Journal Bearings Research Articles

Observation and Prediction of Instability due to RD Fluid Force in Rotating Machinery by Operational Modal Analysis

In rotating machinery, rotordynamic (RD) fluid force is generated in fluid elements such as journal bearings, impellers, and seals. This RD fluid force is generated by the interaction of shaft vibration and fluid force and is difficult to predict because of nonlinearity. The RD fluid force has a significant effect on the stability of rotating machinery and is known to cause instability. In this study, we predicted the instability caused by RD fluid force by using operational modal analysis, which is a method to identify vibration characteristics based only on operating data.

Modelling and Simulation of Aerodynamic Cylindrical Bearings Using ANSYS Hydrodynamic Bearing Element Types

Modern power engine concepts and environmental restrictions demand oil-free lubrication of rotors, for example, by gas bearings. However, the stiffness and damping properties ruling the rotor’s dynamics are poorly documented for aerodynamic bearings and simple calculation methods are lacking. Based on the similarity between aerodynamic and hydrodynamic journal bearings, it is investigated to what extent the hydrodynamic bearing element types of the commercial FE program ANSYS are also suitable for air bearings. Within these elements, the compressibility of the gas is neglected. After verification of the ANSYS hydrodynamic element types with literature data for cylindrical hydrodynamic bearings, the stiffness and damping coefficients of a cylindrical aerodynamic bearing are calculated by using the ANSYS hydrodynamic element types. In the examined speed range, the results agree well with literature data that consider gas compressibility. Therefore, the FE elements designed for hydrodynamical journal bearings may also be used for simulating cylindrical aerodynamic bearings. The presented calculation approach provides a compact and easy-to-use method for rotordynamic simulations with cylindrical aerodynamic bearings in a single development environment.

Modeling of Journal Bearings for Wear Diagnosis and Its Verification Using SVM

Recently, deterioration of infrastructure facilities has become problem. To reduce inspection costs, wear diagnosis of journal bearings in operating conditions using machine learning has been studied. However, constructing a highly accurate machine learning model requires training data, and it may be difficult to conduct numerous tests depending on the application. In this study, a mathematical model of a rotor system for wear diagnosis of journal bearings was developed, and the vibration data was obtained when the clearance changed due to wear. Then, changes in the features used for condition monitoring were examined. Furthermore, the important features for wear diagnosis were selected and SVM models were constructed to verify the mathematical model.

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.

Hydrodynamic analysis of journal bearing considering the effects of cavitation and minuscule particle

Journal bearing is the general element in the mechanical systems, which can provide the rotational motion of joints. The hydrodynamic analysis model of journal bearing is established and the effects of cavitation and minuscule particle are considered in the simulation model. The cavitation effects would be represented by the mixture model. Based on the CFD and DPM technology, the mixture lubrication medium of journal bearing is developed, which includes the minuscule element of solid in the lubrication film. And, the effects of structural parameters and operation conditions on the hydrodynamic characteristics of journal bearing is investigated. The simulation results could provide the suggestion for the design of structure and working condition.

Experimental Detection of Lubrication Characteristics in a Solid–Liquid Two-Phase Flow Supported Bearing-Rotor System Using Vibration Monitoring Techniques

This work aims to investigate the friction and vibration behaviors of a liquid–solid two-phase flow supported bearing-rotor system for the early monitoring and assessing of oil contamination resulting from externally ingested particles. Based on a Jeffcott rotor test rig, the lubricating oil in journal bearing was mixed with micron-scale silica particles of different sizes and concentrations. The vibration monitoring techniques utilizing eddy current, photoelectric, and piezoelectric sensors were conducted to detect the rotor displacement amplitude and bearing acceleration online. According to the quantitative evaluation, the vibration frequency spectrum, shaft trajectory, and the bearing surface characteristics were analyzed and classified at different conditions of particle parameters. Furthermore, the lubricating mechanism at bearing interface which possesses a strong interactive coupling effect with rotor vibration was deduced and illustrated. The results showed that although the sizes of ingested micron particles were less than the minimum oil-film thickness, they usually exhibited detrimental effects on the flow stability and fluid support. As the particle size or concentration increased, the interaction between particles and bearing surfaces led to the burrs in time-domain waveform, reverse displacements in rotor orbit, higher frequency harmonics in vibration spectrum, and the scratches on the bearing surface. The occurrence of continuous three-body friction could induce misalignment, blockage, oil starvation, and rub-impact fault. Furthermore, the detectability of particle contamination and damage microstructure of bearing surface was described for reference.

