Elliptical Journal Bearings Research Articles

Computational fluid dynamics study to investigate the performance of fluid film journal bearings with different geometries

The geometry of a hydrodynamic journal bearing plays a vital role in the rotating machinery. In this work, the performance characteristics of the plain and elliptical journal bearings are carried using Computational Fluid Dynamics (CFD) approach. An alternative approach to thermo-hydrodynamic analysis is presented assuming that all the heat that is generated by viscous shear in the fluid film is dissipated only in the fluid (no heat conduction through the boundaries). The effect of lubricant viscosity and bearing geometry on the pressure distribution is presented. The analysis is done for a wide range of speed (500–1000 rpm.) and lubricant viscosity at 1000 N load. In this paper, the theoretical results obtained are validated by computational methodology. The pressure distribution in the elliptical bearing is highly increased as compared to the plain bearing. The percentage increase upto 370.44 % is observed in the elliptical bearing. The Computational Fluid Dynamics (CFD) method can be very useful tool for study on the bearing lubrication problem and can accurately predict the performance characteristics of hydrodynamic journal bearing.

Analiza performansi eliptičnog ležaja podmazanog eksperimentalno karakterizovanim nano-mazivom s obzirom na toplotni efekat korišćenjem CFD tehnike

This study uses computational fluid dynamics (CFD) to quantitatively examine the performance of an elliptical journal bearing (EJB) lubricated with TiO2 and ZnO nano-lubricant considering thermal effect. In an experiment, nanoparticles with particle concentrations varying from 0 to 2 weight percent are mixed with SAE15W40 engine oil to create these lubricants. The impact of weight fractions, rotational speed, eccentricity, and ellipticity ratios on the thermal performance of the EJB has been examined. The Kreger-Dougherty model is employed to understand the effects of oil film temperature as well as nanoparticle concentration on lubricant viscosity. The pressure and temperature determined by (Dang 2020) and (Wang 2021were evaluated against the CFD model with good agreement. The findings show that for 2 wt% nanoparticles, e of 0.6 and N of 5000 rpm, the load-carrying capacity increased by 5.5% and 4% and the side leakage flow decreased by 24.4% and 18%.

Mass conserving analysis of steadily loaded, oscillating elliptical journal bearings

This note addresses the effect of surface ellipticity on self-acting partial arc journal bearings under steady load and sinusoidal oscillation accounting for mass conserving cavitation. A generalized Warner bearing (GWB) formulation developed in a previous publication is employed for computational efficiency. A set of non-dimensional design charts and a sample application show that bearing performance, as measured by cyclic-minimum film thickness ratio, is substantially improved with an elliptical sleeve at small oscillation amplitudes typically found in practice. The results also suggest that a fully hydrodynamic lubrication regime can be established at small oscillation amplitudes from a wearing-in process of the sleeve surface.

Effect of Ellipticity on Cavitation Mechanism and Thermal Effect of Elliptical Journal Bearings

Effect of Ellipticity on Cavitation Mechanism and Thermal Effect of Elliptical Journal Bearings

Effect of micro protrusions on the performance of elliptical journal bearings operating with couple stress lubricant

1. Xiao-Li Wang, Ke-Qin Zhu, Shi-Zhu Wen. Thermo-hydrodynamic analysis of journal bearings lubricated with couple stress fluids. Tribology International 2001; 34: 335–343. https://doi.org/10.1016/S0301-.... CrossRef Google Scholar

Thermo-hydrodynamic simulation study of twin-groove elliptical (two-lobe) journal bearing of steam turbine with experimental investigations

The present paper reports an experimental and theoretical investigation on performance behaviour of twin-groove elliptical (two-lobe) white metal hydrodynamic journal bearing used in steam turbines. The experiments are performed on a fully automatic journal bearing test rig with provisions to various operating conditions (i.e. load, speed, and lubricant temperature). The performance behaviour in terms of coefficient of friction, lubricant inlet temperature, load carrying capacity, journal displacement, weight loss etc. has been presented. In addition to this, numerical investigations have also been performed with the numerical solution of governing Reynolds equation using FEM (finite element method) technique and Jakobsson-Floberg-Olsson (JFO) boundary condition. The experimentally obtained and theoretical results have been correlated.

