Stability of Unsymmetrical Rigid Rotor Supported by Self-Acting Gas-Lubricated Journal Bearings

1983 ◽  
Vol 105 (4) ◽  
pp. 656-661 ◽  
Author(s):  
S. Yoshimoto ◽  
Y. Nakano
Keyword(s):  
Theoretical Approach ◽  
Journal Bearings ◽  
Center Of Gravity ◽  
Rigid Rotor ◽  
Load Bearing ◽  
Bearing Clearance ◽  
Axial Deviation ◽  
Bearing Load ◽  
Theoretical Results ◽  
Good Agreement

In order to determine the threshold of instability for an unsymmetrical rigid rotor supported by two identical self-acting, plain-cylindrical gas journal bearings, a theoretical approach is made by the use of the quasi-static nonliner PH method. Influence of various parameters affecting the threshold of instability of the unsymmetrical rotor is experimentally shown and compared with the theoretical results. The experimental variables considered in this paper include bearing load, bearing length, bearing clearance, the axial deviation of the center of gravity from the center of the rotor span. Good agreement was obtained between the experimental and theoretical results.

Comparison Between Theories and Experiments for the Threshold of Instability of Rigid Rotor in Self-Acting, Plain-Cylindrical Journal Bearings

1964 ◽  
Vol 86 (2) ◽  
pp. 321-327 ◽  
Author(s):  
C. H. T. Pan ◽  
B. Sternlicht
Keyword(s):  
Experimental Data ◽  
Journal Bearings ◽  
Experimental Results ◽  
Stable Operation ◽  
Rigid Rotor ◽  
Bearing Load ◽  
Comparison With Experimental Data ◽  
Good Agreement

The threshold of half-frequency whirl for a rigid rotor in self-acting, plain-cylindrical journal bearings is analyzed by several methods, and the results are compared. The correlation among the various approaches appears to be good. The simplest method of analysis is, therefore, used for comparison with experimental data. Experimental results showing the effect of bearing length and bearing load are compared with theory. The influence of bearing length on the threshold speed follows closely the trend of the calculated results; however, the experimental threshold speeds are always a little higher. In comparing the effect of bearing load it is seen that the calculated threshold speed is consistently somewhat over-pessimistic, but the influence of rotor inclination is in very good agreement with experimental data. The methods presented in this paper can be used readily in design to insure stable operation with plain-cylindrical journal bearings.

Thermal Behavior and Friction in Journal Bearings

1970 ◽  
Vol 92 (3) ◽  
pp. 373-380 ◽  
Author(s):  
Al. Nica
Keyword(s):  
Experimental Data ◽  
Thermal Behavior ◽  
Heat Dissipation ◽  
Journal Bearings ◽  
Friction Torque ◽  
Operating Characteristics ◽  
Lubricant Flow ◽  
Theoretical Predictions ◽  
Theoretical Results ◽  
Good Agreement

This paper deals with friction and the field of temperature in the lubricant film of journal bearings. Theoretical results regarding the thermal behavior are checked with experimental data and good agreement is found. Emphasis is put on the variation of temperature and lubricant flow with the operating characteristics of the bearing and it is seen that theoretical predictions for minima of friction torque are backed by temperature measurements. Further on, the friction torque and the mechanism of heat dissipation in bearings are dealt with, in order to verify the assumptions used in the calculation schemes. The means of efficiently cooling the bearing are also discussed, as well as the part played by the divergent zone in this process.

Study of Electrical Conductivity in WO3-doped Nonstoichiometric LiTaO3

2012 ◽  
Vol 57 (8) ◽  
pp. 834
Author(s):  
M. Tahiri ◽  
N. Masaif ◽  
A. Jennane ◽  
E.M. Lotfi
Keyword(s):  
Experimental Data ◽  
Electrical Conductivity ◽  
Ternary System ◽  
Curie Temperature ◽  
Solid Solutions ◽  
Theoretical Approach ◽  
Defect Structure ◽  
Experimental Conductivity ◽  
Theoretical Results ◽  
Good Agreement

The results of experimental and analytical studies of the electrical conductivity for different solid solutions synthesized in a vicinity of LiTaO3 in the ternary system Li2O–Ta2O5–(WO3)2 are presented. It is shown that the electrical conductivity increases linearly with the Curie temperature. The experimental conductivity between 200 and 700 ºC was measured using an LCR bridge HP4192A on ceramics sintered at 1250 ºC. Within the theoretical approach to the defect structure analysis combined with our proposed vacancy models, the theoretical results are in a good agreement with the experimental data.

