HIGH SPEED JOURNAL BEARINGS LUBRICATED WITH ELECTRO-RHEOLOGICAL FLUIDS: AN EXPERIMENTAL INVESTIGATION

1996 ◽  
Vol 10 (23n24) ◽  
pp. 3045-3055 ◽  
Author(s):  
P.G. NIKOLAKOPOULOS ◽  
C.A. PAPADOPOULOS
Keyword(s):  
Electric Field ◽  
High Speed ◽  
Journal Bearing ◽  
Dynamic Properties ◽  
Relative Viscosity ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Radial Clearance ◽  
Shear Strain Rate ◽  
Er Fluid

It is well known that the imposition of an electric field on an Electro-Rheological (ER) fluid alters the viscosity and as a consequence the f flow properties of the f fluid. If such a fluid is used to lubricate a journal bearing system, it is expected that the imposition of an electric field between the rotor and the stator will cause the alteration of the dynamic properties of the journal bearing. For the present, it has been proved that this is valid only for low speeds and high radial clearances of Couette type viscometers. In this paper an experiment in a high speeds (16000 to 65000 s −1) journal bearing with small radial clearance is presented. The experiment performed has showed the phenomenon and has proved that the ER FLUID at high shear rates under constant temperature, follows the Bingham model in realistic bearings. Properties such as wall shear stress, dynamic yield stress relative viscosity are experimentally determined as functions of the electric field, for different particle concentrations and the shear strain rate under constant or free to vary temperature (due to operating conditions, angular velocity, friction). Concluding the ER fluids can be used to create “smart” journal bearings. Vibration controllers can be constructed to control the stability of the ER fluid lubricated bearings.

Influence of geometric parameters and operating conditions on the thermohydrodynamic behaviour of plain journal bearings

2000 ◽  
Vol 214 (5) ◽  
pp. 445-457 ◽  
Author(s):  
I Pierre ◽  
M Fillon
Keyword(s):  
High Speed ◽  
Journal Bearing ◽  
Three Dimensional ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Thermal Dissipation ◽  
Radial Clearance ◽  
Geometric Factors ◽  
Essential Components ◽  
Mass Flowrate

Hydrodynamic journal bearings are essential components of high-speed machinery. In severe operating conditions, the thermal dissipation is not a negligible phenomenon. Therefore, a three-dimensional thermohydrodynamic (THD) analysis has been developed that includes lubricant rupture and re-formation phenomena by conserving the mass flowrate. Then, the predictions obtained with the proposed numerical model are validated by comparison with the measurements reported in the literature. The effects of various geometric factors (length, diameter and radial clearance) and operating conditions (rotational speed, applied load and lubricant) on the journal bearing behaviour are analysed and discussed in order to inform bearing designers. Thus, it can be predicted that the bearing performance obtained highly depends on operating conditions and geometric configuration.

scholarly journals Internal Damper Characteristics of Rotor System with Submerged ER Fluid Journal Bearing

1997 ◽  
Vol 3 (1) ◽  
pp. 61-71 ◽  
Author(s):  
Siyoul Jang ◽  
John A. Tichy
Keyword(s):  
Shear Stress ◽  
Electric Field ◽  
Shear Strain ◽  
Yield Stress ◽  
Electric Fields ◽  
Journal Bearing ◽  
Shear Strain Rate ◽  
Newtonian Flow ◽  
Damping Coefficients ◽  
Er Fluid

Electro-Rheological (ER) fluid behavior is similar to Bingham fluid’ s. Only when the shear stress magnitude of ER fluid exceeds the yield stress, Newtonian flow results. Continuous shear strain rate equation about shear stress which simulates Bingham-like fluid shows viscosity variations. Shear yield stress is controlled by electric fields. Electric fields in circumferential direction around the journal are also changeable because of gap distance. These values make changes of spring and damping coefficients of journal bearings compared to Newtonian flow case. Implicit viscosity variation effects according to shear strain rates of fluid are included in generalized Reynolds' equation for submerged journal bearing. Fluid film pressure and perturbation pressures are solved using switch function of Elord's algorithm for cavitation boundary condition. Spring and damping coefficients are obtained for several parameters that determine the characteristics of ER fluids under a certain electric field. From these values stability region for simple rotor-bearing system is computed. It is found that there are no big differences in load capacities with the selected electric field parameters at low eccentric region and higher electric field can support more load with stability at low eccentric region.

Dynamic Properties of Tilting-Pad Journal Bearings: Experimental and Theoretical Investigation of Frequency Effects due to Pivot Flexibility

2006 ◽  
Vol 129 (3) ◽  
pp. 865-869 ◽  
Author(s):  
Waldemar Dmochowski
Keyword(s):  
High Speed ◽  
Dynamic Properties ◽  
Three Dimensional ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Damping Properties ◽  
Frequency Effects ◽  
Tilting Pad ◽  
Stiffness And Damping ◽  
Tilting Pad Journal Bearings

Tilting-pad journal bearings (TPJBs) dominate as rotor supports in high-speed rotating machinery. The paper analyzes frequency effects on the TPJB’s stiffness and damping characteristics based on experimental and theoretical investigations. The experimental investigation has been carried out on a five pad tilting-pad journal bearing of 98mm in diameter. Time domain and multifrequency excitation has been used to evaluate the dynamic coefficients. The calculated results have been obtained from a three-dimensional computer model of TPJB, which accounts for thermal effects, turbulent oil flow, and elastic effects, including that of pad flexibility. The analyzes of the TPJB’s stiffness and damping properties showed that the frequency effects on the bearing dynamic properties depend on the operating conditions and bearing design. It has been concluded that the pad inertia and pivot flexibility are behind the variations of the stiffness and damping properties with frequency of excitation.

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].

