Lubrication Of Journal Bearings Research Articles

Scratch geometry effects on lubrication and performance of two-lobe journal bearings: A detailed study

Scratches on bearing surfaces can significantly affect the performance and lifespan of journal bearings. This study investigates the impact of scratches on two-lobe journal bearings through both theoretical and numerical analyses. The theoretical approach provides insights into how scratches influence lubrication, while the numerical simulations investigate how the three key scratch parameters, namely width, position, and depth, affect bearing performance. Key metrics analyzed include pressure, velocity distributions, temperature profiles, eccentricity, attitude angle, minimum film thickness, and maximum temperature. The findings offer valuable guidance for optimizing bearing design, maintenance, and condition monitoring, contributing to enhanced reliability and operational efficiency.

Numerical Study on Characteristics of Lead-Bismuth Lubricated Hydrodynamic Bearing Considering Non-Condensable Gas

Lead-Bismuth Eutectic (LBE) is an interesting candidate as a coolant for Generation IV nuclear power plants. Lead-bismuth lubricated radial guide bearing is the key component of the mechanical pump in a lead-bismuth coolant system. In this paper, the transient calculation model of multiphase lubrication flow field of journal bearing is established by using Singhal full cavitation model and structured dynamic grid technique. Due to the saturated vapors of LBE being very low, the effects of different Non-Condensable Gas (NCG) contents on the characteristics of lead-bismuth lubricated journal bearing systems were analyzed. The results show that the NCG content has an obvious influence on the working state of the bearing. With the increase in NCG content, the bearing load capacity decreases. Under the same load, with the increase in NCG content, the eccentricity of the static equilibrium position will be larger, which will increase the risk of bearing contact with the bearing bush. Moreover, the increase of NCG content will lead to the increase of tangential oil film force work, which is helpful to improve rotor stability.

Visco-elastohydrodynamic lubrication and wear model amended by deformation velocity

The deformation velocity caused by viscoelasticity is one of the drives of the Lubrication flow field and significantly influences the mixed lubrication and wear characteristics of journal bearings under dynamic loads. However, research considering the deformation velocity has yet to be reported. To address this research gap, we defined three-dimensional (3D) deformation velocities to amend the bearing surface velocity and proposed its calculation method based on the derivative function of the temporal association deformation equation and the finite element method. Therefore, a new mixed visco-elastohydrodynamic lubrication model amended by 3D deformation velocities was built and a nested solution method was proposed in which the sub-iterative process for deformation velocities was embedded into the oil film pressure iterative process. Furthermore, the lubrication model was coupled with the Archard model to predict wear. The viscoelastic parameter of the bearing was experimentally measured, and numerical simulations of lubrication and wear were performed for an ordinary bearing under a simple dynamic load and for the crankshaft main bearing of an internal combustion engine (ICE) under impact. The simulation results indicate that the deformation velocities reduce the extrusion effect and increase the contracting effect in the lubrication flow field. This enables the new model to identify the micro asperity contact, impact, and early wear features of bearings more accurately than the traditional mixed lubrication model. In addition, an increase in the ICE load intensifies the early wear of the bearing.

A machine learning-driven approach to predicting thermo-elasto-hydrodynamic lubrication in journal bearings

Traditional methods of evaluating the performance of journal bearings, for example thermal-elastic-hydrodynamic- lubrication theory, are limited to simplified conditions that often fail to accurately model real-world components. Numerical models that include additional phenomena such as cavitation and fully coupled effects like deformation, temperature, pressure and viscosity can be more accurate but require a large amount of computational overhead, making analysis slower and more costly. To address this limitation, a novel machine learning-driven approach is developed to predict the 2D distribution of surface deformation, film thickness, temperature, and pressure across the bearing surface as a function of design variables such as load and speed. The training dataset, generated using a fully coupled Reynolds’ Equation solver implemented in OpenFOAM, contains a significantly extended range of conditions than in previous studies with approximately 39000000 points encompassing 4925 different test cases. Modelled bearing speeds range from 2000 to 10000rpm, while load values are varied between 1 and 30kN. Predicting surface deformation, film thickness, temperature and pressure across the bearing surface results in a mean absolute percentage error below 0.4% or better. The work also demonstrates that the trained models have a strong ability to generalise the prediction beyond the original training data range with only a 1% error at up to 200% of the highest trained speed. This work also demonstrates that machine learning-based processes are a practical alternative to physics-based numerical modelling, especially in cases where rapid performance evaluation is desired as real-time calculation is possible with significantly reduced computational cost. This has the potential to enable development of rapid design optimisation tools and real-time performance monitoring at high resolution and with low latency. Using consumer hardware, it is found that the neural network-based approach is faster than the existing numerical modelling technique by a factor of over 10000, enabling real-time predictions of lubrication systems.

