‘Inlet suction’, a load support mechanism in non-convergent, pocketed, hydrodynamic bearings

Olver, A.D.; Fowell, Mark; Spikes, H. A.; Pegg, Ian

doi:10.1243/13506501jet168

Cited by 107 publications

(81 citation statements)

References 6 publications

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“…In these two papers it was clearly shown that load support is over predicted and friction coefficient under-predicted when a non-mass conserving formulation is applied. This criticism has been supported by previous contributions of the current authors [10,11], in which a semi analytical mass-conserving formulation of the Reynolds equation including the effects of cavitation was used to show that the critical pressure enhancement in textured bearings occurs downstream of the cavitation reformation boundary and is therefore critically affected by the boundary conditions in the reformation zone. A mass conserving algorithm was identified as key in correctly predicting bearing performance.…”

Section: Introductionmentioning

confidence: 89%

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Transient effects in lubricated textured bearings

Medina

Fowell

Vlădescu

et al. 2015

Proceedings of the Institution of Mechanical Engineers, Part J:

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The aim of this paper is to study transient phenomena in hydrodynamic textured bearings. Both convergent and convergent-divergent reciprocating textured bearings are considered. A massconserving formulation of the Reynolds equation recently proposed by some of the authors and used to capture cavitation in steady-state lubricated contacts has been implemented to study transient effects in lubricated textured bearings. It is shown that the proposed solver is capable of capturing the frictional response of bearings characterised by various geometries and loading conditions in both steady-state and transient configurations.Depending on the boundary conditions governing the problems under investigation, changes in load support or film thickness variations are correctly predicted, demonstrating that the methodology developed in this paper is suitable to provide an efficient tool for the design and optimisation of textured bearings. A qualitative comparison with preliminary experimental data obtained using an apparatus developed to study reciprocating textured surfaces is performed, showing that the characteristic transient behaviour of such surfaces in different loading regimes can be correctly captured using the proposed numerical implementation. Current limitations of the proposed methodology and possible extensions of the technique to study elasto-hydrodynamic and mixed lubrication regimes are also discussed.

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Section: Introductionmentioning

confidence: 89%

“…This is particularly true in cases where cavitation and reformation may occur multiple times within the computational domain of interest (e.g. rough contacts [28], textured surfaces [8,10,11,[29][30][31] and dynamically loaded journal bearings [9,16]). …”

Section: Introductionmentioning

confidence: 99%

Transient effects in lubricated textured bearings

Medina

Fowell

Vlădescu

et al. 2015

Proceedings of the Institution of Mechanical Engineers, Part J:

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“…Over the last decade, researchers at Imperial College compared the performance of a wide range of texture geometries, under various operating scenarios, in both experimental and theoretical studies [5][6][7][8][9][10]. Recently, the group's experiments showed that, under reciprocating piston-liner type conditions, beneficial or detrimental effects of surface texture could be achieved depending on which lubrication regime the contact operated under [9].…”

Section: Introductionmentioning

confidence: 99%

The Transient Friction Response of a Laser-Textured, Reciprocating Contact to the Entrainment of Individual Pockets

et al. 2016

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To shed light on the mechanisms with which surface texture improves the tribological performance of piston-liner contacts, we have measured the transient friction response as individual pockets pass through a reciprocating sliding contact. Tests were performed at different sliding speeds and results compared to those from a non-textured, reference specimen under different lubrication regimes. At low speed when the contact is in the boundary regime, friction force falls abruptly as each pocket leaves the contact zone, before gradually returning to an approximately steady-state value. This suggests that each pocket acts to temporarily increase the film thickness, which then decays to its non-textured value as oil is squeezed out. At higher speeds, friction is seen to reduce in a stepwise fashion, since the period between pockets being entrained is less than the time taken for the film to decay. In addition, friction results obtained when the contact is operating in the middle of the mixed regime point to a temporary film thickness collapse as the pocket enters the contact, and this agrees with recent modelling predictions. At higher speeds, the compound effect of successive pockets is to shift the contact to the right on Stribeck curve. These results imply that each pocket gives rise to an increase in film thickness that is both short-lived and small in magnitude (we estimate a few tens of nm). However, the resulting effect on friction can be significant (up to 82 % in this study) for two reasons: (1) provided the pocket frequency is sufficiently high, each successive pocket entrainment builds the film up without there being time for it to reduce back to its steady-state value; (2) when the contact is in the mixed regime, the Stribeck curve is at its steepest and friction is therefore most sensitive to film thickness changes. This has important practical implications in that pocket spacing on piston liners should be varied as a function of reciprocating sliding speed.

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“…If cavitation occurs in the divergent zone at a pressure lower than the ambient pressure, the pressure difference between the surroundings and the cavitation zone generates a Poiseuille flow that introduces the lubricant into the lubricated area. This is the basic concept underlying the inlet suction suggested by Olver and colleagues [13][14][15]. A lower cavitation pressure generates a stronger Poiseuille flow, inducing a higher pressure in the convergent zone of the dimple, as shown in Fig.…”

Section: Discussionmentioning

confidence: 93%

“…Olver et al [13] suggested that cavitation occurring in a single pocket located on the leading side of pad bearings generates a Poiseuille flow; this phenomenon has been termed "inlet suction." This Poiseuille flow introduces more lubricant into the lubricated area, resulting in an increased load-carrying capacity.…”

Section: Introductionmentioning

confidence: 99%

On the Magnitude of Load-Carrying Capacity of Textured Surfaces in Hydrodynamic Lubrication

2015

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This paper investigates the magnitude of the load-carrying capacity enabled by textured feature in hydrodynamic lubrication. The numerical model is a two-dimensional fixed pad bearing with a single dimple. The Reynolds equation was numerically solved using the Elrod algorithm. Two boundary conditions at the inlet and outlet were compared: a periodic boundary condition and an atmospheric boundary condition. The load-carrying capacity for the atmospheric boundary condition is negative while that for the periodic boundary condition is positive when a dimple is located at the centre of the lubricated area. The atmospheric boundary condition, when a dimple is located on the inlet side and is opened to the outside, exhibits greater load-carrying capacity than that in the enclosed dimple case.

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‘Inlet suction’, a load support mechanism in non-convergent, pocketed, hydrodynamic bearings

Cited by 107 publications

References 6 publications

Transient effects in lubricated textured bearings

Transient effects in lubricated textured bearings

The Transient Friction Response of a Laser-Textured, Reciprocating Contact to the Entrainment of Individual Pockets

On the Magnitude of Load-Carrying Capacity of Textured Surfaces in Hydrodynamic Lubrication

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