Journal Bearings

In current era machineries in modern industries are operated a high speed and subjected to various static and dynamic loads. Apart from this journal bearing journal bearing are also used rural area in form of machines used for irrigation purpose, in Agricultural Machines like Tractors, irrigation Pumps, Harvester, etc. In such application hydrodynamic journal bearings are employed. When bearing subjected to critical loads heat is generated due to presence of friction which alters the lubricating film which ultimately affects the performance characteristic of bearing and the rise in temperature lower the viscosity of the bearing lubricant. In order to analyze performance characteristic of thin film lubrication thermo hydrodynamic analysis should be carried out by the means of three dimensional computational fluid dynamics analysis. The Navier Stokes compressible equations for 3D model were adopted to simulate the flow. The simulation is been carried out by using GAMBIT software in which the bearing is simulated a different boundary condition and parametric analysis has been carried to in order to validate the obtained results shows good agreement with the compared results and are within acceptable limits.

A turbocharger is a relatively simple, but very precisely made component working in conditions, which should be considered hard. Due to hard working conditions, among others: high exhaust temperatures, very high rotational speeds reaching up to 250 000 rpm, precise design and difficult assembly, turbochargers should be considered particularly subject to damage and failure. It is confirmed by data showing an increasing number of failures of such components, which is caused, among others, by the increasing number of vehicles equipped with turbochargers. The considerable cost of a new turbocharger and its relatively easy disassembly coupled with easy access to spare parts in Poland result in establishing of ever more new companies remanufacturing this type of device. The effectiveness of repairs carried out in such plants varies strongly, often being of poor quality due to lack of knowledge, both practical and theoretical, inadequate training of personnel, and many other factors. A com...

We discuss ongoing work on the addition of a statically condensable bubble enrichment to capture kinks (surfaces where the function is continuous but its gradient exhibits a jump) in the velocity field at immersed interfaces not conforming with the element boundaries. Such kinks are frequent in multi-fluid flows because they arise whenever there are viscosity jumps or thermo-capillary effects. The enrichment is applied only at those elements of the finite element mesh cut by the interface, which is parameterized in this case with a level set function. The bubble function used in this work was introduced elsewhere (see Codina and Coppola-Owen, Int. J. Num. Meth. in Fluids 2005; 49:1287-1304) to capture discontinuities in the pressure gradient for two-phase flows, which arise because of density discontinuities under gravity. Its applicability as enrichment of the velocity field is not obvious due to a consistency error it creates in the variational formulation (the enrichment velocity fields are not in H 1 (Ω), since they are discontinuous at some inter-element boundaries). In this work we assess the accuracy, robustness and limitations of this new enrichment in some problems involving interfaces. In its current form, the non-conformity of the bubbles introduces an unphysical numerical error which is of the same order as the interpolation error the bubbles are there to alleviate. Notice that these same bubble functions, when used for the pressure, do not lead to consistency error because they do belong to L 2 (Ω).

An experimental assessment of the influence of lubricant feed temperature (T f ) on the behaviour of twin groove hydrodynamic journal bearings has been undertaken. Several loads, shaft speeds and bearing geometries were tested under constant lubricant feed pressure (p f ), while T f took four different values between 29°C and 58°C. It was found that the increase of T f has an effect in bearing performance which is analogous in many ways to the effect of the increase in eccentricity: increase in lubricant flow rate (especially in the low eccentricity range), in outlet temperature (Tout) and in maximum bush temperature (Tmax). Nevertheless, the latter increase was lower than the corresponding increase in T f . Also, in the high eccentricity range the increase in flow rate due to the increase of T f could be deceiving in the sense that the additional flow was supplied mainly to the inactive region of the bearing (the unloaded land of the bearing).

Herringbone thrust bearings (HTB) are widely used for their high load capacity, low friction, and good stability, making them ideal for various applications like turbomachinery applications and automotive engines. In this research, the effect of changing the groove depth, which affects the thickness of the fluid film, was studied on the dynamic coefficients of the HTB up to the second order. This investigation is really important in studying the dynamic behavior of the rotor-bearing system. The Reynolds equation was solved to obtain the performance parameters for the HTB. Then, the infinitesimal perturbation method was used to obtain the perturbed Reynolds equations up to the second order. The Finite Difference Method (FDM) was used with the Successive-Over Relaxation (SOR) technique to obtain the stiffness and damping coefficients of the HBT. The variation of the first the second order bearing coefficient with the change in groove depth was studied. The results showed that with increasing groove depth, there is a decrease in the dynamic coefficients of the herringbone thrust bearings. These results can be further used in studying the dynamics of rotor-bearing system for machines operating at high speeds.

