO2 centrifugal compressor without and with the hub cavity and the labyrinth seal at the designed flow coefficient equal 73.2% and 72.1% respectively. The effects of the hub cavity leakage on the pressure ratio of the SCO2 centrifugal compressor are limited. The hub cavity leakage decreases with the flow coefficient increasing. The similar isentropic efficiency of the SCO2 centrifugal compressor without and with the hub cavity and the labyrinth seal at the largest flow coefficient is obtained. The axial thrust of the SCO2 centrifugal compressor with the hub cavity and the labyrinth seal ranges from 1000N to 2000N at different flow coefficients, as well as keeps the same direction. The maximum equivalent (von-Mises) stress of the impeller is 109.95 MPa and less than the allowable stress 137 MPa (using 304 steel as the impeller material). The maximum deformation of the seal teeth is less than 0.003 mm. This work provides the reference of the compressor design and safety operation for the SCO2 centrifugal compressor.