Thermal and viscoelastic coupled influences analysis on mixed lubrication in dynamic journal bearings

The interaction of temperature variations and viscoelastic deformation is critical in dynamically loaded journal bearings, especially under fluctuating heavy load conditions. Previous studies have not fully explored the coupling of these two factors. Addressing this gap, this research introduces a novel transient mixed lubrication model that simultaneously considers thermal and viscoelastic effects. This model reveals intricate dynamics influencing the lubrication performance of journal bearings. The findings show that the combined impact of thermal and viscoelastic factors significantly alters the amplitude and phase of lubrication performance parameters. Notably, thermal effects tend to decrease oil film pressure while increasing asperity contact pressure, whereas viscoelastic effects enhance the oil film pressure peak and adjust its phase, concurrently reducing asperity contact pressure. Moreover, varying the eccentric speed profoundly influences the interplay between bearing thermal and viscoelastic effects. This study contributes to a deeper understanding of mixed lubrication in journal bearings and provides technical support for more accurate and predictive reliability improvement in complex mechanical systems.

Piezo-viscous-polar lubrication of hybrid conical journal bearing with slip boundary conditions

Various anti-wear and anti-corrosion coatings are applied on the surface of journal and bearing to maximise service life of a bearing system. These coatings influence the wettability of surfaces consequently causes velocity slip phenomena in the bearing system. This article addresses a novel investigation to examine the influences of velocity slip and PVP (Piezo-viscous-polar) lubrication on multirecessed hybrid conical journal bearing (MHCJB). For various cases of velocity slip, novel forms of Reynolds equation are derived and solved numerically by using FEM. The results reveal that velocity slip severely affects the generation of oil film pressure. Consequently, it deteriorates the bearing characteristics viz. load carrying capacity, oil flow rate and rotordynamic coefficients. Further, PVP lubricant offers substantial enhancement in bearing characteristics.

An Algorithm for Starved Lubricated Journal Bearings With Optionally Locked Lube Oil Feed Grooves

Abstract Starved lubrication occurs intentionally or unconsciously in many journal bearing applications. However, the determination of its concrete distribution in a journal bearing is rather complex as the different lube oil feed grooves interact with each other due to their connection by the lubricant flow along the pad surfaces and the periodic geometric property of the entire bearing. A robust numerical procedure to determine the lube oil distribution between the different feed grooves in a starved lubricated fixed-pad journal bearing is presented as an extension to Elrod's cavitation algorithm. The enhanced algorithm partly integrates flow rate boundary conditions into the linear system of equations for the solution of Reynolds equation and the transport equation. A strategy to couple these flow rate boundary conditions with the iterative procedure to determine the binary cavitation index is proposed. In particular, the algorithm enables an appropriate modeling of lube oil grooves with locked oil supply including the consideration of groove-specific dissipation or design features like bleed notches. The novel algorithm is implemented as a submodule of a thermo-elasto-hydrodynamic bearing code and validated with test data for a high-speed two-lobe bearing with embedded arc. Furthermore, a comprehensive parametric study provides an insight on the robustness of the implemented numeric procedure. Results, current limitations, and possible extensions to the algorithm are discussed.

Performance Optimization of a Multi-groove Water Lubricated Journal Bearing with Partial Slip by Taguchi Analysis

The importance of preserving the ecological balance has paved the way for developing water lubricated bearings for marine vessels and other various applications. These bearings have found widespread applications in high pressure water pumps, water-power plants and power generation stations in sea, mining industries, ships, boats and submarines. To investigate the performance envelope of a water lubricated journal bearing (WLJB) with partial slip/no slip pattern, a multi-groove bearing model is developed and analyzed using CFD in the present study. Taguchi analysis method is utilized to determine the highest influential parameter affecting the pressure distribution and load-carrying capacity of a water lubricated journal bearing. From Taguchi method, optimum values identified for design parameters such as attitude angle, groove angle, groove height and number of grooves are 60°, 9°, 7 mm and 2, respectively. For the optimum combination model, a higher load bearing capacity of 1484.5 N is attained. Approximately, 2.88 times increase in peak pressures are noted from the current optimal bearing model by comparing with previous findings. Results indicated that the number of grooves and groove angle are the most influential parameters affecting the bearing load capacity. Partial slip conditions are applied at the grooved surfaces of a bearing model designed based on the identified optimal groove parameters. Influence of varying slip intensity on bearing load capacity is analyzed using CFD simulation. Appropriate selection of slip regions and slip amplitude is found to play a major role influencing the performance of the water lubricated journal bearing.