An experimental study on vibration suppression of adjustable elliptical journal bearing-rotor system in various vibration states

The working principle of an adjustable elliptical journal bearing was introduced in the previous work, and the physical model has been designed and manufactured. As a continuation of research work, the vibration suppression behavior of the bearing-rotor system in various vibration states are studied experimentally this paper. Two bearing-rotor test rigs are established based on the adjustable bearing. The rigid rotor test rig is built up to study the forced vibration suppression when the rotor is operated at a relatively large unbalance and far lower from the critical speed. The flexible rotor test rig is built up to study the suppression of resonance vibration and the elimination of self-excited vibration. The resonance vibration is tested during the flexible rotor passing through the critical speed. The oil whip self-excited vibration is tested when the flexible rotor is operated near twice of critical speed. Under heavier static load, the forced vibration amplitude of the rigid rotor is suppressed by 50% through increasing the elliptical ratio of the bearings. The suppression effect of forced vibration is up to 60% under lighter static load. During passing through the critical speed, the maximum resonance vibration amplitude of the flexible rotor is suppressed about 30% through decreasing the elliptical ratio of the bearing. When the flexible rotor is operated near twice of the critical speed, the oil whip self-excited vibration is weakened and eliminated eventually through decreasing the elliptical ratio of the bearing.

Geometrical analysis of elliptical journal bearings and its effects on friction and load capacity

Elliptical bearings are one type of non-circular journal bearings which has two main advantages over the conventional circular bearings: lower temperature rise and lower vibrations. In this study, the energy equation and Reynolds equation are simultaneously solved under adiabatic boundary conditions. The predicted pressure and temperature are compared to the results of published literature for verification purposes. A parametric study is then conducted on the effect of geometrical parameters of the elliptical journal bearing on the load capacity, friction force, pressure, and oil temperature. Effect of geometric parameters of the bearing on the performance is studied. The results show that non-circularity parameter is the most influential parameter in the bearing, and an increase in the non-circularity results in the decrease in maximum pressure and temperature as well as the friction force. Increasing the eccentricity ratio, on the other hand, will cause an increase in the pressure, temperature, and the friction force. Changes in the angle between the major axis of the bearing and load direction decrease the load-carrying capacity and the non-dimensional pressure and results in an increase in the friction coefficient.

The Static and Dynamic Characteristic of Elliptical Journal Bearing Lubricated with Couple-Stress Fluid

The Static and Dynamic Characteristic of Elliptical Journal Bearing Lubricated with Couple-Stress Fluid

Vibration suppression mechanism research of adjustable elliptical journal bearing under synchronous unbalance load

Abstract A concept of an adjustable elliptical journal bearing with variable elliptical ratio was proposed in order to suppress the vibration amplitude of a rotor under synchronous unbalance load at normal speed operating condition. In numerical simulations, dynamic lubrication program is programmed and it could predict the journal center orbits of the bearing. In experiments, adjustable elliptical journal bearing device and testing system are established. With the elliptical ratios adjusting from 0 to 0.7, journal vibrations are simulated and tested. The results obtained from the experiments are in good agreement with that from the numerical simulations. The results indicate that the effects of vibration suppression are satisfied. The proposed adjustable elliptical journal bearing provides an effective way in forced vibration suppression.

Multiple-relaxation-time lattice Boltzmann method of hydrodynamic lubrication in lemon-bore bearing

The lattice Boltzmann method has superiority over conventional computational fluid dynamics methods, particularly for the flow simulations in complex geometries. In the present work, the performance of hydrodynamic lemon-bore (elliptical) journal bearings was investigated with the implementation of the lattice Boltzmann method. The steady-state laminar flow of a homogeneous oil was considered in the computations. A linear interpolation method was exploited to obtain the surface curvatures. The comparison of the results obtained from the proposed methodology with available literature data showed a satisfactory agreement. The effect of geometrical parameters on the hydrodynamic lubrication in an elliptical journal bearing was analyzed. It was found that the ellipticity ratio has profound effects on the bearing load capacity, oil flow rate and bearing power loss.

