Dynamic Characteristics Of Journal Bearings Research Articles

Effect of wear on the dynamic characteristics of a rigid rotor supported by journal bearings

The purpose of this work is to examine the effects of wear severity on the static and dynamic characteristics of journal bearings, and on the vibration response of a rigid rotor supported by journal bearings. Numerical simulations using MATLAB was conducted for three different operating regimes, namely low loaded operating regime (ϵ0=0.15\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\epsilon _0 = 0.15$$\\end{document}), moderately loaded operating regime (ϵ0=0.45\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\epsilon _0 = 0.45$$\\end{document}) and highly loaded operating regime (ϵ0=0.75\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\epsilon _0 = 0.75$$\\end{document}) with wear depth parameter ratio (δ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\delta$$\\end{document}) varied from 0 to 0.5 at increments of 0.1. Numerical results showed that the vibration response of the rotor generally increases with the increase of the wear depth for all cases of low, moderately and highly loaded operating regimes of the bearings. For the values of parameters considered in this work, it was shown that the vibration response amplitude of the rotor in worn journal bearings may be six times larger compared to the response amplitude of the rotor in non-worn bearings.

Effect of texture shapes and additives in lubricants on the dynamic characteristics of the hydrodynamic journal bearing

PurposeThis study aims to understand how the texture shape, number of textures and addition of nanoparticle additives in lubricants impact the dynamic characteristics of journal bearing by comparing six different texture shapes like triangle, chevron, arc, circle, rectangle and elliptical applied in pressure-increasing region under various geometrical and operating conditions.Design/methodology/approachThe finite element method approach has been employed to solve governing Reynold’s equation, assuming iso-viscous Newtonian fluid, for computation of performance parameters like stiffness and damping coefficient, threshold speed, etc. By using a regression model, the impact of adding nanoparticles Al2O3 and CuO to the base lubricant on viscosity variation is calculated for selected temperature ranges and weight fractions of nanoparticles.FindingsThe arc-shaped texture with an area density of 28.27%, eccentricity ratio of 0.2 and texture depth of 0.6 exhibited 35.22% higher direct stiffness and 41.4% higher damping coefficient compared to the lowest value in the circle-shaped texture. Increasing the number of arc-shaped textures on the bearing surface with low area density led to declining stiffness and damping parameters. However, with nanoparticle additives, the arc-shaped texture further showed 10.75% and 8.11% improvement in stiffness and 9.99% and 4.87% enhancement in damping coefficient for Al2O3 and CuO, respectively, at 90 °C temperature and 0.5% weight fraction.Originality/valueBy understanding the influence of texture shapes on the dynamic characteristics, engineers can design bearings that exhibit improved stability and enhance overall performance.

Load sharing performance analysis of planetary gear system considering the coupling effects of gear pair and journal bearing

In this paper, a load-sharing performance analysis method of the planetary gear system is proposed considering the coupling effects of double-helical gear and journal bearing. Firstly, the coupling effects between the meshing characteristics of the double-helical gear pair and the dynamic characteristics of journal bearing under the actual operation state are studied, the dynamic model of the double-helical gear planetary transmission system is established, and the load sharing coefficient before and after considering the coupling effects are calculated; secondly, the load sharing characteristic test rig of planetary transmission system is built, and the load sharing coefficient of gear system under the test condition is measured to verify the accuracy of the proposed method; finally, the effects of operating parameters and structural parameters on the load sharing characteristic of gear system are discussed.

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.

Identification of Distributed Dynamic Characteristics of Journal Bearing with Large Aspect Ratio under Shaft Bending

The classical theory of centralized dynamic characteristics with eight coefficients is adopted for traditional journal bearings. However, under cantilevered load, distributed dynamic characteristics along the axial direction will be generated for the journal bearing with a large aspect ratio (L/D). A double-section loading method simulating shaft bending and excitation was developed, a dynamic characteristic test-rig of a large-aspect-ratio bearing was set-up, the novel four-time vertical excitation method and eight-time cross excitation method were put forward, and the equations of 16 dynamic characteristic coefficients of the bearing were deduced. The dynamic characteristic test was carried out. The results showed that the four-time vertical excitation method had a small response amplitude in the horizontal direction, and was vulnerable to interference by the vibration of the test-rig. The eight-time cross excitation method had a higher SNR with more accurate identification results. When the cantilevered load was not applied, the dynamic characteristic coefficients were evenly distributed along the axial direction, the stiffness coefficients fluctuated slightly as the rotation rate increased, while the main damping coefficients decreased significantly. Shaft bending resulted in a significant increase in local dynamic characteristic coefficients, in which the relative increase in the stiffness coefficients was greater than that of the damping coefficients. Increasing the rotational speed can weaken the effect of shaft bending, and key factors that cause the axially nonuniform distribution of dynamic characteristic coefficients of the bearing are shaft bending and large aspect ratio under low speed and cantilevered load.

