Mechanism of Lubrication in Porous Journal Bearing. Effects on Dimensionless Oil-Feed Pressure on Frictional Characteristics.

Abstract

The frictional characteristics of a porous bronze bearing are experimentally studied in hydrodynamic and mixed lubrication regimes. The results show that the relationships between the coefficient of friction μ and Sommerfeld number S obtained for a range of oil-feed pressure and shaft speed could be rearranged using dimensionless oil-feed pressure ps. With decreasing S, μdecreases in the hydrodynamic regime and then steeply increases in the initial stage of the mixed regime. However, at lower values of S, μbecomes steady and its value remains almost the same for various ps. The value of S at the transition point from the hydrodynamic regime to the mixed regime is significantly affected by ps, becoming smaller for higher ps. To estimate μ in the mixed regime, a simple frictional model is proposed on the basis of the observed results that the extent of the oil film in the bearing clearance in the mixed regime remains steady and nearly corresponds to that at the transition point. The calculated values for μ using the model are found to approximately agree with the experimental results.