Optimization of hydrodynamic lubrication performance based on a heterogeneous slip/no-slip surface

Abstract

Purpose This paper aims to use the method of curve splicing to combine the slip zone and the no-slip zone to further improve the lubrication performance of the liquid film. The combination of the slip zone and the no-slip zone of an existing heterogeneous surface is still a single line stitching method so that a very large residual space at the surface of the friction pairs remains present, necessitating further improvement of the joining scheme between the slip zone and the no-slip zone in heterogeneous surfaces. Design/methodology/approach A set of discrete sinusoids is used as the splicing track for both the slip zone and the no-slip zone, the starting point and amplitude of the curve are introduced as the simulation variables and the effects of these variables on the bearing capacity and friction coefficient of the liquid film are comprehensively analyzed. Findings The results show that the method of selecting the sinusoidal curve as the slip zone and the no-slip zone trajectory, which is based on the existing method of linear stitching, can further enhance the bearing capacity and reduce the friction coefficient of the liquid film. Originality/value This method can further enhance the bearing capacity and reduce the friction coefficient of the liquid film.

CFD Analysis of Journal Bearing with a Heterogeneous Rough/Smooth Surface

“…The so-called heterogeneous rough/smooth pattern introduced here is inspired by the construction of heterogeneous slip/no-slip surface. As reported by numerous researchers, for example [14,[19][20][21][22][23][24], the heterogeneous slip/no-slip configuration was proven to increase the load-carrying capacity and reduce the friction force significantly. It is believed that a configuration of rough/smooth regions will lead to enhanced journal bearing properties.…”

“…This finding is interesting, and hence, the heterogeneous rough/smooth bearing can be compared to the heterogeneous slip/no-slip pattern. Based on the reference [19,22], even though there is no wedge effect in the case of concentric journal bearing, the heterogeneous slip/no-slip pattern could produce a relatively high load-carrying capacity. It indicates that the behavior of a "rough" surface can be correlated to the wettability of the surface (in particular the surface with hydrophobic coating) inducing the slip boundary.…”

An optimal method of distribution of the slip zone on thrust bearing surfaces

“…Assuming that the liquid velocity near the pad surface is not necessarily equal to the velocity of the pad surface, the liquid is considered to be an incompressible laminar flow, the viscosity of the liquid is constant, and the effect of inertia is ignored. Appling the analysis method of the micro-element, the mathematical formula of the circumferential velocity u and radial velocity v at any point of the liquid film can be obtained by 6 : where p is the liquid pressure, u 0 and v 0 are the circumferential and radial velocities of the liquid near the tilting pad surface, and η is the dynamic viscosity of the liquid, respectively.…”

“…With the linear stitching: The above mathematical model was discretized by using the finite difference method and programmed in the Matlab environment. 6 Based on the existed researches, a slip zone is arranged on the surface of the tilting pad, wherein the stitch of the slip zone and the no-slip zone is performed by a straight line. The discretized node number is given to parameterize the position of the splicing line, and its expression is defined as follows: where, δ is the number of the circumferential grid node where the boundary line is located ( δ = 1, 2, ···, m + 2), when δ = 1 then the entire surface of the tilting pad that has no-slip zone is a conventional surface, and when δ = m + 2 then the entire surface of the tilting pad is a slip surface.…”

“…4,5 It had been proved that when the liquid film flowed through the heterogeneous slip/no-slip surfaces, the maximum pressure was mainly distributed near the boundary line between the slip and no-slip zone, thus, it was proposed that the boundary line between the slip/no-slip zone was not spliced by a straight line to improve the lubrication parameters of the liquid film. 6,7 Particularly, for devices such as thrust bearings, it was difficult to obtain a scientific method to reasonably distribute the slip zone to achieve better results due to the different cutting speeds and film thickness distribution of the sliding pair surfaces. 8,9 Therefore, the reasonable distribution of the slip/no-slip zone of this heterogeneous surface played an important role, and the optimization of the distribution of the slip/no-slip zone to improve the lubrication performance of the sliding pairs is necessary to further study.…”