Experimental investigation on dynamic characteristics of journal bearing

The aim of this experimental investigation is to investigate the dynamic characteristics of journal bearing. The process involves lubrication using couple stress fluid. The theoretical study has been analyzed based on the dynamic Reynolds governing equation for various lengths to diameter ratios, ratio of eccentricity, damping coefficient and stiffness of the systems and the results have been reported. The work involves using Newton’s multivariate interpolation, the empirical relationship is derived at different ratio of eccentricity, L/D ratio as well as dynamic coefficients. It is observed that beyond 0.7 eccentricity ratio, small disturbances affect in a higher stability in the journal bearing system. The theoretical study results have been compared to experimental test kit result for various L/D ratios. The dynamic characteristics such as displacement, velocity and acceleration values have been noted from the test kit and the instability conditions of the system have been verified from the theoretical results.

Static and Dynamic Characteristics of Journal Bearings Under Uncertainty: A Non-Probabilistic Perspective

Abstract This paper provides a comprehensive evaluation of crucial performances of hydrodynamic journal bearings subject to inherent uncertainties from a non-probabilistic perspective. Uncertainties can arise for various reasons such as the evolving service environment, manufacturing errors and assembling imperfections. An efficient non-intrusive frame named the Chebyshev interval finite difference method is proposed to solve the interval Reynolds equations, which allows accurate predictions of variabilities of performance parameters. The uncertain geometrical properties, lubricant viscosity and external load are considered and their effects on the static and dynamic characteristics of the uncertain journal bearing are intensively discussed in different situations. New insightful results are found in various case studies and numerical validations of the proposed method are carried out. Moreover, the sensitivity analysis was carried out and the application of the proposed frame to a Jeffcott rotor was demonstrated. The interval uncertainties are found to have severe effects on the hydrodynamic journal bearings, causing potential critical influences in the corresponding rotating systems. Results and methods in the current study provide references to robust assessment and design of journal bearings, and further guide the investigations on rotor-journal bearing systems.

Effects of Texture Bottom Profile on Static and Dynamic Characteristics of Journal Bearings

The purpose of this paper is to numerically study the effect of texture bottom profile on static, dynamic, and stability performance parameters of hydrodynamic journal bearings. The different performance parameters of square textured journal bearings with different bottom profiles are numerically investigated and compared with those of smooth journal bearing. There are five bottom profiles of this square texture: flat, curved, isosceles triangle (T1), oblique triangle (T2), and oblique triangle (T3). The static and dynamic coefficients are calculated by solving the steady-state Reynolds equation and the perturbation equations with FDM numerical technique. The performance characteristics under different texture distribution, depth, and bottom profiles are studied, and the current numerical results show that the selection of texture parameters is crucial to improve the static, dynamic, and stability performances of hydrodynamic journal bearing. Meanwhile, it is also found that the square texture with a flat bottom profile has a higher improvement in the values of static performance parameters in comparison to those other bottom profiles. Moreover, the simulation results indicate that the dynamic and stability performances improvement of textured journal bearing is also significant, especially when the eccentricity ratio is smaller.

Analysis and Experimental Validation of the Tribological and Dynamic Characteristics of Journal Bearings

Sliding bearings are the main kinematic pair of a Stirling engine, and one of the main sources of friction power loss and excitation force. There is a coupling effect between the lubrication state and the excitation force. In this paper, the dynamic model of a Sapphire bearing fatigue test bed, which includes thermo-elasto-hydrodynamic (EHD) property, is established and the accuracy of the model is verified by the experimental data. Based on the model, the effects of the load, the oil supply temperature, the oil supply pressure, the bearing clearance on the tribological and dynamic characteristics are studied. With an increase in the load, the orbital path of the journal moves downward, the lubrication state changes from the full hydrodynamic lubrication to the boundary lubrication, the friction power loss increases, and the bearing excitation frequency increases. Due to the decrease of the oil viscosity, the hydraulic friction power loss decreases, but the friction power loss derived from the asperity contact increase, so does the total friction power loss. With the increase of the radial clearance, the shape of the orbital path and the minimum oil film thickness remain unchanged. The increase of the bearing clearance results in the collisions between the journal and bearing bush, thus the amplitude of the frequency multiplication component in the bearing load increases, and the asperity and the total friction power loss increase.

