Fluid Film Stiffness Research Articles

Optimization of twin grooved two-lobe textured hydrodynamic journal bearing design by using genetic algorithm

Surface texture plays a role in enhancing the performance of hydrodynamic journal bearings by reducing friction coefficients and increasing load-carrying capacity. However, its impact on the dynamic performance of the bearings remains largely unexplored. This study aims to fill this gap by investigating the optimized surface texture of twin-grooved two-lobe hydrodynamic journal bearings using genetic algorithms. Through the optimization of surface texture, significant enhancements in the dynamic performance of the bearings, including improvements in fluid film damping, stiffness, and omega threshold speed, are achieved. Utilizing GA optimization, textured bearings demonstrate a remarkable enhancement in dynamic performance, with an impressive increase of 195.55% in omega threshold speed. These findings provide valuable insights for enhancing bearing designs and stability, thereby contributing to advancements in tribological engineering.

Influence of 3D surface irregularities on the performance of hydrostatic rectangular tilted thrust pad bearing configurations

Tribological behavior of tribo-pairs is strongly dependent on the surface topography. Further, the structural deformation, manufacturing, and assembly errors cause the hydrostatic thrust pad bearings to tilt slightly. The work in this article is aimed to study the effect of tilt and three-dimensional (3D) surface irregularities on the performance of hydrostatic rectangular thrust pad bearings (HRTPB) compensated with capillary restrictors. The 3D surface irregularities are assumed to follow cosine curve. To perform the analysis, a source code has been developed in MATLAB and the Finite Element Method has been used to solve the governing Reynold's equation. The numerical simulation results indicate that the effect of tilt reduces the value of fluid film reaction, fluid film stiffness, and fluid film damping coefficients. The study reveals that 3D surface irregularities results in a higher value of fluid film stiffness and damping coefficient as compared to that of smooth-bearing surfaces.

Effect of partial surface waviness on the dynamic and stability performance of journal bearing

AbstractThis study presents the impact of full and partial surface waviness on the dynamic and stability performance of the journal bearing. The Reynolds equation is modified to account for the impact of surface waviness, and the lubricant domain is discretized using the Finite element method to obtain dynamic characteristics such as stiffness and damping coefficients and stability parameters, that is, threshold speed. Different wave numbers in the axial, circumferential and mixed directions are considered at variable wave amplitudes in different regions at an average eccentricity ratio of 0.6 to obtain the optimum values. The obtained results reveal that by application of waviness in the full region and partial waviness in the pressure‐reducing region on the bearing surface provides the enhanced value of stability parameter, fluid film stiffness and dynamic coefficients as compared to the simple journal bearing under the same working conditions.

Analysis of MR fluid lubricated slot entry hybrid conical journal bearing with texturing arrangements

This paper proposes a study of slot-entry ‘hybrid conical journal bearing system’ (HCJBs). The slot restrictor acts as compensating device, i.e., no need for an external compensation element. Three zonal arrangements of the spherical-shaped textured surfaces (Partial-I, Partial-II, and Full texturing) over the surface of the conical bearing have been considered. Further, the effects of the smart behavior of magnetorheological fluid (MRF) on textured slot-entry HCJBs have been analyzed. The mathematical modeling of the modified Reynolds equation has been done with the Finite element method and the Gauss-Seidel method. The numerical simulation indicates that applying textured surfaces and MR fluid improves minimum fluid film thickness, stiffness and stability of the hybrid conical bearing system.

Micro-grooved hybrid spherical thrust bearing with Non-Newtonian lubricant behaviour

Recent tribology research has primarily focused on leveraging engineered grooved surfaces to enhance the lubrication performance of tribo-contacts. The performance of fluid film bearings may be improved by using a properly designed micro-groove on the surface of bearing. This paper deals with the performance of micro-grooved hole-entry hybrid spherical thrust bearing (HSTB) considering Non-Newtonian behavior of the lubricant. To analyse the Non-Newtonian behaviour of lubricant the cubic law model has been used. The solution of the governing Reynold equation in the fluid film domain of the hole-entry hybrid spherical thrust bearing is obtained by the FEM. In this study, the influence of rectangular and circular shaped micro-groves has been analysed. The parametric analysis has also been performed to obtain the optimum attributes (i.e. w¯g,d¯g,l¯gr) of the micro-grooves for both the shapes. The present investigation shows that the performance of the hole-entry hybrid spherical thrust bearing gets enhanced by considering the micro-grooves on the surface of bearing. Furthermore, the bearings performance is affected by the geometry of the micro-groove used. The value of fluid film reaction (F¯y) and stiffness coefficient (S¯) is observed to be increased by 23.33% and 343.98% at εy = 0 and κ¯=1 for the case of rectangular-shaped micro-grooved hole-entry HSTB configuration.

