Hydrodynamic Lubrication Model Research Articles

Effect of composite textured rough surfaces on the lubrication performance of cylindrical roller bearings

PurposeThe purpose of this paper is to study the impact of different types of textures on the friction lubrication performance of cylindrical roller bearings.Design/methodology/approachIn the present study, the composite texture hydrodynamic lubrication model that takes into account the effects of surface roughness is established, and the Reynolds equation for the oil film is numerically solved using the finite difference method. The study investigates the oil film carrying capacity and maximum pressure of bearings under two different arrangements of four composite textures and conducts a comparative analysis of the oil film characteristics under various texture parameters and surface roughness levels.FindingsWhen the roughness of the inner texture surface and the contact surface are equal, the bearing capacity of the composite texture is intermediate between the two textures. The impact trend of surface roughness on fluid dynamic pressure effects varies with the type of composite texture; the internal roughness of the texture affects the micro-hydrodynamic pressure action. Composite textures with different depths exhibit improved bearing capacities; elliptical cylindrical parallel and elliptical hemispherical parallel textures perform better when their area densities are similar, while other types of composite textures show enhanced bearing performance as the ratio of their area densities increases.Originality/valueThis paper contributes to the theoretical investigations and analyses on designing the textured rolling bearings with high lubrication performance.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-02-2024-0050

Analysis of Influence of Different Running Speeds on Lubrication Performance of Plain Bearings

Abstract Given the influence of the running speed of rotating machinery on the lubrication performance of sliding bearings, based on the hydrodynamic lubrication theory, a numerical analysis model of hydrodynamic lubrication of rolling bearings is established and solved by the finite difference method. The lubrication characteristics of rolling bearings, such as oil film pressure, oil film temperature, oil film thickness, and temperature rise at different running speeds (10 r/min, 30 r/min, 120 r/min, 160 r/min), are obtained. The results show that the sliding bearing shows different trends at different rotational speeds, the maximum oil film temperature is 70.49℃, the film thickness ratio corresponding to the minimum oil film thickness is much more than 3, and the maximum oil film pressure and temperature rise meet the allowable requirements.

Effects of the cavitation and fluid inertia on the performance in dimpled mechanical seal

To develop a hydrodynamic lubrication model of mechanical seals considering cavitation and fluid inertia and investigate the effects of cavitation and fluid inertia on the sealing performance of a textured mechanical seal, a finite element numerical procedure combined with a Newton-downhill scheme is developed. The numerical model was validated by comparing the results of the Reynolds equation with JFO theory (RE-JFO) and CFD simulation. The effects of fluid inertia and cavitation on the sealing performance are numerically compared and analyzed. Compared with the RE-JFO, the present model gives a better description of cavitation and fluid inertia. The results show that the centrifugal inertia can produce a throttling effect, and thus the leakage rate is reduced. The occurrence of cavitation improves the load-carrying capacity and reduces the coefficient of friction. The textures have a dominant influence on the sealing performance.

Experimental and numerical study of the mixed lubrication under the action of magnetic ionic liquid additives

In this paper, the tribological characteristics of an oil-soluble magnetic fluid additive under mixed lubrication are studied by experiments and numerical simulation. [bmim][FeCl4] is dissolved in CF10W-40 lubricating oil as a magnetic liquid additive, and its friction coefficient is tested by a point contact friction tester at different temperatures, rotational speeds and magnetic field intensities. The transition condition of lubrication state is obtained through analyzing the Stribeck curves based on the experiments, and the strength model of boundary film is established accordingly. A mixed lubrication model is established by substituting the boundary film strength model and the surface roughness model into the hydrodynamic lubrication model based on Reynolds equation. The results show that the magnetic solution as an additive can obviously reduce friction and wear, and the effect is more obvious under the condition of magnetic field. The boundary film strength model can accurately reflect the transition characteristics of lubrication state in the presence of boundary film, and the mixed lubrication model based on boundary film strength model can more precisely reflect the tribological characteristics of friction pairs, so this study provides a new theoretical method for the related research on the influence of boundary film on lubrication characteristics.

