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Article
Publication date: 19 June 2009

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…

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.

Details

Industrial Lubrication and Tribology, vol. 61 no. 4
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 17 August 2010

Satish Sharma, Satish Jain, J. Sharana Basavaraja and Neeraj Sharma

Hole‐entry hybrid journal bearings are widely used in many applications owing to their favourable characteristics. Ever increasing technological developments demand much…

Abstract

Purpose

Hole‐entry hybrid journal bearings are widely used in many applications owing to their favourable characteristics. Ever increasing technological developments demand much improved performance from these class of bearings operating under the most stringent, exact and precise conditions. Therefore, it becomes imperative that the hole‐entry journal bearings be designed on the basis of more accurately predicted bearing characteristics data. The purpose of this paper is to describe a theoretical study to demonstrate the combined influence of the effect of pocket size at the outlet of supply holes and the journal misalignment on the performance of an orifice compensated hole‐entry hybrid journal bearing system.

Design/methodology/approach

Finite element method is used to solve the Reynolds equation governing the flow of an incompressible lubricant in the clearance space between the journal and bearing together with equation of flow through an orifice. The journal misalignment has been accounted for by defining a pair of misalignment parameters sigma and delta. The effect of pocket size at the outlet of supply holes has been accounted by defining a non‐dimensional parameter which is function of diameter of pocket and journal diameter.

Findings

The results presented in this paper indicate that the effect of journal misalignment is, in general, to cause a reduction in bearing dynamic characteristics parameters whereas the effect of pocket size is to slightly compensate this loss. Performance of a two lobe four recessed journal bearing, a proper selection of bearing offset factor along with type of restrictor (capillary or orifice) is essential.

Originality/value

This paper presents valuable data relating to hole‐entry hybrid journal bearings useful for bearing designers.

Details

Industrial Lubrication and Tribology, vol. 62 no. 5
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 16 September 2013

H.C. Garg and Vijay Kumar

The purpose of this paper is to describe the static performance characteristics of orifice compensated hole-entry hybrid journal bearing considering the combined influence…

Abstract

Purpose

The purpose of this paper is to describe the static performance characteristics of orifice compensated hole-entry hybrid journal bearing considering the combined influence of rise in temperature and non-Newtonian behavior of the lubricant. The required governing equations have been solved using the finite element method and a suitable iterative technique. The non-Newtonian lubricant has been assumed to follow the cubic shear stress law. The thermohydrostatic (THS) rheological performance of asymmetric hole-entry hybrid journal bearing configurations are studied. The computed results indicate that variation of viscosity due rise in temperature and non-Newtonian behavior of the lubricant affects the performance of asymmetric hole-entry hybrid journal bearing system quite significantly.

Design/methodology/approach

The THS rheological solution of a hole-entry hybrid journal bearing system requires the simultaneous solution of Reynolds equation, 3D energy equation and 3D conduction equation along with appropriate boundary conditions. In present study an iterative numerical solution scheme is used to establish pressure and temperature fields in the lubricant fluid-film.

Findings

The computed results indicate that variation of viscosity due rise in temperature and non-Newtonian behavior of the lubricant affects the performance of asymmetric hole-entry hybrid journal bearing system quite significantly.

Originality/value

The available literature concerning the orifice compensated asymmetric hole-entry hybrid journal bearings indicates that the thermal effects together with non-Newtonian behavior of lubricant due to additives mixed in the lubricants have been ignored in the analysis so as to obviate the mathematical complexity. The bearing performance characteristics have been presented considering the combined influence of rise in temperature and non-Newtonian behavior of the lubricant for asymmetric bearing configurations.

Details

Industrial Lubrication and Tribology, vol. 65 no. 6
Type: Research Article
ISSN: 0036-8792

Keywords

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Article
Publication date: 4 March 2014

H.C. Garg and Vijay Kumar

The changing technological scenario necessitated hybrid journal bearings to operate under severe conditions of heavy load and high speed resulting into temperature rise of…

Abstract

Purpose

The changing technological scenario necessitated hybrid journal bearings to operate under severe conditions of heavy load and high speed resulting into temperature rise of the lubricant fluid-film and bearing surface. To predict the performance of a bearing realistically, theoretical model must consider the combined influence of the rise of temperature and non-Newtonian behavior of the lubricant. The aim of the present paper is to study the effect of viscosity variation due to temperature rise and non-Newtonian behavior of the lubricant on performance of constant flow valve compensated multiple hole-entry hybrid journal bearings.

Design/methodology/approach

Finite element method has been used to solve Reynolds equation along with restrictor flow equation, 3D energy equation and 3D conduction equation using suitable iterative technique. The non-Newtonian lubricant has been assumed to follow cubic shear stress law.

Findings

The thermohydrostatic rheological performances of symmetric and asymmetric hole-entry hybrid journal bearing configurations are studied. The computed results illustrate that variation of viscosity due to rise in temperature and non-Newtonian behavior of the lubricant affects the performance of hole-entry hybrid journal bearing system quite significantly.

Originality/value

In the present work, the influences of the viscosity variation due to temperature rise and non-Newtonian behavior of the lubricant on the performance characteristics of non-recessed hole-entry hybrid journal bearing with symmetric and asymmetric configurations compensated with constant flow valve restrictors have been investigated for generating the design data to be used by bearing designer. The design data computed in the present thesis are a contribution in field of knowledge of bearing design.

