Effect of the hub cavity leakage on the aerodynamic performance and strength characteristics of the 150 kW SCO₂ centrifugal compressor

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 presented.) 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.