Transient mixed-lubrication and contact behavior analysis of metal liquid film under magneto-thermal effect

To investigate the contact state and interface behavior of the armature-rail (A/R) interface under magneto-thermal shock, this study employs the lubrication theory and considers the coupling effect of electromagnetic and temperature fields. A transient mixed hydrodynamic lubrication model is established using the finite difference method. The study investigates the evolution mechanism of rough surface metal liquid film, electrical contact behavior, and transient mixed lubrication characteristics at the interface under complex magneto-thermal excitation. The study suggests that the electrical contact behavior of the metal liquid film during electromagnetic launch process exhibits significant fluctuation characteristics, which have a crucial influence on the temperature distribution of the metal liquid film. Moreover, due to the fluctuation behavior of electrical contact and factors such as surface roughness, the temperature of the metal liquid film exhibits a complex spatial distribution pattern. The temperature peak continuously increases as the electromagnetic launch progresses. Furthermore, the initially uniform distribution of the metal liquid film gradually transforms into a non-uniform, island morphology due to the joint action of the magneto-thermal effect. However, the liquid metal film still exhibits excellent lubricating properties, which play a crucial role in reducing friction and wear in the electromagnetic launcher system (EMLs).

A Mixed Hydrodynamic Lubrication Model for Armature-Rail Interface Considering Surface Contact Characteristics

A Mixed Hydrodynamic Lubrication Model for Armature-Rail Interface Considering Surface Contact Characteristics

Research on the Secondary Motion of Engine Piston Considering the Transport of Lubricating Oil

<div>At present, it is generally considered in the analysis of the secondary motion of engine piston that the piston skirt–cylinder liner friction pair is fully lubricated in an engine operating cycle. However, in practice, when the piston moves upward, the amount of lubricating oil at the inlet may not ensure that the friction pair is fully lubricated. In this article, the secondary motion of piston is studied when the transport of lubricating oil is considered to determine the lubrication condition of piston skirt–cylinder liner friction pair. The secondary motion of piston is solved based on the combined piston motion model, hydrodynamic lubrication model, asperity contact model, and lubricating oil flow model. The secondary motion equation of piston is solved by the Broyden method. The hydrodynamic lubrication equation is solved by the finite difference method. The asperity contact between piston skirt and cylinder liner is calculated by the Greenwood model. The flow of lubricating oil is analyzed based on the theory of fluid mechanics. The results indicate that, when the actual transport of lubricating oil is considered to determine the lubrication condition of piston skirt–cylinder liner friction pair, the secondary motion of piston is remarkably different from that in which the flooded lubrication is assumed in an engine operating cycle. Therefore, it is helpful to improve the accuracy and make the analysis closer to the actual engine operating situation that the transport of lubricating oil is considered in the analysis of the secondary motion of engine piston.</div>

Research on Lubrication Characteristics of Ship Stern Bearings Considering Bearing Installation Errors

The installation quality of a propulsion shaft system directly affects the lubrication statuses of the bearings. The quality of the shaft system installation not only affects the progress of ship construction, but also the safety, stability, and reliability of the shaft system. This article takes sliding bearings in ship shafting as the research object and establishes a hydrodynamic lubrication model of sliding bearings while considering installation errors to address the issue of installation errors of ship stern bearings. The finite difference method and super-relaxation iteration method are used to solve the problem, and the influences of bearing installation errors on bearing lubrication characteristic parameters are explored. An installation error of the stern bearing can lead to an increase in the film pressure at both ends of the stern bearing in the axial direction, leading to a decrease in the lubrication status of the bearing. Poor lubrication and wear faults of the stern bearing are prone to occur at both ends of the stern bearing. As the installation error of the stern bearing increases, the minimum film thickness of the stern bearing decreases and the maximum film pressure increases, and as the installation error increases, the sensitivity of the aft stern bearing to the vertical installation error is greater than that of the lateral installation error, and the sensitivity of the fore stern bearing to the lateral installation error is greater than that of the vertical installation error. The sensitivity of the lateral and vertical film forces at both ends of the aft stern bearing and the fore stern bearing is greater than that of the middle part; the installation error of bearings has a significant impact on the lubrication characteristics of bearings.