Mixed thermo-elasto-hydrodynamic lubrication and wear coupling simulation analysis for dynamical load journal bearings

In the crankshaft-connecting rod system of the diesel engine, the complicated lubrication and wear mechanisms of journal bearings are comprehensively affected by the elastic deformation effect, the asperity contact effect, the thermal effect as well as the lubricating oil viscosity-temperature effect. This paper proposes an adaptive iterative method based on a mixed thermo-elasto-hydrodynamic (TEHD) lubrication and wear coupling model to investigate the lubrication and wear behaviors of journal bearings in the mixed lubrication. The evolution laws of the oil film thickness, the hydrodynamic pressure, the asperity contact pressure, the friction power loss, and the wear distribution are discussed and compared under different running times, oil temperatures, external loads, and shaft rotational speeds. The three-dimensional surface models based on the asperity contact power loss and the maximum wear depth with the variation of the running time and the oil temperature are fitted under specific external loads and shaft rotational speeds. The simulation results demonstrate that the bearing wear process includes the initial wear stage and the stable wear stage, which has a significant influence on the changing trend and distribution of lubricating parameters. The three-dimensional surface fitting models can provide theoretical guidance for the future performance prediction of journal bearings under time-varying working conditions.

MICROPOLAR FLUID LUBRICATION OF FINITE ROUGH POROUS JOURNAL BEARING WITH SQUEEZING EFFECT

In this paper, a theoretical analysis of the effect of surface roughness on the squeeze film lubrication of finite porous journal bearings with micropolar fluids is studied. A more generalized form of surface roughness is mathematically modeled by a stochastic random variable with non-zero mean, variance and skewness. The generalized average Reynolds type equation is derived for the squeeze film lubrication of finite rough porous journal bearings with micropolar fluids as lubricant. The closed form expressions are obtained for the fluid film pressure, load carrying capacity, journal centre velocity and locus of the journal centre. The cases of a constant applied load and an alternating applied load are analyzed under a cyclic load the micropolar fluids provide a reduction in the journal centre velocity. Further, it is numerical computations of the results show that the negatively skewed surface roughness pattern increase fluid film pressure, load carrying capacity and decreases the journal centre velocity. Where as adverse effects were found for the positively skewed surface roughness pattern. The effect of porous parameter causes reduction in fliud film pressure, load carrying capacity and enhances the journal centre velocity.

Non-Newtonian couple stress lubrication of MHD elastic journal bearings

PurposeThis paper aims to present a numerical model to examine the finite magneto-hydrodynamic (MHD) journal bearings performances including both non-Newtonian couple stress and bearing deformation impacts.Design/methodology/approachBased upon the MHD and Stokes theories, a novel expression of modified Reynolds equation including bearing deformation is obtained. The bearing elastic deformation impact is predicted by means of the Winkler model. Using the numerical differentiation approach, the film pressure is iteratively solved. Different bearing characteristics are then numerically calculated. The validity of the proposed model was verified by comparing with some particular cases from literature.FindingsFrom the numerical presented results, it is demonstrated that the conducting couple stress lubricant with an applied radial magnetic field results in an induced electric current density and thus significantly improves the performances of elastic journal bearings. Particularly, the load-carrying capacity is increased, whereas a reduction in friction factor is observed.Originality/valueThis numerical model is original, which combines both non-Newtonian couple stress and bearing deformation impacts on finite MHD journal bearings performances. It provides useful information in designing MHD journal bearings, given the lack of experimental studies.

