Thrust Bearing Research Articles

A Thermal Hydrodynamic Model for Emulsified Oil-Lubricated Tilting-Pad Thrust Bearings

On maritime vessels, external factors such as explosions, collisions, and grounding can cause the emulsification of lubricating oil by seawater pollution, which can affect the lubrication of a ship’s thrust bearing. To explore the influence of the mixed emulsification of lubricating oil and seawater on the lubrication performance of thrust bearings, this study conducted an emulsification experiment, from which the viscosity equation of the oil–water mixture was obtained. A thermal hydrodynamic model (THD) of bearings considering oil–water mixed emulsification was established, and the Finite Difference Method (FDM) was used for analysis. The results show that according to the characteristics of the manifold, the mixture is divided into water-in-oil (W/O) and oil-in-water (O/W). In the W/O flow with higher viscosity, the film thickness becomes higher, but the power loss increases. In the O/W manifold with low viscosity, the thin film easily causes mixed friction. In the demulsification stage of the mixed liquid, the thickness loss of the film is huge, and the collision between the thrust-bearing pad and the inference plate may cause the pad to be ablated. The influence of specific heat capacity on temperature is greater than the temperature rise caused by viscosity.

Study of dependence of lubrication layer thickness in a plain thrust bearing of a sealed pump with a magnetic clutch on area of the working wheel equalizing holes

BACKGROUND: Nowadays, using sealed pumps for transferring various liquids is widespread. Increasing the service life and operation reliability of sealed pumps with a magnetic clutch is a relevant technical task.
 AIM: Search for relatively simple ways of increasing the service life and operation reliability of sealed pumps with a magnetic clutch, in particular, study of influence of area of the working wheel equalizing holes on lubrication layer thickness in a thrust bearing.
 METHODS: In the mathematical model, the diagram of forces acting at a rotor of a centrifugal pump with hydrostatic bearings operating with the transferred liquid was analyzed and the equilibrium equation was obtained. The influence of such centrifugal pump geometric parameters as area of the working wheel equalizing holes on lubrication layer thickness in a thrust hydrostatic bearing was taken into account in the calculation.
 RESULTS: In the paper’s conclusion, there is dependency graph of lubrication layer thickness in a thrust bearing on area of the working wheel equalizing holes. As it is shown in the graph, the axial force is quite sensible to area of an equalizing hole of a centrifugal pump working wheel.
 CONCLUSION: The practical value of the study lies in the formulated influence of area of the working wheel equalizing holes on lubrication layer thickness in a thrust bearing of a centrifugal pump, given in the paper’s conclusion.

Research on influencing factors of oil film temperature field characteristics for adaptive hydrostatic thrust bearing

Adaptive hydrostatic thrust bearing represents a mechatronic answer to the fast-growing industrial needs of high-performance rotary machineries. The aim of this research is to study the influencing factors of the temperature field characteristics of the adaptive hydrostatic thrust bearing, such as rotational speed, load, viscosity, and inlet flow rate. The temperature rise equation of the micro-gap oil film is derived, and a three-dimensional model of micro-gap oil film is established. Finite Volume Method and ANSYS FLUENT are used to explore the influence factors of the temperature rise of the micro-gap oil film based on the principle of Computational Fluid Dynamic. The results show that temperature rise on the downstream side of the oil cavity is higher than that on the countercurrent side, and the temperature rise on the edge of the outer oil sealing edge is higher than that on the inner oil sealing edge. The rotational speed has the greatest impact on the oil film temperature rise, followed by viscosity, inlet flow rate, and then load. The increment of oil film temperature rise with the load less than 16 t is higher than the increment of oil film temperature rise with the load greater than 16 t. When the rotational speed is lower than 80 rpm, the temperature rise of the oil film increases faster with the increase of the rotational speed than when the rotation speed is above 80 rpm. The inlet flow rate increases, the maximum temperature and average temperature rise of the oil film decreases, but there is little variation. The maximum temperature and average temperature rise increase with the increase of viscosity, and the greater the viscosity, the more obvious nonlinear.