Shear-Thinning and piezoviscous lubricant behavior of spiral grooved hybrid thrust pad bearing configurations

The present study investigates the effects of shear-thinning and piezoviscous lubricant on the behavior of inwardly and outwardly spiral grooved hybrid annular thrust pad bearing configurations. The performance of spiral grooved circular and annular hybrid thrust pad bearing configurations with a capillary restrictor is also compared in this study. The influence on fluid film reaction, lubricant flow rate, fluid film stiffness, and damping coefficients have been carried out. The numerically simulated results show that the synergistic effect of spiral grooves and shear-thinning and piezoviscous behavior of the lubricant, have a significant impact on lubrication performance. The maximum percentage difference in the value of fluid film stiffness between outwardly spiral grooved annular recessed hybrid thrust pad bearing with non-Newtonian lubricant and inwardly spiral grooved annular recessed hybrid thrust pad bearing with Newtonian lubricant is found to be 80.6 percent.

Research on the Dynamic Characteristics of Mechanical Seal under Different Extrusion Fault Degrees

In order to explore the dynamic characteristics of the mechanical seal under different fault degrees, this paper selected the upstream pumping mechanical seal as the object of study. The research established the rotating ring-fluid film-stationary ring 3D model, which was built to analyze the fault mechanism. To study extrusion fault mechanism and characteristics, different dynamic parameters were used in the analysis process. Theoretical analysis, numerical simulation, and comparison were conducted to study the relationship between the fault degree and dynamic characteristics. It is the first time to research the dynamic characteristics of mechanical seals in the specific extrusion fault. This paper proved feasibility and effectiveness of the new analysis method. The fluid film thickness and dynamic characteristics could reflect the degree of the extrusion fault. Results show that the fluid film pressure fluctuation tends to be more intensive under the serious extrusion fault condition. The extrusion fault is more likely to occur when the fluid film thickness is too large or too small. Results illustrate the opening force is affected with the fluid film lubrication status and seal extrusion fault degrees. The fluid film stiffness would not always increase with the rotating speed growth. The seal fault would occur with the increasing of rotating speeds, and the leakage growth fluctuations could reflect the fault degree.

Performance analysis of rough surface hybrid thrust bearing with elliptical dimples

Surface roughness is inherent to all machining processes. Therefore, even a high precision machining process renders micro-roughness to some extent on the surface of conventional materials. The asperities height of many rough engineering surfaces follows Gaussian distribution. The surface roughness on the bearing surface may significantly affect the bearing performance. Surface texturing is emerging as a new technique to improve the tribological behavior of the mating surfaces. Usually dimensions/height of micro-roughness is of order of the depth of surface textures in fluid film bearings. Neglecting micro-roughness while numerically simulating a textured surface bearing may generate inaccurate bearing performance data. In presented work, finite element simulation of textured surface hybrid thrust bearings has been performed. Surface texture is provided over thrust pad in the form of regular arrays of elliptical dimples. A parametric optimization is carried out to determine optimum attributes of elliptical dimple (axis, depth, texture length and orientation) so that the load-carrying capacity and fluid film stiffness should be maximized and film frictional power losses should be minimized. Use of textured surface (with optimum elliptical dimple attributes) results into a significant enhancement in load-carrying capacity (91.3%), film stiffness coefficient (+98.8%) and reduction in frictional power losses (−48.3%). It is also observed that elliptical dimple and micro-roughness (transverse orientation) generate synergistic effects in further enhancing the load-carrying capacity (+101.4%) and film stiffness coefficient (+112%) of the bearing.