Temperature analysis of hydrodynamic journal bearing lubrication with a moving journal and a fixed bearing

ABSTRACT The need for bearings in a variety of heavily loaded machines, including the influence of pressure and temperature, is generating increasing interest in studying the operating environment for magazine bearings. The purpose of this work is to develop a semi-analytical solution by introducing a new delta profile concept of the location of zero velocity gradients to obtain the simplest form of the equation of energy and Reynolds. In the journal bearing, assuming that journal is rotating and bearing is fixed, a hydrodynamic lubrication is modelled with the Power Law fluid. The lubricant temperature effect is examined under isothermal limits and the results obtained are much more realistic with the experimental results.

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.

Evaluation of Wear Models for the Wear Calculation of Journal Bearings for Planetary Gears in Wind Turbines

To increase the power density of the electromechanical drive train of wind turbines, journal bearings can be used as planetary gear bearings instead of rolling bearings. This technological change presents new challenges. For example, wind turbine drive systems are subject to dynamic and low-speed operating conditions, which can lead to accelerated abrasive wear of the journal bearings. In addition, oil supply failure or peak loads due to wind gusts and grid and power converter faults could potentially result in catastrophic failure due to adhesive wear in a very short time. Such operating characteristics are, therefore, critical regarding the journal bearing wear lifetime and must be considered in the design. The successful implementation of journal bearings in wind turbines depends on a reliable estimation of adhesive and abrasive wear. In this paper, five different models for the wear calculation of journal bearings are evaluated regarding their suitability for the wear calculation of planetary gear bearings in wind turbines. For this purpose, the following evaluation criteria were defined: parameter uncertainty, parametrization effort, in particular number of parameters, parameterization method, load case dependency of parameters and calculation effort. In order to be able to evaluate the wear models, the wear models are numerically implemented, and the wear of a test journal bearing is exemplarily calculated under load conditions, which are comparable to load conditions in a wind turbine. Relevant influences from the wind turbine system, such as lubricant, material and manufacturing-dependent surface influences, such as roughness and hardness, are considered. The wear models are evaluated with respect to their fulfillment of the defined criteria. The resulting evaluation allows the selection of a wear model that can be used to calculate the wear of planetary gear journal bearings in wind turbines, considering the available input variables.

Simplified transformation matrices of journal bearings in vertical application

Rotodynamic simulation of complex or/and large systems, for instance hydropower machines, may consist of models with many degrees of freedom and require multidisciplinary computations such as fluid-thermal-structure interactions or rotor-stator interactions due to electromagnetic forces. Simulating such systems is often computationally heavy and impractical, especially in the case of optimization or parametric study, where many iterations are required. This has, therefore, created a need for simplified dynamic models to improve computational efficiency without significantly affecting the accuracy of the simulation result. The purpose of this paper is to present simplified coordinate transformation matrices for journal bearings in vertical rotors, which require less computational effort. Matrix multiplications, which appear during coordinate transformation, were eliminated, and the bearing stiffness and damping matrices in the fixed reference frame were represented by local coefficients instead. The dynamic response of a vertical rotor with eight-shoe Tilting pad journal bearings was simulated using the proposed model for two operational conditions, i.e., when the rotor was spinning at constant and variable speeds. The results from the proposed model were compared to those from the original model and validated through experiments. The conclusion was that the presented simulation model is time efficient and can effectively be used in rotordynamic simulations and analyses.

