Lubricant Inertia Research Articles

Effects of turbulence and lubricant inertia on dynamics of journal bearings lubricated with molten zinc in a galvanizing process

In a galvanizing process a continuous sheet of steel is passed through a bath of molten zinc around a series of rotating rollers. One or more of these rollers are submerged in the bath of molten zinc and are supported by journal bearings that are lubricated with molten zinc. Dynamic characteristics of these bearings influence the quality of the finished galvanized sheet and also determine the production speed. This work presents a theoretical study of these bearings in terms of the damping, stiffness, and inertia coefficients of the film of molten zinc separating the journal from the bearings. This work also addresses the influence of turbulence on the bearing dynamics. The damping, stiffness, and inertia coefficients of journal bearings lubricated with molten zinc are determined for different zinc alloys at 450,650, and 850 °F.

Predicted Performance of a Tri-Taper Journal Bearing Including Turbulence and Misalignment Effects

The performance predictions of a particular tri-taper journal bearing are shown to confirm known operating conditions. The importance of manufacturing tolerances on the resulting performance characteristics are highlighted. Design guidance for a family of these bearings including journal misalignment and lubricant inertia effects is also provided.

Effect of lubricant inertia in externally pressurized conical bearings with temperature dependent viscosity

The influence of convective inertia on the characteristics of a parallel gap conical bearing which rotates with a uniform angular velocity is investigated. The lubricant is assumed to be incompressible and the viscosity varies exponentially with temperature. Inertia terms in the governing equations have been averaged across the film-thickness and the resultant system of equations is solved numerically to determine various bearing characteristics. It has been observed that the inclusion of inertia terms causes a decrease in the dimensionless load capacity for a lubricant whose viscosity is weakly dependent on temperature, irrespective of the temperature setting of the slider. However, for a lubricant with strong temperature dependence of viscosity, there is a slight decrease in the load capacity when the slider temperature is lower than that of the pad. As the slider temperature increases, the situation reverses. The dimensionless torque on the slider increases with the inclusion of inertia.

Re-Examination of Film Rupture Boundary Condition in Hydrodynamic Lubrication Under Inertia Effect

This paper presents discussions on the choice and handling of film rupture boundary conditions for the hydrodynamic lubrication under the effect of lubricant inertia forces. Many researchers have analyzed this inertia effect in converging-diverging hydrodynamic wedge and squeeze films without careful consideration of the problem caused by the film rupture boundary conditions used. To reveal the importance of the problem, the marked difference in pressure distribution produced by the difference in boundary conditions is presented for an infinitely long, steadily loaded, cylindrical journal bearing.

Centrifugal inertia effects in misaligned radial face seals

This investigation presents the analysis of customarily neglected centrifugal inertia effects in fluid-film-lubricated misaligned radial face seals. The forces and moments that act upon the primary seal ring due to axial translation and angular rotation are obtained for the complete range of angular misalignment. Lubricant inertia is found to be helpful in attaining the dynamic stability in the performance of misaligned face seals. It is also helpful in minimizing the wobbling of the primary seal ring and the leakage across the seal.

Effect of inertia in a lubricant on the thermophysical processes in the radial slip bearings of turbine-driven machinery

The results from a numerical solution of the spatial nonisothermal problem of lubricant flow and heat transfer in a radial bearing are presented in conjunction with consideration of the lubricant inertia.

A Finite Element Analysis of the Navier-Stokes Equations Applied to High Speed Thin Film Lubrication

The performance of a cylindrical bore bearing fed by two axial grooves orthogonal to the load line is analyzed by solving the Navier-Stokes equations using the finite element method. This produces detailed information about the three-dimensional velocity and pressure field within the hydrodynamic film. It is also shown that the method may be applied to long bearing geometries where recirculatory flows occur and in which the governing equations are elliptic. As expected the analysis confirms that lubricant inertia does not affect bearing performance significantly.

Lubricant Inertia Effects and Recirculatory Flow in Load-Capacity Optimized Thrust Pad Bearings

An analytic investigation into the flow pattern in load-capacity optimized-profile-film thrust bearings is presented. This work shows that recirculatory flow can occur near to the inlet with some film shapes and becomes more extensive as bearing width increases. Of the film profiles investigated, lubricant flow reversal was most, significant in the quadratic type. When compared with linear film, the profile geometries gave enhanced load-carrying ability, but this was accompanied by a decrease in lubricant flowrate and an increase in power consumption. Lubricant inertia effects were most significant for the linear film profile giving increase in load-carying capacity and a decrease in lubricant flow over that where lubricant acceleration was excluded, power losses were affected only marginally.

Effects of Fluid Inertia Forces on the Performance of a Plane Inclined Sector Pad for an Annular Thrust Bearing Under Laminar Condition

The hydrodynamic wedge of a plane inclined sector pad is analyzed in relation to the lubricant inertia forces under incompressible laminar conditions. Based on the usual assumptions of thin film lubrication theory without the thermal effects, modified Reynolds equations are derived by averaging out all the inertia terms of the Navier-Stokes equations across the film thickness. The equations are linearized with respect to the inertia parameter, and solved numerically for a plane inclined, sectorial configuration. The boundary value of the film pressure at the leading edge is set at the ambient pressure, under the assumption of a negligibly small rampressure thereat. The inertial effects on the static and dynamic performance such as the load carrying capacity, flow rate, frictional torque, position of pressure center, film stiffness, and damping coefficient are discussed, in which the effects of the centrifugal force and those of the other convective inertia forces are compared with each other.

