Flow and energy dissipation of supercritical carbon dioxide in the flow channels of a labyrinth regulating valve

The labyrinth regulating valve demonstrates distinctive capabilities in achieving stepped-by pressure decompression and flow velocity control within the confined trim spaces. Utilizing a labyrinth regulating valve in supercritical carbon dioxide (S-CO2), Brayton cycles can potentially mitigate shock and vibration from substantial pressure differentials during bypass control. However, the thermodynamic properties of S-CO2, especially low dynamic viscosity and strong coupling between temperature and pressure, introduce significant complexity to the flow dynamic behavior within labyrinth channels. This study employs numerical simulations to investigate the fluid dynamics and thermodynamics of S-CO2 in the typical array and zigzag channels. The mechanisms governing energy dissipation across various channel structures are elucidated using entropy analysis, primarily attributed to viscous dissipation. By analyzing the influence of energy dissipation, kinetic energy, and pressure potential energy across various channel structures, this study identifies that the normal gradient of stream velocity is the key strategy for increasing viscous dissipation and limiting outlet kinetic energy. By leveraging these insights, we establish critical metrics for assessing the stability of pressure drop and constraining kinetic energy in channel structures and provide a prospective channel structure for S-CO2 that achieves stepped pressure reduction and flow velocity control.