A 3D Conservative Model for Self-Lubricated Porous Journal Bearings in a Hydrodynamic Steady State

1999 ◽  
Vol 121 (3) ◽  
pp. 529-537 ◽  
Author(s):  
Marie-He´le`ne Meurisse ◽  
Bernard Giudicelli
Keyword(s):  
Steady State ◽  
Film Thickness ◽  
Outer Surface ◽  
3D Model ◽  
Journal Bearings ◽  
Capillary Effects ◽  
Porous Bearing ◽  
Proposed Model ◽  
Inner Surface ◽  
Theoretical Results

Successive steps in constructing a realistic conservative 3D model for hydrodynamic porous bearings are presented. They consist in iterative comparisons between theoretical results and industrial knowledge. This model is based on Darcy’s law for the porous bearing and an adaptation of Elrod’s model to a generalized Reynolds’s equation for the flow in the gap between the shaft and the bearing. Capillary effects at the outer surface of the bearing, and pore obstruction at its inner surface, leading to loss of permeability in the region where film thickness is minimal, are highlighted as phenomena which can prevent bearing leakage. They have been taken into account in the boundary conditions of the proposed model.

Wall Slip in EHD Journal Bearings

2008 ◽  
Author(s):  
A. Fatu ◽  
M. Hajjam ◽  
D. Bonneau
Keyword(s):  
Steady State ◽  
Film Thickness ◽  
Power Loss ◽  
Wall Slip ◽  
Journal Bearings ◽  
Ehd Lubrication ◽  
Lubrication Performance ◽  
Dynamically Loaded

In the present paper the influence of wall slip on the EHD lubrication performance is studed. Steady state and dynamically loaded bearings are investigated. The results show that well-chosen slip/no-slip regions can increase the film thickness and considerably decrease the power loss.

A CFD-Radial Motion Coupled Model for the Evaluation of the Features of Journal Bearings in External Gear Machines

2015 ◽  
Author(s):  
Matteo Pellegri ◽  
Andrea Vacca
Keyword(s):  
Steady State ◽  
Film Flow ◽  
Coupled Model ◽  
Journal Bearings ◽  
Instantaneous Axis Of Rotation ◽  
Proposed Model ◽  
Rigid Model ◽  
Hydrodynamic Effects ◽  
The Impact ◽  
Steady State Solutions

This paper presents an approach for the evaluation of the effects related to the behavior of the journal bearings on the operation of external gear machines (EGMs). In EGMs journal bearings usually support shafts of both gears. The prediction of their instantaneous axis of rotation is a key feature of EGMs, affecting the displacing action of the inter-teeth volumes and the leakages at the tip of each tooth. Past approaches presented in the literature for the evaluation of the radial micro-motions of the gears are based on classic simplified models for the hydrodynamic journal bearings based on steady-state solutions of the fluid film neglecting important hydrodynamic effects due to film squeeze — which can be relevant in case of significant radial loads variations — or they concentrate the focus of the study on the journal bearing itself regardless of the impact on the global machine operation. This work presents a CFD model coupled with a rigid model for the evaluation of the radial motions of the journal that permits to overcome the above-mentioned limitations of the existing approaches of study. The paper details the proposed model, in particular as concerns the CFD approach to solve the film flow and its coupling with a previously developed model (HYGESim) developed by the authors’ team for the evaluation of the overall operation of the EGM, used also to find the instantaneous loads on the gears. The potentials of the proposed approach are shown for the case of a pump for high pressure applications. For this case the results show how it is necessary to have a detailed approach for the evaluation of the journal bearings for a correct evaluation of the overall EGM behavior. In particular, the importance of hydrodynamic squeeze effects are shown, by comparing the model prediction with those given by the commonly used simplified steady-state approach. The comparison of simulation results with experimental data is also shown as pertain to pump case wear associated to the break in process.

A Generalized Solution on the Static Characteristics of Short Hydrodynamic Journal Bearings Using Harmonic Components

2016 ◽  
Author(s):  
Baisong Yang ◽  
Jiale Tian ◽  
Jian Zhou ◽  
Lie Yu
Keyword(s):  
Steady State ◽  
Film Thickness ◽  
Load Capacity ◽  
Harmonic Component ◽  
Generalized Solution ◽  
Journal Bearings ◽  
Hydrodynamic Bearing ◽  
Static Performance ◽  
Harmonic Components ◽  
The Relationship

A theoretical analysis has been done to investigate the static performance of short hydrodynamic journal bearings with a generalized film thickness expression by a sum of Fourier series equation. The hydrodynamic film thickness was written into a summation of an infinite harmonic component of trigonometric function. Reynolds equation with short bearing theory is solved for steady-state operations. In this paper, the steady-state analysis of the generalized hydrodynamic bearing has been done and compared with some typical journal bearings with respect to their harmonic components of film thickness, pressure distribution and load capacity. The relationship between the k-th order harmonic component of the film thickness H0,k and the static pressure component P0,k was established. It was found that the value of P0,k is directly determined not only by the k-th order harmonic component H0,k but also the (k−1)-th order component P0,k−1 indirectly produced by the previous harmonic component H0,k−1.This new investigation method can used to improve the performance of hydrodynamic journal bearings for shape optimization of hydrodynamic journal bearings.

