Volumetric Behavior of Some Motor and Gear-Boxes Oils at High Pressure: Compressibility Estimation at EHL Conditions

Abstract

Characterization of elastohydrodynamic lubrication, EHL, contacts requires an appropriate EoS for the lubricant. Experimental viscosities and speeds of sound of six lubricants from 278.15 to 398.15 K at 0.1 MPa together with densities up to 120 MPa are reported. Tammann-Tait and the two EoSs based on the scaling concept describe the experimental densities of the six oils with average deviations lower to 0.03%. DowsonHigginson and Zhu and Wen equations currently used in numerical simulations of the EHL regime predict these experimental densities with AADs lower than 0.5%. The prediction ability for volumetric properties, mainly isothermal compressibility, of these five EoSs up to 3000 MPa, which can be reached in EHL lubrication, was evaluated. An asymptotic behavior is observed when density is plotted versus pressure for Dowson-Higginson and Zhu and Wen equation, which is not a realistic behavior. The EoSs used in the correlations predict more reasonable trends with pressure