The Accuracy of Short Bearing Theory in Presence of Cavitation

1990 ◽  
Vol 112 (4) ◽  
pp. 650-654 ◽  
Author(s):  
A. T. Prata ◽  
R. T. S. Ferreira
Keyword(s):  
Asymptotic Expansion ◽  
Numerical Integration ◽  
Reynolds Equation ◽  
Matched Asymptotic Expansion ◽  
Aspect Ratios ◽  
Very High

The accuracy of the short bearing approximation in presence of cavitation is tested for bearing aspect ratios (length/diameter) ranging from 0.1 to 1, and for eccentricity to clearance ratios from 0 to 1. Results for short bearings are obtained via the method of matched asymptotic expansion of [3]. These results are compared to those for finite bearings, which are calculated by numerical integration of the Reynolds equation utilizing boundary fitted coordinates that accommodate to the cavitation boundary. Except for very high eccentricities, the short bearing theory was shown to be accurate in predicting the load, within ten percent, for bearing aspect ratios up to 0.5. For large aspect ratios the short bearing theory overpredicts the load.

The Effect of Journal Bearing Misalignment on Load and Cavitation for Non-Newtonian Lubricants

1986 ◽  
Vol 108 (4) ◽  
pp. 645-654 ◽  
Author(s):  
R. H. Buckholz ◽  
J. F. Lin
Keyword(s):  
Reynolds Equation ◽  
Numerical Solutions ◽  
Journal Bearings ◽  
Surface Boundary ◽  
Film Rupture ◽  
Aspect Ratios ◽  
Free Surface Boundary Condition ◽  
Load Carrying ◽  
Boundary Location ◽  
Surface Boundary Condition

An analysis for hydrodynamic, non-Newtonian lubrication of misaligned journal bearings is given. The hydrodynamic load-carrying capacity for partial arc journal bearings lubricated by power-law, non-Newtonian fluids is calculated for small valves of the bearing aspect ratios. These results are compared with: numerical solutions to the non-Newtonian modified Reynolds equation, with Ocvirk’s experimental results for misaligned bearings, and with other numerical simulations. The cavitation (i.e., film rupture) boundary location is calculated using the Reynolds’ free-surface, boundary condition.

A Theoretical Analysis of Floating Bush Journal Bearing With Axial Oil Film Rupture Being Considered

2002 ◽  
Vol 124 (3) ◽  
pp. 494-505 ◽  
Author(s):  
Kiyoshi Hatakenaka ◽  
Masato Tanaka ◽  
Kenji Suzuki
Keyword(s):  
Steady State ◽  
Reynolds Equation ◽  
Speed Ratio ◽  
Shaft Speed ◽  
Film Rupture ◽  
State Behavior ◽  
Oil Film ◽  
Rotordynamic Coefficients ◽  
The Stability ◽  
Very High

A new modified Reynolds equation is derived with centrifugal force acting on the hydrodynamic oil film being considered. This equation, together with a cavitation model, is used to obtain the steady-state equilibrium and calculate the rotordynamic coefficients of lightly loaded floating bush journal bearings operating at very high shaft speeds. The bush-to-shaft speed ratio and the linear cross-coupling spring coefficients of the inner oil film is found to decrease with the increase in shaft speed as the axial oil film rupture develops in the inner oil film. The present model can give reasonable explanation to the steady-state behavior and the stability behavior of the bearing observed in actual machines.

scholarly journals Thermodynamic properties of thermonuclear fuel in inertial confinement fusion

2016 ◽  
Vol 34 (3) ◽  
pp. 539-544 ◽  
Author(s):  
V. Brandon ◽  
B. Canaud ◽  
M. Temporal ◽  
R. Ramis
Keyword(s):  
Kinetic Energy ◽  
Inertial Confinement Fusion ◽  
Hot Spot ◽  
Inertial Confinement ◽  
Direct Drive ◽  
Aspect Ratios ◽  
Confinement Fusion ◽  
Thermonuclear Fuel ◽  
Target Family ◽  
Very High

AbstractHot-spot path in the thermodynamic space $({\rm \rho} R,T_{\rm i} )_{{\rm hs}} $ is investigated for direct-drive scaled-target family covering a huge interval of kinetic energy on both sides of kinetic threshold for ignition. Different peak implosion velocities and two initial aspect ratios have been considered. It is shown that hot spot follows almost the same path during deceleration up to stagnation whatever the target is. As attended, after stagnation, a clear distinction is done between non-, marginally-, or fully igniting targets. For the last, ionic temperature can reach very high values when the thermonuclear energy becomes very high.

Method of Theoretical Investigation of Externally Pressurized Gas-Lubricated Bearings

1969 ◽  
Vol 91 (1) ◽  
pp. 166-170 ◽  
Author(s):  
L. G. Stepanyants ◽  
N. D. Zablotsky ◽  
I. E. Sipenhov
Keyword(s):  
Numerical Integration ◽  
Theoretical Investigation ◽  
Reynolds Equation ◽  
Spherical Bearing

An “unevenly distributed supercharging” pattern is suggested for treating externally pressurized bearings. The scheme simplifies the problem and is applicable in calculating any type of externally pressurized bearings Results of numerical integration of Reynolds’ equation for a section spherical bearing using this treatment are given.

Dynamic stability of micropolar lubricated hydrodynamic offset-halves journal bearings

2020 ◽  
pp. 135065012093685
Author(s):  
Sanyam Sharma ◽  
Chimata M Krishna
Keyword(s):  
High Speed ◽  
Reynolds Equation ◽  
Journal Bearing ◽  
Critical Mass ◽  
Journal Bearings ◽  
Aspect Ratios ◽  
Input Parameters ◽  
Output Characteristics ◽  
The Stability ◽  
Offset Factor

The plain circular journal bearings are not found to be stable by researchers when used in high speed rotating machineries. Hence, extensive research in the study of stability characteristics of non-circular bearings or lobed bearings assumed importance, of late. Present article deals with the stability analysis of non-circular offset bearing by taking selected set of input and output parameters. Modified Reynolds equation for micropolar lubricated rigid journal bearing system is solved using finite element method. Two kinds of input parameters namely, offset factors (0.2, 0.4) and aspect ratios (1.6, 2.0) have been selected for the study. The important output characteristics such as load, critical mass, whirl frequency ratio, and threshold speed are computed and plotted for various set of values of input parameters. The results obtained indicate that micropolar lubricated circular offset bearing is highly stable for higher offset factor and higher aspect ratio.

scholarly journals Very-High-Eccentricity Librations at Some Higher Order Resonances

1992 ◽  
Vol 152 ◽  
pp. 153-158 ◽  
Author(s):  
J.C. Klafke ◽  
S. Ferraz-Mello ◽  
T. Michtchenko
Keyword(s):  
Phase Space ◽  
Numerical Integration ◽  
Higher Order ◽  
Planar Problem ◽  
High Eccentricity ◽  
Disturbing Potential ◽  
Numerical Exploration ◽  
Numerical Integrations ◽  
Short Period ◽  
Very High

Motions near the 3:1, 4:1 and 5:2 resonances with Jupiter are studied by means of numerical integrations of a semi-analytically averaged Sun-Jupiter-asteroid planar problem. In order to have a model including the very-high-eccentricity regions of the phase space, we adopted a set of local expansions of the disturbing potential, adequate to perform the numerical exploration of regions in the phase space with eccentricities higher than 0.9 (Ferraz-Mello and Klafke, 1991). Individual solutions and qualitative results thus obtained are completely reproduced by numerical integration of the complete equations by filtering off the short-period components of these solutions.

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