Modified Reynolds Equation for Thin Film Lubrication with Arbitrarily Enhanced Viscosity Surface Layers and Lubrication Analysis of Micro-Tapered Pad Bearing

Abstract

This paper formulated a modified Reynolds equation that can calculate the lubrication characteristics of bearings with high-viscosity surface layers on both bearing surfaces expressed by arbitrary viscosity function. From comparison with the measured effective viscosity of engine oil with metallic detergent, the saturated viscosity function was determined, where the effective viscosity saturates to 500 times the bulk viscosity when the gap decreases to the saturated viscosity film thickness 2zc of 100 nm. Then, the lubrication characteristics of micro-tapered pad bearing of 250 µm in length were analyzed. The load capacity was ~70 times the bulk viscosity case when the trailing gap hT decreased to 2zc. Next, the effective viscosity of engine oil with only a viscosity modifier additive can be obtained by using another viscosity function in which the increasing rate in viscosity is maximum on the bearing surface and 2zc is ~60 nm. Using this viscosity function, the bearing characteristics of tapered pad bearing were analyzed. The load capacity was ~13 times the bulk viscosity case when hT was zc. For both the viscosity functions, the load capacity was almost the same if the film thickness of the one-side model is twice as large as that of the two-side model.

Keywords

• thin film lubrication
• modified reynolds equation
• saturated viscosity layer
• engine oil
• additives
• tapered pad bearing
• lubricant rheology
• arbitrary viscosity layer
• adsorbed lubricant film