12th European Conference on Turbomachinery Fluid dynamics & Thermodynamics
Supercritical CO2 (S-CO2) has a density as high as that of its liquid phase while the viscosity remains closer to its gaseous phase. S-CO2 has the potential to be used as a working fluid in compressor since it requires much less work due to its low compressibility as well as relatively small flow resistance. Besides the material properties and design calculations, the thermophysi-cal properties of working gases play a vital role in the design and efficiency of various machinery such as compressors, turbines, etc. For the analysis of the fluid dynamic performance of these machinery, there is, no standard procedure for selecting a suitable equation of state (EOS). Fur-ther, the performance of the compressor is mainly affected by shock waves occurring near blade section at high temperature and pressure. To understand the influence of real gas effects on the formation of a shock wave, in the present work the S-CO2 flow through a convergent-divergent nozzle, is theoretically analyzed. The thermophysical and transport properties calculated with the different equation of state (EOS) are used to estimate the flow characteristics. A series of equations based on one-dimensional gas dynamics theory along with the real gas properties have been theoretically solved with a computer program to predict the compressible flow of S-CO2. The solutions for the shock strength, total pressure loss, and location of the nor-mal shock wave at different back pressure conditions are obtained. Using Becker's solutions with varying viscosity and thermal conductivity estimated from each EOS, the entropy distri-bution inside the normal shock wave and the thickness of the shock front are calculated. The formation of shock wave is found to be significantly influenced by the real gas effects particu-larly at high pre-shock Mach number.