Search

This study presents the impact of full and partial surface waviness on the dynamic and stability performance of the journal bearing. The Reynolds equation is modified to account for the impact of surface waviness, and the lubricant domain is discretized using the Finite element method to obtain dynamic characteristics such as stiffness and damping coefficients and stability parameters, that is, threshold speed. Different wave numbers in the axial, circumferential and mixed directions are considered at variable wave amplitudes in different regions at an average eccentricity ratio of 0.6 to obtain the optimum values. The obtained results reveal that by application of waviness in the full region and partial waviness in the pressure‐reducing region on the bearing surface provides the enhanced value of stability parameter, fluid film stiffness and dynamic coefficients as compared to the simple journal bearing under the same working conditions. [ABSTRACT FROM AUTHOR]

In this paper, the static performance analysis of journal bearing having full and partial surface waviness has been presented. The surface waviness is to be considered in the full, first half, second half, and pressure‐increasing and decreasing regions of the bearing for analysis. The effect of surface waviness is considered by modifying the lubricant flow governing Reynolds equation with the film thickness equation and it is solved with the finite element method to get performance parameters like bearing load capacity, friction coefficient, and so forth operating under eccentricity ratios range of 0.2–0.8. The waviness geometrical parameters like waviness numbers and amplitudes are also considered in circumferential, axial, and both directions in the selected regions. The maximum performance has been found for waviness in the full and pressure‐increasing region in the circumferential direction at a high eccentricity ratio. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to investigate the impact of surface waviness on the static performance parameters of hydrodynamic journal bearings operating with lubricants containing copper oxide (CuO) and cerium oxide (CeO2) nanoparticles. Design/methodology/approach: The static performance parameters of bearings with surface waviness and the addition of nanoparticles in lubricants were calculated using the nondimensional form of Reynolds equation and finite element method. Static performance parameters are calculated at different waviness numbers in the circumferential, axial and both directions at various wave amplitudes with variable viscosities of lubricants with nanoparticles using the viscosity equation forming a relationship between the relative viscosity, temperature and weight fraction of nanoparticles in lubricant developed from the experimental results. Findings: The computed results indicate that the impact of waviness on the bearing surface enhances the load capacity, reduces friction coefficient, and is more effective in the circumferential direction than in the axial direction or in both directions. The addition of CuO and CeO2 to the lubricant enhanced its viscosity which further improved the steady-state parameters of the wave bearing. Research limitations/implications: This study is based on a numerical technique, which has significant limitations, and the simulated results must be tested experimentally. Practical implications: The current findings will be beneficial for designers to improve the performance of hydrodynamic journal bearings. Originality/value: The calculated results demonstrate that the combined effect of the surface waviness on bearings and the addition of nanoparticles to lubricants can greatly increase the performance of hydrodynamic journal bearings. [ABSTRACT FROM AUTHOR]

Journal bearing is one of the most important mechanical parts which can vastly be found in any application of mechanical camcorders such as engine, roterdynamic, aerodynamic and many more. One of the main performance related problems that this mechanical part may encounter during its service life is due to friction and wear over a short period of time, especially at high speeds, a one of the main challenges was to keep the shaft running efficiently for another hours. Many designs and modifications are attempted by researchers to improve certain specifications of the journal. In this construction a new design of the magazine bearing system was developed. It consists of three floors; the second is the bearing (internal and external) and the third is the thrust bearing. All three bearing units are combined into a single case as a magazine assembly. In this configuration, two hydrodynamic pressure profiles can be generated around the inner and outer fluid films in the circumferential direction and one in the axial direction. To predict the journal parameters, a mathematical model for the new magazine bearing design was developed using Reynolds' hydrodynamic equations. Lubrication in two dimensions. The governing partial differential equation was solved using Finite Difference method via MATLAB software. The main bearing parameters such as pressure, load capacity, friction force and so on are evaluated and their effect on journal geometry and operating conditions are investigated. A sample journal model was fabricated using CNC machine and tested experimentally with specially made testing rig, Vibration characteristics and stability of the journal are analyzed and studied also. The stress analysis of the journal housing are performed by using Finite Element method and excited by ANSYS 14. The effect of using Nano additive to the lubricant oil is studied both theoretically and experimentally. The preliminary results of this work indicated that the new suggested journal can significantly increase the ability of withstanding higher pressure and carrying load by about 23.60% and 12.90% respectively more than the traditional journal. Furthermore it exhibits less friction and higher critical operating speed. Using oil with Nano-particles can reduce friction by 16% with higher temperature operation. The optimum design conditions are occurred at 0.92 eccentricity ratio and 0.5 compound size ratio. [ABSTRACT FROM AUTHOR]

