Wyniki wyszukiwania - BazTech

1

Lubrication of asymmetric rollers considering viscosity as function of mean temperature

Lanka Swetha, Sajja Venkata Subrahmanyam, Prasad Dhaneshwar

International Journal of Applied Mechanics and Engineering

|

2023

|

Vol. 28, no. 2

49--63

EN

A theoretical analysis of an asymmetric roller bearing system with cavitation that is hydro-dynamically lightly loaded and lubricated by a thin, incompressible fluid is presented. The lubricant adheres to the non-Newtonian Bingham plastic fluid concept, in which the viscosity of the fluid should change depending on the mean film temperature. The continuity and momentum equations, which regulate fluid flow, are first solved analytically and then numerically using MATLAB. Through graphs and tables, some key bearing features are addressed and further explained. This leads to the conclusion that there is a discernible difference between Newtonian and non-Newtonian fluids in terms of pressure, temperature, load, and traction. The findings are good in line with the body of literature.

2

Elastohydrodynamic analysis of a journal bearing with different grade oils considering thermal and cavitation effects using CFD-FSI

Kadhim Zainab H., Hammed Lekaa, Rahima Fatima A., Ridha Ali Mohammed

Diagnostyka

|

2023

|

Vol. 24, No. 2

art. no. 2023213

EN

This paper investigates a three-dimensional CFD analysis of hydrodynamic journal bearing performance for two different available types of lubricants, SEA 10W50 and SEA 15W40, considering thermal, elastic deformation, and cavitation effects. A 3-dimensional CFD model founded on continuity, momentum, energy, in addition elasticity equations has been implemented. The analysis is performed for a bearing with different journal speeds (1000-3000rpm) and eccentricity ratios (0.1-0.9). The cavitation effect was considered using the model of Zwart-Gerber-Balamri multiphase flow model. The bearing material elastic deformation was considered by implementing the two-way FSI technique through ANSYS-FLUENT 2019 R2. A comparative study of the oil film temperature, thermal pressure, also the load capacity by the bearing has been performed. By comparing the current work's oil film temperature results with those obtained by Ferron et al (1983), with a maximum deviation between the results not exceeding 3 percent, the mathematical model was validated. The findings demonstrate that, once the cavitation consequence is taken into account, the lubricant film pressure decreases. Furthermore, at what time the bearing rotates at greater eccentricity ratios and rotational speeds, more deformation material of the bearing is seen. The current research may help in predicting the bearing performance parameters in real-world situations.

3

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

|

2022

|

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.

4

Influence of engine load on piston ring pack operation of an automotive IC engine

Wolff Andrzej, Koszałka Grzegorz

Combustion Engines

|

2022

|

R. 61, nr 3

88--94

EN

A piston-rings-cylinder (PRC) assembly determines the blowby, engine oil consumption, and friction and wear processes accompanying the system's operation. Thus, it is crucial for the whole IC engine efficiency and lifetime. A lot of research effort is put into increasing the performance of this complex and highly dynamic system. Advanced, comprehensive models play an important role in understanding and improving the PRC system. In the presented work, the effect of load on the operation of the ring pack of an automotive gasoline engine is analyzed. A comprehensive model that covers the gas flow through the crevices of the PRC system, ring displacements in the groove, and ring lubrication was used for this analysis. The results of the simulations show that the local thickness of the oil film, especially near the piston top dead center is compared to the height of the combined surface roughness of a cylinder liner and piston rings, and friction-related asperity contact strongly increases as the engine load increases. The simulations also show that the engine load affects the axial displacements of the rings in the grooves but practically does not affect the thickness of the oil film left by the ring pack on the cylinder liner.

5

Effect of lubricant compressibility and variable viscosity on the performance of three-lobe journal bearing

Mahdi Mushrek A., Abass Basim Ajeel

Archive of Mechanical Engineering

|

2022

|

LXIX, nr 2

203–-219

EN

Different configurations of journal bearings have been extensively used in turbo- machinery and power generating equipment. Three-lobe bearing is used due to its lower film temperature and stable operation. In this study, static performance of such a bearing has been investigated at different eccentricity ratios considering lubricant compressibility and variable viscosity. The effect of variable viscosity was considered by taking the viscosity as a function of the oil film thickness while Dowson model is used to consider the effect of lubricant compressibility. The effect of such parameters was considered to compute the oil film pressure, load-carrying capacity, attitude an- gle and oil side leakage for a bearing working at (ε from 0.6 to 0.8) and (viscosity coefficient from 0 to 1). The mathematical model as well as the computer program prepared to solve the governing equations were validated by comparing the pressure distribution obtained in the present work with that obtained by EL-Said et al. A good agreement between the results has been observed with maximum deviation of 3%. The obtained results indicate a decrease in oil film pressure and load-carrying capacity with the higher values of viscosity coefficient while the oil compressibility has a little effect on such parameters.