Hydrodynamic journal bearings are widely used due to their high load carrying capacity and good damping properties. Journal bearings have been widely used in rotating machinery. The bearing carries higher loads which reduce s film thickne ss and al so increa se temperature of bearing due to fluid film temperature increment. The pressure distribution i s important in both load capacity e stimations (static performance) and dynamic analysi s. We can analyze the pressure of fluid film and total deformation of hydrodynamic journal bearing by Fluid Structure Interaction technique. This paper describes FSI technique with optimization.

Abstract In this paper, numerical and experimental analyses
of external curling of thin-walled round tubes are presented.
An elasto-plastic finite element model was used for simulating
the process over a conical die with fillet. A commercial tube of
copper with a thickness of 0.7 mm was selected for this work.
The friction present at the contact interfaces between the tube
and the die during curling operation is examined to suggest a
success of the forming mode of deformation. The investigation
is focused mainly on understanding the modes of deformation
which may encounter during the axial compression
until achieving the double-walled tube to establish the forming
kinematics and the typical deformed shape at each mode. The
numerical results show that the whole process went through
eight forming stages and demonstrate accuracy of the final
deformed shape for each of them. The experimental results
confirmed that compared with the finite element simulations,
the current model provides an accurate prediction on the
forming kinematics and the deformed shape.

ARTICLE INFO Turbochargers typically comprise a body in three parts; the turbine and compressor housings and the bearing housing. The reliability and characteristics of systems depend on the different properties of the joint. The preferred method of joining these three parts, is to use a band clamp with a flat bottomed V-shaped cross section mating with appropriate flanges on the body sections. This method of clamping allows for rapid assembly and infinitely variable relative rotational orientation of parts. V-Band clamp is considered as the critical joint. Leakage being the major environmental issue due to V clamp loosening is the common failure and the mechanism of the failure is the load applied in the transverse and rotational directions causes self-loosening FEA parameters have significant impact on the results hence appropriate modelling of the joint is essential for predicting the behaviour of the systems very accurately and efficiently. Hence this work is initiated to develo...

The journal bearing is a complex system with high film convergence and with cavitation hydrodynamic phenomena. The surface texturation influence study on journal bearing performances requires unavoidably experimental investigations followed by a numerical modelling of the problem. This work consists in modellization and understanding of the journal bearing characteristics in both cases of presence or absence of textures onto the bearing surface. The finite difference method is used as numerical approach in the analysis. The textured bearing performance enhancement passes essentially by an improvement of a minimum film thickness, a maximum pressure and a friction torque through an appropriate surface texture geometry and appropriate texture distribution on the contact surface. It is found that the simulations results are in good concordance with litteratures. The texture area position on the bearing surface is the primary endpoint for journal bearing performance enhancement. The best design of textured area depends strongly on the geometrical parameters and the journal bearing operating conditions.

This paper evaluates how tilting pad bearings can affect the forced response of a vertical rotor. The stiffness and damping for a tilting pad bearing is dependent on the position in the bearing (load on pad or load between pad) and the magnitude of the load. In a vertical machine the position of the shaft in the bearing will change for each time-step and produce a periodic stiffness and damping. This periodic stiffness has shown to produce higher frequency components depending on the number of pads. For the four pad bearing considered in this paper these frequency components are 3Ω and 5Ω in the stationary coordinate system. The aim of this study is to evaluate if the periodic coefficients in the bearing could excite the system and cause resonance problems. It is found that for high loads the system can be excited due to the bearing dynamics at Ω/ω n = 0.33 and Ω/ω n = 0.2. However at low loads this effect is negligible.

The paper discusses the results of testing a prototype of the active vibration control of radial sliding bearings with the use of piezoactuators. The main aim of active control is to prevent instability due to the oil film and thus to extend the operating speed range of a bearing journal. The effect of the controller gain and the amplitude of the parametric excitation on the operating speed range will be demonstrated by experiments.

