Critical Conditions for Hydrodynamic Lubrication of Porous Metal Bearings

Abstract

The theory of the operation of porous metal bearings as given in the 1957 Conference on Lubrication and Wear has now been extended. The analysis of a 360° porous bearing leads to a critical value of the Sommerfeld reciprocal 1/δ below which full fluid lubrication cannot be obtained. The magnitude of this critical value 1/Δ_c is found to vary only with the length to diameter ratio of the bearing L/D, and with the design variable Ψ, a dimensionless parameter dependent upon the Darcy permeability Φ, wall thickness H, and radial clearance c, and defined as + = ΦH/c ³. In the absence of a full computed solution of the modified Reynolds equation, variation of the L/D ratio has been allowed for by applying the same correction factors that apply to non-porous bearings. Experimental work has been carried out using + values varying from 1.95 × 10-⁴ to 2.91 × 10-² (a factor of 150) and within this range good agreement with the theory was obtained.