Hydrodynamic Bearings Research Articles

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.

Microgroove optimization to improve hydrodynamic bearing performance

Several researches on hydrodynamic bearings has looked for alternatives to increase their performance. Solutions involving modifications in oil feeding grooves and bearing geometry, as well as the development of new concepts are examples of these studies. Among these proposals, surface texturing gained a lot of attention with the promising results achieved. In this context, a new approach is investigated to optimize the hydrodynamic bearing performance, considering microgrooves with different depth distributed on the bearing surface. In this work, metrics that evaluate the bearing performance were chosen, in order to establish objective functions to optimize the bearing surface. The results obtained show that a proper microgrooves distribution can increase the bearing performance, allowing the increase of the load capacity, reduction of the viscous shear force and reduction of the average temperature in the bearing. In order to simplify the results obtained for the optimal surface, artificial filters were applied to provide surfaces with greater ease of manufacture, without compromising the improvements achieved in the optimization process. Based on these results, the proposed approach in this paper showed to be a promising alternative to increase the performance of hydrodynamic bearings.

Numerical analysis of a hydrodynamic air bearing with electromagnetic assistance

An air bearing system with active electromagnetic assistance is proposed, and its dynamic characteristics are numerically analysed. The system is based on herringbone groove hydrodynamic journal bearings. The air bearing system adopts electromagnetic force to assist in lifting the rotor and lowering the lift-off speed of the bearing and adjusting the dynamic stiffness. The characteristics of the bearings are examined using the two-way coupled fluid-structure interaction method for different operating environments. The fluid simulation is performed in ANSYS Fluent and coupled with the motion equations. The fluid-structure interaction analytical model is cross-examined with the published experimental results and is used to analyse the proposed system. The results demonstrate that the lift-off speed is lowered by 46.04% and that the electromagnetic force can compensate for the loss of stiffness at an altitude of 4000 m.

Dynamic Performance Improvement of Journal Bearing by Using Dimple and Protruded Textured Surfaces

In the present numerical study, the effect of V-shape textures on the dynamic performance characteristic of hydrodynamic journal bearing is obtained by using fluid flow governing Reynold’s equation which has been solved with finite element method (FEM) by assuming that the fluid is Newtonian and iso-viscous in nature. Four different cases of texture depths/heights and distributions have been selected to compute the dynamic performance parameters (non-dimensional damping, stiffness and threshold frequency) and compared with un-textured hydrodynamic bearing. From simulated results, the maximum value of direct stiffness and damping coefficient for protruded textured bearing is found at full textured bearing and second half textured region as compared to dimple and un-textured bearing respectively. The value of threshold speed is maximum for fully textured region at higher value texture depth and eccentricity ratio for dimple textured bearing. Similarly its value is higher at higher texture height operating at lower eccentricity ratio for protruded bearings.

Sensitivity analysis of geometrical design parameters on the performance of conical plain bearings for use as main bearings in wind turbines

The failure of a wind turbine’s main bearing causes very high repair costs, as the entire drivetrain has to be disassembled with the help of an external crane. Just the costs for a crane for an offshore turbine can sum up to 200.000€ per day [1]. In contrast, segmented hydrodynamic plain bearings offer the advantage that individual bearing segments can be replaced on the tower without the use of an external crane, which offers great potential for savings in repair costs. However, this application requires new, innovative plain bearing concepts for which the current design guidelines are not applicable. This paper presents a simulation-based design approach for a plain bearing concept with conical sliding surfaces. Such a simulation-based approach with a multi-objective optimization is necessary, because due to the geometric complexity the manual, iterative design process is not efficient. In this paper, a bearing geometry optimized in terms of load distribution and friction losses was developed by applying this approach.

