Performance Of Journal Bearing Research Articles

Reviewing experimental and theoretical efforts and key findings regarding hydrodynamic journal bearing geometry

Abstract Journal bearing operation particularly in regard to marine applications is significantly affected by the performance of the most critical operational factors. Specifically, the lubricating oil film within journal bearing is so often than not subject to hazardous deterioration and ultimate failure in real operating conditions. Considering such fact, the current study is intended to carry out a literature survey regarding the efforts towards enhanced journal bearing performance based on proper selection of geometrical design for journal bearing. The aggregated data were thoroughly analyzed and assessed utilizing experimental, theoretical as well as numerical means. The outcomes derived from the conducted review represent firm grounds for carrying out extensive modifications into journal bearing design for marine applications. Further, such data will possibly be employed in future research investigations to extend the capability of journal bearing and its functions to attain the most possible enhanced performance in actual operating conditions. Apparently, the vast majority of both experimental and theoretical studies into journal bearing geometrical designs for enhanced performance, 66 in all, have been focused on surface texture accounting for 26.67 % (29 research studies) and 32.43 % (33 research studies) of the total investigations under study respectively. Regarding the experimental studies, realizing promoted performance of lubricating oil film by working on pressure profile has evidently obtained the largest contribution representing 35.5% of the overall bulk of the reviewed efforts, Figure 6.

Effect of varnish on the performance and stability of journal bearings

This paper is dedicated to characterizing the steady-state and dynamic behavior of journal bearings with the provision for varnishing. Degraded base oils and additives cause varnish at high temperatures. Once the varnishing initiates, the oil flow is restricted due to the reduction in film thickness, which leads to an increase in the operating temperature and further accelerated varnishing. The effect of the varnish on the bearing performances is predicted by solving the Reynolds equation for the pressure distributions with the mass conservation algorithm coupled with the energy equation through the viscosity. The solution of the Reynolds equation with the perturbations of the displacement and the velocity is used to calculate the stiffness and damping coefficients and determine the dynamic behavior of the bearing. At a given eccentricity ratio, the maximum pressure and temperature with the varnish become considerably higher than those without the varnish due to the reduced film thickness. Results are presented for both single and double axially grooved journal bearings. Results show that the maximum pressure decreases when the varnish size extends circumferentially at a given varnish thickness, but the maximum temperature still remains relatively constant. For both single and double-grooved bearings, the critical speed decreases considerably, leading to the reduction of the stability of the system.

On the importance of the experimental setup design in hydrodynamic journal bearing friction measurement

Improving operating conditions and reducing the friction-related power losses of hydrodynamic journal bearings could lower emissions and contribute to efforts for a faster green transition. Experimental studies play an important role in evaluating and improving the performance of plain journal bearings. The concept of the experimental setup for friction measurements of journal bearings is well defined in the relevant standards, but the actual design is always left to the researchers conducting a particular study. Our study reveals that common practical assumptions about the frictional power losses caused by components of the experimental setup can lead to misleading conclusions about the measured coefficient of friction. The research premises were tested on the developed experimental setup using two methods for measuring the coefficient of friction and different load interfaces. In particular, the direct torque measurement using strain gauges on the shaft demonstrated the strongest correlation with theoretical values. However, the result was affected by the correct evaluation of the frictional losses of the support ball bearings. Conversely, the Stribeck curves showed that the combination of the indirect cantilever method and load interface with direct radial force application led to inferior results. The intricate interactions between setup components and unknown frictional conditions made straightforward geometric corrections challenging. The study encourages researchers in the field to critically assess their experimental setups and to rely on their own assessment of frictional losses.

Influence of starvation and cavitation on hybrid journal bearing under limited supply pressure

A new starvation model is established to explore the effect of starvation on cavitation and their couple influence on the performance of hybrid journal bearing. The starvation region is located in the recessed circumference and symmetry with the axial center. The novel starvation model aims to solve the issues of flow non-conservation by the axial starvation model and avoid calculation limitation by the JFO cavitation condition under severe starvation. The cavitation areas obtained by the approach, JFO model, and Reynolds model are compared to indicate the influence of starvation on cavitation. The static and dynamic performances are investigated by the three methods and the relative pressure distribution is given to analyze the effect of starvation and cavitation on the hybrid journal bearing. The result indicates that starvation has a significant impact on the cavitation region and has a slight effect on the bearing’s performance.