Analysis of the Turbulent Lubrication of a Textured Hydrodynamic Journal Bearing

In order to investigate the turbulent lubrication performance of a textured hydrodynamic journal bearing (THJB), a model of turbulent lubrication was established in this paper. The variations in the Reynolds number, oil film thickness, oil film pressure, bearing capacity, attitude angle, and side leakage flow with structural and working parameters were studied, and the axis whirl orbit was further analyzed. The results show that turbulent lubrication is suitable for the actual operating conditions of THJBs. The Reynolds number decreases with the eccentricity ratio in the pressure-bearing zone but increases with rotational speeds, whereas the variation in the maximum oil film pressure increases and the minimum oil film thickness decreases with the eccentricity ratio under various Reynolds numbers. The bearing capacity decreases with the dimple diameter, depth, oil film thickness, and clearance ratio but increases with the length/diameter ratio and dimple spacing. As the eccentricity ratio increases, the attitude angle decreases, but the side leakage flow increases. In addition, the system tends to be unstable as the rotational speed and length/diameter ratio increase, and the friction and wear on the surface are three-body friction. This work not only helps in analyzing the characteristics of a THJB under actual operating conditions but also provides support for research on the simulation of THJB’s lubrication mechanism of THJB via computational fluid dynamics.

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

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

Thermal-elastohydrodynamic lubrication study of misaligned journal bearing in wind turbine gearbox

Owing to the simple structure, large load-carrying capacity and long life, journal bearings supporting planet gears (JBSP) are increasingly used in the wind turbine gearbox. The moment caused by the asymmetric meshing leads to the misalignment of the JBSP and further deteriorates its lubrication behaviors. A thermal-elastohydrodynamic (TEHD) model is developed for the misaligned JBSP, where the finite element method (FEM) and influence coefficient method are used to compute the temperature and deformation of this bearing, respectively. Besides, the above model is also experimentally verified. It is found that the misalignment of the JBSP can be suppressed through reducing its modification amount, helix angle and radial clearance, which have the optimal values to improve the TEHD behavior of the JBSP.

Influence of Bearing Wear on the Stability and Modal Characteristics of a Flexible Rotor Supported on Powder-Lubricated Journal Bearings

This study has investigated the influence of journal bearing wear on the dynamic behaviour of a flexible rotor with a central disc. Rotors supported on journal bearings are susceptible to self-excited whirling, leading to unstable conditions. Prior knowledge of the stability limit speed is important to avoid the excessive vibration of rotating machines. For the study in this paper, journal bearings were lubricated with powder owing to high-temperature applications where conventional oil lubricants would fail to perform. The governing equations for lubrication were derived using a simplified grain theory based on the theory of dense gases. The rotor shaft was discretized considering Timoshenko beam elements. Modal analysis was conducted to obtain the system’s natural frequencies, mode shapes, damping factors, stability limit speed, and unbalance response. This study has also evaluated the influence of wear depth on the dynamic behaviour of the rotor shaft system and found that bearing wear significantly affects the stiffness and damping characteristics of lubricating film. Consequently, free and forced vibration behaviour is also affected. It has been found that increased wear depth improves stability limit speed but has little influence on the unbalance response.

Static Characteristics of Water-Lubricated Hydrodynamic Spiral-Groove Journal and Thrust Bearings for Motorized Spindle

Abstract Oil-lubricated hydrodynamic bearing is a typical support for motorized spindle. However, a motorized spindle supported by the oil-lubricated hydrodynamic bearing has disadvantages regarding high-temperature rise and low rotational speed. To overcome this problem, this technical brief proposes novel water-lubricated hydrodynamic spiral groove bearings for the motorized spindle. A rotor-bearing static model for the motorized spindle was established considering the external loads and the tilting effect of bearings. An experimental prototype for the motorized spindle was developed, and the theoretical calculation and experimental research on the bearing static characteristics were carried out. The result shows that the water-lubricated hydrodynamic spiral groove bearings have significant advantages in terms of low-temperature rise, good high-speed performance, and moderate spindle stiffness, together with the inherent low manufacture cost and high rotation accuracy of the bearings, and the proposed bearings can be a potential alternative to the fluid bearing for the high-speed motorized spindle.

