Study on Mechanism of Lubrication in Porous Journal Bearings. Static Characteristics of Porous Journal Bearings With Sealed Ends at Start of Operation.

Abstract

A theoretical investigation of static characteristics at the start of operation is developed for a porous journal bearing with sealed ends lubricated only by the oil initially provided within its structures. Numerical results show that a negative pressure region exists in the porous matrix just below the oil-film rupture zone. Hence, air penetrates into the porous matrix at the oil-film rupture zone as the oil in the porous matrix moves inwards, which causes the reduction of oil content within the porous matrix. With decreasing Sommerfeld number Sw, the oil-film force f^^^ and the oil leakage flow q^^^(SUB)oce at the axial ends through the clearance gap increase in the hydrodynamic regime due to an increase of the angular extent of oil-film β, although the values of β and q^^^(SUB)oce in the mixed regime are constant and are the same as those at the transition point from the hydrodynamic regime to the mixed regime since the value of f^^^ is assumed to be equal to that at the transition point. Furthermore, with decreasing Sw, the coefficient of friction μ decreases in the hydrodynamic regime and then 0steeply increases in the initial stage of the mixed regime. At lower ranges of Sw, μ approaches the value of the coefficient of boundary friction.