Finite element analysis of multirecess hybrid spherical journal bearing system

The present work deals with finite element method analysis of a multirecess hybrid spherical journal bearing system. The governing equations have been discretized using Galerkin’s technique and are solved simultaneously using a suitable iterative technique. The effect of span angle on the static and dynamic behavior of a hybrid spherical journal bearing compensated with membrane restrictor is investigated in the present work. Numerical results indicate that larger values of span angle provide enhanced value of minimum fluid-film thickness [Formula: see text], reduced lubricant flow requirement [Formula: see text], and higher value of frictional torque [Formula: see text]. Further, the results have been compared with a correspondingly similar capillary-compensated bearing. The comparison of numerically results demonstrates that the value of direct fluid-film stiffness coefficient [Formula: see text] could be 45.90% higher than that of correspondingly similar capillary-compensated bearing. The numerical results presented in this work may be useful as design guidelines for a recessed hybrid spherical journal bearing.

A Simulation Study on the Behavior of Magnetorheological Fluid on Herringbone-Grooved Hybrid Slot-Entry Bearing

In recent years, extensive use of smart lubricants has been made in order to control the tribological performance of fluid film bearings. The grooved surfaces of the journal bearing greatly influence the performance of bearings. In the present work, various geometric shapes of herringbone grooves (rectangular, triangular, and parabolic) with groove angles (30° and 60°) have been considered to numerically simulate the performance of slot-entry bearings. The work reported in this article deals with the numerical simulation of magnetorheological (MR) fluid–lubricated slot-entry herringbone-grooved hybrid journal bearings. Dave equation, a constitutive relation of the Bingham model, was employed to simulate the flow behavior of MR fluid. Using the finite element method (FEM), the governing Reynolds equation for a hybrid slot-entry bearing model was solved. The result shows that the use of a herringbone-grooved surface and application of MR fluid in a slot-entry bearing offers better stability and higher fluid film stiffness and minimizes frictional torque.

Elastohydrostatic simulation of thrust bearing Compensated with orifice restrictor operation with non-Newtonian lubricant

In the present work influence of elastohydrostaic lubrication on orifice compensated bearing has been shown. The thrust pad has been modeled by using three-dimensional mesh and lubrication domain has been modeled by using two dimensional mesh. The analysis of Reynold equation is coupled with the analysis of solution of equilibrium equation of thrust pad domain. The Present results shows that elasticity of thrust pad results a significant decrement in the fluid film Elasticity and it results an increase in fluid film stiffness. In the present case Circular, Elliptical, square and rectangular shape of recess has been taken from the analysis.

Boundary Lubrication in Transient Elliptical Contact: Part 1—Theoretical Formulation and Results

The transient elliptical contacts in boundary lubrication widely exist in modern mechanical systems with high durability. However, little attention has been paid to the squeeze effect of fluid film in this condition. A deterministic model which combines the contact mechanics with the pure squeeze lubrication model has been developed with the aim of understanding the squeeze effect of fluid film under the transient boundary lubrication. The leakage coefficient was introduced to capture the fluid leakage of rough surfaces. The squeeze effect of trapped fluid film was confirmed through comparing the fluid film stiffness in boundary lubrication with that of the elastohydrodynamic lubrication. Additionally, the effects of fluid film entrapment/leakage on the boundary lubrication performance were numerically analyzed during transients. The load capacity of the squeeze films is built up due to the trapped fluid film in the micro-valleys, which can be significantly affected by the interfacial shear coefficient of the boundary films. The simulation results show a good agreement with the experiments and justify the present numerical model is feasible in the boundary lubrication regime.

Influence of dimple geometry and micro-roughness orientation on performance of textured hybrid thrust pad bearing

The present study deals with numerical simulation of textured hybrid thrust pad bearing. Influence of providing micro-dimples of different cross-sectional shapes on the bearing surface has been theoretically investigated on the performance of thrust pad bearing. Reynolds equation has been solved using mass-conserving algorithm based on Jakobsson–Floberg–Olsson cavitation boundary conditions. A parametric study is carried out to optimize dimple shapes from the viewpoint of load carrying capacity of bearings. The textured bearing surface is noticed to be beneficial in reducing the frictional power losses. Providing half-section dimples (second half in the direction of runner rotation) towards the leading edge of thrust pad, enhance the load carrying capacity and fluid film stiffness coefficient of bearings. Micro-roughness in a textured surface having transverse orientation is seen to improve the dynamic characteristics of hybrid thrust pad bearings.