6

Static Characteristics of Offset 8-Lobe Journal Bearings

Strzelecki Stanisław

Tribologia

|

2021

|

nr 1

39--51

EN

The 8-lobe journal bearings have found application in the bearing systems of spindles of grinding machines. The design of bearings and the large number of lobes and oil grooves assures good cooling conditions of bearing. These bearings can be manufactured as the bearings with cylindrical, non-continuous operating surfaces separated by six lubricating grooves, bearings with the pericycloidal shape of the bearing bore, and as offset journal bearing. This paper presents the results of the computation of static characteristics of an offset 8-lobe journal bearing operating under the conditions of an aligned axis of journal and bush, adiabatic oil film, and at the static equilibrium position of journal. Different values of bearing length to diameter ratio, relative clearance, and lobe relative clearance were assumed. Reynolds' energy and viscosity equations were solved by means of an iterative procedure. Adiabatic oil film, laminar flow in the bearing gap, and aligned orientation of journal in the bearing were considered.

PL

Łożyska ślizgowe 8-powierzchniowe stosowane są w układach łożyskowania wrzecion szlifierek. Konstrukcja tych łożysk i znaczna liczba powierzchni ślizgowych oraz rowków smarowych zapewniają dobre warunki chłodzenia. Łożyska te mogą być wykonywane z segmentami o powierzchni kołowej, zarysie nieciągłym lub ciągłym; z przesuniętymi segmentami, a powierzchnie ślizgowe są oddzielone rowkami smarowymi. Artykuł przedstawia obliczenia charakterystyk statycznych łożysk 8-powierzchniowych z przesuniętymi segmentami pracujących w warunkach równoległych osi czopa i panewki i statycznego położenia równowagi czopa. Założono różne wartości względnej długości łożyska, luzu łożyskowego i względnego luzu segmentu. Równanie Reynoldsa, energii i lepkości rozwiązano metodą różnic skończonych autorskim kodem numerycznym. Przyjęto adiabatyczny i laminarny model przepływu środka smarowego w szczelinie smarowej.

7

Calculations of tilting-pad thrust bearings

Murdzia Edward, Strzelecki Stanisław

Tribologia

|

2021

|

nr 4

27--36

EN

The application of thrust bearings in different engineering designs generates problems of thermal state, which generates the wear of the fixed or tilting pads of bearings. These problems can be avoided by means of proper methods and numerical algorithms of calculations of the bearing static characteristics, including the maximum oil film temperature. The knowledge of thermal state of bearings should assure safe, reliable, and durable bearing operation and is important for the designers of thrust bearings. This paper presents the results of calculations of some static characteristics of a tilting-pad thrust bearing, including its maximum oil film temperature. Numerical solution by means of finite differences was applied for the solution of geometry, Reynolds, energy, and viscosity equations. Adiabatic oil film laminar flow in the bearing gap was considered. The developed code of the computation of bearing performances creates a tool that leads to the solution of thermal problems. Different values of operating speeds were assumed.

PL

Stosowanie ślizgowych łożysk wzdłużnych wiąże się z problemami stanu cieplnego i zużycia stałych lub wahliwych segmentów łożyska. Zastosowanie odpowiednich metod obliczeniowych i algorytmów numerycznych charakterystyk statycznych łożyska włącznie z maksymalną temperaturą filmu smarowego pozwala na uniknięcie problemów eksploatacyjnych. Znajomość stanu cieplnego łożyska powinna zapewnić bezpieczną, niezawodną, trwałą jego eksploatację oraz jest ważna dla konstruktorów łożysk wzdłużnych. W artykule przedstawiono wyniki obliczeń niektórych charakterystyk statycznych łożyska wzdłużnego z segmentami wahliwymi. Podstawowe równania teorii smarowania hydrodynamicznego Reynoldsa, energii i lepkości oraz geometrii rozwiązano metodą iteracyjną. Opracowany algorytm obliczeń numerycznych łożyska z nieizotermicznym filmem smarowym stwarza narzędzie pozwalające na rozwiązywanie problemów cieplnych łożysk wzdłużnych. Założono różne wartości prędkości obrotowych. Przyjęto adiabatyczny, laminarny model filmu smarowego.

