On the thermohydrodynamic performance of aerated lubricants in steadily- and dynamically-loaded journal bearings

Abstract

The effect of aerated oil, containing air bubbles, on the steadily and dynamically loaded journal bearing is investigated. The study is based on the thermohydrodynamic (THD) lubrication theory, which fully couples the Reynolds equation with the energy for the oil and heat conduction equations for solids through the oil viscosity. The oil’s effective viscosity is influenced by the presence of bubbles via the surface tension and/or the volume fraction. The Reynolds equation is solved using the mass conservation algorithm and the two-dimensional equations for the temperature fields both in oil and solids are solved simultaneously to save computational time. The bubble radius, density, and viscosity are directly influenced by the pressure and temperature fields, requiring updating their values at each pressure and temperature. The simulations show that with a realistic viscosity model, the effect of the air bubbles in the lubricating oil on the pressure and temperature fields is small at normal operating speeds, while the density and the effective viscosity are reduced noticeably due to bubbles.