Finite element application to the study of hydrostatic thrust bearings

A finite element method was developed using linear triangular elements to solve the two-dimensional Reynolds equation in the polar coordinate system including the rotational lubricant inertia term. The validity of the method was verified by comparison with the finite difference solution for parallel and non-parallel operation of the hydrostatic thrust bearing. The method was applied to the study of plane and conical hydrostatic thrust bearings with circular recesses. Experiments were conducted to estimate the load-carrying capacities for a typical case and the test results were compared with the finite element solution.

Characteristics of multipad hydrostatic thrust bearings under rotation

A theoretical study of the characteristics of a multipad plane hydrostatic thrust bearing was made taking into account the effect of rotational lubricant inertia. Design data for the load capacity, flow and stiffness and damping characteristics were obtained for practically useful radius and resistance ratios for capillary and orifice compensation.

Analysis of multirecess conical hydrostatic thrust bearings under rotation

Abstract The characteristics of multirecess conical hydrostatic thrust bearings were studied theoretically taking into account the effect of rotational lubricant inertia. Load capacity, flow, stiffness and damping characteristics were computed for the practically useful aspect and resistance ratios for capillary and orifice compensations. The results are presented in a form for the convenience of designers.

Analysis of a Plane Inclined Guide Bearing Under Transverse Vibration and Translation of a Plate

Analysis of the load capacity, friction force, and lubricant flow of a infinite width, plane guide during transverse vibration and translation of a plate is presented. The effect of lubricant inertia on these variables is investigated and found to be significant. Analysis is facilitated through assumption of a parabolic velocity distribution across the film thickness as suggested by lubrication theory. The parabolic profile assumption is found to underestimate the contribution of lubricant inertia to the load capacity during plate vibration.

Effects of radial and rotational lubricant inertia on the performance of externally pressurized magnetohydrodynamic bearings

Expressions are obtained for the pressure distribution, bearing loadcarrying capacity, lubricant volume flow rate and frictional torque for an externally pressurized magnetohydrodynamic bearing under conditions when one bearing surface is rotated. The influence of centripetal acceleration and the combined effect of rotational and radial inertia terms are included in the analysis. It is demonstrated that neglect of the radial inertia term tends to underestimate the load and the lubricant flow rate. Neglect of the rotational inertia term leads to overestimation of the load and underestimation of the lubricant flow rate.

Characteristics of conical hydrostatic thrust bearings under rotation

The static and dynamic characteristics of annular recess conical hydrostatic bearings with capillary and orifice restrictors were studied. The effect of rotational lubricant inertia was allowed for. Computations for various aspect and resistance ratios and speeds are tabulated in a form useful to designers.

The effect of lubricant inertia in externally pressurized bearings using a viscoelastic lubricant

The inertia effects in an externally pressurized bearing with a viscoelastic lubricant were considered using the methods of averaged inertia and of iteration. The inertia forces reduce the load-bearing capacity at a given flow rate. The effect of the elasticity of the liquid is to increase the pressure and the load-bearing capacity at any point. The effects of the elastic number S, the volume flow rate Q, the ratio σ of the inner radius of the bearing to the outer radius of the bearing and H = h a on the pressure and the loadbearing capacity are presented graphically. The results obtained by the two methods are in good agreement.

Lubricant inertia effects in externally pressurized rectangular gas bearings

The flow in a sliding externally pressurized rectangular gas bearing was investigated including the effects of lubricant inertia, which are usually ignored in the analysis of rectangular bearings. It is shown that the lubricant inertia has a detrimental effect on the load-carrying capacity of the bearing.

Turbulent Lubrication Theory Using the Frictional Law : 3rd Report, Theoretical Analysis Considering the Lubricant Inertia

Turbulent Lubrication Theory Using the Frictional Law : 3rd Report, Theoretical Analysis Considering the Lubricant Inertia

Effect of axial current-induced pinch on the lubricant inertia for a squeeze film between circular disks

The effect of axial current-induced pinch on the behaviour of a squeeze film between parallel circular disks, including consideration of the inertial effect, is discussed. The solution is obtained using the regular perturbation method. Analytic results for the pressure distribution and the load-carrying capacity are obtained. It is found that a load proportional to the square of the current can be sustained even when there is no flow. Moreover, it is observed that the axial pinch affects the bearing characteristics through non-inertial terms only.

Effect of radial and rotational lubricant inertia on the pressure distribution in externally pressurised thrust bearings

Expressions are obtained for the pressure distribution in an externally pressurised thrust bearing for the condition when one bearing surface is rotated. The influence of centripetal acceleration and the combined effect of rotational and radial inertia terms are included in the analysis. Rotation of the bearing causes the lubricant to have a velocity component in an axial direction towards the rotating surface as it spirals radially outwards between the bearing surfaces. This results in an increase in the pumping losses and a decrease in the load capacity of the bearing. A further loss in the performance of the bearing is found when the radial inertia term, in addition to the rotational inertia term is included in the analysis.