8

Effect of micro protrusions on the performance of elliptical journal bearings operating with couple stress lubricant

Abass Basim Ajeel, Mahdi Mushrek A.

Diagnostyka

|

2021

|

Vol. 22, No. 2

97--104

EN

Elliptical bearing is characterized by low induced temperature and high stability at higher speed in comparison with the cylindrical journal bearing. The performance of such bearings can be affected by the type of oil used and its surface properties. The main goal of this work is to study the surface micro protrusion effect on the steady state operation of elliptical journal bearing lubricated with couple stress lubricant. The modified Reynolds’ equation to take into account the effects of couple stress lubricant and micro protrusions of the bearing surfaces is solved using finite difference method. The governing equations were solved using a prepared FORTRAN computer program. Pressure distribution, load carrying capacity and coefficient of friction have been studied for a bearing in laminar flow regime. The mathematical model was validated by comparing pressure results for the elliptical bearing of the present work with that obtained by Hussain et al.(1996). The obtained results demonstrate that the lubricant pressure and the load carried by the bearing decrease for the bearing with higher ellipticity factor while the load carried by the bearing increases for the bearing with higher protrusions or when using a couple stress fluid with higher couple stress variable.

9

Wpływ rodzaju zasilania i klasy oleju na nośność filmu olejowego

Mazurkow Aleksander, Witkowski Waldemar

Zeszyty Naukowe Politechniki Rzeszowskiej. Mechanika

|

2020

|

z. 92 [300]

45--52

PL

W artykule przedstawiono wpływ rodzaju zasilania i klasy oleju na nośność filmu olejowego. Pokazano równania rozkładu ciśnienia i temperatury oleju w szczelinach smarowych oraz równanie wysokości szczeliny smarowej. Są one uzupełniane równaniem modelu matematycznego oleju smarującego łożysko. Stwierdzono istotny wpływ lepkości η = η(T) na nośność filmu olejowego. Wpływ ten rośnie wraz ze wzrostem wartości mimośrodowości względnej ε, niewielki wpływ sposobu zasilania łożyska dla mimośrodowości ε ≤ 0,55.

10

Numerical Analysis of Operating Parameters of Hydrodynamic Thrust Bearings Lubricated with Magnetic Fluid

Szczęch Marcin, Horak Wojciech, Tarasevych Yuliia

Tribologia

|

2020

|

nr 3

43--51

EN

The paper presents the results of numerical simulations (CFD) of hydrodynamic thrust slide bearings lubricated with magnetorheological (MR) fluid. The analyses were carried out to evaluate the influence of the rheological properties of the lubricant, as well as the geometry of the bearing's thrust pad surface. Bearing load conditions were considered on the key functional features of the system, i.e. axial force and torque. The paper presents a comparative analysis of various geometries of thrust bearings and points out possible functional features of hydrodynamic thrust bearings lubricated with fluids with controlled rheological properties.

PL

W pracy przedstawiono wyniki symulacji numerycznych (CFD), hydrodynamicznych wzdłużnych łożysk ślizgowych smarowanych cieczą magnetoreologiczną (MR). Przeprowadzone analizy dotyczyły oceny wpływu właściwości reologicznych cieczy, sposobu ukształtowania powierzchni oporowej łożyska, jak również warunków obciążenia węzła tarcia na kluczowe cechy funkcjonalne układu, tj. siłę osiową oraz moment obrotowy. W pracy przestawiono analizę porównawczą różnych geometrii łożysk wzdłużnych oraz wskazano na możliwe do uzyskania cechy użytkowe wzdłużnych hydrodynamicznych łożysk ślizgowych smarownych cieczami o sterowanych właściwościach reologicznych.

