An Assessment of the Value of Theory in Predicting Gas-Bearing Performance

1961 ◽  
Vol 83 (2) ◽  
pp. 195-200 ◽  
Author(s):  
S. Cooper
Keyword(s):  
Steady State ◽  
Slip Velocity ◽  
Reynolds Equation ◽  
Energy Equation ◽  
Experimental Methods ◽  
Experimental Results ◽  
Theoretical Investigations ◽  
Gas Bearing ◽  
Theoretical Results

The object of the paper is to indicate the value of theoretical investigations of hydrodynamic finite bearings under steady-state conditions. Methods of solution of Reynolds equation by both desk and digital computing, and methods of stabilizing the processes of solution, are described. The nondimensional data available from the solutions are stated. The outcome of an attempted solution of the energy equation is discussed. A comparison between some theoretical and experimental results is shown. Experimental methods employed and some difficulties encountered are discussed. Some theoretical results are given to indicate the effects of the inclusion of slip velocity, stabilizing slots, and a simple case of whirl.

Transient Dynamics of a Tilting Pad Gas Bearing System

1967 ◽  
Vol 89 (4) ◽  
pp. 499-507 ◽  
Author(s):  
V. Castelli ◽  
J. T. McCabe
Keyword(s):  
Steady State ◽  
Reynolds Equation ◽  
Journal Bearing ◽  
Degree Of Freedom ◽  
Performance Characteristics ◽  
Experimental Results ◽  
Transient Dynamics ◽  
Tilting Pad ◽  
Gas Bearing ◽  
Bearing System

A method for obtaining the performance characteristics of a rotor-tilting pad gas lubricated journal bearing system by solving the appropriate dynamics equations together with the time-transient Reynolds’ equation is outlined. Results for a 4 degree of freedom and an 18 degree of freedom system are given. Comparison with steady-state and experimental results are also discussed.

Analysis of Thermal Effects in Hydrodynamic Bearings

1986 ◽  
Vol 108 (2) ◽  
pp. 219-224 ◽  
Author(s):  
R. Boncompain ◽  
M. Fillon ◽  
J. Frene
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Thermal Effects ◽  
Reynolds Equation ◽  
Energy Equation ◽  
Heat Transfer Equation ◽  
Reversed Flow ◽  
Theoretical Results ◽  
Generalized Reynolds Equation ◽  
Good Agreement

A general THD theory and a comparison between theoretical and experimental results are presented. The generalized Reynolds equation, the energy equation in the film, and the heat transfer equation in the bush and the shaft are solved simultaneously. The cavitation in the film, the lubricant recirculation, and the reversed flow at the inlet are taken into account. In addition, the thermoelastic deformations are also calculated in order to define the film thickness. Good agreement is found between experimental data and theoretical results which include thermoelastic displacements of both the shaft and the bush.

Surface Roughness Effects in High-Speed Hydrodynamic Journal Bearings

1997 ◽  
Vol 119 (4) ◽  
pp. 776-780 ◽  
Author(s):  
H. Hashimoto
Keyword(s):  
Surface Roughness ◽  
High Speed ◽  
Reynolds Equation ◽  
Computation Time ◽  
Experimental Results ◽  
Roughness Effects ◽  
Modified Reynolds Equation ◽  
Nonlinear Simultaneous Equations ◽  
Theoretical Results ◽  
Good Agreement

This paper describes an applicability of modified Reynolds equation considering the combined effects of turbulence and surface roughness, which was derived by Hashimoto and Wada (1989), to high-speed journal bearing analysis by comparing the theoretical results with experimental ones. In the numerical analysis of modified Reynolds equation, the nonlinear simultaneous equations for the turbulent correction coefficients are greatly simplified to save computation time with a satisfactory accuracy under the assumption that the shear flow is superior to the pressure flow in the lubricant films. The numerical results of Sommerfeld number and attitude angle are compared with the experimental results to confirm the applicability of the modified Reynolds equation in the case of two types of bearings with different relative roughness heights. Good agreement was obtained between theoretical and experimental results.