Multiscale Analysis of Hydrodynamic Step Bearing with Ultra Low Surface Separations

The paper presents the multiscale analysis for the hydrodynamic step bearing with ultra low surface clearances where only the physical adsorbed layer is present in the outlet zone and the continuum fluid flow mainly occurs in the inlet zone. This bearing can occur under heavy loads. The flow in the outlet zone is described by the nanoscale flow equation, while the flow in the inlet zone is described by the multiscale flow equation incorporating both the adsorbed layer flow and the intermediate continuum fluid flow. The pressure and carried load of the bearing were derived. Exemplary calculations show that the fluid-bearing surface interaction has the strongest influence on the pressure and carried load of this bearing when the bearing surface clearance is as small as possible, the bearing step size is close to the surface clearance in the outlet zone and the value of the geometrical parameter is the optimum one, which depends on the fluid-bearing surface interaction. For the strong fluid-bearing surface interaction, the carried load of the bearing can be 10 times higher than that calculated from the classical hydrodynamic lubrication theory.

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.

Modeling of hydrodynamic bearings with a novel boundary parameterization approach

Modeling of hydrodynamic bearings with a novel boundary parameterization approach

Summary of Research on Oil Film Temperature Characteristic of Hydrostatic and Hydrodynamic Thrust Bearings

Background: This study was conducted to explore the temperature rise and distribution of the micro-gap lubricating oil film of the hydrostatic and hydrodynamic thrust bearing, solve the problem of thermal deformation of the friction pair of the hydrostatic and hydrodynamic support, and improve the operation accuracy and stability of the hydrostatic and hydrodynamic thrust bearing. Objective: Combined with the theory of dynamic and static pressure bearings, the problem of lubricating oil film temperature rise is analyzed, and specific research directions are proposed. It is hoped that it will be helpful to improve the research of bearing stability and provide a theoretical basis for the structural design and operational reliability of heavy hydrostatic bearings. Methods: This article summarizes the research status of the oil film temperature rise of hydrostatic and hydrodynamic thrust bearings, especially focusing on the influence of hot oil carrying on the temperature rise of the lubricating oil film, and finally, the specific research directions and methods of the oil film temperature rise are prospected. Methods: Current and future developments of the oil film temperature rise of hydrostatic and hydrodynamic thrust bearings are finally provided and discussed. It provides theoretical support for the thermal deformation control of the bearing friction pair, and provides a basis for the highprecision and stable operation of the bearing. Conclusion: Aiming at the research hotspots of lubricating oil film temperature rise and distribution, based on the analysis of the principle of hydrostatic and dynamic pressure bearings, the domestic and foreign literature on the influence of the micro-gap lubricating oil film temperature rise and distribution of hydrostatic and hydrodynamic thrust bearings is collected and analyzed. The research shows that although some research results have been made in this area, current research methods and angle analysis still have certain limitations, so the study of the oil film temperature rise is not comprehensive, and further detailed discussion and analysis are still needed.

Performance of water-lubricated ceramic journal hybrid bearing

Strong shear force developed in the lubrication film in the high-speed spindles will resulting high temperature rise and expanding the mandrel, which would arouse safe servicing problem. This study aimed to address the temperature rise issue in spindles through the use of substitutes in the spindle bearing material. To this end, we developed a spindle with a water-lubricated ceramic hydrodynamic and hydrostatic journal bearing. To support the selection of ceramic materials for the water-lubricated journal bearing, we initially performed application-oriented tests; to this end, the water absorption and porosity among alumina, silicon nitride, and silicon carbide were considered. To investigate the performance, and particularly the temperature characteristics of the hybrid bearing, a water-lubricated ceramic hydrodynamic and hydrostatic bearing test rig was designed to include temperature sensors. At the test rig, the radial clearance was measured for solving the temperature distribution of the bearing during the simulation. The experimental results helped verify that the water temperature increased by approximately 0.7°C as the rotation speed increased from 1200 rpm to 5400 rpm without an external radial load. The increase in temperature with and without radial load under a rotation speed of 3600 rpm was compared, and the results revealed a difference of 0.14°C. This indicates that the developed ceramic bearing improves the thermal stability of the spindle which shows its potential for industrial application in machine tools or other high rotation speed machines.

