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1 – 10 of over 5000Rajneesh Kumar and Suresh Verma
In the present scenario of high-speed machines, the use of non-circular hole-entry bearing configuration, i.e. two-lobe, multi-lobe, lemon bore, etc., has becomes unavoidable, as…
Abstract
Purpose
In the present scenario of high-speed machines, the use of non-circular hole-entry bearing configuration, i.e. two-lobe, multi-lobe, lemon bore, etc., has becomes unavoidable, as the journal bearings with non-circular configurations provide better stability at high operating speed and heavy dynamic loading. Further, this research aims to show that the presence of micro particles in the lubricants greatly affects performance of the bearings, as their presence leads to non-Newtonian behaviors of the lubricant. Therefore, to consider the effect of these micro particles, the lubricant is modeled as a micropolar lubricant. The present work analyzes the effect of these micropolar lubricants on the performance of hole-entry circular and non-circular (two-lobe) hybrid journal bearings compensated with constant flow valve restrictor and compares with that of Newtonian lubricants.
Design/methodology/approach
The modified Reynolds equation governing the laminar flow of iso-viscous, incompressible micropolar lubricant in the clearance space of a journal bearing system has been solved using finite element method and appropriate boundary conditions. Further, a comparative analysis between circular and non-circular (two-lobe) hybrid journal bearing compensated with constant flow valve restrictor operating with Newtonian and micropolar lubricant has been presented.
Findings
The numerically simulated results reveal that the non-circular bearing configuration provides better performance vis-à-vis the circular bearing configuration. Further, the increase in the micropolar effect of the lubricant enhances the performance of circular and the non-circular bearing configurations compared with the Newtonian lubricant. Also, in the case of the non-circular bearing configuration with an offset factor (δ = 1.5), the bearing performance improved compared with (δ = 1.25).
Originality/value
Many research studies have been done in the area of non-circular hybrid journal bearing with Newtonian lubricants with different types of restrictors, but the non-circular hole-entry constant flow valve-compensated hybrid journal bearing operating with the micropolar lubricant has not been analyzed. Therefore, in the present work, an effort has been made to fill this research gap.
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The non-circular journal bearings may be used over circular journal bearings because of their superior thermal stability. The paper aims at experimental study of thermal…
Abstract
Purpose
The non-circular journal bearings may be used over circular journal bearings because of their superior thermal stability. The paper aims at experimental study of thermal performance of two different true elliptical and orthogonally displaced non-circular journal bearing profiles.
Design/methodology/approach
The experiments have been conducted on a specially designed test rig which simultaneously evaluates oil film pressure and temperature along the circumference of non-circular journal bearing. The tests are conducted for the designed true elliptical and orthogonally displaced journal bearing at three different rotational speeds of 2,000, 3,000 and 4,000 rpm under the influence of steadily applied load varied from 0.5 to 2.0 kN. The data collected during experimentation have been used to evaluate thermal performance parameters such as maximum pressure, flow rate and effective temperature of the bearings under study.
Findings
It has been observed experimentally that two lobes of pressure and temperature have been obtained for both the elliptical and orthogonally displaced journal bearing. The negative pressure zone (cavitation area) has been observed to be reduced along the circumference for both the journal bearings which results in less thermal degradation of an oil as compared to circular journal bearing. The oil film pressure and temperature increases with the increase in radial load of both the bearings. The maximum temperature rise of oil film is more in case of elliptical bearing as compared to the orthogonally displaced bearing.
Originality/value
The experimental data presented in this paper will help the designers to select such kind of non-circular journal bearing for various applications. The designed bearings have resulted in reduced cavitation zone and two positive pressure lobes have been observed which may result in application of such bearings as an alternate for circular journal bearing.
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Bin Huang, Le-qin Wang and Jia Guo
– The purpose of this paper is to study the different performance of circular, two-lobe and elliptical journal bearings by TEHD analysis.
Abstract
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.
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R. Rashidi Meybodi, A. Rasoolizadeh Shooroki and M. Zare Mehrjardi
The purpose of this study is to examine the thermo-hydrodynamic performance of tilted non-circular journal bearings lubricated with a micropolar fluid. The investigated bearing…
Abstract
Purpose
The purpose of this study is to examine the thermo-hydrodynamic performance of tilted non-circular journal bearings lubricated with a micropolar fluid. The investigated bearing types are two- and three-lobe journal bearings with finite length.
Design/methodology/approach
For this purpose, modified Reynolds, energy and three-dimensional Laplace equations are solved numerically by using generalized differential quadrature method. The effects of micropolarity characteristics of lubricants, such as characteristic length and coupling number, as well as tilt angle as a design parameter, on the performance of non-circular two- and three-lobe journal bearings are studied.
