Numerical investigation of the rotating instability uniqueness in a MWe scale supercritical carbon dioxide centrifugal compressor

Flow instability attracts much attention for air compressors but little for a supercritical carbon dioxide (CO 2 ) compressor that is a critical component in the supercritical CO 2 Brayton cycle. This paper presents a numerical investigation of the rotating instability in a megawatt-scale (MWe-scale) supercritical CO2 centrifugal compressor from the Institute of Engineering Thermophysics. Unsteady full annulus simulations were carried out at different operating conditions and validated by the experimental data. According to the validated method, we analyzed the blade tip leakage flow, the rotating instability, and the propagation speed of the stalled flow cell. The findings are that (1) the blockage effects of leakage flow are responsible for rotating instability, and (2) the propagation speed of rotating cells is approximately 16.67% of the rotor speed. The novelty is that the figure is lower than that in air compressors, close to that found in water pumps.