A Compressible Thermohydrodynamic Analysis of Journal Bearings Lubricated With Supercritical CO₂

In this study, a compressible thermohydrodynamic (THD) model was developed to examine the flow dynamics of a journal bearing lubricated with supercritical carbon dioxide (sCO₂). This model employed a general form of the Reynolds equation governing compressible lubricant flows with a well-known analytical equation of state, and a viscosity model that depends on both pressure and temperature. In order to verify the model, we first compared the results of this compressible Reynolds equation to the full Navier-Stokes solutions. The accuracy of the model was found to be reasonable when the operating condition is sufficiently far from the thermodynamic critical point. Additionally, the numerical solution suggests that different temperature boundary conditions give slight different results due to the small variations of density and temperature across the gap. Finally, the general approach presented in this study introduces a new single parameter — effective bulk modulus that characterize both the frictional and thermodynamic fluid response. The model developed in this study can provide guidance for further studies of CO₂-lubricated bearings operating in the full supercritical regime.