Enhancing supercritical CO2 compressor performance in closed brayton Cycle: Exploring inlet guide vane adjustment in gas-like and liquid-like states

The optimization of closed Brayton cycle (CBC) typically maintains CO2 in supercritical state (sCO2) at the compressor inlet. While, the existing trans-scale characteristics of gas-like and liquid-like emerge as critical consideration in designing supercritical compressors. To explore the performance disparities of sCO2 compressors in gas-like and liquid-like states and propose effective active control strategies, this research focuses on integrating inlet guide vanes (IGVs) with the MW-class compressor. The interplay of IGV regulation and fluid state on compressor performance, internal phase changes, compression capability, flow losses and structural strength is analyzed. Effective IGV control strategies are delineated for diverse flow rate conditions. The results demonstrate that the impact of IGV on the inlet flow of liquid-like impeller is comparatively less than in the gas-like state, necessitating more pronounced IGV adjustments. Implementing low and high positive pre-swirl angles effectively suppresses two-phase structures under the two states. This also reduces the compression coefficient of the fluid and weakens vorticity, consequently decreasing enthalpy loss coefficients to 0.121 and 0.129, respectively. Concurrently, significant structural deformations in gas-like state are averted and the fatigue life of material in liquid-like state is enhanced. Furthermore, for long-term compressor operation and two-phase control, adjusting the IGV reasonably towards negative pre-swirl angles as the flow rate increases is recommended, thereby expanding operational boundaries. As a result, a theoretical and technical framework for the active control of sCO2 compressors operating under different supercritical states is established.