Textured conical hybrid journal bearing with ER lubricant behavior

Abstract This work examines the ER lubricant behavior on the performance of conical hybrid journal bearing. The influence of micro-texture with different shapes used on the bearing surface is studied. FEM is used to solve the modified Reynolds equation using GMRES method. A parametric study is carried out to optimize the dimple attributes on the basis of radial load. The numerical results show that a textured surface and ER lubricant enhances the values of load carrying capacity ( W ¯ R and W ¯ A ) and fluid film stiffness coefficients ( S ¯ i j ) for conical journal bearing. Further, it has been observed that the use of ER lubricant enhances the value of minimum fluid film thickness ( h ¯ m i n ), thereby reducing the chances of metal to metal contact.

A study on performance of slot entry hybrid journal bearing considering effect of surface irregularities

PurposeThis study aims to deal with the performance of symmetric/asymmetric slot entry hybrid journal bearing system considering the effect of three dimensional irregularities in the analysis.Design/methodology/approachThe asperity profile of three-dimensional irregularities has been modeled in both circumferential and axial directions. To compute the bearing performance characteristics parameter, finite element formulation of governing Reynolds equation has been derived using Galerkin’s technique.FindingsBased on the numerically simulated results, it has been observed that the three-dimensional irregularities enhance the value of minimum fluid film thickness (h̄min), lubricant flow (Q̄) and fluid film damping coefficients (C̄11,C̄22) approximately by order of magnitude of 24-26, 43-51 and 18-66 per cent, respectively, for the case of asymmetric slot entry configuration. Whereas, the values of fluid film stiffness coefficients (S̄11,S̄22) and threshold speed (ω̄th) reduces approximately by order of 1-6 and 0-3 per cent, respectively, for the case of symmetric slot entry configuration.Originality/valueThe present paper describes that the influence of three-dimensional irregularities on bearing surface on the performance of slot entry hybrid journal bearing is original in literature gaps. The numerically simulated results presented in this study are expected to be quite useful to the bearing designers.

Performance Analysis of a Conical Hydrodynamic Journal Bearing

Many turbo-machines such as turbines and compressors generate axial and radial load during their operation. Conical hydrodynamic journal bearing is proposed to sustain radial load and adjust the effect of axial load on rotating elements. The present study has proposed the performance analysis for conical hydrodynamic journal bearing of semi-cone angles (γ = 5°, 10°, 20°, 30°) for a wide range of radial load ($$\bar{W}_{\text{r}} = 0.1 - 0.9$$) on rotating journal. Finite element method has been used to solve the modified Reynolds equation for investigating the flow of lubricant in the clearance space between journal and bearing. Performance characteristics such as load-carrying capacity, fluid film thickness, stiffness coefficients, damping coefficients and threshold speed for various configurations of conical hydrodynamic journal bearing have been presented and discussed. Results show that threshold speed ($$\bar{\omega }_{\text{th}}$$) of conical journal bearing is considerably reduced as the semi-cone angle increases to γ = 30° as compared to the base bearing of semi-cone angle γ = 5°.

Finite element method analysis of hydrostatic thrust pad bearings operating with electrically conducting lubricant

A theoretical investigation has been carried out to explore the use of electrically conducting fluids as lubricants in circular and elliptical hydrostatic thrust pad bearings subjected to transverse magnetic field. Flow of electrically conducting fluid in the presence of external transverse magnetic field is represented by the addition of Lorentz force in Navier–Stokes equation. A MATLAB source code based on finite element formulation of the modified Reynolds equation is developed for obtaining static and dynamic characteristics parameters of the bearing. Influence of aspect ratio (major/minor-axis) and magnetic field (Hartmann number) are analyzed on the performance of elliptical pad bearing. Application of electrically conducting lubricant in the elliptical pad is observed to provide higher values of fluid film stiffness (44.93%) and damping (139.37%) coefficients as compared to the circular pad operating with Newtonian lubricant.