Frequency-dependent adaptive noise cancellation-based tracking controller (ANC-TC) is a known technique for the stabilization of several nonlinear dynamical systems. In recent years, this control strategy has been introduced and applied for the stabilization of a flexible rotor supported on full-lubricated journal bearings. This paper proposes a theoretical investigation, based on robust immersion and invariance (I&I) theory, of a novel ANC-frequency estimation (FE) technique designed to stabilize a flexible rotor shaft affected by self-generated sinusoidal disturbances, generalized to the case of unknown frequency. A structural proof, under assumptions on closed-loop output signals, shows that the sinusoidal disturbance rejection is exponential. Numerical simulations are presented to validate the mathematical results in silico. The iterative Inexact Newton method is applied to the disturbance frequency and phase estimation error point series. The data fitting confirms that the phase estimation succession has an exponential convergence behavior and that the asymptotical frequency estimation is a warm-up phase of the overall close-loop disturbance estimation process. In two different operating conditions, the orders of convergence obtained by phase and frequency estimate timeseries are p φ = 1 ,   p ω , u n c = 0.9983 and p ω , c a v = 1.005 . Rejection of the rotor dynamic disturbance occurs approximately 76% before in the cavitated than in the uncavitated condition, 2 (s) and 8.5 (s), respectively. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to evaluate the theoretical performance of elliptical dam bearing (EDB). The objective of this paper is to study the influence of eccentricity ratio, dam parameters and micropolarity parameters on the stability of EDB with respect to micropolar lubrication. Design/methodology/approach: In this study, the modified Reynolds' equation for dynamic state is solved using the finite element method and Galerkin technique. A MATLAB code is written to compute pressure and stability and also to analyse the characteristics. The stability parameters of an EDB are computed for selected values of eccentricity ratios at four levels in the range of 0.20 to 0.35 and for length-diameter ratio of 2.0. Findings: The results from stability analysis reveal that micropolar lubricated EDB provides better stability at smaller material length due to increased effective viscosity. Hence, it is better to select the smaller characteristic length and higher dam width to achieve optimum performance of these bearings. Originality/value: Very few researchers investigated the effects of working eccentricity, bearing dam and micropolar fluid parameters on the EDB in the past. It is important to study these aspects for optimum performance of bearings. [ABSTRACT FROM AUTHOR]

This paper explores the influence of the frequency of shaft sleeve rotation and radial load on a journal bearing made of tin-babbitt alloy (Tegotenax V840) under hydrodynamic lubrication conditions. An experimental test of the frictional behaviour of a radial plain bearing was performed on an originally developed device for testing rotating elements: radial and plain bearings. Using the back-propagation neural network, based on experimental data, artificial neural network models were developed to predict the dependence of the friction coefficient and bearing temperature in relation to the radial load and speed. Using experimental data of the measured friction coefficient with which the artificial neural network was trained, well-trained networks with a mean absolute percentage error on training and testing of 0.0054 % and 0.0085 %, respectively, were obtained. Thus, a well-trained neural network model can predict the friction coefficient depending on the radial load and the speed. [ABSTRACT FROM AUTHOR]