11

Effect of the Misalignment of Journal and Sleeve Axis on the Operation of Turbo Unit Journal Bearings

Strzelecki Stanisław

Tribologia

|

2020

|

nr 5

73--84

EN

In journal bearings the misalignment of the journal and sleeve axis causes a load concentration on their edges, mixed lubrication conditions, an increase in the bearing temperature, rotor instability, and intensive wear of mating parts. The rotating machines are controlled by means of the temperature and vibration transducers, which are placed in the middle plain of the bearing housing. This arrangement of transducers gives no information about the real distance between the journal surface and bearing edges, and, in case of misaligned shaft, it has crucial meaning for the correct operation of turbo unit. This paper presents the theoretical and some experimental results of turbo unit journal bearing operating in misaligned conditions. The results point out the necessity of the precise control of the lubricating gap and the temperature generated on the bearing edges. It was also found that the increase in misalignment also generates an increase in power loss.

PL

W warunkach niewspółosiowości osi czopa i panewki w łożysku występuje koncentracja nacisków na jego krawędziach, tarcie mieszane oraz zwiększone zużycie i niestateczna praca. W maszynie wirnikowej tempe ratura pracy łożysk oraz ich drgania kontrolowane są czujnikami umieszczonymi w płaszczyźnie środkowej obudowy łożyska. Brak jest danych o rzeczywistej odległości między powierzchnią ślizgową łożyska i jego krawędziami. W przypadku niewspółosiowości takie informację są bardzo ważne dla prawidłowej pracy tur bozespołu. Wyniki badań teoretycznych oraz pomiarów przemieszczeń na rzeczywistym obiekcie, jakim jest turbozespół wskazują na konieczność sprawdzania temperatury na krawędziach łożysk. Wzrost niewspółosiowości osi czopa i panewki powoduje m.in. wzrost strat mocy.

12

Determination of Random Friction Forces on the Biological Surfaces of a Human Hip Joint with a Phospholipid Bilayer

Wierzcholski Krzysztof

Tribologia

|

2019

|

nr 2

131--142

EN

The paper presented concerns a new mathematical form of the stochastic theory of hydrodynamic friction forces occurring on real human hip joint surfaces with a phospholipids bilayer. This paper particularly presents a new review of stochastic analytical considerations realized by the authors for friction forces estimation during hydrodynamic lubrication of biological surfaces performed on the basis of the gap height measurements in the human hip joint. After numerous experimental measurements, it directly follows that the random unsymmetrical increments and decrements of the gap height of human joints have an important influence on the load carrying capacities and finally on the friction forces and wear of cooperating cartilage surfaces. The main topic demonstrates the impact of the variations of expectancy values and the standard deviation of the human joint gap height on the friction forces occurring in the human joint. Moreover, an evident connection is observed between the apparent dynamic viscosity and the features of the cartilage surface coated by the phospholipid cells. Hence, after the abovementioned remarks, follows the corollary that the influence of the gap height stochastic variations and random surfaces coated by the PL cells tend indirectly from the apparent viscosity into the friction force variations. The synthetic, complex elaborations of the results obtained indicate the influence of the random roughness and stochastic growth of living biological cartilage surfaces on the friction forces distribution.

PL

Celem badawczym podjętym w pracy jest wpływ zmian losowych wysokości szczeliny stawu na zmiany wartości sił nośnych oraz sił tarcia i współczynników tarcia. Do oddziaływań losowych zaliczamy między innymi: ciągłe zmiany architektury kształtów mikrochropowatości powierzchni chrząstki stawowej z udziałem komórek fosfolipidów, ciągły wzrost żywych komórek chrząstki stawowej, mikrometrowej wielkości odkształcenia hipersprężystej warstwy wierzchniej chrząstki stawowej. Głównym rezultatem pracy jest oszacowanie funkcji oczekiwanej sił tarcia i współczynników tarcia dla biołożysk w postaci ogólnych wzorów analitycznych w zależności od pomierzonych wartości funkcji gęstości prawdopodobieństwa. Według informacji autora przedstawiony w niniejszej pracy model stochastyczny układu równań ruchu i energii dla hydrodynamicznej teorii smarowania jest nowy, ponieważ ujmuje losowe zmiany wszystkich parametrów jednocześnie w odróżnieniu od dotychczasowych modeli probabilistycznych ograniczających się jedynie do zmian losowych wysokości szczeliny biołożyska. W pracy wprowadzono nowe pojęcie funkcji oczekiwanej w odróżnieniu od wartości oczekiwanej. Przedstawiony cel badawczy jest w niniejszej pracy realizowany poprzez badanie rozwiązań analitycznych stochastycznego modelu hydrodynamicznego smarowania stawu w postaci układu równań ruchu oraz przez probabilistyczną analizę parametrów smarowania stawu w zakresie odchyleń standardowych w powiązaniu z wynikami doświadczalnie pomierzonych wysokości szczeliny stawu. W pracy uwzględnia się wpływ wysokości i kształtu mikroszczeliny stawu na wartość lepkości pozornej cieczy synowialnej o własnościach nienewtonowskich w ruchu ustalonym pomiędzy dwoma współpracującymi powierzchniami chrząstek stawowych.