Linear models and synchronous response are generally adequate to describe and analyze rotors supported by hydrodynamic bearings. Hence, stiffness and damping coefficients can provide a good model for a wide range of situations. However, in some cases, this approach does not suffice to describe the dynamic behavior of the rotor-bearing system. Moreover, unstable motion occurs due to precessional orbits in the rotor-bearing system. This instability is called ''oil whirl'' or ''oil whip''. The oil whirl phenomenon occurs when the journal bearings are lightly loaded and the shaft is whirling at a frequency close to one-half of rotor angular speed. When the angular speed of the rotor reaches approximately twice the natural frequency (first critical speed), the oil whip phenomenon occurs and remains even if the rotor angular speed increases. Its frequency and vibration mode correspond to the first critical speed. The main purpose of this paper is to validate a complete nonlinear solution to simulate the fluid-induced instability during run-up and rundown. A flexible rotor with a central disk under unbalanced excitation is modeled. A nonlinear hydrodynamic model is considered for short bearing and laminar flow. The effects of unbalance, journal-bearing parameters and rotor arrangement (vertical or horizontal) on the instability threshold are verified. The model simulations are compared with measurements at a real vertical power plant and a horizontal test rig.

A material property which is often used in the comparison and selection of polymer based materials used for dry rubbing journal bearings is the limiting pressure-velocity (LPV) value. In this paper the thermal network method (TNM) is used to model an LPV test-rig and the results of this model are verified with some experiments.

A finite-element approach to thermoelastohydrodynamic lubrication analysis is developed by extending a previous mass-and energy-conserving algorithm to include wall-convection boundary conditions, groove-mixing theory, and thermo-mechanical deformations. To this end, the cross-film-averaged energy equation is coupled with the heat conduction equations relevant to the bearing sleeve and the journal by fitting the temperature profile across the film thickness with a fourth-order polynomial. A finite-element condensation technique is used to reduce the unknowns in heat conduction equations in the bush and in the journal to the temperatures of the sleeve surface and journal axis, respectively. Applied to the analysis of steadily loaded journal bearings, the proposed method shows good agreement with published experimental results and incurs low computational cost.

In this paper, we analyze the impact of the cavitation model on the numerical assessment of lubricated journal bearings. We compare results using the classical Reynolds model and the so-called p-θ model proposed by Elrod and Adams [1974, “A Computer Program for Cavitation and Saturation Problems,” Proceedings of the First LEEDS-LYON Symposium on Cavitation and Related Phenomena in Lubrication, Leeds, UK] to fix the lack of mass conservation of Reynolds’ model. Both models are known to give quite similar predictions of load-carrying capacity and friction torque in nonstarved conditions, making Reynolds’ model the preferred model for its better numerical behavior. Here, we report on numerical comparisons of both models in the presence of microtextured bearing surfaces. We show that in the microtextured situation, Reynolds’ model largely underestimates the cavitated area, leading to inaccuracies in the estimation of several variables, such as the friction torque. This dictates that onl...

In this paper, a theoretical study of the combined effects of viscosity variation and surface roughness on the squeeze film performance of journal bearings lubricated with micropolar fluid is made. The modified averaged Reynolds equation for micropolar fluids accounting for the randomized surface roughness structure and variation of viscosity is mathematically derived. The Christensen's stochastic theory for hydrodynamic lubrication of rough surfaces is used to study the effect of two types of one dimensional surface roughness patterns on the squeeze film characteristics of a journal bearing with micropolar fluid. Closed form expressions for the mean pressure load carrying capacity are obtained for the infinitely short journal bearing. It is observed that, the transverse surface roughness pattern improves the squeeze film characteristics where as the adverse effects are observed for the one-dimensional longitudinal surface roughness pattern. The effect of variation of viscosity in micropolar fluid on the squeeze film characteristic of rough short journal bearings is analyzed.

A centrifugal compressor known as a turbocharger is powered by a turbine powered by exhaust fumes from moving vehicles. Usually used in internal combustion engines to increase the air pressure entering the engine and increase engine efficiency. The main benefit of turbochargers is that they provide a significant increase in engine power for just a little extra weight. The research was carried out by direct observation and then recorded the damage that occurred. The results show that damage to the turbocharger includes damage to rotation, damage to the bearings and damage as a result of the main engine. To avoid damage, adequate maintenance is needed so that ship components will last longer.

