Supercritical carbon dioxide (S-CO2) gas turbines can generate power at high cycle thermal efficiency, even at modest temperatures of 500–550°C, because of their markedly reduced compressor work near the critical point. Furthermore, the reaction between Na and CO2 is milder than that between H2O and Na. A more reliable and economically advantageous power generation system could be achieved by coupling with a sodium-cooled fast reactor. At Tokyo Institute of Technology, numerous development projects have been conducted for development of this system in cooperation with JAEA. Supercritical CO2 compressor performance test results are given as described herein. A centrifugal compressor is chosen for the performance test. Main compressor parts are stored in a pressure vessel. Maximum design conditions of the supercritical CO2 test apparatus are pressure of 11 MPa, temperature of 150°C, the flow rate of 6 kg/s and rotational speed of 24,000 rpm. The centrifugal compressor has an electric motor with permanent magnets on the rotor surface, with speed control by an inverter up to 24,000 rpm, a rotor shaft for the impeller, and a motor supported by gas bearings. Different compressor design points are examined using impellers of three kinds; test data are obtained using those impellers under steady state conditions with changing pressure, temperature, flow rate, and compressor rotor speed. The pressure ratio (compressor outlet pressure/inlet pressure) is obtained with the function of compressor rotational speed and the fluid flow rate. The data cover a broad region from sub-critical to supercritical pressure. Such data were obtained for the first time. No unstable phenomenon was observed in the area where the CO2 properties change sharply. Data of the pressure ratio vs. flow rate were coincident with the fundamental compressor theory.

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