Numerical Study of Thermal Effects in the Hydrodynamic Behavior of Textured Journal Bearings
N. Tala-Ighil
a, M. Fillon
b, A. Brick Chaouche
aand A. Mokhtari
aa Welding and NDT Research Center (CSC), BP 64 CHERAGA - ALGERIA
bInstitute Pprime, CNRS - University of Poitiers - ISAE - ENSMA, FRANCE
Abstract. The journals bearing characteristics with texture presence on the bearing surface are investigated. The thermal effect has been studied. The used numerical approach in this analysis is Finite Difference Method. The textured bearing performance enhancement passes essentially by a minimum film thickness and a friction torque improvement through an appropriate surface texture geometry and right texture distribution on the bearing surface. It is found that the simulation results are in good concordance with those issued from the litterature. The obtained results by considering the temperature effect are more realistic.
Keywords: Hydrodynamic lubrication, journal bearing, texturation, dimple.
PACS: 81.40.Pq Friction, lubrication, and wear / 46.55.+d Tribology and mechanical contacts
INTRODUCTION
The journal bearing is a complex system with high film convergence and with cavitation hydrodynamic phenomena. These bearings are commonly used in industry due to their simplicity, efficiency, and low cost. A lubricant separates the surfaces and hence reduces the frictional force, which leads to wear [1]. Surface texturing is claiming progressively more attention and is expected to be a major component in future bearing structure design [2]. The deterministic roughness (dimples) that is known as surface texture was introduced deliberately on the bearings by using micro-fabrication techniques. Microtextures act as micro- hydrodynamic bearings, enhance load support and increase film thickness, which leads to lower friction compared to untextured surfaces. Lu and Konshari [3] have presented experimental results concerning the dimples effect on the Stribeck curve. Load, oil type, dimple size, depth and shape were varied to explore their influence on the friction characteristics. The bearing temperature field and pressure field are considerably influenced by the journal bearing parameters [4]. The average temperature is evaluated using a very simple hypothesis. Hydrodynamic lubrication problem is governed by the known Reynolds’ equation [5] which is second order elliptic partial differential equations. The solution for the exact finite- length bearing can be calculated using the Finite Difference numerical Method (FDM) [6] to solve the two- dimensional Reynolds equation. The variations in the bearing static characteristics (load capacity, maximum hydrodynamic pressure, friction torque, axial film flow, attitude angle, and the energy dissipated in the contact) can be predicted with reasonable accuracy using the Reynolds boundary conditions. Recently, the authors [7] have shown that the most significant characteristics can be improved through an appropriate textured area arrangement on the contact surface.
THEORY
In a hydrodynamic lubrication problem, the governing equations for a full hydrodynamic lubrication region can be described by the known Reynolds’ equation [8].
( ) »¼ º
«¬ ª
∂
− ∂
=
¸ ¹
¨ ·
©
§
∂
∂
∂
¸ ∂
¹
¨ ·
© + §
¸ ¸
¹
·
¨ ¨
©
§
∂
∂
∂
∂
ω θ ω
μ R h
Z h P Z L R ș
h P
ș 2 3 6 2 2 1
3
(1)R is the bearing radius, L the bearing length. ω1 and ω2 are respectively, the rotational speeds of the journal and the bearing (figure 1). The film thickness h is:
( 1 cos ) h ( , Z )
C
h = + ε θ + Δ θ
(2)Δh(θ,Z) is the film thickness variation due to the dimple surface, ε the relative eccentricity of the journal and C the radial clearance bearing.
Proceedings of the International Conference on Numerical Analysis and Applied Mathematics 2014 (ICNAAM-2014) AIP Conf. Proc. 1648, 850076-1–850076-4; doi: 10.1063/1.4913131
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850076-1
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