Experimental investigation on performance test of 150-kW-class supercritical CO2 centrifugal compressor

Supercritical CO2 is a promising working fluid for next generation power conversion systems. The key component in a supercritical CO2 power generation system is turbomachinery, which particularly includes the compressor. Supercritical CO2 has high density and low compressibility, similar to the liquid state near the critical point. Therefore, when the compressor is operated near the critical point of CO2, significant reduction of compression work can be attained, as compared to conventional air Brayton cycles. However, there are technical challenges concerning the design and operation of the compressor. Therefore, in this experimental study, a 150-kW-class supercritical CO2 centrifugal compressor for a 500-kW power generation system is designed and investigated. The design point of compressor, pressure ratio, and efficiency, are 1.75, and 80% at rotational speed 36000 RPM. The purpose of this test is to evaluate the performance of the supercritical CO2 centrifugal compressor and obtain accessible fundamental data. During the performance test, which is conducted by controlling the rotational speed of the impeller and the opening rate of the control valve, the compressor is operated by an electric motor, and the generated pressure from the compressor is consumed using a control valve. Repeated tests are conducted on the compressor to confirm the practicality of the designed compressor for the supercritical CO2 power generation system. The compressor achieves a higher efficiency of 80% than the target efficiency during the repeated four tests. In addition, the reliability of the compressor performance is examined. Furthermore, the results of the test are analyzed to understand the effects of the opening rate of the control valve for load changing and the rotational speed of the impeller.