Experimental research on the performance improvement of aerodynamic journal bearing with a new bore design

An experimental research on the performance improvement of a rotor-bearing system has been presented herein employing aerodynamic journal bearings (AJBs) with a new bore design. The new bore design geometrically involves the segments of rigid and compliant bores together. The dynamic performances of rotors supported on the new bore AJBs have been experimentally studied and compared with that of conventional rigid and conventional compliant bores. The vibration amplitudes achieved with the new bore are found the lowest among all the studied cases. Moreover, the rotor orbit centers with the new bore are found closest to the bearing center, which is indicating improvements in the dynamic stability and load-carrying capacity. The sub-synchronous and higher-order harmonic vibrations are found insignificant with the new bore.

Static Characteristics of High-Speed Water-Lubricated Journal Bearing Considering Turbulence and Cavitation Effects

Abstract The water-lubricated bearings tend to be turbulent and cavitating when running at a high speed. However, the modeling of the water-lubricated bearing considering the turbulence and cavitation effects has not been studied thoroughly. For high-speed water-lubricated journal bearings, a turbulent flow model considering cavitation effect was proposed on the basis of two-phase flow theory. The simulation was conducted to show the influence of turbulence and cavitation effects on the static characteristics of the water-lubricated journal bearing. The proposed model was validated with the test by using a self-developed experimental setup. The result shows that the turbulence effect has a great impact on static characteristics of bearing, and cavitation effect significantly affects the minimum film thickness and leakage flowrate, while the friction torque is hardly affected by the cavitation effect.

Wavelet lifting method for the numerical solution of micropolar lubrication problem of porous journal bearing

The pivotal aim of this paper is to develop the wavelet lifting method for the numerical solution of the micropolar lubrication problem of porous journal bearings. To ensure the applicability of the proposed method initially, test problems are considered and the numerical findings are presented in figures and tables elucidate that, the proposed method is more efficient and promising with the consumption of lesser computational CPU time. Subsequently, the effect of micropolar fluid on the porous journal bearing is analyzed by solving the corresponding non-dimensional Reynolds equation of the lubrication problem is considered. The obtained results for pressure distribution and load carrying capacity with varied parameters show that the squeeze film pressure and load carrying capacity are significantly increased by the micropolar fluid effect as compared to the Newtonian case.

Computer Aided Design Techniques for Dynamically Loaded Journal Bearings

In this paper a generalized computer aided design methodology is developed to design the dynamically loaded journal (aircraft and engine) bearings with comprehensive study. As part of procedure development a typical dynamic load case of inline engine connecting rod bearing and main bearings are taken for analysis. The determinate method of bearing force evaluation is adopted. The mobility concept is employed to predict the figures of merit (minimum film thickness, maximum film pressure). It is shown that the mobility expressions based on Goenka curve fits predict performance parameters in close agreement with data based on experiences. The entire generalized design strategy is also programmed with graphic interactions. The results are available within a few seconds from an interactive computer terminal, once initial data describing the application have been entered.

Influence of Cavitation and Shaft Deformation in the Analysis of Lubrication of the Stern Bearing

The cavitation phenomenon and shaft deformation have a significant impact on the tribological performance of the journal bearing. A mixed lubrication model is developed that takes into account surface roughness and asperity contact, as well as the effects of cavitation and deflection. The fluid–solid coupling effect in bearing deformation, asperity contact, and film pressure are investigated. The effect of boundary conditions on the lubrication regimes is discussed. The results of simulations with and without cavitation are compared under steady-state conditions. The results show that when cavitation is considered by the mixed lubrication model under a given load, the eccentricity is reduced, and the maximum oil film pressure is also reduced. The speed range of the bearing simulated with the mixed lubrication model increases after considering deflection deformation. The mixed lubrication model proposed in this paper is able to provide accurate results of pressure distribution and coefficient of friction and can be applied in the design and analysis of journal bearings.