RANS Simulation of a Radial Compressor With Supercritical CO₂ Fluid for External Loss Model Development

From the observation of previous experimental results, it was recognized that the amount of external losses at the external flow paths can be substantial. Understanding the external loss mechanisms, and reducing the external losses are crucial to the design of a high performance S-CO₂ compressor. Therefore, this study first focused on verifying the existing external loss models by estimating the internal loss accurately through a high fidelity CFD calculation and then substituting from the total losses. By analyzing the CFD result and energy balance data obtained from the experiment, the authors are suggesting the best combination of the external loss models for the S-CO₂ compressor. This is followed by the investigation of the condensation effect in the impeller by utilizing a two-phase VOF model with metastable properties. As a result, it is re-confirmed that there is a negligible amount of condensation effect.