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Influence of pressure changes on the viscosity of lubricating oil in CFD simulations of conical bearing hydrodynamic lubrication

Czaban Adam, Miszczak Andrzej

Journal of KONBiN

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2022

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Vol. 52, iss. 3

259--277

EN

The aim of this study is to consider the effect of pressure on the viscosity of lubricating oil in the adopted model of hydrodynamic lubrication and on the calculated flow parameters and operating parameters of a conical slide bearing. The numerical analysis consisted in solving the Reynolds type equation for the process of stationary hydrodynamic lubrication.

PL

Celem niniejszej pracy jest zbadanie, w jakim stopniu uwzględnienie wpływu ciśnienia na lepkość oleju smarnego, w przyjętym modelu hydrodynamicznego smarowania, oddziałuje na obliczane parametry przepływowe i eksploatacyjne analizowanego stożkowego łożyska ślizgowego. W badaniach wykorzystano znane z literatury równanie typu Reynoldsa, określające proces stacjonarnego hydrodynamicznego smarowania.

2

Simulations of the influence of the heat flux at the shaft surface of the conical slide bearing on its hydrodynamic lubrication and operating parameters

Czaban Adam, Miszczak Andrzej

Journal of KONES

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2019

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Vol. 26, No. 4

29--37

EN

The aim of this work is to investigate, how in the adopted model of hydrodynamic lubrication of a conical slide bearing, the change of the heat flux value at the bearing shaft, affects bearing operating parameters. In this research, the authors use, the known from the literature, Reynolds type equation, describing the stationary hydrodynamic lubrication process of a conical slide bearing. The analytical, solutions, that determine the components of the lubricating oil velocity vector and the equation (analytical solution of energy equation) determining the threedimensional temperature distribution in the lubrication gap, was also adopted from previous works. In order to obtain numerical solutions, the Newton’s method was used, and the derivatives in the Reynolds type equation were approximated by the finite differences. An application of the method of subsequent approximations allowed considering the influence of temperature, pressure and shearing rate on the viscosity of lubricating oil. The considerations were performed by adopting the Reynolds condition of the hydrodynamic oil film. It was tested, how the assumed value of the heat flux on the bearing shaft surface affects the values of the obtained operating parameters, i.e. the transverse and longitudinal component of the load carrying capacity, friction force and coefficient of friction.

3

Numerical analysis of influence of bearing material thermal conductivity coefficient on hydrodynamic lubrication of a conical slide bearing

Czaban A.

Journal of KONES

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2018

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Vol. 25, No. 2

89--96

EN

One of the main parameters affecting the hydrodynamic lubrication of slide bearings is the viscosity of lubricating oil. Many studies show, that significant changes in the viscosity of oil occur along with changes in its temperature. The influence on the temperature distribution in the lubrication gap of the slide bearing have a variety of factors, and one of them is the amount of heat exchanged between the lubricant and the environment. The temperature of the lubricating oil of operating bearing is usually higher than the ambient temperature. In addition to the convection, which occurs during the flow (heat exchange related to the oil supply and discharge system) some amount of heat is transferred to the bearing sleeve material (and also to the bearing shaft), and then it is conducted to sleeve outer surface. The amount of heat transferred through the bearing sleeve is mainly dependent on the difference of temperatures between inner and outer sleeve surfaces and also depend on the heat conduction coefficient of sleeve material. This article presents the results of modelling of the influence of amount of heat conducted through the bearing material, on the hydrodynamic lubrication of a conical slide bearing. The study concerned various values of the heat conduction coefficient of the bearing material to investigate its influence on the temperature values of lubricating oil, and thus, on its viscosity, on the distribution of hydrodynamic pressure and on the calculated values of bearing load carrying capacities and friction forces.

4

CFD analysis of influence of axial position of shaft on hydrodynamic lubrication of slide conical bearing

Czaban A.