The paper discusses the results of testing a prototype of the active vibration control of radial sliding bearings with the use of piezoactuators. The main aim of active control is to prevent instability due to the oil film and thus to extend the operating speed range of a bearing journal. The effect of the controller gain and the amplitude of the parametric excitation on the operating speed range will be demonstrated by experiments.

In this paper, the squeeze film behaviour of curved circular plates using micropolar .fluid as lubricant has been investigated theoretically. The pressure, load and the time of approach derived for the squeeze formed form the generalized Reynolds's equation. The Numerical solution obtained for the performance of circular plates such as pressure, load and approaching time for distinct values of curvatures parameters for lower and upper plates , coupling number and couplestress parameter. The pressure ,load and approaching time increase when curvatures parameters for upper plates , coupling number and couplestress parameter lead to increase , but these characteristic of bearing are observed to decrease as curvature parameter for lower plate decrease.

In this paper, the squeeze film behaviour of curved circular plates using micropolar .fluid as lubricant has been investigated theoretically. The pressure, load and the time of approach derived for the squeeze formed form the generalized Reynolds's equation. The Numerical solution obtained for the performance of circular plates such as pressure, load and approaching time for distinct values of curvatures parameters for lower and upper plates , coupling number and couplestress parameter. The pressure ,load and approaching time increase when curvatures parameters for upper plates , coupling number and couplestress parameter lead to increase , but these characteristic of bearing are observed to decrease as curvature parameter for lower plate decrease.

Misalignment is one of the most common challenges that the normal operation of journal bearings faces. This type of problem may be the result of a wide range of reasons, such as bearing wear, shaft deformation, and errors related to the manufacturing and installation process. The main undesirable consequences of the misalignment, such as pressure rise and lubricant film reduction, are concentrated on the bearing edges. Therefore, chamfering the bearing edges reduces such misalignment-related drawbacks. This work presents a novel numerical solution to the problem of finite-length journal bearing considering edge chamfering. This solution involves the determination of the levels of lubricant layer thickness and pressure distribution in addition to the journal trajectory under impact load with the related stability limits. The finite difference method is used in this solution, and the equations of motion are also solved numerically using the Runge–Kutta method. The Results of this nove...

Grease life in hybrid bearings is longer than that in all-steel bearings. This will be shown in this paper by means of grease life tests with a large number of greases for both Deep Groove Ball Bearings (DGBB) and Cylindrical Roller bearings (CRB). The results show that grease life for hybrid bearings is always larger than that for equivalent all-steel bearings and that this varies between a factor 2 and 9 depending on the grease type that is used. For cylindrical roller bearings grease life does not increase with decreasing speed below a minimum value. However, also at these relatively low speeds, hybrid bearings give a longer grease life than all-steel bearings.

Grease life in hybrid bearings is longer than that in all-steel bearings. This will be shown in this paper by means of grease life tests with a large number of greases for both Deep Groove Ball Bearings (DGBB) and Cylindrical Roller bearings (CRB). The results show that grease life for hybrid bearings is always larger than that for equivalent all-steel bearings and that this varies between a factor 2 and 9 depending on the grease type that is used. For cylindrical roller bearings grease life does not increase with decreasing speed below a minimum value. However, also at these relatively low speeds, hybrid bearings give a longer grease life than all-steel bearings.

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Highlights • Bearing's cavitation effects can affect the rotor dynamic response. • Stability threshold is changed due to bearing cavitation effects. • Cavitation effects has low influence in normal operational conditions.

Understanding the influence of surface texturation on journal bearing performances inevitably involves experimental investigations pending being followed by a numerical modeling of the problem. This work consists to model and to understand the evolution of journal bearing characteristics with and without presence of textures on the bearing surface. The numerical approach based on the finite difference method is used in this analysis. Improving performance of textured bearing with spherical dimples suggest that contact characteristics such as minimum film thickness, maximum pressure, and friction torque may be improved through an appropriate surface texture geometry and appropriate texture distribution on the contact surface. The results of our simulations are in good agreement with those obtained experimentally [1].