Details

Industrial Lubrication and Tribology, vol. 66 no. 2
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 1 March 2013

Nathi Ram and Satish Sharma

The purpose of this paper is to study theoretically the combined influence of journal misalignment and wear on the performance of a hole‐entry hybrid journal bearing…

Abstract

Purpose

The purpose of this paper is to study theoretically the combined influence of journal misalignment and wear on the performance of a hole‐entry hybrid journal bearing system. The bearing is assumed to be operating in a turbulent regime.

Design/methodology/approach

The modified Reynolds equation based on Constantinescu lubrication theory has been solved by using finite element method together with orifice and capillary restrictors flow equations as a constrain together with appropriate boundary conditions.

Findings

It has been observed that for a symmetric hole‐entry journal bearing configuration the value of min is more for the bearing compensated by orifice restrictor as compared to capillary restrictor when bearing operates in turbulent regime under worn/unworn conditions. From the point of view of stability threshold speed ω¯th, the reduction in the value of ω¯th for capillary compensated bearing is around −3.89 percent whereas for orifice compensated bearing it is −7.85 percent when misaligned worn bearing is operating in turbulent regime.

Originality/value

The present work is original of its kind, in case of misaligned hole‐entry worn journal bearing. The results are quite useful for the bearing designer.

Details

Industrial Lubrication and Tribology, vol. 65 no. 2
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 13 November 2017

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…

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.

Details

Industrial Lubrication and Tribology, vol. 69 no. 6
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 9 June 2021

Prashant G. Khakse and Vikas M. Phalle

This paper aims to describe how successfully a particular restrictor delivers its best in increasing the conical journal bearing performance. The restrictors are used in…

Abstract

Purpose

This paper aims to describe how successfully a particular restrictor delivers its best in increasing the conical journal bearing performance. The restrictors are used in the hole-entry conical journal bearing subjected to hybrid mode. Thus, the restrictors, like constant flow valve (CFV), orifice and capillary, are studied comparatively.

Design/methodology/approach

Numerical simulation for the bearing results with the three restrictors are obtained by using finite element method (FEM) under the well-known modified Reynolds equation.

Findings

When the hole-entry conical journal bearings, with the restrictor design parameter range C¯s2 = 0.03 – 0.09, are operated, the results obtained are quite distinctive and significant. It indicates that the CFV restrictor-based conical bearing gives enhanced performance in comparison to orifice and capillary restrictors. Moreover, it suggests the performance-wise sequence of the restrictors in hybrid bearings as CFV > Orifice > Capillary.

Originality/value

The outcome of the research paper will give insight to help the bearing designer to choose the particular restrictor in hybrid conical bearing depending on the industrial need.

Details

Industrial Lubrication and Tribology, vol. 73 no. 5
Type: Research Article
ISSN: 0036-8792

Keywords

Content available
Article
Publication date: 27 November 2018

Sanjay Rangrao Pawar and Vikas M. Phalle

Hybrid conical journal bearings have received great attraction by design engineers and researchers due to their incomparable performance. However, performance of these…

Abstract

Purpose

Hybrid conical journal bearings have received great attraction by design engineers and researchers due to their incomparable performance. However, performance of these bearings is affected due to wear. This paper aims to present an analytical study concerning the performance of hole entry worn hybrid conical journal bearings.

Design/methodology/approach

The Reynolds equation governing the flow of lubricant in the clearance space along with the restrictor flow equations has been solved using finite element method.

Findings

The numerically simulated results of worn bearing performance parameters indicate significant change in the performance due to wear. Therefore, for semi cone angle γ = 25°, the value of C¯22 reduces by 24.6 per cent at the wear value of about 50 per cent of radial clearance for the given configuration of bearing.

Originality/value

The present results are original of its kind and surely useful to bearing designers and researchers in predicting actual performance of worn hole entry hybrid conical journal bearing.

Details

Industrial Lubrication and Tribology, vol. 71 no. 2
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 10 July 2018

Pankaj Khatak and H.C. Garg

Hybrid journal bearing have long been used in machines requiring large load and high speed capacity operating under wide range of temperatures. Different compensating…

Abstract

Purpose

Hybrid journal bearing have long been used in machines requiring large load and high speed capacity operating under wide range of temperatures. Different compensating devices are used in for efficient operation of bearings. This paper aims to help in selection of optimum compensating device by evaluating the comparative performance of constant flow valve, capillary compensated and slot entry hybrid journal bearing under the combined influence of thermal effects and micropolar nature of lubricant.

Design/methodology/approach

The variation in micropolar parameters and viscosity change due to temperature increase of lubricant are considered in present study. Finite element method is used for combined iterative solution of micropolar Reynolds, energy and conduction equations. Micropolar lubricant is assumed to be governed by two parameters, coupling number and characteristic length. The results in the study are presented for symmetric and asymmetric configurations of hole entry and slot entry non-recessed hybrid journal bearings

Findings

The results indicate that constant flow valve compensated hole entry hybrid journal bearing is the highest performing bearing for the given range of micropolar parameters of lubricant in terms of maximum fluid pressure and dynamic coefficients.

Originality/value

The performance variations of various configurations of hybrid journal bearing are presented in a single paper. The reader can get overview of combined effects of micropolar parameters and viscosity decrease due to temperature increase of the lubricant.

Details

Industrial Lubrication and Tribology, vol. 70 no. 6
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 12 September 2016

Rajneesh 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…

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.

Details

Industrial Lubrication and Tribology, vol. 68 no. 6
Type: Research Article
ISSN: 0036-8792

Keywords

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