It is a known fact that incorporating textures in the contact surfaces can significantly enhance bearing performances. The purpose of this paper is to outline the effects of texture bottom profiles and contour geometries on the performances of hydrodynamic textured journal bearings. The analysis was conducted using computational approach to test eight texture shapes: rectangular, cylindrical, spherical, triangular (TR, T1, T2, T3) and chevron. The steady-state Reynolds equation for modelling the hydrodynamic behaviour of thin viscous film was solved using finite difference technique and mass conservation algorithm (JFO boundary conditions), taking into account the presence of textures on both full film and cavitation regions. The comparison with the benchmark data shows good consistency and an enhancement in bearing performances (load carrying capacity and friction). The results clearly show that the mechanisms of wedge effect and micro-step bearing for the full/partial texturing feature are the main crucial parameters, where the convergent wedge effect present in T2 triangular texture shape can significantly enhance the load-carrying capacity, while the divergent wedge action causes a net load loss. Considering the right arrangement of textures on the contact surface, their surface contours can have a significant impact on the performance of hydrodynamic journal bearings at high eccentricity ratios. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to evaluate the various dynamic performance parameters of hydrodynamic journal bearings. For this, the bearing's inner surface is textured with chevron-shaped textures with different texture depths and number of textures in different regions/locations. Design/methodology/approach: In the present study, the effect of chevron-shaped texture having different values of texture depths, locations and number of textures has been numerically simulated. The dynamic performance characteristics have been calculated by solving the fluid flow governing Reynolds equation using the finite element method, assuming iso-viscous and Newtonian fluid. Findings: The obtained results indicate that the bearing stability can be improved with the help of surface texture. Among all the investigated texture locations, the maximum increase in stability threshold speed is observed for fully textured distribution. Moreover, for the chevron-shaped texture considered in the present study, the optimum values of texture depth and number of textures have also been determined for maximum bearing stability. Practical implications: While designing, designers should focus on those optimum values of texture depth, texture location and number of textures which lead to maximum enhancement in bearing stability. Originality/value: This study is useful in the appropriate selection of chevron-shaped texture parameters on bearing surface for the maximum bearing stability. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to provide the various steady state parameters of hydrodynamic journal bearings have been determined to get maximum performance enhancement ratio. For this, the bearings inner surface is textured with triangular shape with different texture depths and a number of textures in pressure increasing region. The textured region acts as a lubricant reservoir, which provides additional film-thickness and reduce friction. Therefore, enhance the overall performance of bearing. Design/methodology/approach: In the present study, the effect of triangular shaped texture on the static performance characteristics of a hydrodynamic journal bearing has been studied. Different values of texture depths and a number of textures have been numerically simulated in pressure developing region. The static performance characteristics have been calculated by solving the fluid flow governing Reynolds equation using the finite element method, assuming iso-viscous Newtonian fluid. The performance enhancement ratio, which is the ratio of load carrying capacity (LCC) to the coefficient of friction (COF) has been calculated from results to finalized optimum design parameters. Findings: The paper provides numerically obtained results indicate that surface texturing can improve bearing performance if the textured region is placed in the pressure increasing region. Moreover, surface texturing is the most effective at bearing performance enhancement when the bearing operates at lower eccentricity ratios and texture depth. The performance enhancement ratio, which is the ratio of LCC to the COF is found to be a maximum value of 2.198 at texture depth of 1.5, eccentricity ratio of 0.2 and the textured region located in the increasing pressure region. Research limitations/implications: The present study is based on a numerical based research approach, which has its limitations. So, researchers are encouraged to investigate the same work experimentally. Practical implications: The paper includes implications to be beneficial for designers for designing better hydrodynamic journal bearings. Originality/value: For the triangular shaped texture, considered in the present study, the optimum values of texture depth and texture distribution region have also been determined. While designing, designers should focus on those values of texture depth, texture region and a number of textures, which give the maximum value of performance enhancement ratio, which represents maximum LCC at the lowest value of the COF. [ABSTRACT FROM AUTHOR]