ELASTOHYDRODYNAMIC EFFECTS IN LUBRICATION OF JOURNAL BEARINGS UNDER TURBULENT CONDITIONS

The current paper is aimed to investigate the deformability effects of the bearing surface on the lubrication performance of cylindrical journal bearing with finite length under turbulent conditions. The bush is coated with a thin resilient layer with a smooth surface, the radial distortions of which are of the same order of magnitude as the film thickness. The elastohydrodynamic problem is studied under elasticity conditions in accordance with the plain strain hypothesis (Winkler model). The modified Reynolds equation is carried out on the base of the turbulent lubrication model of Hirs (bulk flow model). The partial differential equation is solved numerically by successive over-relaxation technique on a finite difference grid, considering different values of coating materials, lubricant viscosity, and journal speed. Results for the performance characteristics of the bearing are given for several selected values of Reynolds number and elasticity parameters of the soft liner on the bush.

Research on the Support Performance of Internal Feedback Hydrostatic Thrust and Journal Bearing Considering Load Effect

This study aims to analyze the impact of uniform and eccentric load conditions on the performance of internal feedback hydrostatic thrust and journal bearing. Two distinct models are established: a three-degrees-of-freedom uniform load model and a five-degrees-of-freedom eccentric load model. The support stiffness, overturning stiffness, and flow rate for both thrust and journal bearings are calculated. Additionally, numerical analysis is conducted to examine the influence of oil film thickness, inlet pressure, and restrictor size on the operational characteristics of the bearings, revealing the interplay between an eccentric load and journal bearing speed. The validity of the theoretical algorithm is verified through finite element simulation. The research outcomes hold significant guiding implications for the design and application of internal feedback hydrostatic bearings.

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.

A Comparative Study on Hydrodynamic Analysis with and without Cavitation Modelling: A Study on Textured Slip Journal Bearing

In journal bearing modeling, the phenomenon of cavitation is very important to improve the accuracy of the simulation results. This is because cavitation will almost certainly occur because there are convergent and divergent geometries. The results of the simulation will be close to real conditions so that it can have a positive effect on researchers in order to design optimal journal bearings. The effect of modeling without cavitation and with cavitation on journal bearing modeling has a great influence on the lubrication performance of journal bearings. In modeling with cavitation, the maximum hydrodynamic pressure and load carrying capacity that the journal bearing is capable of relying on has a fairly rapid increase. The modeling results also relate to the friction force that occurs in the journal bearing. The aim of the present study is to explore the effect of inclusion of modeling of the Hydrodynamic pressure. The finite volume method based on software is used to compare the result with and without cavitation. Here, The mixture multiphase cavitation is adopted. The numerical result show t he effect of modelling without cavitation and with cavitation on journal bearing modelling has a great influence on the lubrication performance of journal bearings. In modelling with cavitation, the maximum hydrodynamic pressure and load cmarrying capacity that the journal bearing is capable of relying on has a fairly rapid increase. The modelling results also relate to the friction force that occurs in the journal bearing.

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.

Thermal Tribo-Dynamic Behaviors of Water-Lubricated Bearings during Start-Up with Journal Shape Error

In practical scenarios, journal bearings often exhibit shape errors due to machining imperfections and operational wear. These deviations from perfect roundness can significantly impact the performance of journal bearings during start-up. This study investigates the impact of journal shape errors on transient mixed lubrications, such as water film temperature and asperity contact, as well as on the rotor dynamics of water-lubricated bearings (WLB) at start-up. The simulation results of the developed numerical model are compared with the experimental data from existing studies to verify their accuracy. Following this validation, parametric analyses are conducted using the model. The analytical results indicate that journal shape error increases the temperature rise of the water-lubricated bearing system during start-up. The greater the error in journal shape, the higher the temperature rise, both in terms of shape amplitude and waviness order. Interestingly, the thermal deformation caused by the temperature effect decreases the vertical displacement during start-up. The study also finds that higher start-up speeds lead to quicker temperature increases when shape errors are present. However, these speeds enable the bearing to more rapidly reach the elastohydrodynamic lubrication (EHL) stage, where the temperature rise stabilizes. Therefore, start-up speeds must be carefully selected.

Exploring magnetic properties and dynamic performance of magnetic-hydraulic double-floating journal bearing based on offset load

An innovative structural system of magnetic-hydraulic double-floating journal bearing is designed to improve the ability to resist offset loads. By considering the magnetic force to the water-lubricated journal bearing and the magnetic structure design, a force model of the innovative bearing is proposed. The magnetic force and water film force for the bearing are simulated by comparing the load-carry capacity of only water film force. Experimental results showed the load-carry capacity and stability test of the innovative bearing. The design of innovative bearing with the upper suction and lower magnetic repulsion based on the Halbach array can provide a larger supporting magnetic force. The axially non-uniform magnetic structure deployment can manipulate the changes of the magnetic force in the axial direction to hold the offset load. The test found that by comparing the traditional water-lubricated bearing, the bearing has a certain vibration suppression ability in the vertical direction. Under the test speed, the bearing stiffness hardly changes with the change of the speed, which also shows a slightly decreasing trend with the increase of the excitation frequency.

