μPIV measurement of grease velocity profiles in channels with two different types of flow restrictions

Li, J.X.; Höglund, Erik; Westerberg, Lars G.; Green, T.M.; Lundström, T. Staffan; Lugt, Piet M.; Baart, Pieter

doi:10.1016/j.triboint.2012.03.007

Cited by 26 publications

(15 citation statements)

References 23 publications

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“…Li et al 3 detected that the grease displays weak uidity in the experimental channel and a certain distance is required to let the ow develop fully. 1,2 Therefore, a high pipe resistance would be shown when the grease is delivered by the centralized lubrication system, which is a disadvantage for the centralized lubrication system application.…”

Section: Introductionmentioning

confidence: 99%

Effect of heat treatment on the lubricating properties of lithium lubricating grease

2015

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Owing to the potential oxidation and thermal degradation of lithium lubricating grease when the grease is heated to improve its fluidity in the pumping process, fresh NLGI 3 lithium lubricating grease samples were heated to obtain experimental samples to simulate the static thermal degradation by using a drying oven.The microstructure and infrared spectra were studied by using field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FTIR) techniques respectively. The rheological properties were estimated by a rotational rheometer and the tribological properties were evaluated on a four-ball testing machine. Finally, the action mechanisms of the effect of heat treatment on the tribological properties of lithium lubricating grease are discussed. The experimental results showed that the lithium lubricating grease samples exhibited better antifriction and antiwear properties after heat treatment at 120 C, which is not obvious during 0-4 h, while the coefficient friction and extreme pressure progressively decreased during 4-24 h. Meanwhile, oxidative and thermal degradation do not proceed after heat treatment for 0-24 h according to the FESEM and FTIR results. Finally, it was confirmed that the variation of physical entanglement, which was caused by a short heat treatment, would vary the tribological properties of the lithium lubricating grease.

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Section: Introductionmentioning

confidence: 99%

Effect of heat treatment on the lubricating properties of lithium lubricating grease

2015

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“…The grease flow properties as a function of the rheology were studied by Westerberg et al [4], who used flow visualizations to investigate the grease flow through a straight channel. Focusing on grease particle migration, Li et al [5] studied the effect of channel restrictions on the grease flow and how the restrictions affect the particle migration. They found that the rate of shear distribution in the flow domain is important as regions with low shear may serve as particle traps.…”

Section: Introductionmentioning

confidence: 99%

Contaminant Particle Motion in Lubricating Grease Flow: A Computational Fluid Dynamics Approach

et al. 2018

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Abstract:In this paper, numerical simulations of particle migration in lubricating grease flow are presented. The rheology of three lithium greases with NLGI (National Lubricating Grease Institute) grades 00, 1 and 2 respectively are considered. The grease is modeled as a single-phase Herschel-Bulkley fluid, and the particle migration has been considered in two different grease pockets formed between two concentric cylinders where the inner cylinder is rotating and driving the flow. In the wide grease pocket, the width of the gap is much smaller compared to the axial length scale, enabling a one-dimensional flow. In the narrow pocket, the axial and radial length is of the same order, yielding a three-dimensional flow. It was found that the change in flow characteristics due to the influence of the pocket lateral boundaries when going from the wide to the narrow pocket leads to a significantly shorter migration time. Comparing the results with an existing migration model treating the radial component contribution, it was concluded that a solution to the flow in the whole domain is needed together with a higher order numerical scheme to obtain a full solution to the particle migration. This result is more pronounced in the narrow pocket due to gradients in the flow induced by the lateral boundaries.

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“…for the flow in seals, to deformable, free-surface flows important for the re-lubrication process and inside bearings as they typically only are filled to about 30% to avoid heavy churning. Modelling grease flow analytically is only possible in simple geometries like channels, pipes and cylinders; see, for example, Westerberg et al [1] and Li et al [2,3], for grease flow models in rectangular channels and concentric cylinder configuration, and Cheng et al [4]; Sisko [5] for flow in a pipe. For more complex flows, numerical models are needed.…”

Section: Introductionmentioning

confidence: 99%

Lubricating Grease Flow in a Double Restriction Seal Geometry: A Computational Fluid Dynamics Approach

et al. 2017

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In this paper, numerical simulations of lubricating grease flow in the grease pocket of a double restriction seal geometry using computational fluid dynamics are presented. The grease is treated as a singlephase Herschel-Bulkley fluid with different rheological properties corresponding to NLGI grade 00, 1 and 2. The numerical code and rheology model have been validated with a semi-analytical solution based on flow measurements using microparticle image velocimetry. The flow has been modelled for low and high rotational speeds driving the flow, and elevated temperatures. Also, the evolution of contaminant particles in the grease pocket is investigated. It was found that the flow and velocity distribution in the pocket-and consequently the contaminant particle concentration evolution, is characterized by the shear thinning rheology of the grease. With higher shear rates in the grease and higher temperatures, the grease approaches a more Newtonian type of behaviour leading to a reduced yield and shear thinning characteristics directly affecting the grease ability to transport contaminant particles.

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μPIV measurement of grease velocity profiles in channels with two different types of flow restrictions

Cited by 26 publications

References 23 publications

Effect of heat treatment on the lubricating properties of lithium lubricating grease

Effect of heat treatment on the lubricating properties of lithium lubricating grease

Contaminant Particle Motion in Lubricating Grease Flow: A Computational Fluid Dynamics Approach

Lubricating Grease Flow in a Double Restriction Seal Geometry: A Computational Fluid Dynamics Approach

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