Mixing Inlet Temperatures in Hydrodynamic Bearings

1986 ◽  
Vol 108 (2) ◽  
pp. 231-244 ◽  
Author(s):  
H. Heshmat ◽  
O. Pinkus
Keyword(s):  
Experimental Investigation ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Flow Dynamics ◽  
Fluid Film ◽  
Empirical Equations ◽  
Critical Problem ◽  
Hydrodynamic Bearings ◽  
Hydrodynamic Bearing

Cold and hot lubricant mixing at the inlet to a hydrodynamic bearing has been an unresolved and critical problem in determining bearing performance. The paper offers a conceptual and experimental investigation of the mechanism of mixing in the groove, in terms of the relevant flows and temperatures. The carryover from pad to pad of the discharging hot fluid film, the flow dynamics in the groove and the effects of cavitation are all determined in detail in the light of available experiments. Results of an extensive series of tests aimed at measuring the mixing inlet temperatures as a function of a range of operating conditions and bearing sizes are correlated in terms of an appropriate mixing function. Empirical equations based on the above correlation for the determination of the inlet temperatures are then given for both thrust and journal bearings.

scholarly journals Mixed and Fluid Film Lubrication Characteristics of Worn Journal Bearings

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Toshiharu Kazama ◽  
Yukihito Narita
Keyword(s):  
Frictional Coefficient ◽  
Journal Bearings ◽  
Mixed Lubrication ◽  
Operating Conditions ◽  
Fluid Film ◽  
Asperity Contact ◽  
Lubrication Regimes ◽  
Lubrication Characteristics ◽  
Film Lubrication ◽  
Fluid Film Lubrication

The mixed and fluid film lubrication characteristics of plain journal bearings with shape changed by wear are numerically examined. A mixed lubrication model that employs both of the asperity-contact mechanism proposed by Greenwood and Williamson and the average flow model proposed by Patir and Cheng includes the effects of adsorbed film and elastic deformation is applied. Considering roughness interaction, the effects of the dent depth and operating conditions on the loci of the journal center, the asperity-contact and hydrodynamic fluid pressures, friction, and leakage are discussed. The following conclusions are drawn. In the mixed lubrication regime, the dent of the bearing noticeably influences the contact and fluid pressures. For smaller dents, the contact pressure and frictional coefficient reduce. In mixed and fluid film lubrication regimes, the pressure and coefficient increase for larger dents. Furthermore, as the dent increases and the Sommerfeld number decreases, the flow rate continuously increases.

Momentum Exchanges and Energy Transfers in Cross Flow Fans

1987 ◽  
Author(s):  
Joseph Mazur ◽  
Trilochan Singh
Keyword(s):  
Experimental Investigation ◽  
Flow Field ◽  
Cross Flow ◽  
Operating Conditions ◽  
Energy Transfers ◽  
Cross Flow Fan

An experimental investigation of the flow in a cross flow fan at three operating conditions is reported. Velocity and pressure maps for the flow field are presented along with a determination of the momentum exchanges and energy transfers between the blading and the flow field regions.

Jumping Phenomenon in Journal Bearing

1991 ◽  
Author(s):  
Krystof Kryniski
Keyword(s):  
High Speed ◽  
Standard Procedure ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Theory And Practice ◽  
Fluid Film ◽  
Design Parameters ◽  
Radial Clearance ◽  
Rotor Systems ◽  
Rotating Machine

Abstract Due to their reliability and low maintenance costs over an extended service time, the journal bearings, also known as fluid-film bearings, are commonly incorporated in the super-critical rotor systems. Together with proven balancing methods, they allow rotating machine to pass smoothly through the various of critical speeds, both during start-ups and shut-downs. However, journal bearings need to be designed very carefully, as at some operating conditions (speed and load), they may introduce the undesired effects, such as unstable operations or sub-harmonic resonances. The standard procedure leading to the optimum fluid-film bearing design is based on the bearing capacity, defined by the Sommerfield number [1][2]. When Sommerfield number is determined, all design parameters, such as viscosity, radial clearance, diameter and rotation speed, etc. are matched to satisfy the engineering requirements specified. The procedure is considered to be completely reliable and is commonly used in turbo-machinery and high-speed compressor design. However, the significant divergences between theory and practice were observed with the increase of a bearing radial clearance [3].

Vibration Analysis of Statically Indeterminate Rotors With Hydrodynamic Bearings

1998 ◽  
Vol 120 (4) ◽  
pp. 781-788 ◽  
Author(s):  
N. S. Feng ◽  
E. J. Hahn
Keyword(s):  
Vibration Analysis ◽  
Operating Conditions ◽  
System Stability ◽  
Hydrodynamic Bearings ◽  
Hydrodynamic Bearing ◽  
Unbalance Response ◽  
Tilting Pad ◽  
The Stability ◽  
Rotor Bearings ◽  
Stiffness And Damping

In statically indeterminate rotor bearings systems, where the rotor is supported by one or more hydrodynamic bearings, the reactions at each hydrodynamic bearing, and hence its stiffness and damping properties depend not only on the bearing type, the operating conditions and the bearing dimensions but also on the relative lateral alignment between the journal and the bearing housing; the alignment, therefore, has a significant influence on the system stability and unbalance response. Additional complications arise if nonsymmetric bearing types such as elliptic or tilting pad bearings are present. An iterative procedure is outlined which enables the bearing reactions to be determined at any speed, thereby enabling even large systems such as turbomachinery to be rapidly analyzed in conjunction with existing linear rotor bearing vibration analysis software. Sample numerical examples show how misalignment and bearing type can affect the natural frequencies, the stability threshold, and the unbalance response of such statically indeterminate systems.