Findings
The results show that the tilt angle can affect the temperature and pressure profiles causing variation in the performance of non-circular bearings. Increasing coupling number and decreasing characteristic length cause the load-carrying capacity to decrease because of the increase in maximum oil temperature of the fluid film of lubricant and decrease in the minimum oil base viscosity. So, it is possible to select suitable values of tilt angle for achieving optimum performance of these bearings.
Originality/value
The non-circular bearings suggest several design parameters such as tilt angle for designers. By considering thermal effects for micropolar lubricant, the requirements of a specific application can be fulfilled.
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Chandra B. Khatri and Satish C. Sharma
The aim of the present paper is to study the combined influence of textured surface and micropolar lubricant behaviour on the performance of two-lobe hole-entry hybrid journal…
Abstract
Purpose
The aim of the present paper is to study the combined influence of textured surface and micropolar lubricant behaviour on the performance of two-lobe hole-entry hybrid journal bearing system. The bearing performance parameters of the textured circular/two-lobe hole-entry hybrid journal bearing system have been computed against the constant vertical external load supported by the bearing.
Design/methodology/approach
In this work, Eringen’s micropolar fluid theory has been used to derive the governing Reynolds equation. The consequent solution of the governing Reynolds equation has been obtained by using finite element method (FEM) numerical technique.
Findings
The present study indicates that the use of the textured surface, two-lobe profile of bearing and micropolar lubricant, significantly enhances the bearing performance as compared to non-textured circular journal bearing.
Originality/value
The present study concerning the influence of surface texturing on the behaviour of the two-lobe hole-entry hybrid journal bearing lubricated with micropolar lubricant is original. The theoretically simulated results of the present study will be useful to design an efficient journal bearing system.
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The current trend of modern industry is to use machineries which rotate at high speed along with the capability of carrying heavy rotor loads. This paper aims at static thermal…
Abstract
Purpose
The current trend of modern industry is to use machineries which rotate at high speed along with the capability of carrying heavy rotor loads. This paper aims at static thermal analysis of two different profiles of non-circular journal bearings – a true elliptical bearing and orthogonal bearing.
Design/methodology/approach
The Reynolds equation has been solved through finite difference method to compute the oil film pressure. Parabolic temperature profile approximation technique has been used to solve the energy equation and thus used for computation of various bearing performance characteristics such as thermo-hydrodynamic oil film pressure, temperature, load capacity, Sommerfeld number and power loss characteristics across the bearing. The effect of ellipticity ratio on the bearing performance characteristics has also been obtained for both the elliptical and vertical offset bearing using three different commercially available grades of oil (Hydrol 32, 68 and 100).
Findings
It has been observed that the thermo-hydrodynamic pressure and temperature rise of the oil film is less in orthogonal bearing as compared to the true elliptical bearing for same operating conditions. The effect of ellipticity ratio of non-circularity on bearing performance parameters have been observed to be less in case of elliptical bearing as compared to orthogonal bearing. It has been concluded that though the rise in oil film temperature is high for true elliptical bearing, but still it should be preferred over orthogonal profile under study, as it has comparably good load-carrying capacity.
Originality/value
The performance parametric analysis will help the designers to select such kind of non-circular journal bearing for various applications.
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Satish Jain, Satish Sharma, J. Sharana Basavaraja and Prashant Kushare
In recent years, researchers have focused a great deal of attention on multirecess hybrid journal bearing systems. The non‐circular journal bearings are widely used in industry on…
Abstract
Purpose
In recent years, researchers have focused a great deal of attention on multirecess hybrid journal bearing systems. The non‐circular journal bearings are widely used in industry on account of their better stability, simplicity, efficiency and low cost. The purpose of this paper is to present a theoretical investigation into the performance of a two‐lobe multirecess hybrid journal bearing system.
Design/methodology/approach
The Reynold's equation governing the lubricant flow in the clearance space between the journal and bearing together with restrictor flow equations has been solved using finite element method. The bearing static and dynamic performance characteristics have been presented for the various values of the offset factors (0.75, 1, 1.25 and 1.50) for the hybrid mode of operation of the journal bearing system compensated by capillary and orifice restrictors for the commonly used bearing operating and geometric parameters. The offset of the journal has been accounted for by defining a non‐dimensional factor called offset factor delta.
Findings
The numerically simulated results indicate that a two‐lobe four recessed hybrid journal bearing provides a better performance than the corresponding similar circular recessed journal bearing system. The study further reveals that in order to get an improved performance of a two‐lobe four recessed journal bearing, a proper selection of bearing offset factors along with type of restrictor (capillary or orifice) is essential.
Originality/value
The results presented in this paper are useful for bearing designers.
