Wyniki wyszukiwania - Biblioteka Nauki

1

Pressure distribution in a curvilinear thrust bearing with pseudo - plastic lubricant

100%

Walicka A. , Walicki E. , Ratajczak M.

Applied Mechanics and Engineering

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1999

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tom Vol. 4, no spec.

81-88

EN

It is well known that lubricating oils, with viscosity index improver added, exhibit the non-Newtonian behavior the same as pseudo-plastic fluids. Starting from the most general fluid flow equation of the power law type expressing rate of shear in terms of powers of shear stress for non-Newtonian lubricants a modified form of Reynolds' equation is derived. The equation is solved by a perturbation method for the thrust bearing. The squeeze film bearing formed by two disks is discussed in detail.

2

Differences method topology of hydrodynamic pressure calculations from Reynolds equation

100%

Wierzcholski K.

Journal of KONES

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2010

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tom Vol. 17, No. 4

583-590

EN

The main topic of the presented paper concerns the method of determination and calculations of the general and particular numerical solutions of modified Reynolds equation in curvilinear orthogonal coordinates for curvilinear boundary conditions for hydrodynamic pressure distributions in bearing gap. A general solution matrix was derived and determined for various orthogonal coordinates of two cooperating bearing surfaces separated by the oil existing in slide Journal bearings. From mathematical point presented method of solution of modified Reynolds equation leads this problem to resolving the partial recurrence non homogeneous, linear equation of second order with variable coefficients. As an example the numerical hydrodynamic pressure calculation for slide bearing two cylindrical surfaces limited bearing gap with various eccentricities was in this paper performed. In numerical calculations are applied the formulae and calculation algorithm derived in this paper. Moreover, presented numerical topology of calculations in this paper enables to find the optimum way of determination of pressure values for an applied difference method regarding to the stability of solutions, convergences of the obtained values with various orthogonal shapes of cooperating surfaces. An adaptation of the known numerical difference method to the various curvilinear orthogonal boundary conditions applied during the hydrodynamic pressure determination on the two various curvilinear cooperating surfaces, to be decisive after author knowledge about a new achievement consisted in presented paper.

3

Elastohydrodynamic contact model for calculation of axial and angular stiffness in thrust bearing

89%

Temis M. , Lazarev A. , Temis M. , Lazarev A.

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nr 4

4

A New Star-Like SurfaceTexture for Enhanced Hydrodynamic Lubrication Performance

88%

Uddin M. S. , Liu Y. W. , Shankar S.

Archives of Metallurgy and Materials

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2017

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tom Vol. 62, iss. 3

1863--1869

EN

This paper presents a numerical modelling and optimization of a new ‘star-like’ geometric texture shape with an aim to improve tribological performance. Initial studies showed that the triangle effect is the most dominant in reducing the friction. Motivated with this, a ‘star-like’ texture shape consisting of a series of triangular spikes around the centre of the texture is proposed. It is hypothesised that by increasing the triangular effect on a texture shape, the converging micro-wedge effect is expected to increase, hence increasing the film pressure and reducing the friction. Using the well-known Reynolds boundary conditions, numerical modelling of surface texturing is implemented via finite difference method. Simulation results showed that the number of apex points of the new ‘star-like’ texture has a significant effect on the film pressure and the friction coefficient. A 6-pointed texture at a texture density of 0.4 is shown to be the optimum shape. The new optimum star-like texture reduces the friction coefficient by 80%, 64.39%, 19.32% and 16.14%, as compared to ellipse, chevron, triangle and circle, respectively. This indicates the potential benefit of the proposed new shape in further enhancing the hydrodynamic lubrication performance of slider bearing contacts.

5

The influence of the microgrooves on the hydrodynamic pressure distribution and load carrying capacity of the conical slide bearing

88%

Czaban A.

