Textured Journal Bearing Research Articles

Lubrication mechanism analysis of textures in journal bearings using CFD simulations

Purpose This paper aims to study the lubrication mechanism of textured journal bearings. Design/methodology/approach CFD models for textured journal bearings are established. The effect of texture coverage on the pressure distribution is studied to find the proper texture distribution. To enhance the local load-carrying capacity at textures, the micro-hydrodynamic pressure and microflow at different texture depth ratios are captured. The interaction between the texture-induced microflow and the bearing lubrication film is analyzed from the microflow perspective. Findings The bearing performance is on the one hand enhanced by the micro-hydrodynamic pressure generated by textures. On the other hand, the main bearing land and maximum pressure can be interfered by textures, leading to the reduction of load-carrying capacity. To minimize the interference effect, textures are suggested to distribute downstream of the minimum film thickness location. As the lubrication film thickness increases, the corresponding optimum texture depth ratio rises. The vortices influence the local flow rate through the lubrication film at textures and further affect the micro-hydrodynamic pressure and local load-carrying capacity. The texture depth ratio, at which vortices begin to occur, generates the maximum micro-hydrodynamic pressure. Originality/value The proper texture distribution is introduced, which is capable to generate the micro-hydrodynamic pressure without interfering with the primary load-carrying capacity of the bearing. The microflow effect is found to considerably influence the local load-carrying capacity at textures. The necessity of sub-regional optimization in textured journal bearings is pointed out. This study provides the fundamental reference for the design and optimization of textured journal bearings.

Effect of lubricant inertia on textured journal bearing implementing mass conserving (JFO) boundary conditions

Purpose Cavitation plays a significant role in the performance of textured journal bearings. Furthermore, because of the usage of low-viscosity lubricants and the high working speed of machines, it is pertinent to consider the lubricant inertia while analyzing the operating characteristics of bearings. This paper aims to investigate the influence of lubricant inertia in the case of a spherically textured journal bearing, considering both protrusion and dimple texturing and implementing the mass-conserving (JFO) boundary conditions. Design/methodology/approach A novel modified Reynolds equation has been developed to accommodate the effects of lubricant inertia and cavitation. The cavitation is treated by using mass-conserving (Jakobsson−Floberg−Olsson [JFO]) boundary conditions. The governing equation is solved by the Gauss−Seidel method with successive over-relaxation. To enhance computational efficiency and expedite the convergence process, the progressive mesh densification (PMD) method has been integrated into the solution process. Findings The current study indicates that the JFO boundary conditions result in higher load-carrying capacity and lesser friction variables for heavily loaded bearings, whereas the flow coefficient is reduced due to the application of JFO boundary conditions. The lubricant inertia effect enhances the flow coefficients for lightly loaded and protrusion-textured bearings. Originality/value It is crucial to understand the combined effects of lubricant inertia and cavitation for the effective design of textured journal bearings. The findings from this work will help in designing textured journal bearings more effectively and accurately, particularly when low-viscosity oil is used. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2024-0276/

Investigating linear and non-linear dynamic characteristics of textured journal bearings with slip boundary condition and pseudoplastic lubricants: a numerical study

External excitations and unbalanced rotor forces can increase vibration amplitudes and may also cause the breakdown of continuous liquid lubricant film in hydrodynamic journal bearings. The perfect isolation of the journal-bearing system from these undesirable forces and excitations are difficult. However, recent studies suggest that by utilizing advanced manufacturing techniques, smart coating materials, and highly efficient synthetic lubricants; one can improve the reliability of hydrodynamic lubricant film under such critical operating conditions. In the present study, authors observed the influence of micro-scale textures, low surface energy coatings with slip boundary condition, and pseudoplastic lubricants on the stability margin of hydrodynamic journal bearings. To perform this investigation, the unsteady thermo-hydrodynamic Reynolds equation with considering Elrod cavitation algorithm has been solved. Further, to observe variation in stability margin as compared to conventional bearings, the various dynamic characteristics such as stiffness and damping coefficients, critical mass and critical speed parameters, and journal center trajectory are examined in this study. The findings of the study reveal that slip-texture bearings lubricated with pseudoplastic lubricants are highly beneficial in improving the value of direct and cross stiffness coefficients. In addition, it has been observed that under unsteady operating condition, slip-boundary condition and micro-textures are increasing the isolation of the journal-bearing system and showing efficient control over the unstable motion of the rotating shaft.