Pressure Boundary Layer in a Transient or Steady Gas Film and Mass Interaction

1970 ◽  
Vol 37 (4) ◽  
pp. 945-953 ◽  
Author(s):  
F. C. Hsing ◽  
H. S. Cheng
Keyword(s):  
Boundary Layer ◽  
Steady State ◽  
High Speed ◽  
Numerical Scheme ◽  
Reynolds Equation ◽  
Equations Of Motion ◽  
Pressure Profile ◽  
Tilting Pad ◽  
Static Solutions ◽  
Gas Bearing

This paper presents a numerical scheme capable of yielding accurate pressure profile for the transient and steady hydrodynamic gas film generated by high-speed relative motion of two nonparallel surfaces. The numerical difficulties associated with high compressibility numbers for the gas film Reynolds equation were overcome by employing a set of systematically generated irregular grid spacings based on a coordinate transformation. By coupling the fluid-film solution with the equations of motion of a tilting pad, the dynamics of the mass film interaction were treated. Results are presented for both steady-state and dynamical solutions. Static solutions for a 120-deg partial-arc gas bearing have been used for comparison.

Transient Effects in the Lubrication of Hertzian Contacts

1971 ◽  
Vol 13 (3) ◽  
pp. 173-189 ◽  
Author(s):  
J. P. Vichard
Keyword(s):  
Experimental Study ◽  
Steady State ◽  
Reynolds Equation ◽  
Hydrodynamic Theory ◽  
Classical Approach ◽  
Transient Effects ◽  
Thermal Origin ◽  
Squeeze Effect ◽  
Rigid Surfaces ◽  
Theoretical Results

Analysis of the lubrication of mechanisms such as gears, roller bearings and cams shows that their contacts involve a squeeze effect when they operate. The classical approach, however, is to limit investigations to steady state conditions. The aim of our work is to estimate the validity of this hypothesis. First, we shall examine the behaviour of contacts with rigid surfaces and we shall compare the results with the Martin theory. The straightforwardness of the derivation of the Reynolds equation allows us to study the effect thoroughly. The squeeze effect contributes to damp down the variations of the external parameters, such as load or speed. Secondly, this result is confirmed in elasto-hydrodynamic theory. In this case the exact calculation is too complicated and we have used the Grubin's approximation. Finally, an experimental study will confirm the theoretical results and will show a phenomenon which has a thermal origin.

scholarly journals Rotordynamic Coefficients of Long Staggered Labyrinth Gas Seals

1995 ◽  
Vol 1 (3-4) ◽  
pp. 285-291 ◽  
Author(s):  
K. Kwanka ◽  
W. Ortinger
Keyword(s):  
Rotational Speed ◽  
Pressure Difference ◽  
Axial Flow ◽  
Momentum Equation ◽  
Bulk Flow ◽  
Experimental Results ◽  
Rotordynamic Coefficients ◽  
Theoretical Investigations ◽  
Gas Seals ◽  
Theoretical Results

Experimental and theoretical investigations concerning a long staggered labyrinth gas seal are presented. Accurate static measurements help to assess the influence of the entry swirl, the rotational speed and the pressure difference on the conservative and the nonconservative force. For a better understanding of the phenomena the forces in each cavity are investigated. A coupling between the circumferencial flow and the axial flow in the cavity is revealed. The theoretical results are obtained by a one-volume bulk-flow theory which is essentially based on the momentum equation in circumferencial direction and therefore neglects some effects caused by the axial flow. The experimental results are compared to calculated results.

scholarly journals Synergy between Experimental and Theoretical Investigations Reveals the Anti‑Corrosion Efficiency of Imine-Chalcones

2021 ◽  
Author(s):  
Mariana Carlos ◽  
Neubi Xavier Jr. ◽  
Antônio da Silva Jr. ◽  
Marcelo Neves ◽  
Aurea Echevarria ◽  
...  
Keyword(s):  
Electrochemical Techniques ◽  
Steel Corrosion ◽  
Experimental Methods ◽  
Polarizable Continuum Model ◽  
Efficient Inhibitor ◽  
Theoretical Investigations ◽  
Experimental Parameters ◽  
Polarizable Continuum ◽  
Periodic Calculations ◽  
Theoretical Results

