Design and Aerodynamic Performance Investigation of Supercritical Carbon Dioxide Centrifugal Compressor

A centrifugal compressor with rotational speed 60 000 r/min is designed according to 150 kW class supercritical carbon dioxide (SCO2) simple Brayton cycle. The accuracy of the physical property tables of SCO2 significantly affect the stability and accuracy of SCO2 compressor aerodynamic performance predictions due to the dramatic variation of the physical properties of SCO2 near the critical point. A 400×400 precision physical property table is able to lead to a reliable SCO2 compressor aerodynamic performance. The aerodynamic performances of the designed SCO2 centrifugal compressor in designed and off-designed conditions are numerically evaluated with the three-dimensional Reynolds-averaged Navier-Stokes (RANS) and k-ε turbulence model. The centrifugal impeller tip leakage flow is also analyzed in detail. The numerical results show that the aerodynamic efficiency of the designed SCO2 centrifugal compressor reaches 73.2% and the pressure ratio gets 2.207 under the designed condition in consideration of the impeller tip leakage flow loss. The good performance of the SCO2 centrifugal compressor in off-designed conditions is verified. The aerodynamic efficiency of the SCO2 centrifugal compressor in consideration of the impeller tip leakage flow loss decreases by 14.0% compared with the case without impeller tip leakage flow effect. Three regions of the impeller tip leakage flow field, i.e. the separation flow region along the mainstream flow direction, the backflow region of the upper part in tip clearance affected by effect of adverse pressure gradient, and the flow region along the mainstream direction of lower part in tip clearance, are respectively illustrated. The designed centrifugal compressor meets the requirement of aerodynamic performance for 150 kW class simple Brayton cycle. © 2020, Editorial Office of Journal of Xi'an Jiaotong University. All right reserved.