Calculation and interpolation of the characteristics of the hydrodynamic journal bearings in the domain of possible movements of the rotor journals

To visualize the physical processes that occur in the journal bearings of the shafting of power generating turbosets, a technique for preliminary calculation of a set of characteristics of the journal bearings in the domain of possible movements (DPM) of the rotor journals is proposed. The technique is based on interpolation of the oil film characteristics and is designed for use in real-time diagnostic system COMPACS®. According to this technique, for each journal bearing, the domain of possible movement of the shaft journal is computed, then triangulation of the area is performed, and the corresponding mesh is constructed. At each node of the mesh, all characteristics of the journal bearing required by the diagnostic system are calculated. Via shaft-position sensors, the system measures—in the online mode—the instantaneous location of the shaft journal in the bearing and determines the averaged static position of the journals (the pivoting vector). Afterwards, continuous interpolation in the triangulation domain is performed, which allows the real-time calculation of the static and dynamic forces that act on the rotor journal, the flow rate and the temperature of the lubricant, and power friction losses. Use of the proposed method on a running turboset enables diagnosing the technical condition of the shafting support system and promptly identifying the defects that determine the vibrational state and the overall reliability of the turboset. The authors report a number of examples of constructing the DPM and computing the basic static characteristics for elliptical journal bearings typical of large-scale power turbosets. To illustrate the interpolation method, the traditional approach to calculation of bearing properties is applied. This approach is based on a Reynolds two-dimensional isothermal equation that accounts for the mobility of the boundary of the oil film continuity.

Analysis of the Stability of Elliptical Journal Bearings under Vapor Cavitation Erosion

The phenomenon of lubricant cavitation in hydrodynamic bearings and its effect on the stability has been rigorously studied and reported in the literatures. In certain cases, cavitation has significant effect on the dynamic and stability characteristics of the rotor-bearing system. With a proper control of the cavitation condition and groove location, stability can be achieved over a wide range of operating speed, in the case of elliptical journal bearings. On the other hand, the stability is not affected by the presence of vapor cavitation, in the case of multi-lobe journal bearings with the oil supplied at atmospheric pressure. For the unstable, submerged, circular bearings, vapor cavitation phenomena results in a distinctive vibration response observable on the vibration plots. The stability of the elliptical journal bearings under the influence of vapor cavitation erosion was analyzed. It is found that vapor cavitation erosion on elliptical bearings results in instability of the whirling shaft. Collapse of the vapor cavitation bubbles causes erosion wear that falls within the pressure zone of the elliptical bearing, thus causing the instability.

A Comparative Performance Analysis of Gas Lubricated Cylindrical and Elliptical Journal Bearings

The finite element method is employed to perform a comparative analysis of gas lubricated cylindrical and elliptical journal bearings in this work. A finite element procedure, based on the Galerkin weighted residual method, is specially devised to solve the zeroth- and first-order lubrication equations for plain cylindrical and non-cylindrical hydrodynamic journal bearings running on thin gas fluid films. Load-carrying capacity and dynamic force coefficients of gas cylindrical and elliptical journal bearings are computed for some geometric and operating parameters, such as journal eccentricity ratio and rotational speed. Several comparative curves of steady-state and dynamic bearing characteristics depict the differences in the behavior of some gas lubricated fixed-geometry journal bearings.

Design and fast verification of pocket elliptical journal bearings

Purpose – The purpose of this paper was to conceive a fast method to verify design and performance of elliptical pocket journal bearings. Design/methodology/approach – The computer-aided verification of pocket journal bearings is performed by means of a suitable finite element analysis method. Findings – The results of sample analyses indicate that the machining tolerances are very influential on elliptical pocket bearing performances, and they must be included among the input data. Originality/value – Although elliptical pocket bearings are widely used in turbomachineries, the influence of their design on performance has not been specifically investigated. A lot of works about tribological models are available, but few of them focus on their application to bearing design at the industrial level.

