Rheological Characterization of Lubricant-Methanol-Water Emulsions 922283

Rheological measurements were performed on a series of lubricants for flexible fuel vehicles, and blends of water or methanol in these oils. A series of measurements, including kinematic viscosity, viscosity at low and high shear rates, low shear viscosity under borderline pumping conditions, and density were performed on all oils and blends. The effects of mixing conditions, such as mixing speed and temperature on these properties were also studied.
Viscosity increases when water emulsifies in oils. Methanol exhibits limited solubility in all oils, but more so in synthetic base oils. Viscosity tests at 248 K (-25°C) do not indicate the onset of critical pumping conditions, even at high concentrations of water or methanol. Tests at high shear rates at 323 K (50°C) suggest that water-oil emulsions are quite stable, while methanol-oil blends lose their methanol content either due to evaporation or shear-induced separation. Water and methanol appear to have no irreversible effects on the viscometric properties of oil formulations.
Results to date show some potential in ranking oils for lubricating components not exposed to engine combustion. To resolve the problem of piston ring-bore wear, better understanding of the surface properties, and the interaction of emulsions, engine materials and the products of combustion is necessary.


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