Rigid Mode Vibration Control for 250 HP Air Compressor System With Integrated Hybrid Air-Foil Magnetic Thrust Bearing (i-HFMTB)

Abstract This study aims to verify the effectiveness of the 250 HP class compressor system to which the integrated hybrid air-foil magnetic thrust bearing (i-HFMTB) proposed in (Ha et al., 2023, “Integrated Hybrid Air Foil-Magnetic Thrust Bearing (i-HFMTB) Part I: Preliminary Experimental Test for Rotordynamic Parameter Identification and Behavior With PD Control,” ASME Paper No. GT2023-102860) [1] is applied, and the vibration and instability problems of air-foil journal bearing (AFJB) occurring in the rigid mode are controlled by i-HFMTB. The compressor rotor is supported by two AFJB (journal diameter = 60 mm) and an i-HFMTB, and the length and mass of the rotor are 550 mm and 15.24 kg, respectively. i-HFMTB has a structure in which air-foil thrust bearing (AFTB) pads are inserted into eight slotted active magnetic thrust bearings (AMTB), and PD control (proportional gain: 4000; differential gain: 10) is applied. The operating area was identified through AFJB’s dynamic coefficients and rotordynamic analysis. As a result, in the experiment with the 250 HP compressor system supported only by two AFJB, sub- and super-synchronous vibrations were generated owing to the AFJB’s insufficient load capacity and damping in the rigid mode (7000 rpm) region, and this instability did not disappear even upon increasing the speed to 15,000 rpm. However, when i-HFMTB was turned on in rigid mode, it was confirmed that the sub- and super-synchronous vibrations were significantly reduced. The thrust collar tilt angle was calculated through orbit trajectory analysis of the impeller and cooling side, and it was confirmed that the tilt angle of the thrust collar was reduced during i-HFMTB operation.

Numerical Analysis of the Effect of Deformations in Thrust Bearings on the Loading Capacity of the Lubricant Layer

Numerical Analysis of the Effect of Deformations in Thrust Bearings on the Loading Capacity of the Lubricant Layer

Failure mode analysis and severity measurement method for hydropower equipment

To meet the practical needs of effective failure management and safe operation of hydropower systems, the classification and description standardization of the failure modes are studied based on the statistical analysis of historical maintenance data of in-service hydropower equipment. The method of building the failure mode library is then offered, followed by the specification of failure mode codes. Given the characteristics of the hydropower equipment, a severity rating method and the severity measurement model of failure modes for hydropower equipment are proposed, with definition criteria built using fuzzy semantic techniques. Finally, a thrust bearing system of the hydraulic generator sets is used as an example to validate the method of failure mode analysis and severity measurement, and practical suggestions for implementation of severity measurement are given in this paper.

The Technique of Tribological Studies of SiSiC High-Speed Thrust Bearings

This paper is devoted to model tribological experiments and analysis of the research results obtained for new materials and coatings, such as SiSiC, with the aim to rank them and to make recommendations for use in thrust hydrodynamic friction units operating at high speeds and loads.

Static performance analysis of gas foil thrust bearings under inclined thrust disc considering the slip flow effect

As one of the important components in air compressors for fuel cell vehicles, the static performance of the gas foil thrust bearings greatly affects the operating stability of the rotor system. In actual operation, thrust disc tilt and the slip flow effect often occur, which will change the characteristics of bearings. Therefore, this paper focuses on the static performance of gas foil thrust bearings under tilting conditions with account of the slip flow effect. Firstly, the gas film thickness equation is established when the thrust disc is inclined, and the Reynolds equation is modified by the boundary slip conditions. Secondly, the load capacity and friction torque of bearings are solved by the finite difference method and successive over-relaxation method. Finally, the sensitivity of rigid and elastic bearings to tilt angles is analyzed by comparing the static characteristics under tilting conditions. The results show that the load capacity will be overestimated without considering the slip flow effect, and the tilting of the thrust disc increases both the load capacity and friction torque. Furthermore, compared with rigid bearings, elastic foil bearings have better adaptability to tilting conditions, which is conducive to the stable operation of the rotor system.

