Effect Of Lubricant Inertia Research Articles

Effect of lubricant inertia on textured journal bearing implementing mass conserving (JFO) boundary conditions

Purpose Cavitation plays a significant role in the performance of textured journal bearings. Furthermore, because of the usage of low-viscosity lubricants and the high working speed of machines, it is pertinent to consider the lubricant inertia while analyzing the operating characteristics of bearings. This paper aims to investigate the influence of lubricant inertia in the case of a spherically textured journal bearing, considering both protrusion and dimple texturing and implementing the mass-conserving (JFO) boundary conditions. Design/methodology/approach A novel modified Reynolds equation has been developed to accommodate the effects of lubricant inertia and cavitation. The cavitation is treated by using mass-conserving (Jakobsson−Floberg−Olsson [JFO]) boundary conditions. The governing equation is solved by the Gauss−Seidel method with successive over-relaxation. To enhance computational efficiency and expedite the convergence process, the progressive mesh densification (PMD) method has been integrated into the solution process. Findings The current study indicates that the JFO boundary conditions result in higher load-carrying capacity and lesser friction variables for heavily loaded bearings, whereas the flow coefficient is reduced due to the application of JFO boundary conditions. The lubricant inertia effect enhances the flow coefficients for lightly loaded and protrusion-textured bearings. Originality/value It is crucial to understand the combined effects of lubricant inertia and cavitation for the effective design of textured journal bearings. The findings from this work will help in designing textured journal bearings more effectively and accurately, particularly when low-viscosity oil is used. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2024-0276/

Effect of lubricant inertia on steady-state characteristics of textured hydrodynamic journal bearing

PurposeThis paper aims to investigate the effects of inertia of the lubricant on the performance parameters of journal bearings textured with spherical-shaped textures.Design/methodology/approachThe lubricant is assumed to be Newtonian, and the flow is considered laminar. Considering the lubricant inertia effects, the modified Reynolds equation is discretized using the finite difference method and solved with the Gauss–Seidel successive over-relaxation scheme using the progressive mesh densification method.FindingsThe results from this numerical study indicate that the lubricant inertia improves textured journal bearing performance characteristics significantly. The improvement is more significant in the case of heavily loaded bearings. Furthermore, it is observed that protruded texturing in journal bearings shows better results compared to dimple textured journal bearings.Originality/valueUnderstanding the effect of lubricant inertia is essential for efficiently designing textured journal bearings. Thus, the results shown here would be helpful for the researchers and the bearing designers.

The effect of lubricant inertia on fluid cavitation for high-speed squeeze film dampers

This work studies the effect of lubricant inertia on the fluid cavitation for partially sealed high-speed squeeze film dampers (SFDs) executing small amplitude circular-centered orbits (CCOs). The lubricant cavitation is modeled by both the Elrod algorithm and the Gumbel’s cavitation boundary condition to provide the comparison between the most common lubricant cavitation models. Additionally, the fluid inertia is integrated by adapting a finite-length SFD model for partially sealed dampers. The integrated SFD model is incorporated into a numerical simulation model and the results are validated by comparison with experimental data. The results of the analysis demonstrate that the fluid inertia effects significantly extend the cavitation region and influence the cavitation onset and the film reformation.

A Study of Lubricant Inertia Effects for Squeeze Film Dampers Incorporated into High-Speed Turbomachinery

This work proposes a numerical model that incorporates the effect of lubricant inertia on the hydrodynamic pressure distribution, fluid film reaction forces, and the fluid velocity component profiles for finite-length open-ended squeeze film dampers (SFDs). Firstly, the thin film flow equations for the SFD in presence of fluid inertia effects are introduced. Furthermore, a small first-order perturbation by means of the expressions for the fluid film velocity components and the lubricant pressure distribution that are expanded in power series of the squeeze film Reynolds number is applied to the flow equations. Subsequently the developed lubricant flow equations are solved to develop expressions for the velocity component profiles and the hydrodynamic pressure distribution in SFDs. The pressure expression is numerically solved by using Gauss–Seidel method with finite difference discretization. Moreover, the fluid film reaction forces are determined by numerically integrating the hydrodynamic pressure expressions over the journal surface. Additionally, the proposed pressure distribution expression and the numerical SFD forces are incorporated into a simulation model and the simulation results are compared with the existing models in the literature under different operating conditions, including eccentricity ratios and inertia effects (i.e., Reynolds numbers). The simulation results demonstrate the significant influence of both convective and temporal (i.e., unsteady) lubricant inertia terms on the SFD hydrodynamic pressure distribution and the fluid film reaction forces. Furthermore, the proposed SFD model is incorporated into a multi-mass flexible rotordynamic model to evaluate the effect of SFD fluid inertia on the mass unbalance induced steady-state vibrations of the rotor and the nodal transient orbits by implementing finite element method and transient modal integration with predictor–corrector solver. The results of the analysis demonstrate the significant effect of fluid inertia on the resonance frequencies of the rotor and the steady-state vibration amplitudes and the transient orbits at the resonance zone.