Performance comparison of circular, two-lobe and elliptical journal bearings based on TEHD analysis

Purpose – The purpose of this paper is to study the different performance of circular, two-lobe and elliptical journal bearings by TEHD analysis. Design/methodology/approach – A complete 3D TEHD model of journal bearings is set up and applied to the lubricant performance calculation of the conventional circular, two-lobe and elliptical journal bearings. The finite difference method is employed to solve the THD model, and the thermo-elasto deformations on the pad are obtained by the finite element software ANSYS11.0. The data transfer between the THD model and ANSYS11.0 is carried out automatically by Interface Program. Findings – It is found that under the identical geometric parameters and operating condition, the circular journal bearing possesses the greatest magnitude of the maximum oil film pressure, the two-lobe one takes the second place and the elliptical one possesses the smallest magnitude. The thermo-elasto deformations on the pad is the same order of magnitude with the minimum film thickness. Practical implications – A complete 3D TEHD model made up of the THD model and ANSYS11.0 can be applied on journal bearings in practice applications. Originality/value – This paper set up a complete 3D TEHD model that is in common use for the lubricant performance analysis of circular and non-circular journal bearings.

Numerical Analysis of Thermoelastohydrodynamic Behavior of an Elliptical Tow-Lobe Bearing

In this paper the thermoelastohydrodynamic study for analysis of elliptical journal bearing (Two-lobe) operating with Newtonian lubricant has been presented. The thermo-elastic deformations of the solid parts are taken into account. To solve the Reynold's equation generalized, equation of energy and the displacement field, respectively, using two numerical techniques Computational Fluid Dynamic "CFD" and Fluid Structure Interaction "FSI". The "CFD" is used to determine the pressure, temperature and velocity fields in the lubricant film, the stress intensity and displacement field is obtained by "FSI" simulation. The influence of the operate conditions on the fields pressure, temperature displacement and stress intensity is also analysed.

An Experimental Investigation of Oil Film Temperatures in Elliptical Profile Journal Bearing

Hydrodynamic journal bearings experience significant variation in oil film temperature. Reliable data of operating temperatures in these journal bearings are very useful and important for practical bearing designers and mathematical modellers. Here, an elliptical journal bearing has been tested to access the temperature rise at oil-bush interface with three grade oils at loads varying from 100 N to 600 N and speeds = 3000, 3500, 4000 rpm at constant oil supply pressure. The results show that with increase in load at constant speed and pressure, and with increase in speed at constant load and pressure, the oil film temperature increases in the central plane of both the lobes of the bearing for all grade oils under study. Further, it is observed that under the given operating conditions, oil 2 gives the coolest operation of the elliptical bearing under analysis.

Lateral Vibration Analysis of Flexible Shafts Supported on Elliptical Journal Bearings

This paper presents the development of a finite element procedure for the dynamic analysis of flexible rotors supported on fluid-film elliptical journal bearings operating under several operating conditions. The rotating shaft is modeled by using Timoshenko beam theory and the coupled rotating components, such as disks and impellers, are modeled by using lumped masses. The modeling of the elliptical journal bearings is performed by solving the lubrication equations generated from the application of a linearized perturbation method on the classical Reynolds equation. The bearing carrying-load capacity and the linearized dynamic force coefficients can be predicted for elliptical bearings with different preloads and journal eccentricities. The rotor transient whirling unbalance response is estimated by performing the time integration of the finite element equations using Newmark method. Experimental whirling unbalance response of a rotating shaft supported at two identical journal bearings is used to validate the finite element procedure. A comparative analysis of the dynamic response of flexible rotors supported on both cylindrical and elliptical journal bearings is performed to show that some elliptical bearings are capable of attenuating the rotor unbalance response more efficiently than cylindrical bearings are.

Investigations on the thermal effects in non-circular journal bearings

A comparative study based on the thermal performance of elliptical and offset-halves journal bearings has been carried out by solving energy equation while assuming Parabolic Temperature Profile Approximation across the fluid film for faster computation of temperatures. Investigation for the rise in oil film temperatures, thermal pressures, load capacity, and power loss for three commercially available grade oils have been carried out for bearing configurations under study. It has been found that the offset-halves journal bearing runs cooler when compared with elliptical journal bearing profile with minimum power loss and good load capacity using Oil 2 as lubricant for which minimum thermal degradation has been observed.