Analysis of Condensation Effect of Supercritical CO₂ Radial Compressor

This may cause many issues in designing seal, bearing, and leakage flow. The property of the CO₂ adjacent to its critical point shows substantial variation with small change of pressure and temperature. One of the things to consider in S-CO₂ Brayton cycle design is the condensation effect inside the compressor because if the inlet condition of a compressor becomes too close to the critical point, there might be some regions within the rotor in which the pressure and temperature are reaching their critical values. This may lead to unexpected energy losses of the compressor in actual operation. In this study, the condensation effect inside the compressor is examined numerically using CFD approach in conjunction with the implementation of metastable properties. To simulate metastable properties, extrapolated gas properties are used. Since the nucleation mechanism of an S-CO₂ compressor is different from the classical nucleation theory, the non-equilibrium condensation rate was adopted to estimate time constant and other indicators required to estimate the rate of condensation. The two-phase volume of fluid (VOF) technic is used to make a quantitative evaluation of the condensation rate within an already built CFD model of a real compressor geometry and operating conditions matching the ones of the experimental facility.