Purpose This paper aims to investigate how form error of journal affects oil film characteristics, which are composed of several parameters including the maximum film pressure, film moment, frictional coefficient and carrying-load capacity.Design/methodology/approach A new generalized equation based on the small displacement torsor theory is derived, as well as its capability of representing types of form error on the journal, using four specified parameters in a three-dimensional (3D) state. Based on the new generalized equation of form errors, the Reynolds equation is represented and solved numerically using the Swift–Stieber boundary condition.Findings The results show that the form errors of journal have significant influence on all oil film characteristics. However, the film moment remains nearly unchanged as film characteristics, especially eccentricity ratio, become large. All film characteristics investigated vary periodically as the form error. More importantly, it is found that the film pressure distribution transforms to an asymmetric shape along the axial direction of the bearing, no longer a symmetric shape in the case of two-dimensional (2D) form errors. It is necessary to substitute the 3D form error model, which takes the variations of the film characteristics in axial direction into account, for the 2D model in the designing stage of journal bearings.Originality/value First, the effect of the form error of the journal on the performance of hydrodynamic journal bearings is studied in the view of the film characteristics systematically. Secondly, the new generalized equation of form error, derived by SDT theory, is capable of representing any types of form error on the journal, not only representing one type of form error merely. [ABSTRACT FROM AUTHOR]

Abstract A wisely chosen geometry of micro textures with the favorable relative motion of lubricated surfaces in contacts can enhance tribological characteristics. In this paper, a computational investigation related to the combined influence of bearing surface texturing and journal misalignment on the performances of hydrodynamic journal bearings is reported. To this end, a numerical analysis is performed to test three texture shapes: square "SQ", cylindrical "CY", and triangular "TR", and shaft misalignment variation in angle and degree. The Reynolds equation of a thin viscous film is solved using a finite differences scheme and a mass conservation algorithm (JFO boundary conditions), taking into account the presence of textures on both full film and cavitation regions. Preliminary results are compared with benchmark data and are consistent with a positive enhancement in misaligned bearing performances (load carrying capacity and friction). The results suggest that the micro-step bearing mechanism is a key parameter, where the micro-pressure recovery action present in dimples located at the second angular part of the bearing (from 180° to 360°) can compensate for the loss on performances caused by shaft misalignment, while the micro-pressure drop effect at the full film region causes poor performances. Considering the right arrangement of textures on the contact surface, their contours geometries can have a significant impact on the performance of misaligned journal bearings, particularly at high eccentricity ratios, high misalignment degrees and when the misalignment angle α approaches to 0 ° or 180 °. [ABSTRACT FROM AUTHOR]

This paper investigates the stochastic behaviour of hydrodynamic journal bearings by solving the Reynolds equation with random parameters numerically based on finite difference method. The steady state and dynamic characteristics are quantified considering random variabilities in eccentricity and surface roughness that can closely simulate the uncertain service conditions and inevitable manufacturing imperfections. Based on efficient radial basis function, a Monte Carlo simulation (MCS) algorithm is developed in conjunction with the governing equations for quantifying stochastic characteristics of the crucial performance parameters concerning hydrodynamic bearings. Relative sensitivity to stochasticity for different performance parameters is analysed. Physically insightful new results are presented in a probabilistic framework, wherein it is observed that the stochasticity has pronounced influence on the performance of bearing. [ABSTRACT FROM AUTHOR]

Purpose This paper aims to investigate the performance of a ferrofluid-based hydrodynamic journal bearing system.Design/methodology/approach This paper presents a new design of ferrofluid-based hydrodynamic journal bearing. An experimental set-up consisting of a magnetic shaft along with a brass bearing was modified and developed. A permanent magnet was used to make the selected shaft material magnetic. The load and speed were varied to conduct the analyses for different test conditions.Findings The paper provides information about a design of ferrofluid-based journal bearing and its improved performances. For moderate to higher loads at different shaft speeds, it was found that because of the magnetization effect, the maximum film pressure in case of a ferrofluid lubricant increased up to approximately 60 per cent, compared with that of the conventional lubricant-based journal bearing system. Besides, the temperature rise was found smaller for ferrofluid lubricants, thus making the system cooler while running.Originality/value This paper offers a new design of magnetic bearing system for the experimental analysis by utilizing a magnetic shaft with a non-magnetic bearing. The present ferrofluid-based bearing design is less complicated from manufacturing point of view. [ABSTRACT FROM AUTHOR]