Optimum texture shape under different lubrication conditions applied to the start-up phase of journal bearings

This paper presents a parameterized model to optimize the texture units using an improved particle swarm optimization. The texture units are optimized under three lubrication states: boundary lubrication, mixed lubrication, and hydrodynamic lubrication, by utilizing the Stribeck curve. The optimal texture units can be applied to journal bearings and thrust bearings in different operating conditions to achieve maximum load-carrying capacity. The paper applies the optimal textures under the three lubrication states to the start-up stage of journal bearings to examine the lubrication performance and dynamic characteristics of the textured journal bearing system. The results demonstrate that compared to the untextured journal-bearing system, the introduction of optimal textures improves the tribological performance of the journal-bearing system, and the optimal textured units under hydrodynamic lubrication have the best friction reduction effect. Furthermore, it is found that the introduction of textures has no significant effect on the dynamic characteristics of the journal bearings.

Dynamic and stability analysis of crescent geometry-possessing textured journal bearing using nanolubricant

PurposeThis study aims to find the dynamic performance parameters of the journal bearing with micro geometries patterning the arc (crescent) shape textures provided in three specific regions of the journal bearing: the full, the second half and the increasing pressure region. The dynamic behavior of textured journal bearings has been analyzed by computing dynamic parameters and linear and non-linear trajectories.Design/methodology/approachThe lubricant flows between the bearing and journal surface are governed by Reynold’s equation, which has been solved by finite the element method. The dynamic performance parameters such as stiffness, damping, threshold speed, critical mass and whirl frequency ratio are examined under various operating conditions by considering various ranges of eccentricity ratios and texture depths. Linear and non-linear equations of motion have been solved with Ranga–Kutta method to get journal motion trajectories. Also, the impact of adding aluminum oxide and copper oxide nanoparticles to the base lubricant in combination with arc-shaped textures is analyzed to further see any enhancement in the performance parameters.FindingsThe findings demonstrated that direct stiffness and damping parameters increased to their maximum level with six textures in the pressure-increasing region when compared with the untextured surface. Also, nanoparticle additives showed improvements above the highest value attained with no inclusion of additives in the same region or quantity of textures.Originality/valueEngineers may design bearings with improved stability and overall performance if they understand how texture form impacts dynamic properties.

Numerical and experimental investigation of textured journal bearings for friction reduction

This work investigates the mechanisms for friction reduction in textured journal bearings. The measured friction of laser-etched connecting-rod big-end shells was compared with a non-textured reference under engine-like conditions. Experiments covered several working conditions, and the friction and lubricant film temperatures were measured for three texture configurations. The origin of the verified friction reduction was explored using a numerical model that simulates the hydrodynamic lubrication and global thermal effects. The simulation results accurately matched the friction measurements, revealing that the microscopic mechanisms of reduction in lubricant shear stress and effective viscosity due to texture-induced cavitation act simultaneously to reduce the friction coefficient for the textured shells. The findings have practical applications for the optimal design of textured hydrodynamic bearings.

Research on the Optimal Design Approach of the Surface Texture for Journal Bearings

Aiming to improve the comprehensive performance of the journal bearing system, this paper presents a multi-objective adaptive scale texture optimization design approach. A mixed lubrication model for the textured journal bearing system is established by considering the effects of cavitation and roughness. The geometrical parameters of the textures were co-optimized using a multi-objective grey wolf optimizer to obtain the optimal texture schemes that are suitable for different operating conditions. Through this approach, the influences of different texture schemes under transient operating conditions can be investigated. According to the results, it was found that different texture schemes result in different friction reduction effects. Proper surface texture is beneficial in increasing the minimum oil film thickness and reducing the possibility of asperity contact. The adaptive scale texture exhibits strong adaptability and achieves significant hydrodynamic effects. Therefore, the developed approach provides valuable insights for the optimization design of journal bearing systems.