HYDRODYNAMIC CHARACTERISTICS OF ER FLUID FLOWS IN JOURNAL BEARINGS

2003 ◽  
Vol 17 (01n02) ◽  
pp. 205-208 ◽  
Author(s):  
KE-QIN ZHU ◽  
JIE PENG
Keyword(s):  
Electric Field ◽  
Journal Bearing ◽  
Fluid Flows ◽  
Journal Bearings ◽  
Hydrodynamic Characteristics ◽  
Eccentricity Ratio ◽  
High Eccentricity ◽  
Bingham Plastic ◽  
Er Fluids ◽  
Er Fluid

A numerical analysis is performed on the hydrodynamic characteristics of electrorheological(ER) fluid flows in journal bearings based on the basic hydrodynamic equations. The flow field is assumed to be incompressible and isotropic, the Bingham plastic model is used to describe the behavior of ER fluids. The effect of bearing eccentricity ratio and applied electric field intensity has been studied attentively. It shows that control of the journal bearing through external electric field is much more feasible in high eccentricity ratio bearing than in low eccentricity ratio one.

Dynamic Properties of Tilting-Pad Journal Bearings: Experimental and Theoretical Investigation of Frequency Effects Due to Pivot Flexibility

2006 ◽  
Author(s):  
Waldemar Dmochowski
Keyword(s):  
High Speed ◽  
Dynamic Properties ◽  
Three Dimensional ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Damping Properties ◽  
Frequency Effects ◽  
Tilting Pad ◽  
Stiffness And Damping ◽  
Tilting Pad Journal Bearings

Tilting-pad journal bearings (TPJB) dominate as rotor supports in high speed rotating machinery. The paper analyzes frequency effects on the TPJB’s stiffness and damping characteristics based on experimental and theoretical investigations. The experimental investigation has been carried out on a five pad tilting-pad journal bearing of 98 mm in diameter. Time domain and multifrequency excitation has been used to evaluate the dynamic coefficients. The calculated results have been obtained from a three-dimensional computer model of TPJB, which accounts for thermal effects, turbulent oil flow, and elastic effects, including that of pad flexibility. The analyzes of the TPJB’s stiffness and damping properties showed that the frequency effects on the bearing dynamic properties depend on the operating conditions and bearing design. It has been concluded that the pad inertia and pivot flexibility are behind the variations of the stiffness and damping properties with frequency of excitation.

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.

Performance of Stern Tube Bearings under Different Lubrication and Operating Conditions

2009 ◽  
Author(s):  
Jan H. Andersen ◽  
Hiroyuki Sada ◽  
Seiji Yamajo
Keyword(s):  
Journal Bearing ◽  
Hydrodynamic Lubrication ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Water Soluble ◽  
Analysis Tool ◽  
Test Rig ◽  
Experimental Performance ◽  
Shaft Alignment ◽  
Alignment Analysis

This paper presents the results of an investigation into the theoretical and experimental performance of oil lubricated journal bearings. DNV has developed a new calculation tool for the analysis of journal bearing performance as part of shaft alignment analysis. The results of the calculation tool have been compared to other research and analysis methods under static and dynamic conditions. In addition, white metal bearings were tested with decreasing Sommerfeld number until loss of hydrodynamic lubrication. The experiments were carried out in a bearing test rig and with three different lubricants, normal mineral oil, emulsifying oil, and water-soluble oil. The tests were done with increasing water content in the lubricant. Results from the test were compared with calculation using the DNV analysis tool.

Stability Analysis of Two-Layered Finite Hydrodynamic Porous Journal Bearing Using Linear and Nonlinear Transient Method

2007 ◽  
Author(s):  
S. K. Kakoty ◽  
S. K. Laha ◽  
P. Mallik
Keyword(s):  
Journal Bearing ◽  
Journal Bearings ◽  
Operating Conditions ◽  
System Stability ◽  
Rigid Rotor ◽  
Transient Method ◽  
Porous Bearing ◽  
Nonlinear Transient ◽  
Linear And Nonlinear ◽  
The Stability

A theoretical analysis has been carried out to determine the stability of rigid rotor supported on two symmetrical finite two-layered porous oil journal bearings. The stability curves have been drawn for different eccentricity ratios and Sommerfeld numbers. The effect of bearing feeding parameter, L/D ratio on the stability is also investigated. This paper also deals with a theoretical investigation of stability using a non-linear transient method. This analysis gives the journal centre locus and from this the system stability can be determined. With the help of graphics, several trajectories of the journal centre have been obtained for different operating conditions. Finally a comparison between single-layered porous bearing and the two-layered porous bearing is presented here.

Incorporation of THD Boundary Conditions for the Efficient Evaluation of Journal Bearing Performance

2007 ◽  
Author(s):  
P. S. Keogh ◽  
M. M. Khonsari
Keyword(s):  
Boundary Conditions ◽  
High Speed ◽  
Current Practice ◽  
Journal Bearing ◽  
Coefficient Matrix ◽  
Journal Bearings ◽  
Heat Fluxes ◽  
Solid Component ◽  
Influence Coefficient ◽  
Thermal Boundary Conditions

The evaluation of the thermohydrodynamic (THD) performance of journal bearings continues to be an important issue. This is particularly so for high speed or heavily loaded bearing designs. This paper focuses attention on the thermal boundary conditions at the lubricant-bearing interface. The solid component conduction problem is solved in advance of the main THD analysis. Boundary conditions are then imposed on the lubricant THD analysis through use of an appropriate influence coefficient matrix that incorporates the solid component conduction problem. This avoids the current practice of solving the lubricant and solid component problems separately in an iterative loop to achieve continuous temperatures and heat fluxes at the interface. Instead, only the lubricant problem needs to be solved using the boundary conditions imposed by the influence coefficient matrix.

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