Numerical study on axial vibration of water-lubricated small thrust bearing considering grooved pad

This paper presents the effect of pad with transverse grooves on the axial vibration for a small thrust bearing under water lubricated. Due to downsizing of electronic devices, the component part such as the thrust bearing in the micro fabrication becomes small size. Therefore, to study the characteristic of vibration for a small thrust bearing under water lubricated is significant for high precision machining. The hydrodynamic lubrication model was used to predict the water film thickness, the water pressure profile, and the bearing stiffness. A finite difference method (FDM) and a Newton-Raphson scheme are employed to achieve numerical results, i.e. the water pressure distributions, the water lubricating film thicknesses and the bearing stiffness under the variation of groove depths. The grooved shape of pads, that examined in this paper, was elliptical shape. The equation of motion under the impulse excitation considering in the axial vibration for a small thrust bearing was solved by using a Runge-Kutta method. The numerical results showed that the use of elliptical transverse grooves is effective to increases the fluid film stiffness and the maximum displacement in the axial vibration is able to be reduced.

A novel technique to compute static and dynamic performance characteristics of aerostatic thrust bearing

PurposeThis study aims to analyze the dynamic performance of aerostatic thrust bearing for different geometries of recess. Different geometries of recess of equal recess area, i.e. circular, elliptical, rectangular and annular, have been considered in analysis. The work also analyzes the influence of tilt angle on the performance of thrust bearing. To compute the unknown pressure field, the Reynolds equation governing the flow of compressible lubricant (air) has been solved using finite element formulation. Further, separate finite element formulations have been carried out to compute fluid film stiffness and damping coefficients directly. This method provides quick computation of stiffness and damping coefficients of aerostatic thrust bearing than the usual approach.Design/methodology/approachAs the Reynolds equation governing the flow of compressible lubricant is nonlinear partial differential equation, the computation of the stiffness and damping coefficient follows an iterative procedure. It requires a lot of computational energy. Therefore, in the present work, a novel technique based on finite element formulation is suggested to compute air film stiffness and damping coefficient in aerostatic thrust bearing.FindingsA novel technique based on finite element formulation is illustrated to simulate the performance of tilted pad aerostatic thrust bearing. On the basis of simulated results, following key conclusions may be drawn. The static and dynamic performance of a circular aerostatic tilted thrust pad bearing is significantly affected with a change in the value of tilt parameter and the shape of the recess.Research limitations/implicationsImplications are as follows: direct computation of air film damping coefficient is performed without perturbation method in finite element method (FEM); influence of tilt on aerostatic thrust bearing is studied; influence of recess shape on aerostatic thrust bearing is observed; and finite element formulation of aerostatic thrust bearing is performed.Originality/valueThe present work will be quite useful for bearing designer and academicians.

Dynamic characteristics of compensated hydrostatic thrust pad bearing subjected to external transverse magnetic field

This article presents finite element analysis to evaluate the performance of a compensated hydrostatic circular thrust pad bearing in the presence of a magnetic field. The influence of the magnetic field on the flow of an electrically conducting lubricant is expressed by incorporating the Lorentz force in the momentum equation, described by Maxwell equations and Ohm’s law. The modified Reynolds equation has been derived for a lubricant blended with long-chain polymer additives flowing in the presence of a transverse magnetic field. The Stokes couple stress theory has been used to describe effect of such additives on lubricant rheology. A source code has been developed in MATLAB to solve the modified Reynolds equation coupled with restrictor flow equations using the finite element method. The performance characteristics of the bearing system are evaluated in terms of pocket pressure, load-carrying capacity, lubricant flow rate, fluid film stiffness and damping coefficient. Comparative studies have been carried out for orifice and capillary compensated bearings. The limiting cases of the modified Reynolds equation yield performance characteristics of specific lubricants such as electrically conducting couple stress lubricant, couple stress lubricant, electrically conducting lubricant and Newtonian lubricant. It is noticed that the load-carrying capacity, fluid film stiffness and damping capabilities of the bearing get enhanced quite substantially in the presence of couple stress additives and a magnetic field.