Linear and Nonlinear Performance Analysis of Hydrodynamic Journal Bearings with Different Geometries

In rotor dynamics, a traditional way of representing the dynamics of hydrodynamic bearings is using stiffness/damping coefficients. It is thus necessary to carry out a linearization of hydrodynamic forces around the shaft’s equilibrium position. However, hydrodynamic bearings have highly nonlinear nature, depending on operating conditions. Therefore, this paper discusses the applicability of these linear/nonlinear approaches using a computational model of the rotating system, where the finite element method is used for rotor modelling and the finite volume method for bearing calculation. The main goal is to investigate the boundaries for linear approximation of the hydrodynamic forces present in lobed hydrodynamic bearings, with the system operating under high loading conditions. Several numerical simulations were performed varying preload parameter and rotating speed. A comparison of the system’s responses, in time domain (shaft orbits) and frequency domain (full spectrum), is made for linear and nonlinear models. Results showed that trilobed bearings are more susceptible to nonlinearities, even in situations of smaller vibration amplitudes, while elliptical bearings are sensitive only under larger vibration amplitudes. These analyses are of great importance for mapping the influence of nonlinearities in different types of lobed hydrodynamic bearings with fixed geometry, varying the preload parameter to verify the influence on the system’s dynamic response. This study is important and serves as the basis for cases of monitoring and fault diagnosis (in the field of structural health monitoring) since it is crucial to distinguish what would be a fault signature or a standard nonlinear effect created by the use of hydrodynamic bearings.

Echo-guided left ventricular assist device speed optimisation for exercise maximisation

ObjectiveCurrent generation left ventricular assist devices (LVADs) operate with a fixed rotation speed and no automated speed adjustment function. This study evaluates the concept of physiological pump speed optimisation based...

Numerical study of hydrodynamic herringbone-grooved journal bearings combined with thrust bearings considering thermal effects

Abstract Hydrodynamic herringbone-grooved journal bearings (HGJBs) are analyzed by solving Navier–Stokes and energy equations. It is well known that the load capacity of hydrodynamic bearings may be affected by high temperatures and low oil viscosity. Therefore, the main objective of this study is to understand the pressure distribution of hydrodynamic HGJBs under different oil viscosity and eccentricity ratios. In this paper, 3 different configurations are studied, namely, a HGJB, a combined HGJB and thrust bearing, and a combined HGJB and grooved thrust bearing. The bearing characteristics, such as load capacity and attitude angle that vary with different eccentricity ratios, are also discussed. The results show that the load capacity of the bearing decreases with increasing temperature. The pressure difference also increases as the eccentricity ratio increases. The high-pressure region is concentrated at the tip of the groove for the HGJB. In addition, the combined HGJB and grooved thrust bearing can be used to stabilize the journal because of the low attitude angle. These findings may help and facilitate the design of hydrodynamic bearings suitable for working in warm and hot environments in the future.

Development of a Robust Test Rig for Tilting Pad Journal Bearing Validation

Several theoretical models for predicting the performance of tilting pad journal bearings (TPJB) have been developed by the scientific community over the years. However, reliable validation of the predictions based on the theoretical models, taking into account the complexity of TPJBs, demands robustness in the design and assembly of an improved test rig. Test bench designs for testing hydrodynamic bearings must carefully consider construction details as much as possible to observe the effect from the journal bearing and, consequently, improve the predictability of its dynamical behavior. In this context, there are still relatively few test rigs in the specific literature devoted to isolating the dynamic effects from hydrodynamic bearings for analysis purposes. Therefore, a novel test rig project is described in this work, also involving the design versatility characterized by measurement feasibility in rolling-element bearings and fixed-geometry, hydrodynamic journal bearings. This test rig aims to reproduce the most diverse operating conditions in order to measure the involved physical responses and validate the different models applied to the bearings. Therefore, the bearing performance can be properly evaluated, especially when operating under critical operating conditions, thus providing important contributions to the area of lubrication and rotor dynamics.

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.

