ANALYSIS OF UNSTEADY FLOW IN A SUPERCRITICAL CARBON DIOXIDE RADIAL COMPRESSOR STAGE

For nuclear power system, the supercritical CO2-based Brayton cycle is very promising for its potentially higher efficiency and compactness compared to steam-based Rankine cycle. Compressor is the critical component in the supercritical CO2-based cycle, which typically operates at an inlet fluid state close to the fluid critical point for optimal cycle efficiency. As the fluid parameters vary significantly near the critical point, the compressor is more vulnerable to flow instabilities and care must be taken in designing the compressor. The supercritical CO2 radial compressor features a compact design and the unsteady interactions between the impeller and the vaned diffuser are typically strong. A comprehensive understanding of the unsteady flow effects in the compressor is very helpful in guiding the aerodynamic design. However, little work has been performed on the flow analysis of the unsteady impeller-dlifuser interactions in the supercritical CO2 radial compressor In this work, the unsteady flow simulation of a supercritical CO2 radial compressor stage is carried out. Strong flow unsteadiness is observed and the isentropic efficiency shows a variation of over 20% within one revolution.