A lubrication model for bubbly oil lubrication with interfacial effect and thermal effect using the theory of multiphase mixtures

Bubbly oil lubrication is a type of lubrication method. However, the lubrication model of the bubbly oil has not been thoroughly considered. This paper aims to investigate the modelling for bubbly oil lubrication considering the interfacial effect and thermal effect, and a theoretical model is established based on the theory of multiphase mixtures. The interfacial and thermal effects on the static characteristics of a thrust bearing are analyzed. A test rig for the thrust bearing is developed to measure the static characteristics of the bearing under bubbly oil lubrication. The results show that the bearing static characteristics, i.e. bearing temperature rise, film thickness, friction torque, and volume flow, increase with consideration of three interfacial effects; the bearing temperature rise increases but the film thickness, friction torque, and volume flow rate decrease with consideration of the three thermal effects; the thermal effect on the bearing static characteristics is greater than the interfacial effect.

Influence of geometric shapes of recess on the performance of MR lubricated multi-recessed hybrid spherical thrust bearing

This paper aims to investigate the impact of different geometric shapes of recesses/pockets on the behavior of a multi-recessed hybrid spherical thrust bearing (MHSTB) configuration along with MR (magnetorheological) lubricant behavior. The analysis employs a finite element approach to assess the behavior of MHSTB configurations lubricated with MR fluids, with the MR lubricant's behavior modeled using the Herschel–Bulkley model. The governing equations are solved through Galerkin's discretization method combined with a suitable iterative technique. The study reveals significant variations in bearing performance when altering the magnetic field intensity and axial eccentricity ratio. The study explores various geometric recess shapes (i.e., elliptical, circular, triangular, and square) within the MHSTB configuration while maintaining same bearing operating and geometric parameters. Numerical simulations demonstrate that MHSTB systems operating with MR lubricant exhibit higher fluid film reaction and damping coefficients compared to Newtonian lubricant. Furthermore, it is observed that the elliptical recessed bearing configuration outperforms square, triangular, and circular recessed bearing configuration in terms of fluid film reaction and lubricant flow rate.

Study on static and dynamic characteristics of water-lubricated hydrostatic thrust bearings – Effect of feed hole inlet shape on bearing characteristics

Recently, water-lubricated hydrostatic bearings have been attracting attention. However, when water is used as the lubricating fluid, the flow velocity of the feed hole used as a restrictor is higher than that of conventional oil-lubricated hydrostatic bearings, resulting in a larger feed hole inlet flow velocity, making it difficult to analyze its characteristics using conventional hydrostatic bearing analysis methods. Therefore, in this study, a general-purpose fluid analysis tool has been used to numerically analyze the internal flow of two types of pocket-type water-lubricated hydrostatic thrust bearings with different feed hole inlet geometries and found that the pressure loss at the feed hole inlet is large for water-lubricated bearings and that the flow inside the feed hole is different from that of oil-lubricated hydrostatic bearings. The orifice effect at the feed hole inlet is found to account for most of the restrictor function. Furthermore, it was shown that the pressure loss at the feed hole inlet can be increased by adopting a right-angle inflow structure for the feed hole inlet geometry, which can improve the static and dynamic characteristics of the bearing.

A Mixed Zero-Equation and One-Equation Turbulence Model in Fluid-Film Thrust Bearings