13

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

|

2019

|

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.

14

Operating parameters of a slide bearing with parabolic-shaped slide surfaces with consideration of the stochastic changes in the lubrication gap height

Miszczak Andrzej, Wierzcholski Krzysztof

Journal of KONES

|

2019

|

Vol. 26, No. 4

171--178

EN

In this article, the authors present the equations of the hydrodynamic theory for a slide bearing with parabolicshaped slide surfaces. The lubricating oil is characterized by non-Newtonian properties, i.e. an oil for which, apart from the classic oil viscosity dependence on pressure and temperature, also an effect of the shear rate is taken into account. The first order constitutive equation was adopted for considerations, where the apparent viscosity was described by the Cross equation. The analytical solution uses stochastic equations of the momentum conservation law, the stream continuity and the energy conservation law. The solution takes into account the expected values of the hydrodynamic pressure EX[p(ϕ,ζ)], of the temperature EX[T(ϕ,y,ζ)], of the velocity value of lubricating oil EX[vi(ϕ,y,ζ)], of the viscosity of lubricating oil EX[ηT(ϕ,y,ζ)] and of the lubrication gap height EX[εT(ϕ,ζ)]. It was assumed, that the oil is incompressible and the changes in its density and thermal conductivity were omitted. A flow of lubricating oil was laminar and non-isothermal. The research concerned the parabolic slide bearing of finite length, with a smooth sleeve surface, with a full wrap angle. The aim of this work is to derive the stochastic equations, that allow to determine the temperature distribution, hydrodynamic pressure distribution, velocity vector components, load carrying capacity, friction force and friction coefficient, in the parabolic sliding bearing, lubricated with nonNewton (Cross) oil, including the stochastic changes in the lubrication gap height. The paper presents the results of analytical and numerical calculation of flow and operating parameters in parabolic sliding bearings, taking into account the stochastic height of the lubrication gap. Numerical calculations were performed using the method of successive approximations and finite differences, with own calculation procedures and the Mathcad 15 software.

15

Estimation of random friction forces on the microbearing cooperating surfaces

Wierzcholski Krzysztof, Miszczak Andrzej

Journal of KONES

|

2019

|

Vol. 26, No. 2

167--174

EN

Presented paper concerns a new mathematical form of stochastic theory of hydrodynamic friction forces occurring on the real cooperating surfaces in computer micro bearing fan and computer microbearing in hard disc driver HDD. This paper presents particularly a new-review of stochastic analytical considerations realized by the authors for friction forces estimation during hydrodynamic lubrication performed on the ground of the measurements of the gap height between two roughness surfaces. After numerous experimental measurements directly follows that the random unsymmetrical increments and decrements of the gap height of computer microbearings have important influence on the load carrying capacities and finally on the friction forces and wear of cooperating surfaces. The main topic demonstrates the influence of the variations of expectancy values and standard deviation of the computer microbearing gap height on the friction forces occurring in the HDD and microbearing fan. Moreover, it is observed the evident connection between the apparent dynamic viscosity and the features of the microbearing superficial surface. Hence after abovementioned remarks follows the corollary that the influence of the microbearing gap height stochastic variations connected with the surface roughness tend moreover indirect from the apparent viscosity into the friction forces variations. The synthetic, complex elaboration of obtained results indicates finally the influence of the random roughness in micro and nano level of microbearing surfaces on the friction forces distribution. A new results contained in this paper are obtained taking into account 3D variations of dynamic viscosity of the non-Newtonian lubricant, particularly variations crosswise the film thickness and influences of surface superficial layer features on the lubricant apparent viscosity.