The inhibitory action of three imine-chalcones on carbon steel corrosion in HCl was investigated by theoretical and experimental methods. Quantum descriptors were calculated at the conductor-like polarizable continuum model (CPCM)-Becke-3 Parameter-Lee-Yang-Parr (B3LYP)‑D3/def2-TZVPP level allowing the prediction of efficiency inhibition ranking. Electrochemical techniques and mass loss experiments were employed to determine inhibition efficiencies and related experimental parameters. Scanning electron microscopy was employed for metal surface analysis. The N-[(1Z,2E)-1,3-diphenylprop-2-in-1-ylidene]-1-phenethylamine (IM‑F) was pointed out as the most efficient inhibitor in this group, with 96% of corrosion inhibition. Moreover, theoretical results obtained from periodic calculations for the adsorption on the Fe(110) surface corroborated the highest efficacy of IM‑F.

The Development of a Generally Applicable Digital Computer Spokes Tyre Model

1991 ◽  
Author(s):  
M. El-Nashar ◽  
M. Watany
Keyword(s):  
Steady State ◽  
Testing Machine ◽  
Contact Forces ◽  
Experimental Results ◽  
Single Plane ◽  
Tyre Model ◽  
Engineering Department ◽  
Out Of Plane ◽  
Experimental Findings ◽  
Theoretical Results

Abstract An extensive survey is presented for the analysis of both in-plane and out-of-plane pneumatic tyre models. The single plane tyre model[2,9] is developed to represent the influence of tyre width by using many conical shell shapes built from spokes with different head angles. The general form of the new tyre model is based on the well-known single plane steady state version of the tyre model. The mathematical analysis and geometrical form of the developed model is given. A computer program is designed for desk top P.C. without costly running times which makes it useful for representing the pneumatic tyre/road contact forces. Model assumptions and parameters were chosen to give qualitative and quantitative agreements between theoretical and experimental results. The paper also presents an experimental study for investigating the influence of working conditions on tyre/road contact forces. The experimental results were carried out using the steady state tyre testing machine constructed in the Automotive Engineering Department, Helwan University [3,10]. Experimental findings for 145 SR 13 tyres are compared with the new model theoretical results. Experiments on real tyres show good agreement with the predicted theoretical results of the new generally applicable model.

Experimental and Theoretical Investigations of Complex Formation of Substituted Phenylazo-Derivatives of Methylphloroglucinol

2016 ◽  
Vol 12 (8) ◽  
pp. 295-300
Author(s):  
Olga Kovalchukova ◽  
Amangdam A.T. ◽  
Strashnova S.B. ◽  
Strashnov P.V. ◽  
Romashkina E.P. ◽  
...  
Keyword(s):  
Complex Formation ◽  
Organic Ligand ◽  
Spectrophotometric Titration ◽  
Organic Ligands ◽  
Oh Groups ◽  
Tautomeric Forms ◽  
Theoretical Investigations ◽  
Derivatives Of ◽  
Theoretical Results ◽  
Titration Technique

Using spectrophotometric titration technique, the processes of complex formation of some phenylazo-derivatives of methylphloroglucinol (MPG) containing hydroxo-, nitro- and nitroso-substituents were studied. The spectral criteria of neutral and ionized forms of the organic ligands in their different tautomeric forms were determined.It was detected that the complex formation is accompanied by formation of one or two chelate cycles which involve azo- or nitroso-fragments and neighboring OH-groups of the organic ligands. Different types of coordination lead to different changes in the electronic absorption spectra.The DFT-B3LYP modeling of a Ni(II) complex of α-hydroxyphenylazo MPG established the most probable coordination mode of the organic ligand: tridentate chelating dianion, distorted square coordination of Ni-cations including one water molecule.  The theoretical results are in a good accordance with the experimental data.

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