Advanced property calculation approach considering real gas effects in supercritical carbon dioxide compressors

To optimize the performance of supercritical carbon dioxide (sCO2) Brayton cycle, the core component, the compressor inlet, is often positioned at the critical point. This manifests in a strong presence of real gas effect in the flow, directly impacting the predictive performance of the compressor. Addressing the limitations of traditional low-degree linear property calculations in property tables, such as high computational cost and inability to ensure continuity of first derivatives, a high-degree, easily scalable property calculation method is introduced, which simultaneously avoids the low precision associated with solving property derivatives. Beginning with a comparison of property calculation accuracy, the coupled relationship between property calculations and flow field at the stable operating boundaries of sCO2 compressor is explored. Analyses of high-dimensional computational precision and cost are conducted. Results indicate that this high-degree method exhibits the smallest overall deviation in property calculations, together with a reduced deviation along the saturation line. Fully considering the real gas effect leads to performance prediction curves closely align with experiment data within a 5% margin. The movement patterns of low-energy fluid clusters are better captured, yielding flow field consistent with conventional dense property tables while reducing computational costs by 16.9% and 19.7% at operation boundary points.