Journal of KONES

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2017

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Vol. 24, No. 3

37--44

EN

During the operation of a slide bearing, the position of its shaft or sleeve varies due to many factors, such as vibrations, load changes, changes in the lubricating viscosity. The vibrations or varying load can cause, that the position of the bearing shaft, measured along its axis of rotation, changes. This is particularly important for sliding bearing with conical geometry. Due to the geometry of this kind of bearing, i.e. where the radius of this bearing (of the shaft and sleeve) has not a constant value, as in the case of a journal bearing, it is more difficult to obtain proper values and describe its hydrodynamic lubrication. This article shows the results of hydrodynamic lubrication of the slide conical bearing, for which the changes in the position of the bearing shaft in the longitudinal direction, i.e. along its axis of rotation, were taken into account. The commercial CFD software, designed for solving general for flow phenomena problems, was used in the simulations. This article shows the results of simulations, assuming that the lubricating oil behaves as a generalized Newtonian fluid. The hydrodynamic pressure distributions, load carrying capacities and friction torques were calculated for the concerned bearing. The aim of this work is to show how the operating parameters of the slide conical bearing can be influenced, by only changes of the position of the shaft along the axis of its rotation.

5

CFD analysis of effect of misalignment plane position on hydrodynamic lubrication of slide conical bearing

Czaban A.

Journal of KONES

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2017

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Vol. 24, No. 2

65--72

EN

The numerical calculations of the hydrodynamic lubrication of slide bearings can be carried out by modelling the oil flow for a given value of height of bearing lubrication gap. On the basis of the assumed height of the lubrication gap, the values of hydrodynamic pressures, load carrying capacities, friction forces, temperatures, can be determined. The bearing lubrication gap height can be influenced by many effects, e.g. misalignment between the shaft axis and the axis of the sleeve, vibrations, varying load, change in the viscosity value of lubricating oil caused by changes in temperature, pressure, shear rate or by oil ageing, wear of journal and sleeve surfaces. This article presents the results of numerical simulations concerning the influence of the misalignment between the axis of shaft and the axis of sleeve of the sliding conical bearing on its hydrodynamic lubrication, by taking into account the position of the plane in which the misalignment occurs. In this study, there was defined an angle between the plane in which the misalignment occurs and the plane in which lies the line of centres of corresponding bearing without misalignment. In this research, to investigate the impact of the position of the plane in which the misalignment occurs, the CFD software, designed to solve general flow phenomena, was used. It was assumed, that the bearings operate in a steady state conditions, the flow in the bearing lubrication gap is laminar and non-isothermal. A lubricating oil has shear properties as the Ostwald-de Waele fluid.

6

CFD analysis of the impact of a cone opening angle parameter on the hydrodynamic lubrication of the conical slide bearing

Czaban A.

Journal of KONES

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2016

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Vol. 23, No. 3

71--77

EN

The height of the oil lubrication gap is the primary quantity that determines in simulations the operating parameters of a hydrodynamic slide bearing. It is influenced by multiple effects, such as vibrations during operation, varying load, misalignment between the shaft axis and the axis of the bearing sleeve, the roughness of the journal and sleeve surfaces, change in the viscosity value of lubricating oil caused by changes in temperature, pressure, shear rate or by oil ageing, wear of journal and sleeve surfaces etc. It is important to take into account such effects considering hydrodynamic lubrication simulations and design of the slide bearings. The one of the factors influencing the height of the oil lubrication gap of the conical slide bearing is the difference between the opening angle of the cone of bearing shaft and opening angle of the cone of bearing sleeve. The aim of this work is to investigate the impact of the difference between the values of these angles on the hydrodynamic lubrication of the conical slide bearing. The commercial CFD software Ansys Fluent, from the Ansys Workbench 2 platform, was used to determine the hydrodynamic pressure distributions, load carrying capacities and friction torques of the simulated bearings. It was assumed, that the bearings operate in a steady state conditions, the flow in the bearing lubrication gap is laminar and non-isothermal, there is no misalignment between the axis of bearing journal and axis of bearing sleeve, the surfaces of the journal and sleeve are smooth and lubricating oil acts as a liquid described by the Ostwald-de Waele power law model.

7

CFD analysis of non-Newtonian and non-isothermal lubrication of hydrodynamic conical bearing

Czaban A.

