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Lubrication theory

About: Lubrication theory is a research topic. Over the lifetime, 1713 publications have been published within this topic receiving 50261 citations. The topic is also known as: Fluid bearing.


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Journal ArticleDOI
TL;DR: In this article, the effect of turbulence on the steady state performance characteristics of a centrally loaded 120 deg single pad externally adjustable fluid film bearing has been investigated, and the static performance characteristics calculated in terms of load carrying capacity, attitude angle, friction variable, and Sommerfeld number.
Abstract: In an externally adjustable fluid film bearing, the hydrodynamic conditions can be changed as required in a controlled manner. The principal feature of the bearing is the facility to adjust its radial clearance and circumferential film thickness gradient. Unlike a tilting pad bearing, this bearing can have radial adjustments. The tilt adjustments are obtained by providing flexibility to the pad at one corner. This paper deals with the effect of turbulence on the steady state performance characteristics of a centrally loaded 120 deg single pad externally adjustable fluid film bearing. The bearing has an aspect ratio of 1 and operates over a wide range of eccentricity ratios with different radial and tilt adjustments. The Reynolds equation is solved numerically using the finite difference method. The linearized turbulence model of Ng and Pan (1965, “A Linearized Turbulent Lubrication Theory ,” ASME J. Basic Eng., 87, pp. 675–688) as well as the simplified adiabatic model of Pinkus and Bupara (1979, “Adiabatic Solutions for Finite Journal Bearings ,” ASME J. Lubr. Technol., 101, pp. 492–496) are incorporated in the solution scheme. The static performance characteristics calculated are presented in terms of load carrying capacity, attitude angle, friction variable, and Sommerfeld number. A comparative study with the combination of adjustments predicts that the static performance of the bearing is superior with negative radial and tilt adjustments.

18 citations

Journal ArticleDOI
TL;DR: In this article, a comparison between the theoretical and experimental results of minimum oil film thickness in a connecting-rod bearing is presented, where the transient energy equation is solved by adapting the adiahatic boundary condition for considering the thermal effects.
Abstract: The aim of this paper is to study the thermal ejfects on minimum oil film, thickness in a connecting-rod bearing. A comparison between the theoretical and experimental results of minimum oil film thickness in a connecting-rod bearing is presented. The transient energy equation is solved by adapting the adiahatic boundary condition for considering the thermal effects. The minimum oil film thicknesses are measured by the total capacitance method. The minimum oil film thickness over an engine cycle estimated with consideration of thermal effects is closer to that measures than that estimated by using the iso-viscous lubrication theory.

18 citations

Journal ArticleDOI
TL;DR: In this article, a theoretical model was developed to describe the calendering process in viscoelastic sheets of finite initial thickness, and the leave-off distance was determined, considering the influence of the visco-elastic effects in the process.
Abstract: A theoretical model was developed to describe the calendering process in viscoelastic sheets of finite initial thickness. The rheological constitutive equation of the fluid under consideration follows a common form of the Simplified–Phan–Thien–Tanner (SPTT) fluid model. We predict the influence of the viscoelastic effects on the leave-off distance that is related to the exiting sheet thickness in the calendering process. The mass and momentum balance equations, which are based on lubrication theory, were nondimensionalized and solved for the velocity and pressure fields by using perturbation and numerical techniques, where the leave-off distance represents an eigenvalue of the mathematical problem. When the above variables were obtained, the dimensionless leave-off distance in the calendering process was determined, considering the influence of the viscoelastic effects in the process. Moreover, quantities of engineering interest were calculated, including the maximum pressure, the roll-separating force and the power transmitted to the fluid by the rolls. The results show that the inclusion of the viscoelastic effect substantially modifies all dimensionless variables in comparison with those obtained for the Newtonian case.

18 citations

Journal ArticleDOI
TL;DR: In this article, the performance of a finite circular journal bearing with micropolar fluids taking into account the elastic deformation of the bearing liner is presented, where the authors derived the modified Reynolds equation using the micropolastic lubrication theory.
Abstract: Purpose – The performance of finite circular journal bearing lubricated with micropolar fluids taking into account the elastic deformation of the bearing liner is presented. The paper aims to discuss these issues. Design/methodology/approach – The modified Reynolds equation is obtained using the micropolar lubrication theory. The solution of the modified Reynolds equation is determined using finite difference technique. The static characteristics in terms of load-carrying capacity, attitude angle, side leakage and friction coefficient for micropolar and Newtonian fluids are determined for various values of eccentricity ratio and different values of elastic coefficient. Findings – Compared with Newtonian fluids, the micropolar fluids produce an increase in the load-carrying capacity and a reduction in the attitude angle, the friction factor and side leakage for both the rigid and deformable bearings. Originality/value – It is concluded that the influence of elastic deformation on the bearing characteristic...

18 citations

Journal ArticleDOI
J. Adler1
TL;DR: In this article, the authors presented numerical solutions for the variations of surface tension and fuel depth with distance from the burning wick, and an extinction condition was defined and the relationship between the parameter at extinction was obtained.
Abstract: Equations of the kind used in lubrication theory have been developed in order to examine the fluid mechanics of a thin layer of liquid fuel near a burning wick. Under the simplifying assumption made, the problem can be characterised by two dimensionless parameters. An extinction condition is defined and the relationship between the parameter at extinction is obtained. Some numerical solutions are presented for the variations of surface tension and fuel depth with distance from the wick.

18 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202325
202265
202155
202062
201970
201864