Effects of Misalignment on the Performance of Flexible Porous Journal Bearings

Abstract

A n~athematical model is introduced to study the effects of journal misalignment on the hydrodynamic lubrication performance offitlire flexible porous journal bearings. A modified form of Reynolds equation, which was derived from the Brinkman-extended Darcy equations and Stokes' equations, is utilized in the present study. The journal misalignment is allowed to vary in magnitude as well as in direction with respect to the bearing boundaries.The predicted pe~ormance characteristics of porous journal bearings are compared with available theoretical and experin1et1-tal results. The effects of the degree and angle of n~isalignmet~t, and the permeability of the porous liner on the pressure distribution, load-carrying capacity, friction coefficient and misalignment moment are presented and discussed. KEY WORDSJournal Bearings; Hydrodynamic Lubrication; Porous Bearings; Misalignment = radial clearance, m = flexibility parameter, Eq. [I31 . = degree of misalignment = eccentricity, m = modulus of elasticity of the bearing liner, Pa = friction coefficient = cavitation index, Eq. [7] = film thickness, m = dimensionless film thickness, H = h / c = permeability of bearing material, ni2 = dimensionless permeability, K = k / c2 = length of the bearing, m = misalignment moment, N.m 2 2 = dimensionless misalignment moment, mc2 /(poUR L ) = number of internal nodal points in 0 -direction = number of internal nodal points in z-direction = pressure of lubricant film, Pa = cavitation pressure, Pa = oil supply pressure, Pa =dimensionless pressure, P = pc2 I(poUR) = dimensionless cavitation pressure, P = pcc2 I(poUR) z dimensionless supply pressure, P = p c~2 /(poUR) = side leakage flow, m3 /s = dimensionless side leakage flow, Ql = qs /(URc) = radius of the journal, m = stress jump parameter = thickness of the bearing liner, m = velocity of the lubricant film in x-direction, m/s = dimensionless velocity of the lubricant film in x-direction, ii = u/U = surface velocity of the journal, U = oR, m/s = velocity of the lubricant film in z-direction = dimensionless velocity of the lubricant film in z-direction, 4 = w/U = total load capacity of the bearing, N = dimensionless total load capacity of the bearing, w = w ,~,~~ I ( P~U R~L ) = bearing coordinates in circumferential, radial, and axial directions, respectively = dimensionless coordinates in circumferential, radial, and axial directions, respectively, X = x / R, Y = y / c, Z = z / L = dimensionless parameter, a = (p* / p)In = bulk modulus of the lubricant, Pa = dimensionless bulk modulus,D = ,~' c~/ (~~U R ) = angle of misalignment = dimensionless thickness of the bearing liner, A = rl / c = eccentricity ratio, eo / c = under-relaxation factor = angular coordinate, rad = viscosity of the lubricant in the film region, P a s = effective viscosity of the lubricant in the porous matrix, Pa s = viscosity of the lubricant at atmospheric pressure, Pa s = dimensionless viscosity of the lubricant, = @//lo = Poisson's ratio of the porous liner material = lubricant density, kg m-3 = lubricant de...

Steady-state performance analysis of misaligned double-layered porous journal bearings under coupled-stress lubrication with slip flow and additives percolation effect

“…From the figure, it is noted that the positions of the two pressure peaks are on the either side of the mid-plane and they are axially near both ends of the bearing. Similar observation is reported by Elsharkawy 21 for misaligned flexible single-layer porous bearings.…”

“…But these investigations are restricted in plain journal bearings. Elsharkawy 21 showed that under high permeability, the misalignment effect on the performance of porous journal bearing can be neglected. Limited literature are available on the performance of a misaligned double-layered porous bearing under coupled-stress lubrication.…”

On the Characteristics of Misaligned Journal Bearings

“…Elsharkawy [123] in 2003 investigated the effect of journal misalignment on the performance of flexible porous journal bearings. They showed that the effect of misalignment in porous journal bearings can be neglected when the permeability is high.…”

Effects of lubricant additives on the performance of hydrodynamically lubricated journal bearings

“…The iterative numerical scheme presented in Elsharkawy [20] is used to solve the mathematical model, which consists of the modified Reynolds equation and the film thickness equation. In this scheme, Elrod's [21] cavitation algorithm, which satisfied the conservation of mass flow across the rupture and reformation boundaries, was implemented in the numerical scheme to predict the cavitation boundary more accurately than the conventional analysis, which uses the Reynolds condition.…”