16

Influence of piston ring profiles and oil temperature distribution on cylinder liner lubrication of a marine two-stroke engine

Wolff Andrzej

Combustion Engines

|

2019

|

R. 58, nr 3

257--263

EN

In the paper a comprehensive model of a piston-ring-cylinder (PRC) system has been presented. The local thickness of the oil film can be compared to height of the combined surface roughness of a cylinder liner and piston rings. Equations describing the mixed lubrication problem based on the empirical mathematical model formulated in works of Patir, Cheng and Greenwood, Tripp have been applied. The main parts of the model have been experimentally verified abroad by the author at the marine engine designing centre. In contrast to the previous papers of the author concerning the PRC system of combustion engines, new calculation results for a marine two-stroke engine have been presented. Firstly the right selection of barrel-shaped sliding surface of piston rings has been analysed. Secondly the influence of oil temperature distribution along the cylinder liner on the lubrication of the PRC system has been assessed. The developed model and software can be useful for optimization of the PRC system design.

17

The method of lubrication for vegetable grease

Wierzcholski K.

Journal of KONES

|

2018

|

Vol. 25, No. 3

497--504

EN

This article covers new aspects and a method of hydrodynamic lubrication of various friction pair using vegetable non-Newtonian greases. Biological greases and oils are applied in slide journal bearing lubrication occurring in farm and consumption machines working in pollution sensitive areas. Further applications can be found in humanoid robots joint lubrication as well as lubricants in various friction pairs, for example in gear and other friction nods. The following belong to new vegetable greases: Accu-Lube LB10000 as medium to heavy duty machining oil, Accu-Lube LB 4000 – light to medium duty machining oil. Bio-vegetable greases have very important characteristic features and they offer the following benefits: prevention of corrosion protection-preventing premature failure, maximum penetration-ensuring protection at the cable core, extreme wash-off resistance that guarantees protection in wet conditions. Furthermore, the presented vegetable greases have biodegradability properties; hence, this fact has important meaning in temporary environmental problems. The aim of this article is to present a new general analytical and numerical solution of the hydrodynamic lubrication problem, to determine the influence of the vegetable grease and its biological additions on the temperature distribution in the internal surfaces of the slide bearing sleeve and pressure distribution in the bearing gap or on the cooperating surfaces of the friction pair. The research methods and materials used in this article include the following: the Mathcad 15 Professional Program and new semi-analytical methods applied in connection with the theory of hydrodynamic lubrication extended to the curvilinear orthogonal surface and coordinates. Particular solutions are introduced to the cylindrical coordinates. The obtained results of the lubrication of the movable sleeve surface include a new model of the hydrodynamic lubrication theory. As a consequence of the new method of calculation indicated the intervals are provided of the increases and decreases of the dynamic viscosity of greases and the intervals of the hydrodynamic pressure increments and decrements versus of the pH (power hydrogen ion concentration) of greases and wettability of vegetable greases into cooperating surfaces.

18

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

Czaban A.

Journal of KONES

|

2018

|

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.

19

Maximum oil film temperature of a 4-lobe journal bearing with the lobes of small angular length

Strzelecki S.

Tribologia

|

2017

|

nr 5

87--92

EN

Multilobed journal bearings with the lobes of small angular length are often applied in the bearing systems of grinding machine spindles, which is the most important assembly in the grinding machine. The safe operation of such bearings at proper oil film temperature can be assured by the knowledge of thermal state of bearing and its maximum temperature. This paper presents the results of the calculations of some static characteristics of a 4-lobe bearing with the lobes of small angular length and particularly its maximum oil film temperature. The oil film pressure, temperature, and viscosity fields were obtained by an iterative solution of the Reynolds', energy, and viscosity equations. Adiabatic, laminar oil film and the static equilibrium position of journal were assumed.

PL

W ramach opisanych badań wyznaczono rozkłady ciśnienia, temperatury w filmie smarowym 4-powierzchnowego klasycznego łożyska. Wyznaczono maksymalne temperatury filmu smarowego dla założonych parametrów łożysk. Obliczenia przeprowadzono metodą różnic skończonych, rozwiązując równania Reynoldsa, energii i lepkości dla przypadku adiabatycznego filmu. Kod obliczeń numerycznych pozwala na analizę różnych parametrów geometrycznych i eksploatacyjnych łożyska, w tym ciśnienia zasilania środkiem smarowym. Stwierdzono wpływ zasilania ciśnieniowego na wszystkich krawędziach łożyska na charakterystyki statyczne. Zamiany względnego luzu łożyskowego nieznacznie wpływają na przemieszczenie czopa i minimalną grubość filmu smarowego.

20

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

Czaban A.

Journal of KONES

|

2017

|

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.