Comparative study on tribological behavior of foil journal bearings with micro pocket

Abstract This study explores the tribological performance of bump foil journal bearing (FJB) equipped with micro-pocket. The influence of micro-pocket on the load capacity (LC) and friction factor (FF) of FJBs is evaluated for various foil materials, including Inconel X750 (IN), Spring steel EN42J (SP), SS 316, Beryllium copper (BC), and Phosphor bronze (PB). The compressible Reynolds equation is solved numerically to assess the tribological behavior of bump FJB under various operating conditions. Initially, the impact of micro pocket on the tribological characteristics such as load capacity and friction factor of bump FJB is examined by comparing their performance with plain FJB. Subsequently, the effect variable parameters such as pocket depth (PD), bearing number (Λ), and eccentricity ratio (ε), on the tribological behavior is analysed by using response surface methodology (RSM). The multi-objective grey relational analysis (GRA) technique is employed to determine the optimal values of these variable parameters for each foils material. The findings reveal that micro-pocket enhance the dimensionless LC of bump FJB beyond a bearing number of 2.061. Moreover, micro-pocket reduce the friction factor of bump FJBs. Within the presence of micro pocket, SS 316 exhibits the most significant foil material for the better tribological characteristics of bump FJB, while phosphor bronze is the least signifcant. For SS 316, the optimal values of pocket depth (PD), bearing number (Λ), and eccentricity ratio (ε) are 3 μm, 2.061, and 0.5 respectively. Under these optimal conditions, the load capacity (LC) and friction factor (FF) of bump FJBs are 0.7740 and 13.645, respectively. Micro-pocket reduces the friction factor (FF) by 2 to 15%. The impact of pocket depth on the LC and FF of bump FJB is significant for the phosphor bronze. Additionally, increasing the pocket depth enhances the dimensionless LC of bump FJBs while decreasing the friction factor.

A study of surface fatigue wear and influence of contaminated lubricant in journal bearing system using tribological and vibration analyses

In the present work, journal bearing performance was evaluated using condition monitoring processes namely wear debris, vibration signal, lubricant oil degradation and temperature analyses. The journal bearing system was operated at 800 rpm and 200 N constant speed and load over a period of 1200 h. The lubricant oil samples were collected for every 300 h of test duration for oil degradation and wear particle analyses by using Fourier transform infrared radiation (FTIR) and scanning electron microscope/energy dispersive X-ray spectroscopy (SEM/EDS) techniques, respectively. FTIR results provided specific chemical bonds and functional groups contained in the degraded oil. The vibration signals were acquired for every 100 h of operation, and a fast Fourier transform (FFT) frequency spectrum technique was employed for vibration signal analysis. The friction coefficient and specific wear rate parameters were considered to evaluate the tribological performance of the journal-bearing system. Statistical parameters, namely root-mean-square and kurtosis, were evaluated. Wear mechanisms such as abrasive, adhesive and surface fatigue wear were observed on the journal-bearing contact surfaces using a USB optical microscope. The scoring on the bearing element confirmed the fault development and resulted in an increase in vibration amplitudes. Higher mass loss in the bearing material was observed due to high friction and wear rates owing to its being a softer material than that of the journal material. The results obtained from the aforementioned parameter assessment techniques provided a reliable information on the defects which appeared on journal-bearing contact surfaces.

AI techniques for evaluating misaligned journal bearing performance: An approach beyond the Sommerfeld number

This paper presents two novel artificial intelligence-based approaches for evaluating the performance of heavily loaded marine journal bearings including shaft misalignment. Traditionally, the Sommerfeld number has been used as a key parameter to evaluate the performance similarity between different bearings. However, this method has limitations, particularly when dealing with complex elastic geometries, heavily loaded journal bearings and shaft misalignment. The first proposed approach leverages neural networks to analyze key bearing performance parameters and provide a more accurate and comprehensive assessment of bearing performance similarity, including additional parameters beyond the Sommerfeld number limitations. The second method utilizes artificial intelligence convolutional networks to assess the bearing similarity based on their simulated pressure profiles under isoviscous and isothermal hydrodynamic lubrication regime. The effectiveness of the proposed methods is demonstrated and compared to the traditional Sommerfeld number method, discussing various potential applications and extensions of this concept.

