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

Abstract

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.

On the Steady-State Flow and Yielding Behaviour of Lubricating Greases

“…On one hand, the suitable rheological evaluation of the steady-state flow is necessary to deduce accurate values of rheological parameters, like those of the commonly employed Herschel-Bulkley model, to be used in simulations. On the other hand, the strong effect of time to achieve the steady-state viscosity values and the correct extension of the yielding flow regime must be incorporated in more complex analytical models in order to predict and/or simulated the grease fluid dynamics in practical situations like those described in recent literature [11][12][13][14][15][16][17].…”

“…The main objective of this work was to study the steady-state flow behaviour of lubricating greases, analyzing how the microstructural characteristics may affect the yielding flow behaviour.Very recently, different studies have pointed out the importance of the flow behavior in the correct evaluation of the fluid dynamics of greases in practical situations, for instance, by performing numerical simulations. In this sense, numerical simulations applying computational fluid dynamics (CFD) procedures or Runge-Kutta methods have been performed to predict the particle motion/migration in pockets between two-rotating cylinders with different restriction geometries [11,12], the grease flow in journal bearings as a function of surface texture [13], the dynamics of greases in tapered roller bearings [14], or the laminar flow in rectangular cross section channels [15], among other practical situations. Additionally, the dynamics of greases was experimentally studied in both a labyrinth seal geometry [16] and concentric cylinder configurations with a rotating shaft to simulate the grease flow in a double restriction seal geometry [17] using the microparticle image velocimetry technique.…”

Research on the Rheological Characteristics of Wind Power Grease Based on Rheological Parameters

“…The current rheological model that can adequately describe wind turbine spindle bearing grease is the Herschel-Bulkley model, which can accommodate a variety of rheological characteristic curves, including shear stress-shear rate curves, strain scan curves, and viscous temperature curves, etc. [25,26]. At the same time, it can fit the experimental data well, treat grease as a structural system composed of viscoelastic and viscous components, reflect the structural properties of grease, help to analyze and optimize the performance of grease, and improve the prediction accuracy.…”

Effects of Contamination on Selected Rheological and Tribological Properties of Lubricating Greases Working in Underground Mines

“…In the case of greases, the changes greatly depend on the kind of thickener and the way in which the friction junction is lubricated [5,7]. Besides studies on the functional properties of greases subjected to contamination, several numerical simulations aimed at evaluating the behavior of solid contaminants in greases working in friction junctions have been conducted [10].…”