A Review of Performance of Textured Journal Bearing

A Review of Performance of Textured Journal Bearing

Co-optimization for hydrodynamic lubrication and leakage of V-shape textured bearings via linear weighting summation

In this study, the linear weighting summation method is adopted for the co-optimization of V-shape textured bearings to maximize the load-carrying capacity and minimize the leakage and friction. Optimal parameters including texture angle and depth and ratio of the texture width are identified based on the established numerical model. Moreover, to improve the comprehensive performance, especially leakage reduction, two profile modifications are introduced: micro-slope and micro-step. The results show that the two proposed modifications are effective for improving the comprehensive performance of V-shape textured journal bearings, and optimal values exist for both the modifications. Furthermore, the overall performance of a bearing with micro-step modification is superior to that of a bearing with micro-slope modification, but the bearing with micro-slope modification is more sensitive to leakage. In summary, this study aims to provide theoretical foundation for the multi-objective optimization design of V-shape textured bearings.

Comparative investigation on wear properties of 3D-printed textured journal bearings

In this experiment study, the textured journal bearings (TJB) are developed by additive manufacturing process with three different polymers such as acrylonitrile butadiene styrene (ABS), poly-lactic acid (PLA), and nylon. The experimental analysis of these developed 3D-printed TJB is performed based on the response surface methodology based on Box-Behnken design (BBD) matrix. The process parameters such as texture depth (TD), rotor speed (S) and load (L) are considered as input variable. The wear properties of 3D-printed TJB such as wear rate (WR) and rubbing temperature (RT) are output responses that are evaluated by the experimental study. Further, the grey relational analysis (GRA) technique is considered to assess the optimum value of process parameters for each polymer (ABS, PLA and Nylon). These results show that the rotor speed is the most significant process parameter for the better wear properties of 3D-printed TJB followed by load. The Nylon is found to be the most significant polymer for 3D-printed TJB among all the polymers. For the Nylon polymer, the optimal value of texture depth, speed and load are 0.5 mm, 500 rpm and 10 N respectively. Under this optimal condition, the wear rate and rubbing temperature of 3D printed TJB are 0.000118 mg/s and 51.60 °C respectively. Moreover, the thermal deformation in 3D-printed TJB is observed for PLA polymer. However, the rubbing temperature of 3D-printed TJB reduced with increased texture depth.

Experimental investigation of tribological performance of 3D printed textured journal bearings for various polymers

In this study, the 3D-printed textured journal bearings (TJBs) are developed by fused deposition modelling (FDM) process with three different polymers such as ABS, PLA and nylon. For the study, the process parameters such as texture depth (TD), rotor speed (S) and load (L) are considered as input parameters. The experimental analysis of 3D-printed TJB is performed based on the response surface methodology (RSM). With the RSM technique, the influence of these input parameters on the tribological performance of 3D-printed TJBs. The tribological performance of 3D-printed TJBs are wear resistance (WR) and wear temperature (WT). Further, the GRA analysis is performed to evaluate the optimum value of these process parameters for ABS, PLA and nylon polymer. These results demonstrate that the wear resistance (WR) of TJBs is first increases with the texture depth and then starts decreasing. Among all the polymers, the ABS polymer is the most significant, and nylon is the least significant polymer for the 3D-printed TJBs. The maximum WR (i.e. 76.576 m/mm3) of 3D-printed TJBs is observed for the PLA polymer. Whereas, nylon provides the least WR (i.e. 9.572 m/mm3) of 3D-printed TJBs. At the optimal value of process parameters (TD = 1.5 mm, S = 500 r/min and L = 10N), the WR and WT of 3D-printed TJBs (for ABS polymer) are 62.126 m/mm3 and 323.75 K respectively.

Performance of hydrodynamic textured journal bearing with the combined influence of elastic deformation and pseudo-plastic lubricant

This study outlines the performances of finite-length journal bearing with textured liner, shear-thinning Rabinowitsch lubricants, and considers the elastic deformation of the bearing liner. The yielded nonlinear Rabinowitsch-Reynolds PDE system has been solved using the finite difference method combined with Elrod’s algorithm for the case of cylindrical textures. The static performance of hydrodynamic lubrication, in this case, involves different parameters such as depth of texture, eccentricity ratio, elastic deformation factor, rheological index, etc. Results showed that, at a fixed eccentricity ratio, texturing of the bearing’s converging area enhances significantly the load-carrying capacity and reduces the friction coefficient compared to the smooth bearing surface (up to [Formula: see text] in load capacity and [Formula: see text] in friction coefficient). On the other hand, using a lubricant with more pronounced shear-thinning behavior and/or elastic liner reduces the journal bearing performances (up to [Formula: see text] in load capacity and [Formula: see text] in pressure). By applying the optimization technique (particle swarm optimization), an optimal arrangement of textures that can compensate for these losses in performance even at high eccentricity has been found. This optimal texture with dimensionless dimple’s depth set to 1 [Formula: see text] improves the load capacity with [Formula: see text] for a lubricant with a rheological index [Formula: see text] and elastic bearing liner with deformation parameter [Formula: see text].