The aim of this paper is to investigate the effect of one axial groove at the inlet of full film bearing surface on dynamic coefficients and linear stability of rotor-bearing systems supported by two short journal bearings. The DuBois-Ocvirk short bearing approximation is applied to the governing Reynolds equation. The linearized nondimensional dynamic coefficients of stiffness and damping are calculated for both plain and grooved journal bearings. Moreover, using the linear stability analysis, the whirl frequency ratio and the threshold speed are obtained. Finally, results are presented for various eccentricity ratios, groove depth, and groove width a slenderness ratio of L/ D=0.25. The results appeal that dynamic coefficients are mostly affected significantly at low eccentricity ratio regions. In sequence, one axial groove causes a remarkable deviation in the values of threshold speed and whirl frequency ratio. [ABSTRACT FROM AUTHOR]

In the present work, a reduced-order method, “Proper Generalized Decomposition (PGD)” is extended and applied to the resolution of the Reynolds equation describing the behavior of the lubricant in hydrodynamic journal bearing. The PGD model is employed to solve the characteristic ‘Reynolds’ partial differential equation using the separation technique through the alternating direction strategy. The resulting separated-dimension system has a low computation cost compared to classical finite-difference resolution. Several numerical benchmark examples are investigated to verify the validity and accuracy of the proposed method. It has been found that numerical results obtained by the PGD method can achieve an improved convergence rate with a very low computation cost. [ABSTRACT FROM AUTHOR]

Rotary blood pumps ( RBPs) have demonstrated considerable promise while treating heart failure patients, such that they are being placed at an earlier stage of the disease. These devices may therefore be required to operate for prolonged durations which yields the need for RBPs exhibiting high durability, reliability, and blood compatibility. Noncontacting bearings, utilizing magnetic and/or hydrodynamic suspension techniques, appear to provide a suitable solution to these challenges. Hydrodynamic suspension has the advantage that it does not need feedback control systems. Among various hydrodynamic bearing types, the circular journal bearing has the particular benefit of easy manufacturing. This study presents methods to evaluate the performance of short (length to diameter ratio <1) circular hydrodynamic journal bearings ( HJBs) for RBPs. Analytical calculations with specific boundary conditions are presented to predict the rotor's eccentricity under equilibrium states and thus the related performance parameters such as load capacity, power loss, and shear rates. These results and boundary conditions were confirmed experimentally in a specially designed test set-up. The bearing performance was found to correlate to analytical solutions using the full Sommerfeld boundary condition instead of the half Sommerfeld condition conventionally used for such applications. Geometrical and operational parameter variations showed that HJB designs with a short Sommerfeld Number SS >0.02 can provide sufficient fluid film thicknesses and low shear rates. The measurements were further used to evaluate the bearings' stability. The estimation of the stability threshold drawn in relation to a modified stability index and the equilibrium eccentricity of the rotor allows the prediction of stability for short circular HJB designs under full Sommerfeld condition. [ABSTRACT FROM AUTHOR]

This work presents the investigation results of a journal bearing lubricated with magnetorheological fluid that is activated by a local constant magnetic field to vary both the local flow resistance and pressure. The bearing performance is assessed via Finite Element Modelling (FEM) and results are corroborated by experiments. The FEM model uses the Bingham model to describe the fluid film. A dedicated test rig is used to assess the hydrodynamic behavior of the bearing with magnetorheological fluid, and the results are compared with the same geometrical bearing lubricated with oil. Thicker fluid films at low speeds, beneficial pressure distribution, and higher friction losses under all operating conditions are observed in the bearing with magnetorheological fluid compared to the oil lubrication. • Properties of magnetorheological (MR) lubricant were experimentally determined. • Comparative study for bearing lubricated with MR fluid and oil was performed. • Theoretical investigations were positively verified experimentally. • MR lubricated bearing performed better than oil lubricated at low speed conditions. [ABSTRACT FROM AUTHOR]