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J. Sharana Basavaraja, Sathish Sharma and Sathish Jain
The non‐recessed hybrid journal bearings of cylindrical type, when operating at higher rotational speeds can suffer self‐exited vibrations(oil‐whirl Instability), which can cause…
Abstract
Purpose
The non‐recessed hybrid journal bearings of cylindrical type, when operating at higher rotational speeds can suffer self‐exited vibrations(oil‐whirl Instability), which can cause excessive rotor motion causing bearing and sometimes total machine failure. The multi‐lobe journal bearing exhibits better stability as well as a superior capability to suppress oil‐whirl. The paper aims to present a theoretical study pertaining to a two‐lobe hole‐entry hybrid journal bearing by considering the combined influence of surface roughness and journal misalignment on the performance of the bearing.
Design/methodology/approach
The average Reynolds equation governing the flow of lubricant in the clearance space between the rough bearing surfaces together with the equation of flow through a capillary restrictor has been solved using FEM. The bearing performance characteristics have been simulated for a two‐lobe hole‐entry hybrid journal bearing for the various values of offset factor, restrictor design parameter, surface roughness parameter, surface pattern parameter and journal misalignment parameters.
Findings
The two‐lobe hole‐entry hybrid journal bearing system with an offset factor greater than one indicates significant improvement of the order of 15‐25 percent in the values of direct stiffness and direct damping coefficients compared to a circular hole‐entry hybrid journal bearing system. Also the lubricant flow of a two‐lobe hole‐entry hybrid journal bearing is reduced by 25 percent vis‐à‐vis circular bearing.
Originality/value
The present work is original of its kind, in case of two‐lobe hole‐entry hybrid journal bearing. The results are quite useful for the bearing designer.
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Satish C. Sharma, Vikas M. Phalle and S.C. Jain
Noncircular journal bearings are used in industry because of their simplicity, efficiency and low cost. During the life time of a machine, these are required to be operated over a…
Abstract
Purpose
Noncircular journal bearings are used in industry because of their simplicity, efficiency and low cost. During the life time of a machine, these are required to be operated over a number of years and are submitted to several stops and starts. As a result, the bush becomes progressively worn out and the bearing performance changes. The purpose of this paper is to study theoretically the influence of wear on the performance of a non‐circular 2‐lobe four‐pocket multirecess hybrid journal bearing system.
Design/methodology/approach
The Reynolds equation governing the flow of lubricant in the clearance space of a non‐circular 2‐lobe multirecess worn hybrid journal bearing system has been solved using FEM along with appropriate boundary conditions. The defects caused by wear are centered on the load line and range from 10 per cent to 50 per cent of the bearing radial clearance.
Findings
The numerically simulated results based on a Newtonian lubricant and the steady state flow field system have been presented in terms of maximum fluid film pressure, minimum fluid film thickness, lubricant flow rate, direct fluid film stiffness and damping coefficients and stability threshold speed margin. The paper demonstrates that, for the bearing configurations studied, the bearing behavior is clearly affected by wear. The numerically simulated results indicate that for an offset factor of δ=1.2, the value of h¯min reduces by 21.21 per cent at δ¯w=0.5.
Originality/value
The presented results have valuable data in case of 2‐lobe four pocket hybrid journal bearing compensated with constant flow valve restrictor. The paper outcomes are sure to be of interest for researchers and useful for bearing designers.
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Shicheng Yan, Yahong Xue, Liming Wei and Zhanchao Wang
This paper aims to elucidate the effects of lubricant groove shape, vertical load, swing angle and grease injection cycle on the friction and wear performances of journal bearings…
Abstract
Purpose
This paper aims to elucidate the effects of lubricant groove shape, vertical load, swing angle and grease injection cycle on the friction and wear performances of journal bearings under the grease lubrication condition.
Design/methodology/approach
Three different types of lubricant grooves, namely, numeral eight-shaped, axial straight line-shaped and circular blind hole-shaped, were designed and machined in the bearing bush of journal bearings. The tribological behaviors of these journal bearings were investigated on the self-developed reciprocating swing friction and wear tester. Experimental data including the friction coefficient, the friction temperature, the wear loss and wear time were analyzed in detail. The wear morphologies of friction pairs were observed by scanning electron microscope and confocal laser scanning microscope.
Findings
The load carrying capacity and service life of the journal bearing with circular blind hole-shaped lubricant grooves are not affected. However, the load carrying capacities of journal bearings with numeral eight-shaped and axial straight line-shaped lubricant grooves are declined. The coverage areas of lubricating grease in the bearing bush are associated with the swing angle. The smaller the swing angle is, the more limited the coverage areas of lubricating grease get. Among these journal bearings, the maintenance-free time of journal bearing with circular blind hole-shaped lubricant grooves is the longest because of its large grease storage capacity.
Originality/value
The journal bearing with circular blind hole-shaped lubricant grooves exhibits the excellent antifriction and wear-resistant properties, making it suitable for the application in the low-speed and heavy-load engineering conditions.
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