<p>Conventional loss models used in centrifugal compressor performance estimation either assume incompressible or ideal gas behaviour to simplify 1-D analysis. While this approach generally provides reasonable performance estimates, its relevance to high-speed working fluids operating near the critical point is questionable. This is especially the case for supercritical carbon dioxide flows in vaneless diffusers, where the inlet Mach number is greater than 0.4. This study presents a compressible flow-based space marching formulation for vaneless diffuser performance characterization. Real gas effects near the critical point are incorporated in this formulation. The gas properties are obtained using an industry-standard thermodynamic and transport property database (CoolProp) which uses the Helmholtz free energy-based&nbsp;equation of state for carbon dioxide. Like the incompressible method, the proposed formulation does not require multiple iterations for convergence. The results are obtained in a single step using a space marching technique. The new formation is compared numerically with the existing technique for a few test cases with supercritical carbon dioxide as the working fluid. CFD simulations are used as benchmark data. The proposed formulation shows good accuracy, speed, and robustness. Hence, it can be incorporated in standard centrifugal compressor design and analysis tools, especially for supercritical carbon dioxide flows.</p>

Vaneless Diffuser Performance in a Supercritical Carbon Dioxide Centrifugal Compressor With Real Gas Effects

Paper Proceedings: https://asmedigitalcollection.asme.org/GTINDIA/GTINDIA2021/volume/85536

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