Journal of KONES

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2012

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tom Vol. 19, No. 3

85-91

EN

The aim of this work is to determine the hydrodynamic pressure distribution in oil film and the load carrying capacities of conical slide micro bearings with grooved sleeves. The results for some bearings examples are presented. For the bearings taken into account, the Reynolds equation was solved by the method of Finite Differences. In the calculations, the Reynolds boundary condition was applied. The simulation was performed for the conical slide micro bearings with the groves parallel to the cone generating line. The function of lubrication gap height for the conical slide bearings with sleeves covered with microgrooves was assumed on the basis of existing papers. The results obtained for the analogous bearings without the microgrooves are also shown, therefore the influence of microgrooves on the conical slide micro bearings can be observed. On the basis of the results, one can conclude, that applying microgrooves on the bearing sleeve surface causes the increase of the value of hydrodynamic pressure and longitudinal and transverse components of the load carrying capacity of the bearing. Furthermore, the effect of the microgrooves and their impact is noticeable in graphs of hydrodynamic pressure distribution. The applied method of investigation of the impact of microgrooves on a bearing operation is simpler and less expensive than the experimental studies, however it is necessary to verify that the results obtained with this method are correct and whether in fact applying microgrooves, besides form facilitate lubrication, causes the improvement in bearing operating parameters.

6

Nośność płaskiego łożyska ślizgowego przy laminarnym niestacjonarnym smarowaniu

75%

Krasowski P.

Modelowanie Inżynierskie

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2008

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tom T. 5, nr 36

201-206

PL

W artykule przedstawiono przykadowe wyniki rozwiązania zmodyfikowanego równania Reynoldsa opisującego laminarny niestacjonarny przepływ oleju smarującego w szczelinie smarnej płaskiego poprzecznego łożyska ślizgowego o liniowo zbieżnej wysokości szczeliny smarnej. Uwzględniono niestacjonarne zaburzenia prędkości przepływu oleju na powierzchni bieżni i suwaka łożyska. Wyniki rozwiązania dotyczą izotermicznego modelu łożyska o nieskończonej szerokości smarowanego olejem o lepkości dynamicznej zależnej od ciśnienia. Analizowano zmianę nośności hydrodynamicznej łoyska przy różnych zaburzeniach prędkości przepływu oleju w kierunku wzdłużnym łożyska. Wyniki obliczeń przedstawiono w postaci bezwymiarowych charakterystyk zmiany siły nośności i jej położenia

EN

This paper shows results of numerical solutions an modified Reynolds equations for laminar unsteady oil flow in slide journal bearing with planar linear gap. This solution example apply to isothermal bearing model with infinity breadth. Lubricating oil used in this model has Newtonian properties and dynamic viscosity in dependence on pressure. It shows a preliminary analysis change of capacity forces in the bearing by laminar, unsteady lubrication caused by velocity perturbations of oil flow in the longitudinal direction of a bearing.

7

Nośność łożyska ślizgowego przy laminarnym, niestacjonarnym smarowaniu

75%

Krasowski P.

Tribologia

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2004

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tom nr 5

113-126

PL

W prezentowanej pracy przedstawiono wyniki rozwiązania numerycznego laminarnego niestacjonarnego smarowania poprzecznego cylindrycznego łożyska ślizgowego. Przykład rozwiązania dotyczy łożyska o nieskończonej szerokości smarowanego olejem o własnościach newtonowskich i stałej lepkości dynamicznej. Uwzględniono zaburzenia związane z niestacjonarnością prędkości czynnika smarującego w kierunku obwodowym na czopie i na panewce łożyska cylindrycznego. Zaburzenia te mogą być spowodowane drganiami skrętnymi czopa oraz drganiami obrotowymi panewki wraz z obudową. Uwzględnienie obu rodzajów zaburzeń periodycznych o tych samych częstościach działających niezależnie od siebie umożliwia badanie wpływu każdego z nich na parametry eksploatacyjne łożyska ślizgowego: ciśnienie hydrodynamiczne i siła nośności. Wyniki przedstawiono w postaci wykresów bezwymiarowego ciśnienia hydrodynamicznego w poszczególnych chwilach czasowych trwania zaburzenia. Wyznaczono także przebieg nośności hydrodynamicznej łożyska w czasie. Otrzymane rozwiązania porównano z rozwiązaniem przy przepływie stacjonarnym w łożysku ślizgowym o tych samych parametrach geometrycznych i obciążeniu.