A SEM and Light Microscope Study of the Epidermal Leaf Structures of the Carnivorous Plant, Sarracenia purpurea, L.

1971 ◽  
Vol 29 ◽  
pp. 358-359
Author(s):  
B. J. Panessa ◽  
J. F. Gennaro
Keyword(s):  
Methylene Blue ◽  
Toluidine Blue ◽  
Outer Surface ◽  
Microscope Study ◽  
Light Microscope ◽  
Carnivorous Plant ◽  
Sarracenia Purpurea ◽  
Inner Surface

Tissue from the hood and sarcophagus regions were fixed in 6% glutaraldehyde in 1 M.cacodylate buffer and washed in buffer. Tissue for SEM was partially dried, attached to aluminium targets with silver conducting paint, carbon-gold coated(100-500Å), and examined in a Kent Cambridge Stereoscan S4. Tissue for the light microscope was post fixed in 1% aqueous OsO4, dehydrated in acetone (4°C), embedded in Epon 812 and sectioned at ½u on a Sorvall MT 2 ultramicrotome. Cross and longitudinal sections were cut and stained with PAS, 0.5% toluidine blue and 1% azure II-methylene blue. Measurements were made from both SEM and Light micrographs.The tissue had two structurally distinct surfaces, an outer surface with small (225-500 µ) pubescent hairs (12/mm2), numerous stoma (77/mm2), and nectar glands(8/mm2); and an inner surface with large (784-1000 µ)stiff hairs(4/mm2), fewer stoma (46/mm2) and larger, more complex glands(16/mm2), presumably of a digestive nature.

Thermoelectric Power in Quantum Confined Bismuth Under Classically Large Magnetic Field

1990 ◽  
Vol 216 ◽  
Author(s):  
Kamakhya P. Ghatak ◽  
S. N. Biswas
Keyword(s):  
Magnetic Field ◽  
Quantum Dots ◽  
Quantum Well ◽  
Film Thickness ◽  
Quantum Wells ◽  
Thermoelectric Power ◽  
Large Magnetic Field ◽  
Quantum Well Wires ◽  
Electron Dispersion ◽  
Theoretical Results

ABSTRACTIn this paper we studied the thermoelectric power under classically large magnetic field (TPM) in quantum wells (QWs), quantum well wires (QWWS) and quantum dots (QDs) of Bi by formulating the respective electron dispersion laws. The TPM increases with increasing film thickness in an oscillatory manner in all the cases. The TPM in QD is greatest and the least for quantum wells respectively. The theoretical results are in agreement with the experimental observations as reported elsewhere.

Effect of Rolling Velocity and Maximum Hertzian Pressure on Fluid Film in Steady State EHL Line Contact with Rough Surface and Linear Piezoviscosity

2014 ◽  
Vol 592-594 ◽  
pp. 1371-1375
Author(s):  
Nitesh Talekar ◽  
Punit Kumar
Keyword(s):  
Surface Roughness ◽  
Steady State ◽  
Film Thickness ◽  
Rough Surface ◽  
Computer Code ◽  
Fluid Film ◽  
Line Contact ◽  
Rolling Velocity ◽  
Load Carrying ◽  
Lubricated Contact

Consideration of surface roughness in steady state EHL line contact is the first step towards understanding the lubrication of rough surface problem. Current paper investigates the use of sinusoidal waviness in the contact; more precisely it gives performance of real fluid in EHL line contact. The effect of various parameters like rolling velocity (U) and maximum Hertzian pressure (ph) on surface roughness by using properties of linear and exponential piezo-viscosity is taken into consideration to evaluate behavior of pressure distribution of load carrying fluid film and film thickness. Full isothermal, Newtonian simulation of EHL problem gives described effects. Spiking or fluctuation of pressure and film thickness curves is expected to show presence of irregularities on the surface chosen and amount of fluctuation depends on certain parameters and intensity of irregularities present. Rolling side domain of-4.5 ≤ X ≤ 1.5 with grid size ∆X=0.01375 is selected. A computer code is developed to solve Reynolds equation, which governs the generation of pressure in the lubricated contact zone is discritized and solved along with load balance equation using Newton-Raphson technique.

The Compliance of Solid, Wide-Faced Spur Gears

1990 ◽  
Vol 112 (4) ◽  
pp. 590-595 ◽  
Author(s):  
J. H. Steward
Keyword(s):  
Experimental Data ◽  
Contact Line ◽  
Load Distribution ◽  
3D Model ◽  
Spur Gear ◽  
Point Load ◽  
Spur Gears ◽  
Line Load ◽  
Gear Teeth ◽  
Theoretical Results

In this paper, the requirements for an accurate 3D model of the tooth contact-line load distribution in real spur gears are summarized. The theoretical results (obtained by F.E.M.) for the point load compliance of wide-faced spur gear teeth are set out. These values compare well with experimental data obtained from tests on a large spur gear (18 mm module, 18 teeth).

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