An attempt for establishing pressure ratio performance maps for supercritical carbon dioxide compressors in power applications

Carbon dioxide in the supercritical state (sCO2) has drawn much interest lately. It is considered as a promising fluid for next-gen power plants with many researchers investigating this technology. Cycle simulation and control requires compressor performance maps valid for variable inlet conditions. In this paper, an attempt is made for establishing a pressure ratio based performance map for sCO2 compressors in power applications. For that purpose the so-called Glassman approach is considered. This model has been originally established for fluids obeying the ideal gas law. Therefore, a modification is proposed to take into consideration the real gas equation of state and to allow wide variation of the isentropic volume exponent kv. Computational fluid dynamics (CFD) is used to predict the performance of a single stage radial compressor. Results for different kvvalues at the compressor inlet confirms the validity of the proposed model with both the polytropic efficiency and the reduced enthalpy deviations limited to 1 percent. On the other hand, predicted pressure ratio shows difference of around 3 percent from kv=7.1 to kv= 4.1. A further decrease of kv to 2.5 extends the difference up to 8 percent.



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