EN

In this paper are presented results of numerical solution of laminar, unsteady lubrication of cylindrical slide journal bearing. Laminar, unsteady oil flow is performed during periodic and not periodic perturbations of bearing load or is caused by the changes of gap height in the time. Above perturbations occur mostly during the starting and stopping of machine. The particular solutions are limited to infinite width of bearing length and to the constant oil viscosity and additionally to the Newtonian oil properties. The unsteady amplitudes of sleeve vibrations and journal vibrations are taking into account. The results are shown on diagrams of hydrodynamic pressure in dimensionless form in time intervals of displacement duration. Received solutions were compared with the solutions which were made by steady flow in slide bearing with the same geometrical and load parameters.

8

The analysis of oil balance in crank bearing

75%

Kyureghyan K. , Piekarski W.

Teka Komisji Motoryzacji i Energetyki Rolnictwa

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2014

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tom 14

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nr 4

9

Effect of transverse surface roughness on the behaviour of squeeze film in a spherical bearing

75%

Andharia P. I. , Gupta J. L. , Deheri G. M.

Applied Mechanics and Engineering

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1999

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tom Vol. 4, no spec.

19-24

EN

Effect of transverse roughness on the behaviour of a hydrodynamic squeeze film between a non-rotating spherical surface and a hemispherical bearing under a steady load is discussed. It is assumed that the bearing surface as well as the surface of the approaching sphere have random roughness which is distributed throughout the surfaces. The stochastic film thickness characterizing the roughness is assumed to be symmetric with non-zero mean (a) and variance (s2). The modified Reynolds equation is solved and then the expressions for pressure, load carrying capacity and the response time are obtained and numerically computed. The results are presented both in graphical as well as tabular form. It is observed that the composite roughness of the surfaces affects the performance of the bearing adversely.

10

Active damping vibrations of the inertia input for the asymmetric shaft supported on the bearings lubricate liquid

75%

Starczewski Z.

Mechanics and Mechanical Engineering

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2006

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tom Vol. 10, nr 1

126-137

EN

The paper discusses some possibility of the arising damp vibrations under inertia input for asymmetric rotor supported in the cylindrical slide bearing lubricated by electro fluid. It is shown that the effect of the electric field on the individual bearings junction makes it possible to achieve similar vibrations for both journals bearing although with strong asymmetry. The phenomenon discussed that increasing intensity of the electric field causes a reduction of the forced vibration but the self - excitation threshold moves in direction to the lower rotation speed.

11

Elastohydrodynamic Contact Model for Calculation of Axial and Angular Stiffness in Thrust Bearing

75%

Temis M. , Lazarev A.

Archive of Mechanical Engineering

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2012

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tom Vol. LIX, nr 4

453--467

EN

Thrust bearing model is developed for fluid flow calculation and for determination of bearing integral characteristics in the presence of sliding surfaces closure and shaft angular displacements. The model is based on the coupled solution of the problem of incompressible fluid flow between the sliding surfaces and the problem of bearing and shaft elements deformation under the action of the fluid film pressure. Verification of the bearing model results is carried out by the comparison versus the fluid flow calculation results obtained by STAR-CD software and the experimental and theoretical results represented in the certain literature. Thrust bearing characteristics are determined versus sliding surfaces closure and rotating disk (runner) angular displacements. The contribution of the sliding surfaces deformations into bearing integral characteristics is estimated.

