CFD Study on Oil-in-Water Emulsions

Abstract

A commercial CFD code was used to analyze the effects of the rolling speed, oil viscosity, and supplying oil concentration on the pressure distributions of the oil and water phases, as well as the droplet movement and deformation. To simplify the calculations, the assumptions of isoviscous fluid and rigid surface were adopted and the film thickness was assigned. It was found that a more viscous oil phase enables the oil droplets to be drawn forwards easily. Phase inversion (W/O emulsion) occurs when the oil viscosity and the supplying oil concentration increase. However, phase inversion is not a necessary condition for generating significant pressure in the upstream region and the pressure can rise considerably in spite of low oil concentration close to the supplied value. All the simulations suggested that an accelerated increase in pressure happens when the film thickness is approximately equal to the original diameter of an oil droplet. The pressure of the disperse phase is greater than that of the continuous phase and the discrepancy may become significant.

KEY WORDS:

• Emulsion
• Hydrodynamic Lubrication
• CFD

ACKNOWLEDGEMENTS

The authors wish to thank the National Yunlin University of Science and Technology for the use of its facilities. The support from the National Science Council under grants NSC95-2212-E-224-078-MY3 is also gratefully acknowledged.

Review led by Liming Chang