On the Steady Performance of Annular Hydrostatic Thrust Bearing: Rabinowitsch Fluid Model

The present theoretical analysis investigates the simultaneous effect of lubricant inertia and non-Newtonian pseudoplastic lubricant (lubricant blended with viscosity index improver and viscosity thickener)–Rabinowitsch fluid model on the performance of externally pressurized annular hydrostatic thrust bearings. A close form solution is obtained for pressure distribution. The effect of centrifugal inertia on the pressure distribution in the recess region is considered by taking non-constant recess pressure under a hydrodynamic condition. The load capacity and flow rate have been numerically calculated for various values of viscosity index improver together with the centrifugal inertia effects. In the limiting case in which there is an absence of pseudoplasticity, the results are compared with the pre-established Newtonian lubricants and are found to be in good agreement.

Inertia Effect on the Thermohydrodynamic Characteristics of Journal Bearings

In this article, the effect of lubricant inertia on the thermohydrodynamic behaviour of journal bearings is studied. Many researchers have analysed the inertia effect on lubricant flow in bearings using different simplifying assumptions. The purpose of this study is to eliminate most of those assumptions, using computational fluid dynamics (CFD) techniques to solve the exact governing equations. The bearing has a finite length and operates under incompressible laminar flow and steady conditions. Numerical solutions of the full three-dimensional Navier-Stokes equations with and without inertia terms, coupled with the energy equation in the lubricant flow and the heat conduction equations in the bearing and the shaft are obtained. Cavitation effects are also considered using an appropriate three-dimensional cavitation model. In order to study the effect fluid inertia under several different conditions, solutions are obtained for different values of the eccentricity and radial clearance and also for different values of the rotational speed of the shaft. To validate the computational results, comparison with the experimental data of other investigators is made, and reasonable agreement is obtained.

The influence of fluid inertia and heat dissipation in fluid films

It was demonstrated earlier that for laminar, isothermal flow of the lubricant in long journal bearings, inertia has negligible effect on the load carrying capacity and influences only the stability characteristics of the bearing. The question in the present paper is: 'will these conclusions of the isothermal theory remain valid in the presence of significant dissipation, or will lubricant inertia and dissipation interact non-linearly to bring about qualitative changes in bearing performance\ulcorner' The results obtained here assert that the effect of lubricant inertia on load carrying capacity remains negligible, irrespective of the rate of dissipation. The stability of the bearing is, however, affected by lubricant inertia. These results, although obtained here for long bearings with Sommerfeld and Gumbel boundary conditions, are believed to be applicable to practical bearing operations and affirm that bearing load may be calculated from classical, i. e., non-inertial theory.

On the Combined Effects of Lubricant Inertia and Viscous Dissipation in Long Bearings

We have demonstrated earlier that for laminar, isothermal flow of the lubricant in the non-cavitating film of long journal bearings, inertia has negligible effect on the load-carrying capacity and influences only the stability characteristics of the bearing. The question we pose in the present paper is: “will these conclusions remain valid for nonisothermal flow, or will lubricant inertia and dissipation interact and result in significant changes in bearing performance?” The results obtained here assert that the effect of lubricant inertia on load-carrying capacity remains negligible, irrespective of the rate of dissipation. The stability of the bearing is, however, affected by lubricant inertia. These results, although obtained here for long bearings and noncavitating films, are believed to be applicable to some practical bearing operations and suggest that for these, bearing load may be calculated from classical, i.e., noninertial theory.

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.

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.

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.

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.

The Magnetostatie Partial Journal Bearing with Inertia Effect

In the following analysis of the partial Journal bearing with a radial magnetic field, the effect of lubricant inertia is considered. The viscosity and inertia have positive contributions to the loadcapacity. The effect of inertia is to increase the time of approach.

Effect of lubricant inertia in a magneto-gasdynamic externally pressurized bearing

Effect of lubricant inertia in a magneto-gasdynamic externally pressurized bearing

Effect of Lubricant Inertia on Squeeze Film in Spherical Bearing

A theoretical investigation of inertia effects on squeeze film in a spherical bearing is presented. It is shown that inertia forces make a significant contribution to the time of approach.

The Effects of Lubricant Inertia on Soueeze Films in Journal Bearings

A theoretical investigation of inertia effects on squeeze films in full and half journal bearings of infinite length are presented. It is found that the time of approach is increased due to inertia forces. Further it is seen that inertia forces make a significant contribution to the time of approach at large value of ⊼.

Effect of lubricant inertia in a pivoted slider bearing with a convex pad surface

The inertia effect in a pivoted slider bearing with a convex pad surface is considered. It is found that the load-supporting capacity of the pivoted slider bearing and the frictional force on the bearing are increased if the inertia effect is taken into account. It is also shown that the centre of pressure is slightly shifted towards the leading edge by the inertia effect.

Effect of Lubricant Inertia in Bearings

The inertia effects in squeeze film between two curved surfaces and externally pressurized bearing with a converging lubricant film are considered. It is shown that lubricant inertia for squeeze film bearing increases the load supporting capacity and decreases the squeeze. For externally pressurized bearing it is found that there is a negative contribution to the load supporting capacity by inertia forces.