Transient effects in lubricated textured bearings

Abstract

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.

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

“…In the boundary and mixed regime, an overall transient response to pocket entrainment that can be inferred from the above results is (1) film thickness decrease due to contact area reduction, followed by (2) film thickness increase, followed by (3) decay due to squeeze action-a process which agrees qualitatively with recent modelling predictions of load support variation during pocket entrainment [8]. This process is suggested based on the fact that the measured variations in friction result from changes in film thickness.…”

“…The transient friction and film thickness data, obtained by monitoring the entrainment of individual pockets in this way, are in qualitative agreement with recent numerical simulations (such as [8]) of sliding LST surfaces, and further comparison should help to elucidate the friction reduction mechanisms that are occurring. …”

“…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].…”

“…Notably, they demonstrated the importance of aspect ratio and other co-dependent geometric parameters used to describe a textured pattern in controlling the friction performance of a microtextured bearing. Following this, Fowell et al [7] and Medina et al [8] developed numerical techniques to assess the effectiveness of, and interdependency between, texture parameters.…”

Analysis of the coated and textured ring/liner conjunction based on a thermal mixed lubrication model

“…As reported by Gherca et al [33], a textured moving surface can contribute to the generation of hydrodynamic lift on the basis of a squeeze effect. For more information about the difference between the stationary texturing case (or say the textured ring system) and moving texturing case (or say the textured liner system), the interested readers can refer to the works of Medina et al [34] and Gherca et al [33]. Figure 8 shows the simulation results under the warm engine operating condition.…”