Robust and well-designed rotor-bearing systems ensure safe operation and a high level of reliability under severe operating conditions. A deviation in the shaft axis with respect to the bearing longitudinal axis represents one of the most unavoidable problems in bearing systems. This deviation results from installation errors, manufacturing errors, shaft deformation under heavy loads, bearing wear, and many other causes. Each of these deviation sources has its negative consequences on the designed characteristics of the system. This work deals with the geometrical design of a journal bearing using three forms of profiles (linear (n=1), quadratic n=2 and cubic (n=3) profiles) in order to enhance bearing performance despite the presence of the inevitable shaft deviation. In addition, a wide range of bearing profile parameters are considered in the analysis to optimize the bearing profile based on the use of the Taguchi method. A general form of shaft deviation is considered to account...

Robust and well-designed rotor-bearing systems ensure safe operation and a high level of reliability under severe operating conditions. A deviation in the shaft axis with respect to the bearing longitudinal axis represents one of the most unavoidable problems in bearing systems. This deviation results from installation errors, manufacturing errors, shaft deformation under heavy loads, bearing wear, and many other causes. Each of these deviation sources has its negative consequences on the designed characteristics of the system. This work deals with the geometrical design of a journal bearing using three forms of profiles (linear (n=1), quadratic n=2 and cubic (n=3) profiles) in order to enhance bearing performance despite the presence of the inevitable shaft deviation. In addition, a wide range of bearing profile parameters are considered in the analysis to optimize the bearing profile based on the use of the Taguchi method. A general form of shaft deviation is considered to account...

The transmissibility characteristics of short porous journal bearings have been analytically investigated. For horizontally-mounted rotors, it has been shown that porous bearings are better than solid bearings for attenuating unbalance forces when the aij/ug ratio is approximately 1.5 or above. For ratios of uij/oig of approximately one or less, solid bearings have slightly better transmissibility characteristics than porous bearings. For vertically-mounted rotors and for the range of parameters considered, porous bearings are superior to solid bearings for attenuating unbalance forces assuming that both bearings are operating under the same conditions. In addition, porous bearings seem to eliminate the jump phenomenon which is sometimes associated with solid bearings. The rotor-bearing model used to obtain the results presented in this paper is relatively simple. The main purpose of this paper was to present data which would show general transmissibility trends of porous bearings and to compare those trends with those of a similar model using solid bearings. Continuing studies which include shaft flexibility and compressible lubricants are left for future work.

Journal hydrodynamic bearings are used for their high radial load capacity and operation at high speeds. The only disadvantage is the excitation of vibrations, called an oil whirl, after crossing a threshold of the rotational speed. The whirl can be suppressed using the controlled motion of the non-rotating loose bushing which is actuated by piezo-actuators. The displacement of the piezo-actuators is governed by a feedback which reduces the difference between the required and true position of the bearing journal. This new bearing design enables not only to increase the threshold of instability but also serves to maintain the desired bearing journal position with the accuracy of micrometers. The article deals with the design of an actively controlled bearing with special regard to the installation of piezoelectrometers. Part of the article is also a description of the influence of active vibration control on bearing performance characteristics and bearing friction losses.

Misalignment is one of the most common challenges that the normal operation of journal bearings faces. This type of problem may be the result of a wide range of reasons, such as bearing wear, shaft deformation, and errors related to the manufacturing and installation process. The main undesirable consequences of the misalignment, such as pressure rise and lubricant film reduction, are concentrated on the bearing edges. Therefore, chamfering the bearing edges reduces such misalignment-related drawbacks. This work presents a novel numerical solution to the problem of finite-length journal bearing considering edge chamfering. This solution involves the determination of the levels of lubricant layer thickness and pressure distribution in addition to the journal trajectory under impact load with the related stability limits. The finite difference method is used in this solution, and the equations of motion are also solved numerically using the Runge–Kutta method. The Results of this nove...

Many turbo-machines such as turbines and compressors generate axial and radial load during their operation. Conical hydrodynamic journal bearing is proposed to sustain radial load and adjust the effect of axial load on rotating elements. The present study has proposed the performance analysis for conical hydrodynamic journal bearing of semi-cone angles (c = 5°, 10°, 20°, 30°) for a wide range of radial load (W r ¼ 0:1 À 0:9) on rotating journal. Finite element method has been used to solve the modified Reynolds equation for investigating the flow of lubricant in the clearance space between journal and bearing. Performance characteristics such as load-carrying capacity, fluid film thickness, stiffness coefficients, damping coefficients and threshold speed for various configurations of conical hydrodynamic journal bearing have been presented and discussed. Results show that threshold speed (x th) of conical journal bearing is considerably reduced as the semi-cone angle increases to c = 30°as compared to the base bearing of semi-cone angle c = 5°. Keywords Conical journal bearing Á Hydrodynamic lubrication Á Aspect ratio Á FEA List of symbols C ij Damping coefficient (i, j = 1,2) (Ns/m) c r Radial clearance (lm) c r =R j Clearance ratio D Mean bearing diameter (mm) d Mean journal diameter (mm)