Dynamic characteristics of compound textured journal bearing

An investigation of the compound texture effect on the dynamic characteristics of the journal bearing film is conducted. In this work, eight dynamic coefficients of the compound textured journal bearing and critical speed of the rotor supported by textured bearings are obtained and compared. Meanwhile, the elastic deformation effect of the bearing and rotor is obtained using the continuous convolution fast Fourier transform (CC-FFT) method. It is found that the reasonably arranged compound texture brings out an obvious increment in the direct stiffness coefficients and damping coefficients compared with the simple one, which results in the high critical speed of the bearing-rotor system. The above changes are close to the texture distribution, second-layered texture length, and width-length ratios of the compound texture. Moreover, there exists a critical compound texture depth to improve the critical speed of the bearing-rotor system.

Calculation of the Dynamic Characteristics of Ship’s Aft Stern Tube Bearing Considering Journal Deflection

Abstract Dynamic properties are vital for the working reliability of aft stern tube bearings. However, the determination of such properties currently involves several simplifications and assumptions. To obtain its dynamic characteristics accurately, the aft stern tube bearing was divided into several bearing segments. The oil film reaction force was considered in the calculation of shaft alignment, and the journal deflection and actual oil film thickness were obtained accordingly. Subsequently, the perturbed Reynolds equation was solved using the finite difference method when the dynamic characteristics of journal bearings with finite width were evaluated. Then, a calculation program was developed and verified by comparing with the results of other studies. Finally, the dynamic characteristics were calculated under different revolutions. The results showed that the stiffness at the vertical direction of the aft stern tube bearing was several times that of the horizontal direction and varied with the revolutions of the shafting system. These findings can provide the foundation for the precise calculation of the journal trajectory under dynamic conditions, as well as for the evaluation of the oil film thickness. Moreover, the results led to favorable conditions for the accurate calculation of the shafting whirling vibration.

Effect of non-newtonian lubricants on static and dynamic characteristics of journal bearings

Journal bearings play a significant role to increase overall level of reliability in machines. Advancements in lubrication methodology have a great impact on the performance of journal bearings which operate under multifarious parameters and lubrication conditions. Bearing behaviour is monitored by bringing out changes in various aspects like geometry, misalignment value, restrictor design parameter, restrictor types, eccentricity, roughness, aspect ratio, lubricant feeding conditions and lubricating oil properties. Performance of bearings is tremendously dependent on the variation in lubricant properties. This paper presents the state-of-the-art review on the behaviour of lubricants, namely, micropolar, power-law fluids and couple stress lubricants and their effects on journal bearings efficiency. An effort is made to understand the behaviour of different non-Newtonian lubricants on various journal bearing configurations and their comparison with Newtonian lubricants so as to choose the appropriate lubricant for specific bearing configuration. Non- Newtonian lubricants have shown improvements in journal bearing performance when compared with Newtonian lubricants operating at selected conditions.

Investigation of the effect of cavitation and journal whirl on static and dynamic characteristics of journal bearing

The cavitation phenomenon in journal bearing and journal whirl are considered to evaluate the static and dynamic characteristics of journal bearing, to be more consistent with the actual operating conditions of journal bearing. With a 3D CFD method, the cavitation and journal whirl are simulated by adopting mesh deformation technique and mixture phase-change model. By comparing the results with those of the traditional Reynolds equation, we observe that first, the phenomena of cavitation and journal whirl are very consistent with the actual operating conditions of journal bearing. Moreover, for single-phase and two-phase flow models, the distribution features of oil film pressure are similar in convergent wedge zone while largely different in divergent part of the gap. The oil film pressure and vapor phase volume fraction notably vary on different whirl positions of the journal. We also observe that as whirl frequency increases, the oil film force gradually increases and the stability of journal bearing decreases rapidly before reaching a plateau. The efforts of this paper provide an efficient method to accurately evaluate the static and dynamic characteristics of journal bearing and offer a useful insight into the accurate analysis and design of journal bearing.

