Evaluating the Influence of Different Equations of State on Real Gas Effects in Herringbone Grooved Bearings

Abstract The current paper considers several equations of state, namely, the Redlich-Kwong-Anguier and Span-Wagner models as alternatives to the ideal gas equation for modeling journal gas bearings lubricated with carbon dioxide. The proposed real gas models are compared by analyzing key bearing parameters, including eccentricity ratio, attitude angle, critical mass, and stiffness and damping coefficients under specified operating conditions. The calculation results for ideal and real gas models are shown to be closely aligned for air lubrication at ambient conditions and are validated against published data. The nonlinear transient rotor dynamics response of a test rotor supported by bearings modeled with different equations of state is analyzed to assess the impact of real gas effects on machine dynamics. The findings highlight the influence of real gas effects, modeled through different equations of state, on bearing performance and rotor dynamics response. This study helps identify the most suitable approach for modeling herringbone grooved gas journal bearings while accounting for real gas behavior.