PL

Opracowano model łożyska oporowego przeznaczony do obliczeń przepływu płynu i wyznaczania całościowych charakterystyk dla warunków gdy występuje zamknięcie szczeliny między ślizgającymi się powierzchniami i kątowe przemieszczenie wału. Model jest oparty na połączonych rozwiązaniach zagadnienia przepływu nieściśliwego płynu między ślizgającymi się powierzchniami i zagadnienia deformacji elementów łożyska i wału pod wpływem ciśnienia w warstwie płynu. Weryfikacja wyników modelu łożyska jest przeprowadzona przez ich porównanie z wynikami obliczeń przepływu płynu uzyskanymi przy użyciu oprogramowania STAR-CD oraz wynikami eksperymentalnymi i teoretycznymi podawanymi w literaturze. Charakterystyki łożyska ślizgowego są wyznaczone z uwzględnieniem zamknięcia szczeliny smarnej i przemieszczeń kątowych tarczy obrotowej (oporowej). Oszacowano wpływ, jaki mają odkształcenia ślizgających się powierzchni na całościowe charakterystyki łożyska.

12

Ciśnienie w płaskim łożysku ślizgowym przy niestacjonarnym laminarnym smarowaniu

75%

Krasowski P.

Modelowanie Inżynierskie

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2007

|

tom T. 2, nr 33

101-106

PL

W artykule analizowano łożysko płaskie o liniowo zbieżnej wysokości szczeliny smarnej. Uwzględniono niestacjonarne zaburzenia prędkości przepływu oleju na powierzchni bieżni i suwaka łożyska. Uzyskano rozwiązania w postaci zmian ciśnienia dla izotermicznego modelu łożyska o nieskończonej szerokości smarowanego olejem o lepkości dynamicznej zależnej od ciśnienia. Periodyczne zaburzenia prędkości wzdłuż szczeliny smarnej mogą być spowodowane drganiami wzdłużnymi elementów łożyska: bieżni i suwaka.

EN

This paper shows results of numerical solutions an modified Reynolds equations for laminar unsteady oil flow in slide journal plane bearing gap. It shows a preliminary analysis of pressure distribution change in the bearing by velocity perturbations of oil flow in the longitudinal direction of a bearing. Described effect can be used as an example of modeling the bearing friction node operations in reciprocating movement during exploitation of engines and machines. Plane crossbar journal bearing occur in ship combustion engine as a crosshead bearing.

13

Performance of magnetic fluid based rotating rough circular step bearings

75%

Patel H. C. , Deheri G. M. , Patel R. M.

International Journal of Applied Mechanics and Engineering

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2008

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tom Vol. 13, no 2

441-455

EN

An attempt has been made to analyze the performance of a magnetic fluid based rotating rough circular step bearing. The roughness of the bearing surface is modeled by a stochastic random variable with non zero mean, variance and skewness. The associated Reynolds' equation is solved with appropriate boundary conditions to obtain the pressure distribution, which in turn, is used to get the load carrying capacity leading to the calculation of response time. Results are presented graphically as well as in a tabular form. It is noticed that the bearing suffers on account of transverse surface roughness. This article makes it clear that pressure, load carrying capacity and response time increase with increasing the magnetization parameter. However, the negatively skewed roughness and radii ratio induce better performance. It is noticed that the load carrying capacity decreases when both plates rotate in the same direction. This trend reverses when the plates move in the opposite direction. This article reveals that the negative effect caused by porosity and roughness can be compensated to a considerable extent by the positive effect induced by the magnetization parameter and the aspect ratio in the case of negatively skewed roughness when the plates rotate in opposite direction.

14

Effect of surface roughness on the performance of hydromagnetic squeeze film between conducting porous infinitely long rectangular plates

75%

Vadher P. A. , Deheri G. M. , Patel R. M.