Abstract A thrust bearing is a rotary bearing that facilitates rotational movement between components and is specifically engineered to provide support for a load that is parallel to the axis of rotation. The generation of the inter-surface film pressure is attributed to the relative motion (rotation) of the surfaces, which results in the lubricant being drawn into the converging wedge formed between them. The interface between the unmovable and moving parts is demarcated by a slender layer of lubricating fluid, including but not limited to oil, water, air, or other process fluid. The conventional zero-equation model can be enhanced to achieve higher precision in forecasting and reduce dependence on empirical data, owing to its inherent limitations. A novel turbulence model that combines zero-equation and one-equation approaches has been developed and implemented in the recently introduced modeling tool package for thrust bearings. In the Prandtl one-equation turbulence model, the length scale is a necessary but undetermined term. A novel mixed model has been implemented utilizing the Prandtl one-equation along with a novel-length scale. The tool package is a Thermo-Hydrodynamic (THD) code that involves iterative computations between the Reynolds’ equation, turbulence equation, energy equation within the film, and conduction equation in pad and runner. The new model yields an eddy viscosity that exhibits a substantial level of proximity to both eddy viscosity transport (EVT) and direct numerical simulation (DNS), and exhibits significant enhancements in comparison to the traditional Ng–Pan zero-equation turbulence model.

Fluid Film Bearings and CFD Modeling: A Review

This paper is a review of the literature about CFD modeling and analysis of journal, thrust, and aerostatic bearings; the advantages and disadvantages of each are specified, and the bearing problems that have been analyzed are discussed to improve their designs and performance. A CFD transient analysis of journal bearings was conducted using the dynamic mesh method together with movement algorithms while keeping a structured mesh of a good quality in the ANSYS Fluent software to determine the equilibrium position of the journal and calculate the dynamic coefficients. Finally, areas of opportunity for analyzing and designing fluid film bearings to improve their performance are proposed.

Surface Roughness Effect in Hydrodynamic Thrust Bearing with Ultra Low Clearance

Surface Roughness Effect in Hydrodynamic Thrust Bearing with Ultra Low Clearance

Prediction of surface damage behavior in rolling contacts using torsional fatigue results and surface roughness modeling

This paper presents a novel approach to predict the effect of surface roughness on surface damage in rolling contacts. Rolling contact fatigue (RCF) tests were conducted on AISI 4130 case carburized steel specimens at two different roughness levels, Ra=0.3μm and 0.1μm, under boundary lubrication regime. The RCF experiments were performed using a Thrust Bearing Surface Pitting Rig employing a ball-on-flat configuration. Surface damage was assessed at different combinations of contact pressure and fatigue cycles using optical surface profilometry. Subsequently, the surface damage stress-life (S–N) results were generated at both roughness levels. Torsional fatigue experiments were also performed on the same material. The torsional fatigue S–N results were combined with stress concentrations at the RCF test surfaces due to roughness to predict the surface damage S–N results. A dry circular contact model incorporating the surface roughness was developed and utilized to compute the stress concentration at the contact. The S–N results based on the von-Mises stresses were compared for RCF and torsional fatigue. The predicted results corroborated well with the experimental findings. The approach developed in this investigation illustrates the fundamental relationship between RCF and torsional fatigue.

Analytical study of the spherical hydrostatic bearing dynamics through a unique technique

Because of their self-alignment property and design simplicity, the spherical hydrostatic bearings have the advantage over the other bearing configurations. Their static and dynamic performances have been intensively studied. Focusing on the bearing dynamic performance, it could be realized that the researchers used to mechanically excite the bearing in the experimental studies and perturb the rotor (spatial finite displacement) in the theoretical studies, observing its behavior and expressing it by dynamic stiffness and damping coefficient. Owing to a lack of information on bearing oscillation, this study adopts a new method to analyze this bearing behavior theoretically and grasp its nature. Unusually, the bearing vibration is studied hydro-dynamically rather than mechanically, showing the effect of eccentricity, inertia, restrictor type, seat configuration, and the supply pressure on the performance. New and unique formulas have been derived to predict the frequency, stiffness, and dampness, explaining how these parameters create the bearing self-alignment property. Some thrust bearings, designed with different techniques, have been examined where the results show vibration even in the bearing’s stationary state. Also, the newly derived formulas could precisely predict the rotation and rotational speed of the Kugel ball (recently proved and designed as a spherical hydrostatic bearing).

