Technical benefits of the subcritical inlet condition for high-speed CO₂ centrifugal compressor in the advanced power-generation cycle

In the CO₂ power-generation cycles, the compressor inlet condition has significant impacts on the performances of turbomachinery as well as the economies of cycle systems. In this article, based on numerical simulation and system parametric analysis, we compared the subcritical and supercritical inlet conditions of the CO₂ compressor, which is from a prototype in a MWt simple recuperated cycle (SRC). As the result, the advantages and particularities of the subcritical inlet condition for the CO₂ compressor are discussed and confirmed from the aero/thermo-dynamics and thermal/technical economies. In the study, we found the efficiency and pressure ratios of the CO₂ compressor were significantly improved as the inlet pressure reduced below the critical point. And the operation of transcritical compression would not be obviously impacted by phase changes at the far-blockage conditions. In the system parametric analysis, we found the thermal and technical economies of the SRC system obtained significant rises at the subcritical compressor inlet condition. The increase of system efficiency reached 2–3%, while the financial cost reduced by 7.7%. The structural and mechanical safety of key components was also improved. Thereby, the present study provides different views to the benefits of subcritical compressor inlet conditions in CO₂ cycles.