This paper deals with multi-objective shape optimization related to the geometrical design of a hydrodynamic journal bearing. The aim proposed here is to show that optimum shape design with better performance could surpass the limitations of existing bearing profiles. Attempting to remove the difficulty of selecting the weighting factor in multi-objective journal bearing optimization problems, a modified non-dominant sort in genetic algorithm was used as an optimization tool with a penalty to those solutions that violate constraints. Three kinds of optimized shapes were manufactured and taken as experimental objects. Experimental apparatus was described and some experimental data was presented. The comparison was made for the optimized bearings between numeric values and experimental data. The results show that the new method for shape optimization of hydrodynamic journal bearings based on the general film thickness equation is feasible. [ABSTRACT FROM AUTHOR]

Abstract: The present work contributes to the analysis of the interactions between gears, shafts and hydrodynamic journal bearings in geared drives. In contrast to the majority of the models in the literature, the time-varying properties and nonlinearities of gears and bearings are introduced in the simulations. A finite element model is used for the shafts, and a specific gear element is used to account for nonlinear time-varying mesh stiffness as well as tooth shape deviations. The nonlinear hydrodynamic forces are computed with the Reynolds equation for finite-length journal bearings. An iterative Newmark scheme is used to solve simultaneously the motion equations for the shafts, the contact problem for the gears, and the fluid forces in the bearings. The resulting algorithm is applied to a single stage geared system with two shafts, four bearings, a pinion and a gear. Gear-bearing dynamic interactions are demonstrated through the analysis of dynamic gear loads, dynamic bearing loads and bearing displacements. The efficiency of the proposed numerical procedure, the interest of nonlinear models for hydrodynamic bearings and the influence of several parameters ruling the gear assembly are also discussed. [ABSTRACT FROM AUTHOR]

Abstract: In this work generalized differential quadrature (GDQ) method as a simple, efficient and high order numerical technique is used for the solution of modified Reynolds equation to obtain the performance of micropolar lubricated hydrodynamic circular and noncircular lobed journal bearings. Effects of micropolarity of the lubricant as well as noncircularity parameter (preload) of the bearings are investigated. Comparing the GDQ method results with the results of FDM/FEM, good agreement between them is observed. The results also show that though the micropolarity of the lubricants improves the performance of the bearings, however, the rate of enhancement is affected by noncircularity of the bearings. [ABSTRACT FROM AUTHOR]

This paper investigates the variation of nonlinear stiffness and damping coefficients in a journal orbit with respect to equilibrium position. The journal orbit is obtained by the combined solution of equations of motion and Reynolds equation. In the linearized dynamic analysis, dynamic pressure is written as a perturbation of static pressure and pressure gradients at equilibrium position. However, in order to obtain nonlinear dynamic coefficients about equilibrium position, the dynamic pressure gradients in the orbit are also written as the first order perturbation of static pressure gradients and higher order pressure gradients for displacement and velocity perturbations. The dynamic coefficients are functions of bearing displacement and velocity perturbations. The higher order pressure gradients at equilibrium position are evaluated at various eccentricity ratios and L/D ratios of 0.5 and 1.0. The variation of nonlinear dynamic coefficients is analyzed for three Sommerfeld numbers of a two-axial groove journal bearing under the action of an external synchronous load along and perpendicular to the radial journal load. Results indicate that the oil film nonlinearities affect the journal motion at lower eccentricity ratios (higher Sommerfeld numbers) with wide variation in stiffness and damping coefficients. [ABSTRACT FROM AUTHOR]