An Experimental Investigation on the Temperature Distribution in Circular Journal Bearings

1986 ◽  
Vol 108 (4) ◽  
pp. 621-626 ◽  
Author(s):  
Junichi Mitsui ◽  
Yukio Hori ◽  
Masato Tanaka
Keyword(s):  
Experimental Investigation ◽  
Angular Position ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Test Rig ◽  
Clearance Ratio ◽  
Temperature Distributions ◽  
Wide Range ◽  
Lubricant Viscosity ◽  
Good Agreement

The temperature distributions in full circular bearings were measured in a test rig. The effects of journal speed, lubricant viscosity, and clearance ratio on the maximum bearing temperature and its location were discussed. The results were compared with the theoretical analysis by the present authors and good agreement was obtained over the wide range of operating conditions. The maximum bearing temperature is found to increase considerably with the increase of speed or lubricant viscosity and also with the decrease of clearance ratio. Its angular position is found to vary with speed and clearance ratio. These phenomena can be explained by the characteristics of maximum film temperature in the oil film.

THE EFFECT OF HELICAL GROOVE PRESENCE ON THE TRIBOLOGICAL PERFORMANCE OF JOURNAL BEARINGS

Tribologia ◽  
2018 ◽  
Vol 279 (3) ◽  
pp. 131-138
Author(s):  
Jarosław SĘP ◽  
Leszek TOMCZEWSKI ◽  
Lidia GAŁDA
Keyword(s):  
Load Capacity ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Equation System ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Static Characteristics ◽  
Hydrodynamic Bearings ◽  
Oil Flow ◽  
Helical Groove

The hydrodynamic bearings could suffer critical damages operating in contaminated environments that cause machine breakdown. In such hard operating conditions, hydrodynamic bearings with grooved journals are less sensitive to damage compared to plain bearings. The wear resistance of the grooved journal bearings is several times greater than that of smooth journal bearings. Contaminants existing in the oil film are moved out from the bearing clearance by the groove created on the journal surface. The presence, shape, and geometry of the groove strongly influence the bearings performance. The aim of this article is to study the selected static characteristics of bearings consisting of a journal with the helical groove on its surface. The static characteristics were determined based on the flow simulation in the oil clearance. A three-dimensional, adiabatic model of the oil flow was assumed. The oil flow was described with the Navier-Stokes continuity and energy equations. The equation system was solved by the finite volume method. The numerical model of the flow was verified experimentally on a test stand. It has been established that the grooved journal application leads to a decrease of load capacity in whole range of eccentricity and for all examined clearances. The oil flow rate increase was mainly observed due to spiral groove presence on the shaft.

Dynamic Behavior of Unbalanced Rigid Shaft Supported on Turbulent Journal Bearings—Theory and Experiment

1990 ◽  
Vol 112 (2) ◽  
pp. 404-408 ◽  
Author(s):  
H. Hashimoto ◽  
S. Wada
Keyword(s):  
Dynamic Behavior ◽  
Equations Of Motion ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Experimental Results ◽  
Fluid Film ◽  
Force Components ◽  
The Stability ◽  
Nonlinear Equations Of Motion ◽  
Analytical Expressions

In this paper, the combined effects of turbulence and fluid film inertia on the dynamic behavior of an unbalanced rigid shaft supported horizontally on two identical aligned short journal bearings are investigated theoretically and experimentally. Utilizing analytical expressions for the dynamic fluid film force components considering the effects of turbulence and fluid film inertia, the nonlinear equations of motion for the rotor-bearing systems are solved by the improved Euler’s forward integration method. The journal center trajectories with unbalance eccentricity ratio of εμ = 0, 0.1 and 0.2 are examined theoretically for Reynolds number of Re = 2750, 4580, and 5500, and the theoretical results are compared with experimental results. From the theoretical and experimental results, it was found that the fluid film inertia improves the stability of unbalanced rigid shaft under certain operating conditions.

Journal Bearing Lubrication and Design

1948 ◽  
Vol 158 (1) ◽  
pp. 250-254
Author(s):  
A. S. T. Thomson
Keyword(s):  
Experimental Investigation ◽  
Applied Load ◽  
Journal Bearing ◽  
Point Contact ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Experimental Results ◽  
Radial Clearance ◽  
Series Of Experiments ◽  
Loaded Side

The paper summarizes the results of an experimental investigation on the effects of variation in bearing width and radial clearance on the operating conditions of centrally loaded clearance journal bearings, the bearing arc being kept constant at 120 deg. The investigation, which was carried out prior to 1940, is complementary to an earlier paper by the author in which the effects of variations in bearing width and arc of embrace were investigated. The experimental results are compared with theoretical values modified by the relevant leakage coefficients. The measure of agreement obtained indicates that theoretical values so modified may be used with confidence in design. A short series of experiments is described; in these, high-point contact at starting and stopping is eliminated by supplying oil to a groove in the loaded side of the bearing at a pressure sufficiently great to overcome the applied load. The effect of a groove on the loaded side of the brass under various conditions of lubrication is investigated.

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