The Field Equations for Two-Phase Reynolds Film Flow with a Change of Phase

Abstract

The governing equation for dispersed two-phase lubrication film flow is derived. It can be used to predict both the static and the dynamic characteristics of wet vapor lubricants. It is shown that the processes of condensation and/or evaporation are accounted for by a dimensionless phase change number N, which appears respectively as a vapor sink or a vapor source in the governing equation. The analysis shows that this sink (or source) can become the dominant term in determining the static and dynamic characteristics of vapor-lubricated bearings. When the phase change number is zero, the equation reduces to the standard Reynolds equation for gas (noncondensable) lubrication film flow. It is shown that the flow of a wet vapor lubrication film depends on two dimensionless numbers: the standard Strouhal number S, and the phase change number N. The significance of the latter as a scaling criterion is discussed. It is shown that when the ratio N/S is small, the characteristics of a wet vapor film should resemb...