The purpose of the present paper is to investigate the effects of design parameters on the noise produced by rotor-bearing systems supported by oil lubricated journal bearings. To do this, the effects of radial clearance and the width of the bearing, lubricant viscosity, and mass eccentricity of the rotor on the noise of the bearing are investigated, and the numerical results are presented through the graph of the A-weighted sound pressure level of the bearing for various rotational speeds of the rotor. The results show that the A-weighted sound pressure level of the bearing is markedly influenced by the mass eccentricity of the rotor and the radial clearance and the width of the bearing. High viscosity of the lubricant slightly decreases the noise of the bearing, but its effect is relatively low at high speed. The results of the paper could aid in the design of low-noise rotor-bearing systems supported by oil lubricated journal bearings. [Copyright &y& Elsevier]

• A semi-analytical solution of the Reynolds equation for hydrodynamic journal bearings is derived. • The solution is based on the scaled boundary finite element method (SBFEM). • The SBFEM solution is numerically efficient for bearings with large slenderness ratios. • For simplified oil supply pressure boundary conditions, the numerical effort is further reduced. [Display omitted] The behavior of rotor systems with hydrodynamic bearings can be affected crucially by the nonlinear bearing forces. These forces are incorporated in rotordynamic simulations by solving the Reynolds equation in every step of a time integration scheme. Since closed-form analytical solutions of the Reynolds equation are known only for simplified boundary conditions, numerical methods and look-up table approaches are applied. To obtain accurate and convergent results, numerical solutions require a fine discretization, while the look-up tables require a fine grid of interpolation points. In both cases, the numerical effort of the rotordynamic simulation is dominated by the computation of the bearing forces. In this study, a semi-analytical solution of the Reynolds equation based on the Scaled Boundary Finite Element Method (SBFEM) is developed to reduce the numerical effort of the overall simulation. In contrast to a purely numerical solution, the two-dimensional pressure field is discretized in only one coordinate direction, whereas in the other direction, an analytical formulation is used. This results in a system of non-homogeneous ordinary differential equations, which is solved under consideration of the boundary conditions. Since the complexity of the SBFEM model and the resulting numerical effort depend on the modeling of the oil supply groove, three different models are analyzed in this paper. The equations are derived, the solutions are verified, and their numerical efficiency is investigated in comparison to an FEM solution, which is one of the standard numerical approaches. [ABSTRACT FROM AUTHOR]

• This work presents a model for a vertical rotor mounted on hydrodynamic bearing. • Model is validated comparing to available experimental studies in the literature model is validated comparing to available experimental studies in the literature. • Model predicts the behavior of an actual industrial case with irregular pad clearance. • The model developed in this work correctly describes the dynamic behavior of a vertical axis hydrogenerator. In hydropower generating plants the reliable operation of the hydropower unit (hydraulic turbine and generator) is a critical issue. Unexpected failure of the hydropower unit lead to high economic costs. A dynamic model of this type of machine is useful for condition monitoring which allows to detect failures in an early stage without the need to stop the machine. Most hydropower units over 20 MW of power has a vertical rotor and are mounted on hydrodynamic journal bearings. In vertical rotors, the load on the bearings is mainly rotatory and to provide stability tilting-pad journal bearings are used. An accurate dynamic model of hydropower unit must consider vertical tilting-pad journal bearings. The present study proposes a dynamic model of hydropower unit that considers the geometrical characteristics of vertical rotor and the behavior of the vertical tilting-pad journal bearing. The dynamic model is validated in two studies found in literature showing good agreement with published data (laboratory vertical rotor and actual hydropower unit). Then, the dynamic model is used to simulate an actual hydropower unit that was operating with an irregular pad clearance. Dynamic model was able to adequately predict waveform, orbits and spectrums of hydropower unit during operation at different power, startup, and during shutdown. It is concluded that dynamic model correctly predicts the failure in the pad clearance. [ABSTRACT FROM AUTHOR]