Adaptive Rejection of a Sinusoidal Disturbance with Unknown Frequency in a Flexible Rotor with Lubricated Journal Bearings

Frequency-dependent adaptive noise cancellation-based tracking controller (ANC-TC) is a known technique for the stabilization of several nonlinear dynamical systems. In recent years, this control strategy has been introduced and applied for the stabilization of a flexible rotor supported on full-lubricated journal bearings. This paper proposes a theoretical investigation, based on robust immersion and invariance (I&I) theory, of a novel ANC-frequency estimation (FE) technique designed to stabilize a flexible rotor shaft affected by self-generated sinusoidal disturbances, generalized to the case of unknown frequency. A structural proof, under assumptions on closed-loop output signals, shows that the sinusoidal disturbance rejection is exponential. Numerical simulations are presented to validate the mathematical results in silico. The iterative Inexact Newton method is applied to the disturbance frequency and phase estimation error point series. The data fitting confirms that the phase estimation succession has an exponential convergence behavior and that the asymptotical frequency estimation is a warm-up phase of the overall close-loop disturbance estimation process. In two different operating conditions, the orders of convergence obtained by phase and frequency estimate timeseries are pφ=1, pω,unc=0.9983 and pω,cav=1.005. Rejection of the rotor dynamic disturbance occurs approximately 76% before in the cavitated than in the uncavitated condition, 2 (s) and 8.5 (s), respectively.

Non-Newtonian lubrication of hybrid multi-recess spherical journal bearings with different geometric shapes of recess

The present work is aimed to numerically analyze the synergistic effect of the geometric shapes of recess and non-linear behavior of the lubricant on 4-pocket hybrid multi-recess spherical journal bearings. Recesses with square, circular, triangular, and elliptical shapes have been investigated. The influence of non-Newtonian lubricant has been considered using cubic shear stress law model. The performance parameters have been calculated for typically chosen values of non-linear factor. The finite element technique is used to solve the modified Reynolds equation. The results demonstrate that effect of recess shapes and non-linear factor significantly affects bearing performance. The proper selection of recess shapes and non-linear factor is needed to obtain an enhanced performance of hybrid multi-recess spherical journal bearings.

Analysis of Thermoelastohydrodynamic Lubrication of Journal Bearing including the Effect of Surface Roughness and Cavitation

Analysis of Thermoelastohydrodynamic Lubrication of Journal Bearing including the Effect of Surface Roughness and Cavitation

Effect of Nanoparticle on the Performance of Water Lubricated Journal Bearing

Journal bearings have widespread use in machinery with rotating shafts. Hydrodynamic journal bearings have lubricating fluid present between shaft and bearing to reduce friction and allow smooth operation. The lubricating fluid develops pressure when bearing is in operation and this pressure is used to carry load on the shaft. The commonly used lubricants in the industry are petroleum based synthetic oils. To do away with the disposal issues and toxicity regarding synthetic oils, water is used as the lubricating fluid for this study. The effect of adding nanoparticles to water is studied and a program in MATLAB is developed to determine the characteristics of bearing, namely load carrying capacity, coefficients of stiffness and coefficients of damping for shaft speeds 500 rpm, 1000 rpm and 1500 rpm. It is observed that addition of nanoparticles results in increased magnitude of load carrying capacity and the bearing exhibits high value of damping and stiffness coefficients indicating stability of shaft for every speed.

Stochastic Analysis of Lubrication in Misaligned Journal Bearings

Abstract Misalignment is common in hydrodynamic journal bearings and the causes of it can be diversified, making the lubrication performance exhibits stochasticity. Lubricant viscosity often heavily depends on temperature, which may vary during service and result in unexpected deviations. This article analyzes the stochastic lubrications of a cylindrical hydrodynamic journal bearing with misalignment under uncertainties. The stochastic Reynolds equation governing the misaligned journal bearing is discretized by the polynomial chaos expansion (PCE), an efficient uncertainty tracking tool, and then solved by the finite difference method to obtain sampled lubrication. The crude Monte Carlo simulation is used to verify the performance of the PCE frame. Various critical lubrication performance parameters are studied comprehensively by the ensemble mean, standard deviation, probability density function, and cumulative distribution function. Insightful inspections are provided on the stochastic results, and it is found that the misalignment and different stochastic parameters may cause significant effects on the lubrication performance. The new findings in the present study will guide the robust design and analysis of general hydrodynamic journal bearings.