International Journal of Applied Mechanics and Engineering

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2008

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tom Vol. 13, no 2

473-498

EN

An attempt has been made to study and analyze the performance of a hydromagnetic squeeze film between conducting porous rough infinitely long rectangular plates with electrically conducting lubricant in the presence of a transverse magnetic field. The bearing surfaces are assumed to be transversely rough. The random roughness is characterized by a stochastic random variable with non zero mean, variance and skewness. The associated Reynolds' equation is then stochastically averaged with respect to the random roughness parameter. This equation is solved with appropriate boundary conditions to find the pressure distribution, which is then used to obtain the load carrying capacity. Lastly, the response time is calculated. The results are presented graphically as well as in a tabular form. It is seen that the bearing system gets affected adversely owing to transverse surface roughness. But variance (-ve) tends to increase the load carrying capacity. Also, the bearing system resists an enhanced performance due to hydromagnetization. In addition, the load carrying capacity increases considerably due to conductivity while it decreases with respect to the aspect ratio The combined effect of porosity, the aspect ratio and the standard deviation associated with roughness is substantially adverse. However, this negative effect can be compensated to some extent by hydromagnetization and conductivity in the case of negatively skewed roughness. It is also observed that the bearing with magnetic field can support a load even when there is absence of flow. This investigation makes it plain and clear that roughness must be given due consideration while designing the bearing system.

15

Theoretical investigation on the static properties of the finite porous journal bearings

75%

D'Agostino V. , Guida D. , Ruggiero A. , Senatore A.

International Journal of Applied Mechanics and Engineering

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2004

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tom Vol. 9, no spec.

321-328

EN

A theoretical analysis is carried out to determine the analytical approximate description of the fluid film force of porous finite journal bearings. The investigation has been conducted assuming the Warner solution for the pressure field and the approximate analytical solution for the long porous journal bearings proposed by D'Agostino et al. (2004). The analytical approach for studying the behaviour of a system is more effective than a numerical one because of it allows to cover not only the individual case but the whole class to which the system belongs. Furthermore, the model proposed allows a quick analytical determination of the fluid film force for different values of the permeability coefficient, L/D ratio, eccentricity ratio. The results are in good agreement with those achieved by means of the FDM based solution.

16

An analytical solution for the pressure field in the long porous journal bearings

75%

D'Agostino V. , Guida D. , Ruggiero A. , Senatore A.

International Journal of Applied Mechanics and Engineering

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2004

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tom Vol. 9, no spec.

313-319

EN

Analytical solutions of the Reynolds equation for the porous journal bearings are not generally achievable and numerical methods must be involved. This paper presents an approximate mathematical model for the one-dimensional lubrication equation for the infinitely long porous journal bearing, obtaining a good agreement over the ranges of operating conditions of this tribological component.

17

Ciśnienie i nośność w poprzecznym łożysku ślizgowym smarowanym olejem mikropolarnym

75%

Krasowski P.

Zeszyty Naukowe Akademii Morskiej w Gdyni

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2009

|

tom nr 60

105-118

PL

W referacie omowiono i przedstawiono rozwiązanie numeryczne równania Reynoldsa opisującego laminarny, stacjonarny przepływ czynnika smarującego o strukturze mikropolarnej w poprzecznym cylindrycznym łożysku ślizgowym. Założono stałą gęstość oraz lepkości dynamiczne charakteryzujące ciecz mikropolarną. Punktem wyjścia są równania pędu, momentu pędu oraz rownanie ciągłości przepływu, z ktorych otrzymano rownanie Reynoldsa. Wyniki są przedstawione w postaci rozkładu ciśnienia, jego wartości maksymalnej oraz nośności hydrodynamicznej w zależności od wartości liczby sprzężenia N² i bezwymiarowego parametru długości �[lambda]&sub1 cieczy mikropolarnej. Prezentowane wyniki przedstawiono w postaci charakterystyk bezwymiarowych i porównano z rozwiązaniami dla oleju newtonowskiego o stałej lepkości dynamicznej.

EN

Present paper shows the results of numerical solution Reynolds equation for laminar, steady oil flow in slide bearing gap. Lubrication oil is fluid with micropolar stucture. Properties of oil lubrication as of liquid with micropolar stucture in comparison with Newtonian liquid, characterized are in respect of dynamic viscosity additionally dynamic couple viscosity and three dynamic rotation viscosity. Under regard of build structural element of liquid characterized is additionally microinertia coefficient. In modeling properties and structures of micropolar liquid one introducet dimensionless parameter with in terminal chance conversion micropolar liquid to Newtonian liquid. The results shown on diagrams of hydrodynamic pressure and capacity forces in dimensionless form in dependence on coupling number N² and characteristic dimensionless length of micropolar fluid [lambda]&sub1. Presented calculations are limited to isothermal models of bearing with infinite length.

