Thermoelastohydrodynamic turbulent lubrication of supercritical carbon dioxide tilting pad bearing considering surface topography

As supercritical carbon dioxide (S-CO2) Brayton cycle systems advance toward higher power densities and compact designs, the increased demands on S-CO2 lubricated bearings induce a potential mixed lubrication state. This study establishes a novel thermoelastohydrodynamic mixed lubrication model specifically tailored for S-CO2 tilting pad bearings, addressing the challenges posed by high-load and extreme operational conditions. The modified Reynolds equation and an energy equation for rough surfaces are presented, incorporating real gas effect and turbulence to accurately predict lubrication performance. The effects of surface roughness, texture orientation, and variable thermal properties on the mixed lubrication performance of S-CO2 tilting pad bearings have been systematically analyzed, including their impact on load capacity, frictional power, and temperature rise. Results show that under mixed lubrication with high surface roughness, the load capacity of S-CO2 tilting pad bearings is significantly enhanced compared to smooth surfaces, with the peak temperature on the loaded pad shifting from the pivot point toward the trailing edge as surface roughness increases. These findings provide new insights into the design and optimization of S-CO2 bearings, supporting advancements in high-performance power systems.