Расчетно-экспериментальная методика определения предотказного состояния сложнонагруженных подшипников скольжения

The article deals with the types of wear and failures of journal bearings. Based on the physics of failures, a method for determining the pre-failure state of plain bearings is proposed, including: determination of the limiting clearance in the bearing; determination of the limit value of oil viscosity; determination of the limiting value of the ovality of the shaft neck and liners; determination of the maximum area of chipping of the surface of the liners; determination of the limit value of the concentration of active abrasive particles in the lubricant. The solution of these problems is based on the calculation of the determination of the hydromechanical characteristics (HMC) of bearings using the hydrodynamic theory of lubrication, the determination of the zones of contact interaction between the elements of the rolling stock, the duration of the boundary lubrication regime, the amount of wear on the surfaces of the sleeve and the shaft neck. Calculation studies were carried out on the example of calculating the dynamics of the connecting rod bearing of the crankshaft of a heat engine. In particular, it is shown that with a diametrical clearance in the connecting rod bearing of 90–120 μm, the duration of the boundary regime of lubrication is more than 25%, which is the limiting value. Reducing the oil viscosity (measured at 100 С) below 9.5 mPa∙s is unacceptable, as it leads to an increase in the duration of the boundary lubrication regime by up to 42%. For the same reasons, the ellipticity of the liners more than 5 microns is unacceptable. A mass concentration of active abrasive particles in the oil of more than 0.1% leads to a sharp increase in the maximum wear rate of the bearing, and this concentration should be considered the limit in terms of its pre-failure state. The technique allows at the early stages of designing machines, which include hydrodynamic plain bearings, to determine the criteria for their pre-failure state.

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.

Identification of oil starvation in hydrodynamic journal bearing using rotor vibration and Extended Kalman Filter

Oil starvation is a critical fault in hydrodynamic bearings caused by insufficient oil supply. When late detected, this fault can deteriorate the bearings’ performance and damage the rotating machine. Thus, the fault should be identified early to allow preventive maintenance. However, the literature about oil starvation identification is scarce. Among the few studies available, incipient oil starvation fault has been identified using a deterministic technique, which can be jeopardized by model inaccuracy. This paper proposes a novel identification method using the Extended Kalman Filter, which is a stochastic-determinist estimator that deals with modeling and measurement errors. Simulations showed the proposed method is suitable to identify oil starvation in real-time from noisy vibration, representing a promising tool for monitoring rotating machines.

Observer-Based Control of Tilting-Pad Thrust Bearings

The active control of hydrodynamic bearings is beginning to receive more attention in the pursuit of lower power losses and reduced maintenance. This paper presents a method by which, from simple measurements, rich information can be deduced from a running bearing that can used to modify the operating parameters of the unit. The bearing is a line-pivot, unidirectional, steadily loaded, directly lubricated tilting pad thrust bearing. This control is achieved by designing an Observer whose inputs include the output measurement(s) from the bearing. The Observer is, in some ways, an inverse model of the bearing (or Plant) that runs in parallel to the bearing and estimates the states of the bearing, such as the applied load, pivot height, minimum film thickness, maximum temperature, effective temperature and power loss. These estimated parameters can then be used in a control algorithm to modify bearing parameters such as inlet temperature or pivot location. It is demonstrated that disturbances in the load on the bearing can be detected simply by measuring a representative temperature in the bearing or changes in pivot height. Appropriate corrective action can then be employed. Whilst only steady-state operation is considered, the method could be developed to study time-varying situations.

SURFACE STRENGTHENING AND FRICTION WEAR OF THE INNER WALL OF LIQUID SODIUM HYDROSTATIC BEARING

Sodium hydrodynamic bearings are parts which are easy to wear in order to improve the wear resistance of the inner wall and prolong the service life. In this paper, high-temperature element W was used as a variable to prepare cobalt-based alloy coatings with different contents of W. By testing the hardness and anti-wear performance of the coatings at high temperature, the microstructure and wear mechanism of the coatings were further analyzed in combination with crystal phase diagram and microscopic morphology diagram. The results show that the coefficient of friction of cobalt-based alloy coating decreases with the increase of W content under high-temperature dry rubbing, while the wear quantity increases with the increase of W content. Under high-temperature oil lubrication, the coefficient of friction of cobalt-based alloy coating is the lowest when the W content is 12%. The wear amount of cobalt-based alloy coating decreases with the increase of W content, and the wear mechanism changes from adhesion wear to abrasive wear with the increase of W content.