Numerical and Experimental Analyses of the Dynamic Characteristics of Journal Bearings With Square Dimples

Numerous previous numerical studies have investigated the effect of surface texturing upon the static characteristics of journal bearings, including their load-carrying capacity and friction torque. In general, the dynamic characteristics of journal bearings are also important, since they are essential factors in predicting the vibration behavior of actual rotors supported by journal bearings. However, the effects of surface texture upon these dynamic characteristics have not been investigated through either numerical or experimental analysis. Thus, in the present study, such analyses were conducted to investigate the dynamic characteristics of textured journal bearings, such as their dynamic coefficients of oil film and the stability-threshold shaft speed supported by the bearings. Numerical analysis was done using a model that included inertial effects and energy loss; this model agreed well with experimental results concerning static characteristics from our previous study. Dynamic testing based on a sinusoidal-excitation method was also performed using textured journal bearings with uniform square dimples to verify the numerical results, which agreed qualitatively with those of experiment, confirming the validity of the numerical analysis. These results suggest that under the same operating conditions, the main effect of texturing upon the dynamic coefficients is to yield the cross-coupled stiffness coefficients with lower absolute values than the conventional ones with a smooth surface. The linear stability-threshold shaft speed of the rotor supported by the textured journal bearings became higher than that of a smooth bearing, mainly due to the reduction of cross-coupled stiffness coefficients. This tendency became more pronounced for high Reynolds number operating conditions and textured bearings with a large number of dimples.

Stability Analysis of Journal Bearing: Dynamic Characteristics

The purpose of the present study is to provide the dynamic characteristics of Journal bearings lubricated with couple stress fluids. Based upon the dynamic Reynolds governing equation for the different L/D ratio, Eccentricity ratio, the stiffness and damping coefficient of the system are evaluated. At Eccentricity ratio after 0.7, the small disturbances results affect in a higher stability in the journal bearing system. Using the classical Newton's multivariate Interpolation the empirical relation has derived for eccentricity ratio L/D ratio and the dynamic coefficient for finding the experimental stability characteristics.

Effect of Cylindrical Texture on Dynamic Characteristics of Journal Bearing

Effect of cylindrical texture on dynamic characteristics of hydrodynamic journal bearing is presented in this paper. The Reynolds equation is discretized by finite difference method and solved numerically in an iterative scheme satisfying the appropriate boundary conditions. Stiffness and damping coefficients of fluid film and stability parameters are found using the first-order perturbation method for different eccentricity ratios and various texture parameters like texture depth and texture portion. From the present study, it has found that cylindrical texture exhibits better stability than plain journal bearing.

1113 しゅう動面に四角穴を有するジャーナル軸受の油膜動特性の数値解析(OS11-3 機械要素とトライボロジー,オーガナイズドセッション11:「機械要素とトライボロジー」)

1113 しゅう動面に四角穴を有するジャーナル軸受の油膜動特性の数値解析(OS11-3 機械要素とトライボロジー,オーガナイズドセッション11:「機械要素とトライボロジー」)

Nonlinear dynamic characteristics of journal bearing–rotor system considering the pitching and rolling motion for marine turbo machinery

Rotating machinery in marine engine systems experiences the base excitation and the additional gyroscopic moment from the pitching and rolling motion of the ship. For some cases, the motion can cause the rotor system damage. The nonlinear model of the journal bearing–rotor system for marine turbo machinery considering the pitching and rolling motion is established by coupling the basement motion and nonlinear oil film force together. Then the nonlinear dynamic characteristics for the system with the unbalanced mass are studied. By employing the Newmark method, the dynamic response of the rotor-bearing system is simulated. The orbit diagram, spectrum diagram, waterfall diagram, amplitude versus rotating speed diagram and the bifurcation diagram are obtained. The effect of the pitching and rolling motion on the journal bearing–rotor system is investigated. The results indicate that the additional stiffness matrix, additional gyroscopic and additional exciting force vector will act on the journal bearing–rotor system, which are generated from the pitching and rolling motion for marine turbo machinery. The dynamic characteristics of the system such as destabilizing angular velocity will be changed by affecting the nonlinear oil film force.

Numerical Computation of Dynamic Character Coefficient of Journal Bearing

The purpose of this study is to determine the dynamic character coefficient of journal bearing with the consideration of bearing load direction and oil groove. Based on numerical differential method, the oil film pressure distribution on journal bearing is obtained with the point-by-point relaxation iteration method. Then, the dynamic characters are calculated by numerical integral algorithm.The calculation program is developed for the dynamic characteristics of journal bearing. The computation method provides a useful guide for the numerical simulation of rotary parts.

Effect of Misalignment on the Characteristics of Journal Bearings

Due to the renewed interest in the effect of misalignment on the dynamic characteristics of journal bearings, this paper presents a study of the effect of misalignment on the dynamic characteristics of journal bearings. A 2D finite difference program is developed and used for this study. The results show that there are a total of 16 stiffness and 16 damping coefficients considering horizontal and vertical displacements and rotations. The variation of these coefficients with journal tilting (i.e., angular misalignment) is illustrated. It is shown that misalignment can have a significant effect on the bearings’ dynamic characteristics.