Refined Hydrodynamic Lubrication Model with a High-Accuracy Numerical Algorithm for Starved Lubrication with Free Surfaces

Refined Hydrodynamic Lubrication Model with a High-Accuracy Numerical Algorithm for Starved Lubrication with Free Surfaces

Analysis on Lubrication Performance of Piston Ring-Cylinder Liner based on Numerical Simulation

This paper mainly studies the tribological performance of friction pairs and poor lubrication during piston movement. Based on the average Reynolds equation and comprehensively considering the variable viscosity and variable density characteristics of lubricating oil, a transient hydrodynamic lubrication model of the piston ring-cylinder liner friction pair is established. By solving the established lubrication model, the lubricating oil film thickness value, friction value and other parameters that can characterize the lubrication performance of the friction pair throughout the cycle are obtained, whilst revealing the surface roughness, lubricating oil viscosity and piston ring barrel surface height. And the influence mechanism of the friction performance of the friction pair is presented on the basis of the previous analysis. The research shows that improving the surface roughness of the piston ring will help to improve the lubrication, increasing the viscosity of lubricating oil will help to improve the lubricating performance of friction pairs and reduce the peak friction at the top dead centre of piston rings and improving the surface texture of the piston rings can reduce the oil film thickness and reduce the friction caused by fluid shear effect in the high-speed region.

Numerical Study on the Bearing Capacity of Lubricant Film in Journal Bearing with Micro-textured Surface

For studying the hydrodynamic lubrication performance of micro-textured radial journal bearings, a numerical model of hydrodynamic lubrication for journal bearings was established first. Solve the established numerical model using FDM, and the lubricant film pressure distribution and static characteristics of bearings were obtained. Considering the processing cost and feasibility of the processing technology, the cylindrical texture arranged in the radial of the bearing shell surface is applied, the lubricant film thickness equation considering the micro-texture is introduced into the Reynolds equation. According to the height and distribution density of microstructure, the bearing capacity parameters were obtained. The load-carrying capacity of micro structure journal bearing is significantly higher than that of plain bearing. In this paper, a practical model with cylindrical micro-textured surface is given for journal bearing applications with high capacity demand.

Study on transient performance of tilting-pad thrust bearings in nuclear pump considering fluid-structure interaction

To study the lubrication performance of tilting-pad thrust bearing (TPTBs) during start-up in nuclear pump, a hydrodynamic lubrication model of TPTBs was established based on the computational fluid dynamics (CFD) method and the fluid-structure interaction (FSI) technique. Further, a mesh motion algorithm for the transient calculation of thrust bearings was developed based on the user defined function (UDF).The result demonstrated that minimum film thickness increases first and then decreases with the rotational speed under start-up condition. The influence of pad tilt on minimum film thickness is greater than that of collar movement at low speed, and the establishment of dynamic pressure mainly depends on pad tilt and minimum film thickness increases. As the increase of rotational speed, the influence of pad tilt was abated, where the influence of the moving of the collar dominated gradually, and minimum film thickness decreases. For TPTBs, the circumferential angle of the pad is always greater than the radial angle. When the rotational speed is constant, the change rate of radial angle is greater than that of circumferential angle with the increase of loading forces. This study can provide reference for improving bearing wear resistance.

Simulation Study on Bearing Lubrication Mechanism and Friction Characteristics of the Biomimetic Non-Smooth Surface of a Cross-Scale, Second-Order Compound Microstructure

The reasonable design of biomimetic non-smooth surfaces is a novel and effective way to solve problems such as the poor lubricity and serious friction and wear of friction pairs of seawater axial piston pumps. Inspired by cross-scale, second-order compound microstructures on the surfaces of some living organisms, a hydrodynamic lubrication model of a slipper pair with a surface featuring spherical pits containing spherical convex hulls was built. This study analyzed the bearing lubrication mechanism and friction characteristics of cross-scale, second-order compound microstructure from the microflow perspective via the CFD method and optimized the working and geometric parameters using a hybrid orthogonal test scheme. The study’s results show that the cross-scale, second-order compound microstructure can produce a superimposed hydrodynamic pressure effect to improve the bearing capacity of the lubrication film of a slipper pair, reducing the friction coefficient. The orders of factors (the working parameter and geometric parameters) under multiple indices (the total pressure-bearing capacity and the friction coefficient) were found. The optimal combination is a spherical pit with a first order diameter of 0.7 mm, a first order depth-to-diameter ratio of 0.1, an area rate of 20%, an arrangement angle of α/3 and a spherical convex hull with a second order diameter of 0.13 mm, and a second order depth-to-diameter ratio of 0.3. Compared to a smooth surface and a first-order, non-smooth microstructure, the cross-scale, second-order compound microstructure has an 11.0% and 8.9% higher total pressure-bearing capacity, respectively, and the friction coefficient decreased by 9.5% and 5.4%, respectively.

