The Viscosity-Temperature-Pressure Relationship of Lubricating Oils and Its Correlation With Chemical Constitution

Abstract

Viscosities of twenty well-defined, representative mineral-oil fractions have been determined at temperatures from 25 to 90 deg C (77 to 194 deg F) and at pressures up to about 1000 atmospheres (15,000 psi) with the aid of a falling-needle viscometer. An analysis has been made of both the present measurements and reliable data from literature, which chiefly concern mineral oils and pure hydrocarbons, but also include some silicones, fatty oils, and alcohols. Many literature data cover ranges of viscosity, temperature, and pressure that are more extensive than those of the authors. Newly developed empirical formulas are presented for the isobaric viscosity-temperature relationship, the isothermal viscosity-pressure relationship, and the complete viscosity-temperature-pressure relationship. The formulas have been found to be satisfactorily applicable to all the aforementioned liquids in a wide range, that is, generally, from about 20 to 150 deg C (68 to 302 deg F) and up to pressures of at least 3000 atmospheres (44,000 psi). Diagrams derived from these formulas have proved particularly suitable for a systematic study of the correlation between, on the one hand, the temperature and pressure variation of viscosity of the liquids concerned and, on the other hand, their chemical constitution. This is exemplified by the results for the mineral oils investigated. In fact, it proved possible, presumably for the first time, to establish for mineral oils a really satisfactory quantitative correlation between their viscosity-temperature-pressure dependence and their chemical constitution; the latter has been characterized by the carbon distribution according to the “Waterman analysis” in the form of the so-called n-d-M method.

High-order discontinuous Galerkin method for elastohydrodynamic lubrication line contact problems

“…(The lubricant rheology is highly nonlinear in pressure: in this work we have used the viscosity-pressure relationship of Roelands [17] and density model of Dowson and Higgison [18].) The elasticity is included through the film thickness equation which defines the contact geometry for a given pressure solution:…”

Pressure-dependent surface viscosity and its surprising consequences in interfacial lubrication flows

“…Three-dimensional fluids are typically approximated as incompressible; moreover, the viscosity of bulk fluids typically change appreciably only under extreme pressures [17][18][19]. 3D studies of such "piezoviscous" liquids have used exponential and power-law η(p) relations, particularly in the contexts of polymer melt processing [20,21] and lubricating oils under exceedingly high pressures [22,23].…”

Investigation of Couple Stress Fluid and Surface Roughness Effects in the Elastohydrodynamic Lubrication Problems using Wavelet-Based Decoupled Method

“…These values use the calculation of film thicknes pHq, density pρq [25], and viscosity pηq [26], respectively. The Reynolds equation is discretized over a uniform mesh of different mesh sizes using finite difference approximation and solved along with the film thickness equation and force balance equation using the wavelet-based decoupled method as follows, Consider the Reynolds equation of the form:…”