Static Performance Measurements and Model Predictions of Gas Foil Thrust Bearing with Curved Incline Geometry

Gas foil thrust bearings (GFTBs) have been successfully used to support the axial load of oil-free microturbomachinery with low drag friction due to the low viscosity of gas or air used as a bearing lubricant. However, the widespread use of GFTBs in various high-power turbomachinery still needs reliable test data and an accurate predictive model. This research measures the height profile of a test GFTB to determine its actual incline geometry and estimate the drag torque of the GFTB. The measured GFTB height profile demonstrates that the incline geometry is closer to a quadratic curve than a line, which has been conventionally used to model GFTBs mathematically. The newly developed GFTB test rig is used to measure the lift-off speed, drag torque, and maximum load capacity of the test GFTB. A series of rotor speed-up tests estimate that the lift-off speeds of the GFTB increase with the increase in preloads. The maximum load capacity is determined by increasing the static load on the GFTB until a sudden sharp peak in the drag torque appears. The new GFTB model using quadratic incline geometry is in suitable agreement with the measured height profile of the GFTB incline and measured drag torque during the load capacity test. In addition, a comparison of the predicted GFTB performances reveals that the quadratic incline geometry model predicts a higher load capacity than the linear model.

RETRACTED ARTICLE: Tribological Behavior for Vein-bionic Textured Cylindrical Roller Thrust Bearing System Under Starved Lubrication

We, the Editors and Publisher of Tribology Transactions, have retracted the following article: Chao Zhao, Ruxin Liu, Kaiqing Qiao, Lixia Ying, Zhiyong Wang, Jiashuai Hu & Risheng Long (2023) Tribological Behavior for Vein-bionic Textured Cylindrical Roller Thrust Bearing System Under Starved Lubrication, Tribology Transactions, DOI: https://doi.org/10.1080/10402004.2023.2275687. Since publication, significant concerns have been raised about the fact that this article appears to have substantial reuse of figures and images, as well as text overlap with the following article, by one of the same authors, which is not clearly cited or referenced: Long, R., Zhao, C., Zhang, Y. et al. Effect of vein-bionic surface textures on the tribological behavior of cylindrical roller thrust bearing under starved lubrication. Sci Rep 11, 21238 (2021). https://doi.org/10.1038/s41598-021-00800-x. Figure 7 in the Tribology Transactions article has significant similarity to Figure 5 in the Scientific Reports article. Some of the specimens appear to be relabeled to make them look like new and different results. We have also identified some background images, such as test rig set up, that appear copied from the Scientific Reports article to the Tribology Transactions article without acknowledgement of the original source. Upon query, the author has not been able to provide a satisfactory explanation for this significant level of overlap. As this is a serious breach of our Editorial Policies, we are retracting the article from the journal. The corresponding author has agreed to retract the article. We have been informed in our decision-making by our editorial policies and the COPE guidelines. The retracted article will remain online to maintain the scholarly record, but it will be digitally watermarked on each page as ‘Retracted’.

Modelling and performance improvement of an annular grooved thrust air bearing

PurposeThis paper aims to combine the grooves with an annular air thrust bearing with multi-hole restrictors and discusses the influence of the groove parameters on the bearing performance.Design/methodology/approachFour models of aerostatic bearings with grooves of different geometries are established. The pressure distribution, load-carrying capacity (LCC), stiffness and flow characteristics of the flow field in the bearing clearances are obtained by computational fluid dynamics simulation.FindingsThe numerical and simulation results show that air bearing with grooved restrictors can slow down the pressure drop at the air inlet and increase the LCC and stiffness of the bearing. The gas flow in the aerostatic bearing is also studied, and the air vortex in the recess is analyzed.Originality/valueThis research optimizes the structure of the annular air thrust bearing, analyzes the gas vortex in the recess, improves the LCC and stiffness of the bearing and provides a reference for the bearing in the selection of groove parameters.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2023-0006/

The Technique of Tribological Studies of SiSiC High-Speed Thrust Bearings

This paper is devoted to model tribological experiments and analysis of the research results obtained for new materials and coatings, such as SiSiC, with the aim to rank them and to make recommendations for use in thrust hydrodynamic friction units operating at high speeds and loads.