Computational Model Development for Hybrid Tilting Pad Journal Bearings Lubricated with Supercritical Carbon Dioxide

Abstract

Fluid film bearings lubricated with supercritical carbon dioxide (sCO2) eliminate the infrastructural requirement for oil lubricant supply and sealing in turbomachinery for sCO2 power systems. However, sCO2′s thermohydrodynamic properties, which depend on pressure and temperature, pose a challenge, particularly with computational model development for such bearings. This study develops a computational model for analyzing sCO2-lubricated tilting pad journal bearings (TPJBs) with external pressurization. Treating sCO2 as a real gas, the Reynolds equation for compressible turbulent flows solves the pressure distribution using the finite element method, and the Newton−Raphson method determines the static equilibrium position by simultaneously calculating forces, moments, flow rates of externally pressurized sCO2, and pressure drop due to flow inertia. The finite difference method solves the energy equation for temperature distribution. The density and viscosity of sCO2 are converged using the successive substitution method. The obtained predictions agree with the previous and authors’ computational fluid dynamics predictions, thus validating the developed model. Hybrid lubrication increases the minimum film thickness and stiffness up to 80% and 65%, respectively, and decreases the eccentricity ratio by up to 65% compared to those of pure hydrodynamic TPJB, indicating significant improvement in the load capacity. The bearing performance is further improved with increasing sCO2 supply pressure.

Operating characteristics of supercritical carbon dioxide high speed tilting pad bearings considering inertia effect

“…The low viscosity of S-CO 2 resulted in less power loss at high speeds compared to oil lubrication. Mehdi and Kim 11 developed a hybrid S-CO 2 lubricated tilting pad journal bearing (TPJB) computational model to evaluate its static and dynamic performance. The authors compared the hybrid S-CO 2 TPJB with the pure hydrodynamic TPJB and found that the load capacity and stiffness coefficient increased significantly with increasing supply pressure.…”

Structural stiffness and equivalent viscous damping in a supercritical carbon dioxide lubricated hybrid journal bearing under hydrostatic status

“…The results showed that using S-CO 2 as the power lubricant for bearings is feasible. Mehdi and Kim (2022) developed a radial bearing calculation model mainly used to analyze S-CO 2 lubricated tilting-pad radial bearings with external pressurization. The authors showed that, compared to pure fluid dynamically lubricated tilting-pad radial bearings, hybrid lubrication increased the minimum film thickness and stiffness by 80% and 65%, respectively, and reduced the eccentricity by 65%, indicating a significantly improved load capacity.…”

Dynamic Coefficients of Tilting Pad Bearing by Perturbing the Turbulence Model

“…Tilting pad bearings have been widely applied in many kinds of rotating machines, such as gas turbines [1], compressors [2], and so on, due to their ability to improve stability [3]. Tilting pad bearings are also suitable for oil-free operations [4][5][6], so they have the potential for new fields such as electrical submersible pumps [7,8].…”