Effect of lubricant inertia on steady-state characteristics of textured hydrodynamic journal bearing

PurposeThis paper aims to investigate the effects of inertia of the lubricant on the performance parameters of journal bearings textured with spherical-shaped textures.Design/methodology/approachThe lubricant is assumed to be Newtonian, and the flow is considered laminar. Considering the lubricant inertia effects, the modified Reynolds equation is discretized using the finite difference method and solved with the Gauss–Seidel successive over-relaxation scheme using the progressive mesh densification method.FindingsThe results from this numerical study indicate that the lubricant inertia improves textured journal bearing performance characteristics significantly. The improvement is more significant in the case of heavily loaded bearings. Furthermore, it is observed that protruded texturing in journal bearings shows better results compared to dimple textured journal bearings.Originality/valueUnderstanding the effect of lubricant inertia is essential for efficiently designing textured journal bearings. Thus, the results shown here would be helpful for the researchers and the bearing designers.

Theoretical and Experimental Study of Friction Characteristics of Textured Journal Bearing

The proposed lubrication theory of textured journal bearing is a major innovation in the study of the tribological properties of surface morphology. When it comes to the study of surface topography, it is essential to consider the effect of surface roughness when analyzing the characteristics of journal bearing. In this paper, a Reynolds equation containing longitudinal roughness is established for journal bearing and solved by the finite difference principle to obtain the bearing load and friction characteristics. Subsequently, a combination of laser etching and ultrasonic vibration milling processes was used to prepare 5 µm, 20 µm, and 40 µm bearing friction subsets with square micro-texture surfaces. The analysis of the results shows that the surface roughness distributed in the non-texture region can substantially increase the oil film pressure. When the roughness profile and the surface weave work together, the presence of a surface texture with an optimum depth of 5 µm within a roughness range of less than 1.6 µm can improve the load-bearing characteristics by a maximum of 43%. In the study of the preparation of textured bearing friction substrate, it was found that laser etching can ablate the surface of the friction substrate to a depth greater than 20 µm with the ideal effect, while the surface texturing to a depth of 5 µm is more suitable using an ultrasonic vibration processing process. In the simplified journal bearing operating condition, the frictional wear test shows that if the effect of roughness is considered, the frictional force of the depth of 20 µm and 40 µm is significantly reduced and changes less with increasing load, while the frictional force of the textured frictional pair with a depth of 5 µm is improved but significantly affected by the load carrying capacity. Therefore, when the difference between the roughness profile and the depth of the texture is of a small order of magnitude, it indicates that the effect caused by the roughness factor is not negligible.

Investigation of Microflow Effects in Textures on Hydrodynamic Performance of Journal Bearings Using CFD Simulations

Adequately designed and positioned surface textures are recognized as a promising way to increase load-carrying capacity and reduce frictional losses of journal bearings. The aim of this work is to analyze the local lubrication mechanisms of textures in journal bearings from microflow perspective, while considering the interactions between textures and the film formation in the whole bearing. For this purpose, hydrodynamic lubrication models of textured journal bearings are built. The results show that placing textures downstream of the high-pressure region leads to a reduced friction force, with a less severe loss of load-carrying capacity. The effects of textures on the load-carrying capacity include the positive micro-hydrodynamic pressure effect and the negative effect caused by the discontinuity of the high-pressure region. The micro-hydrodynamic pressure of textures can be generated on one hand by limiting pressure drop (cavitation) in the divergent gap and on the other hand by the inertia effect. For the friction, the vortex inside textures affects the friction force by influencing the maximum shear stress at the minimum oil film. In turn the vortex is influenced by the bearing lubrication film. The research provides the fundamental reference and theoretical basis for the design and optimization of textured journal bearings.