Experimental and Numerical Study of the Mixed Lubrication Considering Boundary Film Strength.

For the influence of boundary film on the lubrication state of sliding friction pairs, a boundary film strength model was proposed that can comprehensively reflect the influences of film thickness, pressure, shear stress and temperature. The model parameters were obtained through fitting the test results. Then, a mixed lubrication model considering boundary film strength was established by coupling the boundary film strength model with the hydrodynamic lubrication model and the asperity contact model. The calculation program was developed using the Fortran language, which can effectively capture the tribological characteristics and action ratios of the fluid, boundary film and dry friction components. Simultaneously, the mixed lubrication model was applied to the journal bearing. A parametric analysis was performed to investigate the influences of different working conditions on lubrication performance. Under current operating conditions, the results show that: when the speed is above 200 r/min or the viscosity is higher than 0.09 Pa·s, the boundary film breakdown rate is almost 0 and the friction coefficient is lower than 0.02; when the roughness is reduced from 1.8 μm to 0.8 μm, the ultimate load of the journal bearing rises from 27 MPa to 36 MPa, an increase of about 33%; when the load exceeds 36 MPa or the temperature is higher than 100 °C, more than 25% of the boundary film breaks and the dry friction component accounts for more than 60% of the total friction, which leads to a sudden increase in the friction coefficient. Hence, the study of mixed lubrication considering boundary film strength provides theoretical guidance for accurately reflecting the actual lubrication state and improving the mechanical energy efficiency of friction pairs.

Effect of micro-grooved surface on the static and dynamic characteristics of journal bearings with misalignment

This paper presents a hydrodynamic lubrication model to investigate the static and dynamic characteristics of micro-grooved bearings considering journal misalignment. An averaged Reynolds equation with the mass conservation is derived and numerical procedure is solved by the finite difference method. The influences of eccentricity ratio, misalignment and micro-groove parameters on lubrication performances of aligned/misaligned journal bearings are compared systematically. Mathematical expressions of five micro-grooves with different geometric shapes i.e., straight-groove, left spiral-groove, right spiral-groove, left herringbone-groove and right herringbone-groove are given. The results show that with the increase of degree of misalignment, the load carrying capacity, main stiffness and damping coefficients increase, and the friction coefficient decreases, while the effect of misalignment angle on bearing performance is opposite. The results also indicated that the left herringbone-groove has better performance improvement for aligned journal bearing, while the right spiral-groove has better performance improvement for misaligned journal bearing under the optimal micro-groove parameters, especially at low eccentricity ratio. Moreover, the amount of the performance improvement of micro-grooved bearing depends on the design of the micro-groove parameters. This study can provide theoretical guidance for the design optimization of micro-grooved journal bearings with misalignment.

A hybrid of CFD and PSO optimization design method of the integrated slipper/swashplate structure in seawater hydraulic axial piston pump

An integrated slipper/swashplate structure is developed for seawater hydraulic axial piston pump. Considering the overturning moment of the integrated slipper, the transient hydrodynamic lubrication model of the integrated slipper is established, and the body-fitted grid and five-point finite difference method is employed to accurately solve the model. An optimization design method based on a hybrid of CFD (Computational Fluid Dynamics) and PSO (Particle Swarm Optimization) for the integrated slipper is proposed for the interface structure with the low leakage and power loss. The optimal sealing belt of the integrated slipper is obtained, and the leakage and power loss are reduced by 27.3% and 16.7% under the same gap size, respectively. The effects of working condition on the film-forming characteristics and power consumption characteristics of the lubricating film are analyzed based on the optimized integrated slipper. It is found that the leakage and total power loss increase significantly with the increasement of working pressure and shaft speed, and decrease with the increasement of temperature. The excellent lubrication characteristics and strong anti-overturning ability of the integrated slipper/swashplate structure can improve the performance of the seawater axial piston pump, and its optimization design method proposed in this study can provide a new reference for engineers.