This paper describes the phenomenon of negative flow rate (hot oil reflux) occurring in one of the grooves of twin axial groove hydrodynamic journal bearings. This rarely described phenomenon, which can occur under severe operating conditions, increases the risk of bearing seizure. Existing codes for predicting bearing behaviour do not seem to be suitably incorporating this phenomenon into the analysis. The present work reports some experimental observations of the phenomenon and the way it can be taken into account in theoretical modelling.

The contact between dissimilar materials occurs in many machine elements where one of the contacting parts is manufactured from low modulus materials such as lip seals, o-rings, and metal on polymer prosthetic hip joints. Contacts of this sort of are often operated in the iso-viscous elastohydrodynamic lubrication (I-EHL) regime. Typically, they have been studied using a numerical approach due to lack of sensor of instrumentation for measuring oil film thickness. By developing the technology of sensors such as electromagnetic radiation and magnetic resistance techniques, the phenomenon of lubrication in I-EHL regime has shown results which are better understood. However, the experimental study that has been conducted to date is only appropriate for laboratory-based measurements. This thesis deals with the ultrasonic reflection methods to measure an oil film thickness and contact between dissimilar materials where these methods could be applied in-situ. This warrants special attention because there are two drawbacks of measuring of oil film thickness and contact by using bulk longitudinal wave between dissimilar materials (such as rubber and steel) which have mismatched acoustic impedance. One is the attenuation. The ultrasonic signal will be reduced when passed through the rubber. The other is accessibility. The wave must pass normally through the interface and so the transducer must be mounted on the rubber itself. 5 6. Chapter 6 shows the second experimental work to measure the oil film thickness in the iso-viscous elastohydrodynamic lubrication (I-EHL) regimes. The contact between Perspex disk and a nitrile ball is studied. 7. Chapter 7 presents the third experimental work in measuring contact between soft and hard materials by using Rayleigh waves. A method of ultrasonic reflection is proposed. 8. The last chapter summaries the work done in this study and the future work is also explained. Recommendations are given for future research. Chapter 2 Literature review This chapter presents a literature review to measure oil film thickness in I-EHL regime by numerical and experimental approaches. In the following sections, the comparison between experimental and numerical results for central film thickness is also described. The measurement of contact mechanics using ultrasound is discussed at the end of this chapter.

The hydrodynamic coefficients of a journal bearing set with the bearing subjected to axial oscillation are determined in this work. The Navier‐Stokes equations were used to account for the axial component of the relative motion between the journal and the bearing. Numerical solution of the Navier‐Stokes equations yielded the pressure distribution within the cavity of the bearing. This pressure distribution was then integrated over the surface of the bearing to obtain the two orthogonal force components. The derivatives of these force components were then taken with respect to the displacement and velocity of the journal that are co‐linear with these forces. This yielded the hydrodynamic coefficients. v To conduct a parametric study, the bearing design parameters were chosen such that the Sommerfeld number was equal to one. The axial oscillation of the bearing was modeled as a purely sinusoidal motion, with an amplitude of one millimeter and a frequency range of 0‐304 rads/s. This st...

This work proposes a novel approach to analyze the stability characteristics for the dynamic coefficients of a herringbonegrooved journal bearing. Based on the perturbation method at the equilibrium position of a journal bearing, this study expresses the variation of critical mass as the derivation of eight dynamic coefficients: four stiffness and four damping coefficients. Since the relationship between the critical mass and the eight dynamic coefficients is very complicated, it is difficult to judge the influence in previous studies of an individual dynamic coefficient on stability. The method presented in this paper can investigate quantitatively which dynamic coefficients dominate stability. The results show that the coefficients K xx and K yx increase and improve the stability as the eccentricity ratio increases. As the groove geometry changes, the coefficients governing stability depend on the parameters of groove geometry: groove depth, groove width, and groove angle. When the groove angle changes, variations in K xy always exert negative influences on stability. When the groove depth or the groove width increases, the change in D yy exerts a significant negative influence on stability. With an increase in the groove angle or groove pattern, the negative effect of D yy on the bearing decreases. Accordingly, the influence of variations in the groove depth is similar to that of variations in the groove width.