Surface Finish and Clearance Effects on Journal-Bearing Load Capacity and Friction

1959 ◽  
Vol 81 (2) ◽  
pp. 245-252 ◽  
Author(s):  
F. W. Ocvirk ◽  
G. B. DuBois
Keyword(s):  
Experimental Data ◽  
Film Thickness ◽  
Surface Finish ◽  
Journal Bearing ◽  
Load Capacity ◽  
Journal Bearings ◽  
Oil Film ◽  
Bearing Clearance ◽  
Bearing Load

A method of relating surface finish to minimum oil-film thickness and the corresponding load capacity of plain journal bearings is presented with supporting experimental data. The effect of clearance on load capacity and friction are shown on graphs indicating an optimum bearing clearance.

On the Stability of a Rigid Rotor in Finite Porous Journal Bearings With Slip

1986 ◽  
Vol 108 (2) ◽  
pp. 190-194 ◽  
Author(s):  
Ajit Kumar Chattopadhyay ◽  
B. C. Majumdar
Keyword(s):  
Experimental Data ◽  
Finite Length ◽  
Velocity Slip ◽  
Journal Bearings ◽  
Rigid Rotor ◽  
The Stability ◽  
Theoretical Results

This investigation deals with the stability characteristics of oil filled porous journal bearings of finite length and with velocity slip. The stability curves are drawn for different slip parameters, eccentricity ratios, slenderness ratios, and in the absence of any experimental data, the theoretical results for the solid bearings obtained by this analysis have been compared with the available results of solid bearing.

Experimental Rotor Unbalance Response Using Hydrodynamic Gas Lubrication

1972 ◽  
Vol 94 (1) ◽  
pp. 74-80
Author(s):  
R. D. Dayton ◽  
M. R. Chasman
Keyword(s):  
Theoretical Model ◽  
Reasonable Agreement ◽  
Journal Bearings ◽  
Rotor Speed ◽  
Unbalance Response ◽  
Bearing Load ◽  
Gas Lubrication ◽  
Theoretical Predictions ◽  
Theoretical Results

This paper investigates the adequacy of the theoretical model in predicting the unbalance response of a rotor supported in hydrodynamic gas lubricated journal bearings. The magnitude of experimental whirl amplitudes induced by applying various unbalances to a rotor supported in hydrodynamic journal bearings were measured and compared to the theoretical predictions. Variables investigated were rotor unbalance, rotor speed, and bearing load. Reasonable agreement between the experimental and theoretical results was obtained.

The Study of the Depression Occurred under Different Types of Impellers

2016 ◽  
Vol 841 ◽  
pp. 116-121 ◽  
Author(s):  
Lucian Mândrea ◽  
Gabriela Oprina ◽  
Corina Băbuţanu ◽  
Dorian Marin ◽  
Gabriel Negreanu
Keyword(s):  
Analytical Solution ◽  
Theoretical Approach ◽  
Numerical Results ◽  
Variable Radius ◽  
Different Types ◽  
Hydraulic Turbines ◽  
Theoretical Results ◽  
Good Agreement

The paper presents the analytical solution used to calculate the depression which appears under different types of impellers. This solution can be useful as a preliminary calculus to estimate the magnitude of the depression created at different rotational speeds, in order not to damage the equipment from different systems, such as hydraulic turbines. The authors obtain the variable radius of the depression zone, the pressure inside the depression zone and the depression height. The theoretical approach, the calculus itself and the numerical results presented in the article are original. In order to validate the proposed calculus, experiments were carried out using two experimental setups. The performed measurements showed a good agreement of the experimental and theoretical results.