Journal of KONES

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2014

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Vol. 21, No. 4

49--56

EN

In this work is shown the result of CFD simulation of hydrodynamic conical bearing lubrication with consideration of non-isothermal oil flow in a bearing lubrication gap and also with assumption, that oil has non- Newtonian properties. The determination of hydrodynamic pressure distribution in bearing gap was carried out by using the commercial CFD software ANSYS Academic Research for fluid flow phenomenon (Fluent). Calculations were performed for bearings without misalignment, i.e. where the cone generating line of bearing shaft is parallel to the cone generating line of bearing sleeve. The Ostwald-de Waele model for non-Newtonian fluids was adopted in this simulation. The coefficients of Ostwald-de Waele relationship were determined by application of the least squares approximation method and fitting curves described by this model to the experimental data, obtained for some motor oils, presented in previous work. The calculated hydrodynamic pressure distributions were compared with the data obtained for corresponding bearings, but assuming that the flow in the bearing lubrication gap is isothermal. Some other simplifying assumptions are: a steady-state operating conditions of a bearing, incompressible flow of lubricating oil, no slip on bearing surfaces, pressure on the side surfaces of bearing gap is equal to atmospheric pressure. This paper presents results for bearings with different rotational speeds and of different bearing gap heights.

8

CFD analysis of hydrodynamic lubrication of slide conical bearing with consideration of the bearing shaft and sleeve surface roughness

Czaban A

Journal of KONES

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2014

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Vol. 21, No. 3

35--40

EN

In this work is shown the result of CFD simulation of hydrodynamic conical bearing lubrication with consideration of the effect of the bearing shaft and sleeve surface roughness. The oil flow in a bearing lubrication gap largely depend on the condition of the cooperating surfaces of a bearing. Surface irregularities are formed already at the manufacturing process and furthermore the quality of the surface may change during operation of a bearing. In this work, as a parameter describing surface condition, the Ks roughness height parameter was taken (i.e. sand-grain roughness height). The hydrodynamic pressure distribution in lubrication gaps of investigated bearings were calculated by using the commercial CFD software ANSYS Academic Research for fluid flow phenomenon (Fluent). Calculations were conducted for bearings without misalignment. The Ostwald-de Waele model for non-Newtonian fluids was adopted in this simulation. The coefficients of Ostwald-de Waele relationship were determined by application of the least squares approximation method and fitting curves described by this model to the experimental data, obtained for some motor oils, presented in previous work. The calculated hydrodynamic pressure distributions were compared with the data obtained for corresponding bearings, but assuming that bearings have smooth surfaces and there is no slip on surfaces. This paper presents results for bearings with different rotational speeds and of different bearing gap heights.

9

Hydrodynamics models of conical sidle bearings lubrication in the magnetic field

Koprowski M.

Tribologia

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2006

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nr 3

95-106

EN

In this paper are presented two hydrodynamics models of conical slide bearing lubrication. The first model describes the Newtonian, stationary no isothermal oil (ferrooil) flow in the conical slide bearing in the magnetic field. The second model determines the non-Newtonian case of lubrication of the conical slide bearing in magnetic field. The numerical calculations are performed only for classical Newtonian lubrication.

PL

W referacie zaprezentowane zostały dwa modele hydrodynamicznego smarowania stożkowych łożysk ślizgowych. Pierwszy model przedstawia klasyczny przypadek smarowania łożysk ślizgowych. Drugi adekwatny jest dla nienewtonowskiego przypadku przepływu oleju w szczelinie stożkowego łożyska ślizgowego w obecności pola magnetycznego. Dodatkowo, w pracy przedstawione zostały wyniki obliczeń numerycznych przeprowadzone dla dwóch porównywalnych geometrycznie łożysk ślizgowych, tj. walcowego i stożkowego. Otrzymane wyniki zaprezentowano w formie graficznej.

10

Mechanical parameters of a multilobe conical bearing with ferromagnetic lubricant

Walicki E., Walicka A., Jurczak P., Michalski D.

International Journal of Applied Mechanics and Engineering

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2002

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Vol. 7, Spec. is

119-126

EN

In this paper the authors present a solution to the problem of an inertia effect of ferromagnetic lubricant flow in a multilobe conical bearing. The problem was solved by Galerkin's method after assuming that the bearing is lubricated with an incompressible Newtonian lubricant. The general form of solutions for pressure distribution and axial load for particular cases of the bearing geometry are given

11

Performance of a multilobe conical bearing lubricated by an incompressible Newtonian fluid

Walicki E., Walicka A., Rossa R.

Applied Mechanics and Engineering

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1999

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Vol. 4, no spec.

89-98

EN

In the presented paper the authors provide a solution to the problem of an inertia effect of lubricant flow in a multilobe conical bearing. The problem was solved by Galerkin's method after assuming that the bearing was lubricated with an incompressible Newtonian fluid. General form of solutions for particular cases of the bearing geometry are given.