Study on Lubricating Performance of Soft Slider Bearing in Conformal Contact

ABSTRACTIn this paper, the lubricating performance of soft slider bearing in conformal contact is analyzed. Compared with the hard slider, the soft slider will have greater elastic deformation under low pressure. Three kinds of sliders with different elastic modulus are used for comparative study in this paper. The materials of the three sliders are: steel, glass and PMMA. A hydrodynamic lubrication model of conformal contact considering elastic deformation is established according to the theory of fluid lubrication. A program for calculating dynamic pressure lubrication performance of conformal contact considering elastic deformation is developed by using Matlab and Comsol. The influence of different inclination, different speed and different load on hydrodynamic lubrication performance was studied respectively. The results show that under the same conditions, the elastic deformation on the surface of the slider is more conducive to the formation of oil film, and more conducive to the conditions of high load.

Influence of Pressure Changes on the Viscosity of Lubricating Oil in CFD Simulations of Conical Bearing Hydrodynamic Lubrication

Abstract The aim of this study is to consider the effect of pressure on the viscosity of lubricating oil in the adopted model of hydrodynamic lubrication and on the calculated flow parameters and operating parameters of a conical slide bearing. The numerical analysis consisted in solving the Reynolds type equation for the process of stationary hydrodynamic lubrication.

On the lubrication performance of journal bearing coupled with the axial movement of journal

PurposeUnder the action of many factors, the shaft of the shaft-journal bearing system inevitably moves along the axis direction at work, which will lead to the axial movement of journal in the bearing. However, at present, only the dynamic and squeezing effects caused by the relative rotation and squeezing motion between the journal and the bearing surfaces are considered in the lubrication analysis of misaligned journal bearing and the axial movement of journal in the actual use of bearing is not considered. The purpose of this paper is to analyze the lubrication of journal bearing considering the axial movement of journal.Design/methodology/approachTaking the shaft-journal bearing system as the research object, a hydrodynamic lubrication model of journal bearing is established considering the axial movement and misalignment of journal. The finite difference method is used to solve the Reynolds equation for the lubrication analysis.FindingsThe axial movement of journal has a significant influence on the lubrication characteristics of misaligned journal bearing. The larger the misalignment angles of journal or the eccentricity of bearing, the greater the influence of the axial movement of journal on the lubrication performance of bearing. The lower the speed of bearing or the smaller the clearance of bearing, the more significant the influence of the axial movement of journal on the lubrication performance of bearing is.Originality/valueThe influence of the axial movement of journal on the lubrication performance of journal bearing is studied under different misalignment angles of journal, working conditions and clearances of bearing. The results of this paper are helpful to the design and research of the lubrication performance of journal bearing.

Macro-texture in hydrodynamic lubrication: Effects of dimple parameter, density and distribution

Surface texturing, a well-known method to increase tribo-pair tribological performance, is widely used and of great importance in industrial manufacturing. By designing reasonable surface texture on two contact surfaces, the load-carrying capacity, wear resistance, and coefficient of friction of the tribo-pairs can be significantly improved. To investigate the influence of the macro-texture, millimeter magnitude, on the tribology performance, a large number of simulation cases were carried out in this work. And the influence of texture parameters including the ellipse aspect ratio, the depth-to-diameter ratio, density, and distribution on tribology performance was studied using the hydrodynamic lubrication model which was verified through a sample experiment of piston ring and cylinder liner tribo-pairs. In addition, a Taguchi algorithm was used to find the most suitable texture parameters. The results show that the influence of density on the coefficient of friction and load-carrying capacity is of significance and 20% density is sufficient for tribology performance. Dimple size and distribution had a more significant influence on tribology performance.