Pressure Profile and Stiffness Analysis of Supercritical CO₂ Inside a Rotating Annulus Cooling Passage Using Computational Fluid Dynamics

The recent supercritical CO₂ (sCO₂) power turbine configuration development introduced a cooling zone parametric model to overcome the existing technical challenges. The parametric model is the annulus cooling passage with a supercritical CO₂ coolant consisting of radial clearance, length, and shaft diameter are the geometrical parameters. This study aims to investigate the pressure profile and stiffness coefficient of the cooling passage using computational fluid dynamics and to explore the validity of the assumptions that exist in the simplified analysis. The effect of eccentricity ratio, shaft speed, and axial length are investigated. The result showed that, like the hydrodynamic bearing, the supercritical CO₂ swirling in the annulus passage produces substantial mechanical support on the shaft. Hence, the cooling zone stiffness contribution should be included in the supercritical CO₂ turbine shaft vibration analysis which is not presently taken into consideration.