18

The influence of oil’s exploitation time on load carrying capacity in a slider bearing

75%

Sikora G. , Miszczak A.

Journal of KONES

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2015

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tom Vol. 22, No. 3

207--212

EN

In this paper, authors are presenting conclusions of the numerical calculations of pressure distribution and capacity in a slider bearing with taking changes of oil viscosity in exploitation time into account. Changes of the engine oil’s viscosity, which depend on the exploitation time, were determined on Haake Mars III rheometer and the conclusions were published in Solid State Phenomena and Logistyka in 2015. Numerical calculations were performed by solving of Reynolds equation, using finite difference method and own calculation procedures in Mathcad 15. Reynolds equation was developed by solving the continuity equation and the momentum conservation equation from the fundamentals. For the considerations, the laminar and stationary lubricating of the slider bearing of finite length and full angle of wrap were taken. Assumption of the stationary flow concerns lack of changes in flow parameters in short period of considered phenomena, f. ex. in one hour. Smooth and non-porous bushing were assumed. The aim of this paper was preliminary estimation of influence of viscosity changes in the exploitation time on the load carrying capacities of the cross slider bearing. Wherefore, the viscosity changes dependence on the pressure, temperature and also shear rate, were not taken into account. The basic equations were developed to the non-dimensional form and estimated according to the thin layer theory. In the calculations, the Reynolds boundary conditions concerning pressure distribution were taken into account. Preliminary calculations were performed for different models of viscosity changes in time and circumstances, where the viscosity increases and decreases in exploitation time.

19

Reodynamics of lubricating curvilinear thrust bearings with Ellis pseudo-plastic fluid.

63%

Ratajczak M. , Walicka A. , Walicki E. , Ratajczak P.

Zagadnienia Eksploatacji Maszyn

|

2006

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tom Vol. 41, nr 2

147-158

EN

The paper addresses the problems of flow of Ellis pseudo-plastic fluid in the clearance of thrust bearing with curved surfaces. On the basis of analytic solutions to the equations of motion - presented in the orthogonal curvilinear coordinates system - formulae for pressure distribution are given. The research focuses on the determination of the effect of inertia components (suitably simplified equations of motion) on the flow area. The solutions obtained are illustrated with examples of flows in flat and spherical bearings.

PL

W artykule autorzy przedstawiają zagadnienia przepływu płynu pseudoplastycznego Ellisa w szczelinie krzywopowierzchniowego łożyska wzdłużnego. W oparciu o rozwiązania analityczne równań ruchu - przedstawionych w krzywoliniowym ortogonalnym układzie współrzędnych - podano formuły na rozkład ciśnienia. Badania w szczególności koncentrowały się na określeniu wpływu składników bezwładnościowych (odpowiednio uproszczonych równań ruchu) na pole przepływu. Otrzymane rozwiązania zilustrowano przykładami przepływów w łożyskach płaskich i kulistych.

20

Effect of relative velocity between rough surfaces: hydrodynamic lubrication of rotary lip seal

63%

Lahjouji I. , El Gadari M. , El Fahime B. , Radouani M.

International Journal of Applied Mechanics and Engineering

|

2017

|

tom Vol. 22, no. 2

321--332

EN

Since the sixties, most of numerical studies that model the rotary lip seal lubrication have been restricted by assuming that one of the two opposing surfaces is smooth: either the lip or the shaft. This hypothesis, although it is verified only for a shaft roughness ten times smaller than that of the seal, is the best solution to avoid the transient term “∂h/∂t” in the deterministic approach. Thus, the subject of the present study is twofold. The first part validates the current hydrodynamic model with the international literature by assuming the asperities on the lip and shaft as a two-dimensional cosine function. In the second part the Reynolds equation for rough surfaces with relative motion is solved. The numerical results show that the relative motion between rough surfaces impacts significantly the load support and the leakage rate, but affects slightly the friction torque.