The centrifugal compressor is the core component of supercritical CO₂ power cycle, and its performance and operation stability are research hotspots. However, there are few experimental studies, especially for compressors used in Mwe-scale power cycles. In this paper, based on a 1 MWe supercritical CO₂ power cycle, a single-stage centrifugal supercritical CO₂ compressor is designed with speed of 40,000 RPM, a pressure ratio of 2.5 and a mass flow of 16.3 kg/s. In order to carry out the compressor test, a general experimental platform for MWe sCO₂ compressors is built. In the test, the mass flow range is 13.5~18 kg/s and the maximum experimental pressure ratio is close to 2.0. The performance curve of the compressor of 31,000 ± 1000 RPM is obtained, and the historical curve of the experiment is given. Then, the experimental curve is compared with the design curve using a dimensionless method. The isentropic head coefficient of the experimental curve is lower than the design value, and the experimental curves shift towards the boundary of small flow coefficient. Finally, the influence of compressor inlet condensation on compressor performance and the change of operating boundary is preliminarily explained.

Focusing on the excess temperature problem of supercritical carbon dioxide (SCO₂) turbine shaft, this paper conducts a numerical investigation of flow and heat transfer characteristics with SCO₂ in the high-speed rotating annulus. The numerical method for simulation of SCO₂ Taylor-Couette-Poiseuille (TCP) flow and heat transfer is validated by existing experimental results. The key factors of Taylor vortices formation and shaft cooling performance are analyzed and discussed at the range of Ta = 1.33 × 10¹⁰-6.51 × 10¹¹. As the results show, firstly, the Taylor vortices will be generated in the annulus, which easily leads to the excitation phenomenon on turbines. The initial position of the vortex is related to axial ratio, radius ratio, Taylor number, and axial Reynolds number. Secondly, rotational and axial velocities have important influence on the global heat transfer performance compared with Taylor vortices. Finally, a correlation for SCO₂ TCP flow heat transfer is presented with effective Reynolds number and Prandtl number, and the error of the correlation is within ± 10%.

The flow characteristics of Taylor–Couette–Poiseuille flow induced by supercritical carbon dioxide in an annular gap play a pivotal role in determining the overall performance of the rotating machinery. To accurately design the structural components of rotating machinery and enhance its efficiency, this study employs the large eddy simulation method to investigate the flow behavior of Taylor–Couette–Poiseuille flow with supercritical carbon dioxide within an annular gap. The results reveal that vortices are predominantly generated near the inner wall. Initially, the flow exhibits small swirl vortices, spiral ring vortices, and annular vortices along the flow direction. As the flow progresses, these small vortices at the inlet region transition into hairpin swirl vortices. Finally, turbulent flow disturbances lead to the fragmentation and merging of spiral and annular vortices, resulting in a flow field characterized by high-frequency hairpin swirl vortices and small vortices with strong randomness. An increase in the swirl number causes the initial position of the Taylor vortex to shift toward the inlet, while the turbulent kinetic energy is more active on the outer wall side than the inner wall side. Along the flow direction, the vortices experience a developmental process involving stabilization, diffusion, and mixing. Varying the radius ratio affects the magnitude of vorticity, reduces velocity fluctuations in a regular pattern, and alters the distribution of helicity bands from wide and sparse to compact and dense groupings. As the axial Reynolds number increases, the magnitude of vortices grows, leading to more severe velocity fluctuations and the transformation of the helicity bands from a regular annular pattern to fluctuating vortices bands, accompanied by a decrease in helicity.

A gas cooler is one of the important parts of a carbon dioxide (CO₂) heat pump water heater, and it must meet the needs of not only pressurization but also heat transfer. It is important to study gas coolers. In this paper, a heat exchanger with a spiral channel is studied. ANSYS CFX software was used to analyze the flow and heat transfer characteristics of the heat exchanger (single-plate model). The influences of the cooling pressure of CO₂, the mass flux of CO₂, the mass flux of water and the channel radius of CO₂ are discussed. In this paper, the results show that the cooling pressure of CO₂, the mass flux of CO₂ and the channel radius of CO₂ all have a large influence on the local heat transfer coefficient: with an increase in the cooling pressure of CO₂, the peak value of the heat transfer coefficient of CO₂ decreases and the average heat transfer coefficient decreases; with an increase in the mass flux of CO₂, the peak value of the heat transfer coefficient of CO₂ increases and the average heat transfer coefficient increases; and with a decrease in the channel radius of CO₂, the peak value of the heat transfer coefficient of CO₂ increases. The water mass flux has only a slight effect on heat transfer, and the lower cooling pressure of CO₂ corresponds to a higher peak heat transfer coefficient, which can reach 27.5 kW∙m⁻²∙K⁻¹ at 9 MPa.

An actual one-dimensional(1-D) computation method for a labyrinth seal is proposed. Relevant computation hypotheses for the 1-D method are analyzed and the specificity of internal flow in an SCO₂ (supercritical CO₂) labyrinth seal is explored in advance. Then, the experimental correlation discharge coefficient and the residual kinetic energy coefficient used in SCO₂ labyrinth seals are proposed. In addition, the speed of sound in two-phase flow is corrected in the 1-D method. All recent experimental results of the SCO₂ labyrinth seal are sorted out and the latest experimental results of a stepped-staggered labyrinth seal are proposed to verify the accuracy and applicability of the 1-D method. Finally, the sealing efficiency of the SCO₂ labyrinth seals are analyzed using the 1-D method.

Supercritical carbon dioxide (sCO2) exhibits a characteristic Taylor–Couette–Poiseuille (T–C–P) flow within the narrow gap between the turbine rotor and stator, where the spatial distribution and variation of Taylor vortices significantly influence the performance of the turbine rotor. To predict the spatial variation and the initial position of Taylor vortices in this system, this study employs computational fluid dynamics (CFD) simulations to systematically investigate the effects of heat flux, pressure, Taylor number, axial Reynolds number, aspect ratio, and radius ratio on the initial Taylor vortex position. Based on the CFD results, a predictive model for the initial position of Taylor vortices in sCO2 T–C–P flow was developed. The results reveal that under high heat flux and elevated pressure conditions, the Taylor vortices form closer to the inlet of the axial flow. Increasing the mass flow rate, reducing the rotation speed, and reducing the radius ratio can suppress the formation of the Taylor vortex of sCO2 in the turbine rotor–stator gap. The predictive accuracy of the neural network model for determining the Taylor vortex initiation position is within a margin of ±10%, outperforming the nonlinear regression model. At the design point, the Reynolds number, Taylor number, radius ratio, and aspect ratio are 9000, 6×109, 0.1, and 30, respectively. The variation range is ±5%; the parameter priority in influencing the Taylor vortex is as follows: aspect ratio, radius ratio, Reynolds number, and Taylor number.