In order to obtain rotating machinery with improved energy efficiency, the approach of surface texturing journal bearings has been adopted to reduce the viscous dissipation in the lubricant. A possible reduction in shear viscous forces in the bearings of rotating machines could reduce the amount of heat released along its operation, resulting in a lower operating temperature that tends to improve journal bearings performance and the machine’s energetic efficiency. Thus, this work aims to investigate the texturing of journal bearings under dynamic loading conditions, considering the application in rotating systems. For this, computational simulations are performed through a rotating system model constructed by means of the finite element method in which the hydrodynamic journal bearings that support the rotor are modeled by Reynolds’ equation using the finite volume method and the full multigrid technique. The numerical results show that textured journal bearings can be applied to ro...

In the present study, a numerical investigation on the effect of different manufacturing errors on the performance of a parallel thrust bearing is reported. The calculations have been performed utilising a CFD-based TEHD computational approach. An initial investigation of the pressure build-up mechanism in parallel thrust bearings concluded that the two main reasons of load carrying capacity of parallel thrust bearings are (a) the thermal deformation of the pad upper surface and (b) the initial (non-deformed) “quasi-parallel” pad upper surface, being an outcome of the manufacturing process. The present work investigates the importance of the initial geometry of a “quasi-parallel” thrust bearing, and indicates manufacturing tolerance thresholds, below which, the defects of the pad-fluid interface are not the major factor of pressure generation in the lubricant domain of the bearings. Keywords– Manufacturing Errors, Thermal deformations, TEHD regime, CFD, Parallel thrust bearings.

In this paper, a computational investigation of thermohydrodynamic performance and mechanical deformations of a fixed-geometry thrust bearing with artificial surface texturing is presented. A parallel eight-pad bearing is considered; the surface of each pad is partially textured with square dimples. Here, a CFD-based thermohydrodynamic modeling approach, recently introduced by the authors, is used to calculate the performance of the bearing; the THD results are then used to quantify the deformations of the bearing mechanical parts. The bearing is modelled as a sector-shaped channel, consisting of a smooth rotating wall (thrust collar) and a partially textured stationary wall (bearing pad). The bearing performance characteristics are computed by means of numerical simulations, based on the numerical solution of the Navier-Stokes and energy equations for incompressible flow, as well as on the solution of the elasticity equations for the bearing solid parts. Here, a reference texture geometry is considered, while proper thermal and structural boundary conditions are implemented. For representative film thickness values, the effect of rotational speed and collar thickness on bearing performance is quantified, and the resulting pad and rotor deformation fields are computed. It is found that, due to oil heating, the load carrying capacity decreases with rotational speed for values higher that approximately 2000 rpm. The computed rotor deformation field is representative of a fixed support beam, characterized by substantially higher levels than those of the bearing pad. Rotor deformations increase substantially at low values of collar thickness.

Humans are the most intelligent species on the earth and are very health conscious. The evolution of recent technologies like data science and machine learning has opened the trail for healthcare communities and medical establishments, to observe the diseases earliest as potential and it helps to supply higher patient care. For many medical organizations, disease prediction is very important for making the best possible healthcare decisions. Machine Learning is a field where we can develop a model to learn machines to make decisions on their own from real-time data and from past experience. We proposed a model to predict disease from some symptoms. So, in this experiment, we propose a new knowledge-based system for disease prediction using KNN, SVM, NB, DT, RF, and LR for data modeling and we got maximum 98.36 percent accuracy from the KNN algorithm. This paper is planned to develop multi-disease prediction using the machine learning concept. Our main contribution is to implement feature engineering and standard scaling to optimize our algorithm and better performance. The decision proposed support system for disease diagnosis might be implemented using the suggested methodology, aiding doctors in their work and enhancing patient outcomes. So, future studies will concentrate on increasing the dataset to cover a wider range of patient demographics and improving the machine learning algorithms to better prediction accuracy.