Effect of using hybrid nano lubricant on the thermo-hydrodynamic performance of two lobe journal bearings

Due to the wide range of journal bearings applications in the industrial machine, significant efforts have been made by tribology researchers to improve their performance in recent years. Designing new bearings geometry and using lubricants with new chemical compounds including additives are the most common solutions proposed to enhance the performance of journal bearing supports. New advancements in nanotechnology and producing the various types of nano particles have provided the chance of upgrading the properties of commercial lubricants. According to the different effect of nano fluids on the performance of mechanical systems corresponding to their composition, today they are used to achieve different goals in lubrication systems. Upgrading the steady state performance parameters including load carrying capacity, attitude angle, surface cooling and effective viscosity are among the expected results of applying nano lubricant in journal bearings. So, in this study the performance of hydrodynamic two lobe journal bearings lubricated with SiO2-multiwall carbon nano tubes /SAE40 hybrid nano fluid is presented considering the thermal effects. For this purpose, the governing Reynolds and energy equations as well as the equation of heat transfer in bearing shell are modified based on the properties of assumed rotor-bearing system. Then the effects of solid volume fraction of nano particles on the performance of two lobe bearings are studied for different amount of bearing noncircularity. The results indicate that upgrading the solid volume fraction of added nano particle to the SAE40 base oil, enhances the lubricant pressure distribution, load carrying capacity, and lubricant effective viscosity. Further, by increasing the solid volume fraction, the attitude angle and temperature of lubricant and rotor-bearing surfaces experience a decreasing trend. Generally, it's obvious from the results that choosing the appropriate solid volume fraction of SiO2-multiwall carbon nano tubes in hybrid nano oil composition, especially for high value of preload factor, can improve the performance of two lobe bearings.

Investigating the effect of different slip zone locations on the lubrication performance of textured journal bearings

Purpose This study aims to purpose the suitable location of slip boundary condition and microscale surface textures to enhance the tribological performance of the hydrodynamic journal bearings. Design/methodology/approach Mass conserving Elrod cavitation algorithm with considering slip boundary condition has been used for predicting the static performance characteristics (load carrying capacity, coefficient of friction and volumetric inflow rate) of finite cylindrical shape textured journal bearings. Findings It has been observed that the full textured bearing with slip boundary condition in between 0°–180° circumferential region gives a significant reduction in the lubricant rupture zone. However, the introduction of textures up to the interface of slip and the no-slip region is increasing the load-carrying capacity and reduces the shear stress. This reduction in shear stress with combined slip and surface textures is effective in increasing the volumetric inflow rate of the lubricant. Practical implications The combined effect of slip boundary condition and surface texturing is increasing the scope of liquid lubricants in hydrodynamic journal bearings and further contributing toward the development of small-scale rotating machines. Originality/value The study related to the use of mass conserving Elrod cavitation algorithm for finding the optimum location of slip and surface texture zones has been found rare in the literature. Previous studies show that the mass conserving Elrod cavitation algorithm gives realistic results for textured bearings and its findings show good agreement with the experimental observations.

Theoretical study of oscillating squeezing flow through a porous medium

In this paper, we report a theoretical study of a transient squeezing flow through a thin porous gap driven by an oscillating boundary. The process is governed by the viscous, inertial, and Darcy effects. It shows that when the squeezing depth increases, the alternating dominance of the viscous and inertial effects would increase the oscillation of the velocity profiles. The existence of the porous media effectively stabilizes the fluid field. The study presented herein, revealing the fundamental physics of an oscillating squeezing flow, has significant potential for biomedical and industrial applications, such as the cerebrospinal fluid flow under concussion and the oil film lubrication in journal bearings.

Modelling non-Gaussian surfaces and misalignment for condition monitoring of journal bearings

In the hydrodynamic lubricated journal bearing system, the surface roughness and angular misalignment are two critical factors that affect bearing’s performance. In this paper, the coupled effects of different non-Gaussian properties and misalignments are investigated on the performance of journal bearings. Christensen’s stochastic model is extended by improving the probability density function of random roughness heights, which incorporates the Gram-Charlier expansion including skewness and kurtosis. In comparison with a Gaussian surface, the non-Gaussian rough surface has more significant influence on the bearing static performance. The negative skewness and large kurtosis increase the load capacity and decrease the friction coefficient. According to the simulations and experiments, non-Gaussian properties have more impact on the performance than misalignment when the journal bearing is operated in hydrodynamic lubrication regime based on different pressure distributions and vibration responses. These novel findings provide the basis for monitoring the conditions of hydrodynamic journal bearings.