Nanofluids have extensive applications in hydrodynamic journal bearings used in heavy industry machinery. Inorganic fullerene-like tungsten disulfide nanoparticles (IF-WS2 NPs) are the most common additive for lubrication purpose due to their excellent mechanical characteristics along with their effect on reducing friction and wear. In this work, a computational simulation approach with discrete phase modeling (DPM) of suspended nanoparticles was used to evaluate the application of the IF-WS2 nanofluid lubricant on load carrying capacity of high-load journal bearings where the normal loads are high, considering the bearing dimensions. For accurate simulation, nanofluid viscosity was calculated considering the aggregation effect of NPs by using scanning electron microscopy (SEM) imaging of the nanofluids. A benchmark study was first performed to assess the model accuracy. Hydrodynamic lubrication was simulated under different nanofluid weigh fractions. The simulated pressure distribution was then employed to determine the load capacity of the bearing. The results show an approximately 20% improvement of load carrying capacity at 5% weight fraction of WS2-oil nanofluid. [ABSTRACT FROM AUTHOR]

• A numerical model was developed to simulate the vibration response of hydrodynamic journal bearings with ovalization faults with different severities. • The datasets were augmented to create larger datasets. • A convolutional neural network algorithm was trained to predict ovalization faults on journal bearings. • The fault identification performance was evaluated statistically. • The results demonstrate the feasibility of future applications of deep learning algorithms trained with simulated data. Bearings play a crucial role in machine longevity and is, at the same time, one of the most critical sources of failure in rotor dynamics. Particularly for journal bearings, it is not completely understood how specific damages may influence the response of the rotating system. Consequently, the identification of hydrodynamic bearing faults is challenging. Most of the literature relies on large amounts of training data collections from physical experiments or from the field, which are high in cost. This paper offers a deep learning approach to identify ovalization faults aiming to develop condition monitoring model-based strategies applied to hydrodynamic journal bearings. Therefore, a numerical model was developed to simulate the ovalization fault conditions in order to build training datasets. Afterwards, a deep convolutional neural network algorithm was trained with the generated datasets and used to predict the faults conditions. Finally, the identification performance was evaluated statistically regarding the true-positive identification by both probability density function and subjective logic. The classification accuracy showed promising results for training the machine learning algorithms with simulated data. [ABSTRACT FROM AUTHOR]

The aim of this paper is to derive an equation for the temperature distribution in journal bearing oil film, in order to predict the thermal load of a bearing. This is very important for the prevention of critical regimes in a bearing operation. To achieve the goal, a partial differential equation of the temperature field was first derived, starting from the energy equation coupled with the Reynolds equation of hydrodynamic lubrication for a short bearing of symmetric geometry. Then, by solving the equation analytically, the function of temperature distribution in the bearing oil film has been obtained. The solution is applied to the journal bearing, for which the experimental data are available in the references. Finally, the obtained results have been compared to the corresponding experimental values for two operating regimes, and a good level of agreement was achieved. [ABSTRACT FROM AUTHOR]

• A new FE model is proposed to assess the role of support motions in on-board rotordynamics. • This model is based on the Timoshenko beam theory and six DOFs. • A parametric influence is generated by the rotations and the translations of the support. • This influence creates single-frequency and multi-frequency parametric excitations. • The dynamic stability of the rotor is evaluated through the Floquet theory. In the transportation domain such as automotive turbochargers and aircraft turbines, the vibrations of on-board rotors are induced not only by the mass unbalance excitation but also by various movements of their support. The dynamics of an on-board rotor mounted on hydrodynamic finite-length bearings is investigated in the presence of support motions which create multi-frequency parametric excitations. The developed on-board rotor model is based on the gyroscopic Timoshenko beam finite element with two nodes and six degrees of freedom per node for 3D motions (transverse and axial displacements as well as rotations due to the bending and to the torsion). The equations of motion highlight time-varying parametric terms due to the mass unbalance, the support rotations, the coupling between both phenomena and the combination of mass unbalance and support translations. These parametric terms can yield a dynamic instability because they contribute as generators of internal excitation. In the presented applications, single-frequency and multi-frequency parametric excitations are used. Namely, the rotor is excited either by simple and combined sinusoidal support rotations or by a rotating mass unbalance combined with sinusoidal support translations to examine the stability of the static equilibrium point through the Floquet theory. [ABSTRACT FROM AUTHOR]