Comprehensive analysis of fluid-film instability in journal bearings with mechanically indented textures

This paper theoretically and experimentally investigates the effects of textures produced by a mechanical indentation on the stability of journal bearings. The research primarily aims at lightly loaded journal bearings used, e.g. in vertical rotors and microturbines. The results show that textures located close to the minimum oil film thickness can noticeably improve the stability at low specific loads but have only a negligible effect at a specific load of 0.15 MPa. The texturing also impacts the bearing temperature, which is closely related to the bearing friction. Since the textured journal bearings are prone to the formation of cavities in the oil film, the paper also deals with computational methods. It is demonstrated that an accurate estimate of stability threshold requires very dense computational meshes, which are impractical for mass-conserving treatment of cavitation due to CPU requirements. Interestingly, errors due to non-conservation of mass are up to the same magnitude as uncertainties due to employed numerical algorithms. The results demonstrate that numerical results describing lightly-loaded textured journal bearings are very sensitive to the density of the computational mesh. Hence, the simplified cavitation treatment can be legitimate in applications where the CPU time is a concern, such as the optimisation, iterative algorithms and time-integration of equations of motion.

Experimental Investigations on Temperature and Frictional Behaviors of Textured Journal Bearings

Experimental Investigations on Temperature and Frictional Behaviors of Textured Journal Bearings

Performance analysis of textured journal bearing operating with and without nanoparticles in the lubricant

PurposeThis study aims to investigate the performance improvement of journal bearing by applying the arc-shaped textures on various regions of bearing expressly full, second half and pressure increasing regions operating with and without nanoparticles in the lubricant.Design/methodology/approachThe Reynolds equation is solved numerically by using the finite element method to obtain static performance parameters such as load-carrying capacity (LCC) and coefficient of friction (COF), which are then compared with untextured bearing at eccentricity ratios of 0.2 to 0.8. Aluminum oxide (Al2O3) and copper oxide (CuO) nanoparticles additives are used, and viscosity variation due to the addition of additives in the base lubricant is computed for considering the range of temperatures 50 to 90°C at a weight fraction of 0.1 to 0.5% by using an experimentally validated regression model.FindingsThe results indicate that the maximum LCC and the lower COF are found in the pressure-increasing region. A maximum increase of 34.42% is observed in the pressure-increasing region without nanoparticles, and furthermore, with the addition of Al2O3 and CuO nanoparticles in lubricants in the same region, the LCC increased to 21 and 24%, respectively.Originality/valueDesigners should use optimal parameters from the present work to achieve high bearing performance.

Analysis of textured journal bearing with slip boundary condition and pseudoplastic lubricants

The present study investigates the combined influence of slip boundary condition and non-Newtonian lubricants on the tribological performance of hydrodynamic textured journal bearing. To accurately predict the effect of air/vapor bubble formation in diverging zone of the slip-texture bearing, the modified Reynolds equation with considering the Elrod cavitation model has been solved. In addition, the energy equation under adiabatic condition has been also solved for including the loss of viscosity with the temperature rise of lubricant. It has been observed that slip-texture bearings with change in rheology of lubricant from Newtonian to Pseudoplastic shows significant improvement in the maximum pressure, the average rise in temperature, and lubricant-bearing friction-force. Further findings of the study indicate that the combined effect of slip boundary condition and micro-texture with suitable selection of lubricant rheology is beneficial in increasing the stability of hydrodynamic lubricant film in the journal bearings.

Influence of spherical protruded and dimple texture on the journal bearing performance: A comparative theoretical analysis implementing JFO boundary conditions

PurposeThe purpose of this paper is to compare the spherical protruded and dimple textured journal bearings performance characteristics with the untextured bearing.Design/methodology/approachThe governing Reynolds equation considering the mass conserving (JFO) boundary conditions is solved using the computationally efficient progressive mesh densification (PMD) method. The central difference scheme is used for the discretization of the governing Reynolds equation. The numerical code developed is validated with the experimental results available in the literature.FindingsFrom this numerical study, it has been observed that the protruded textured journal bearing gives better performance compared to the dimple textured and untextured journal bearing for friction variable, whereas dimple textured journal bearing provides better performance compared to the protruded textured and untextured journal bearing for load carrying capacity and flow coefficient. For better performance, dimple and protruded textured bearings must be textured in second-half textured region configuration.Practical implicationsThe results shown here would be quite useful for the researchers generally and the bearing designers particularly.Originality/valueThe load carrying capacity should be maximum whereas, the friction coefficient should be minimum and also the adequate flow of lubricant is necessary to maintain hydrodynamic lubrication and to remove the heat generated within the bearing due to friction, which impacts the bearing performance and life. Thus, this study would be significant in effective bearing design aspect.