Investigating the Nonlinear Optical Response of Pepper Oil under Low Power Irradiation with Continuous Wave Visible Laser Beam

2020 ◽  
pp. 131-138
Keyword(s):  
Refractive Index ◽  
Nonlinear Refractive Index ◽  
Nonlinear Optical ◽  
Continuous Wave ◽  
Diffraction Integral ◽  
Visible Laser ◽  
Limiting Property ◽  
Kirchhoff Diffraction Integral ◽  
Theoretical Results ◽  
Good Agreement

The nonlinear optical properties of pepper oil are studied by diffraction ring patterns and Z-scan techniques with continuous wave beam from solid state laser at 473 nm wavelength. The nonlinear refractive index of the sample is calculated by both techniques. The sample show high nonlinear refractive index. Based on Fresnel-Kirchhoff diffraction integral, the far-field intensity distributions of ring patterns have been calculated. It is found that the experimental results are in good agreement with the theoretical results. Also the optical limiting property of pepper oil is reported. The results obtained in this study prove that the pepper oil has applications in nonlinear optical devices.

Optimum Design of Journal Bearings Dimensions for Rotating Machines

2020 ◽  
Vol 38 (10A) ◽  
pp. 1481-1488
Author(s):  
Tariq M. Hammza ◽  
Ehab N. Abas ◽  
Nassear R. Hmoad
Keyword(s):  
Aspect Ratio ◽  
Dynamic Response ◽  
Numerical Solution ◽  
Critical Speed ◽  
Design Method ◽  
Considerable Effect ◽  
Journal Bearings ◽  
Rotating Machines ◽  
Bearing Clearance ◽  
Study Results

The values of Many parameters which involve in the design of fluid film journal bearings mainly depend on the bearing applied load when using the conventional design method to design the journal bearings, in this study, as well as applied bearing load, the dynamic response and critical speed have been used to calculate the dimensions of journal bearings. In the field of rotating machine, especially a heavy-duty rotating machines, the critical speed and response are the main parameters that specify bearing dimensions. The bearing aspect ratio (bearing length to bore diameter) and bearing clearance have been determined based on rotor maximum critical speed and minimum response displacement. The analytical solution of rotor Eq. of motion was verified by numerical solution via using ANSYS Mechanical APDL 18.0 and by comparing the numerical solution with the preceding study. The final study results clearly showed that the bearing aspect ratio has little effect on the critical speed, but it has a high effect on the dynamic response also the bearing clearance has little effect on the critical speed and considerable effect on the dynamic response. The study showed that the more accurate values of bearing aspect ratio to make the response of rotor as low as possible are about 0.65 - 1 and bearing percent clearance is about 0.15 - 0.2 for different rotor dimensions.

Studies of local structures for Cu2+ centers in M2Zn(SO4)2·6H2O (M = NH4 and Rb) crystals

2021 ◽  
Vol 76 (4) ◽  
pp. 299-304
Author(s):  
Fu Chen ◽  
Jian-Rong Yang ◽  
Zi-Fa Zhou
Keyword(s):  
Crystal Field ◽  
Elongation Ratio ◽  
Paramagnetic Resonance ◽  
Local Structures ◽  
Epr Parameters ◽  
Structure Constants ◽  
Crystal Field Parameters ◽  
Electron Paramagnetic ◽  
Theoretical Results ◽  
Good Agreement

Abstract The electron paramagnetic resonance (EPR) parameters (g factor g i , and hyperfine structure constants A i , with i = x, y, z) and local structures for Cu2+ centers in M2Zn(SO4)2·6H2O (M = NH4 and Rb) are theoretically investigated using the high order perturbation formulas of these EPR parameters for a 3d 9 ion under orthorhombically elongated octahedra. In the calculations, contribution to these EPR parameters due to the admixture of d-orbitals in the ground state wave function of the Cu2+ ion are taken into account based on the cluster approach, and the required crystal-field parameters are estimated from the superposition model which enables correlation of the crystal-field parameters and hence the studied EPR parameters with the local structures of the Cu2+ centers. Based on the calculations, the Cu–H2O bonds are found to suffer the axial elongation ratio δ of about 3 and 2.9% along the z-axis, meanwhile, the planar bond lengths may experience variation ratio τ (≈3.8 and 1%) along x- and y-axis for Cu2+ center in (NH4)2Zn(SO4)2·6H2O and Rb2Zn(SO4)2·6H2O, respectively. The theoretical results show good agreement with the observed values.

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