Numerical Analysis on the Static Performance of Gas Journal Bearing by Using Finite Element Method

In this paper, finite element method is used to calculate the static performance of gas journal bearing, in which rotation speed term is introduced into the stiffness matrix of linear triangular element to realize the performance calculation of the bearing with rotation speed. The results indicate that the average gas film thicknesses corresponding to the maximum load capacity and stiffness, and the minimum attitude angle increase with the growth of orifice diameter. Load capacity and stiffness significantly improved with the increase of rotation speed, eccentricity ratio and supply pressure when the bearing has thin average gas film thickness. Attitude angle increases with the growth of rotation speed, while the growth rate slows down or even decreases at high speed. The most effective way of reducing attitude angle is to increase supply pressure. It can be found that rotation speed affects attitude angle through changing gas pressure difference between two orifices, while other parameters have the same effect by changing gas pressure at orifice outlet.

Multiscale simulation scheme by using a finite-difference derivative framework for lubrication surface

To exactly describe lubrication problems modelling micro-scale influence in rough lubricated contact is unavoidable. In this study a novel computational scheme for lubricated problem is presented based on two-scale homogenization method, which facilitates solving the two-scale problem. Homogenization model of mass fluxes is implemented at the micro-scale domain, and represents the influence of surface topography. A linearization method is developed to derive finite derivatives of mass fluxes at the micro-scale domain defined by scale separation. The key strength of the proposed procedure is the finite difference derivative coupling which represents the lubricated problem inclusive of the effect of surface topography. The effectiveness of the proposed multiscale scheme is validated by comparing with the deterministic method. The numerical results show that increasing topography amplitude can improve the performance of journal bearing in terms of load carrying capacity and friction coefficient.

Investigation of nanoparticle diameter influences on performance of hydrodynamic journal bearings operating with nanolubricant

The nanolubricant's effectiveness on the bearings’ performance depends on the types of nanoparticles, volume ratio, and their size and/or diameter. Although the nanolubricant influences on the characteristics of the journal bearings are well known, cost-effective solutions for using nanolubricants, have continued to need in industrial applications. Because the nanoparticle's diameter plays a key role in the fluid with nanoparticle additives, research on its effect is important for hydrodynamic journal bearing. In this work, the nanoparticle diameter impacts on the characteristics of the hydrodynamic journal bearings are investigated with under thermal effects. At first, four hydrodynamic journal bearings have different parameters such as radial clearance and bearing length–diameter ratio are considered and designed. Then, the lubricant flow through the radial clearance is modeled with Dowson's equation. Besides, the temperature field in the journal and the lubricant are governed by the heat conduction and energy equations, respectively. The physical and thermal properties of the nanolubricant are expressed by considering nanoparticle diameter and the volume ratio. Then, an algorithm is developed to solve the mathematical models based on the finite difference method. Finally, a serial simulation is conducted under different nanoparticle diameters and operational conditions. When the nanoparticle diameter becomes small, the temperature and pressure values of the nanolubricant, load capacity, and stiffness increase.

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.

Mathematical Model and Theoretical Investigation of the Performance of Journal Bearing using a discretized Reynolds Lubrication Equation with Finite Width

Hydrodynamic journal bearings are widely used for a large number of applications such as rotating turbo machinery, axial flow compressors, axial flow turbines, and internal combustion engines. These types of journals are used to support high loads high speed rotating turbo machinery elements mainly shafts and attached components and also for enhancing the quality of these machines. In this work, the importance of journal bearing and an overview of the Reynolds hydrodynamic equation in three dimensions have been studied using the Boundary Value finite-difference method. The second-order nonlinear partial differential equation has been solved using numerical iterations approach with MATLAB software. The numerical solution of the transient Reynolds equation has been studied to investigate the Pressure distribution, pressure gradient as well film lubricant thickness on journal bearings. A numerical solution using ANSYS FLUENT has been applied to investigate the main parameters that have the main influence on the performance of the journal bearing and bearing performance.

Stability analysis of partial journal bearings lubricated with micropolar fluid

PurposeThis study aims to investigate the stability performance of partial journal bearings of 120° and 180° partial angles with micropolar lubricant.Design/methodology/approachTo investigate the stability characteristics of partial journal bearing, a MATLAB source code is written. To solve the Reynolds’ equation, the finite element method is used. Stability performances of 120° and 180° partial journal bearings are computed for a wide range of non-dimensional micropolar fluid parameters and working eccentricities.FindingsThe presented results provide design data for stability parameters in terms of equivalent stiffness, whirl frequency ratio, critical mass and threshold speed of the rotor with respect to eccentricities and material size of the lubricant. The stability of 180° partial journal bearing is found to be higher than 120° partial journal bearing.Originality/valueIn open literature, it is rare to find the stability of a partial journal bearing lubricated with micropolar fluid. Very few researchers have studied the combined effect of eccentricities and micropolar lubricant parameters on the dynamic performance of such bearings. Hence, it is important to study the dynamic stability to explore the complete investigation of the performance of partial journal bearings with micropolar fluid.