The starting point for the pressurization process of a supercritical CO2 Brayton cycle is near the critical point, which may lead to a liquid hammer if the inlet pressure fluctuates. It is important to judge whether the phase change of working fluid occurs during the pressurization process. With CO2 as the working fluid, the pressurization process for a centrifugal pressurization component is attention considered and analyzed. Specifying the inlet temperature, inlet pressure and outlet pressure as 32°C, 7.4 MPa and 24 MPa, respectively, the thermodynamic parameters of key state points of a centrifugal pressurization component are obtained. At the entrance of the impeller, a phase change of CO2 may occur, especially when the inlet points are close to the critical point. A method using enthalpy difference and exergy difference to express the possibility CO2 phase change is proposed. Furthermore, the risk degree of CO2 phase change is represented visibly. In view of the power consumption and efficiency of compressors under different working conditions, the changes of power consumption, isentropic efficiency and internal efficiency of compression components were analyzed under the conditions of constant outlet pressure and constant pressurization ratio. The power consumption is affected by the specific volume of the working fluid and the pressure difference. With the same inlet conditions, the isentropic efficiency under constant pressurization ratio is higher than that under a constant outlet pressure due to the lower power consumption; the internal efficiency is higher than the isentropic efficiency, and the trend is similar. This method can contribute to the setting of safe conditions for pressurization components.
SHI Weixiu
,
JI Xueyuan
,
PAN Lisheng
,
SUN Yin
,
LI Chaoqi
,
WEI Xiaolin
. Centrifugal Pressurization Process in the Near Critical Region for Supercritical CO2 Brayton Cycle[J]. Journal of Thermal Science, 2025
, 34(5)
: 1912
-1924
.
DOI: 10.1007/s11630-025-2188-0
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