HYDRODYNAMIC JOURNAL BEARING TEST RIG WITH ELASTIC ...tk-smolyan.pu-ftf.eu/fileadmin/template/Konferencia_2016/Volume_1… · Abstract: A bearing test rig was developed to measure

Copyright 2016 by Plovdiv University "Paisii Hilendarski" - Plovdiv, Bulgaria.

15th "International Scientific Conference" RE & IT - 2016, SMOLYAN - BULGARIA

HYDRODYNAMIC JOURNAL BEARING TEST RIG WITH ELASTIC DEFORMATIONS OF CONTACT SURFACES

CAPABILITIES

ANELIA MAZDRAKOVA, JULIA JAVOROVA, ALEXANDRU RADULESCU, ANDREI MIREV, YOVKO RAKANOV

Abstract: A bearing test rig was developed to measure hydrodynamic pressure and friction moment of plain journal bearing. The stand is designed and constructed with exchangeable bearing bushes which are coated on the inner side with different finishes with a uniform thickness and various elastic characteristics. Static measurement capabilities include operating eccentricity and continuous circumferential pressure at multiple axial planes. To ensure high quality results, the test rig was designed to minimize the influence of measurement uncertainties by using of a single sensor mounted in the bearing shell, as the latter can be fixed in different angular and axial position. Additional possibilities of the stand presuppose the measurements of the radial displacements of the inner surface points of bearing bush that affect the values of hydrodynamic pressure by the changed lubricant film thickness. The rig is configured to test bearings with 60 mm bore diameters at speeds up to 3000 rpm and loads up to 500 N.

Key words: Hydrodynamic journal bearing, elastic deformations, test rig

1. Introduction Journal bearings are used widely and

successfully for thousands of years. Nowadays, the hydrodynamic bearings are preferred to support rotating shafts in different applications with high rotational speed and also high specific load due to their constructive simplicity, reliability, efficiency, and low cost. In these applications, such as automotive and aircraft piston engines, large steam turbines for electric power generation, etc., the friction is undesirable because it causes wear and generates heat, which frequently lead to premature failure.

The processes management of the contact friction and wear in different machines units leads to new efficient technical solutions. Thus, particularly appropriate are bearings on whose friction surfaces are applied thin elastic coating of polymer materials, which have low values of the modulus of elasticity. The radial displacements of these elastic coatings significantly modify the shape and thickness of the oil layer, which in its turn

changes the distribution of HD pressure and influence. This affect the values of the main bearing characteristics 1.

The choice of the correct lubricant can also help to minimize friction and thus increase available power output 2. In this regard, many studies are carried out to clarify the effects of the lubricants additives on the performance characteristics of thin film bearings 3.

Difficulties in the study of Non-Newtonian lubricants and their influence on the behavior of the bearings comes from the wide variety of models and different analytical approaches. Therefore, the conclusions are often controversial and thus need verification of the received results or published in literature experimental data.

For these reasons to study the influence of rheological properties of the lubricating fluid, the deformability of the contact surfaces on the process of hydrodynamic lubrication and some operational characteristics (at varying speeds) of the radial plain bearing was designed and made presented below

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Copyright 2016 by Plovdiv University "Paisii Hilendarski" - Plovdiv, Bulgaria.

experimental rig. The testing stand allows measurements of hydrodynamic pressure, friction moment and eccentricity ratio in the studying of plain journal bearing at varying speeds and different loads.

2. Description of the test rig The shaft (1) of the bearing is mounted

steady on the shaft of an adjustable electric motor (fig.1). On it is slipped on the outer shell (2), which can be fully metal, or with inner polymer covering. The shell is removable, so different tests are possible, because the rig is completed with some shells.

Two diametral opposite radial holes are maked. The first serve for gravity-feed of the lubricant, as flexible pipe (3) is connected with him. At different angular positions of the shell, this hole is on the upper half side.

The second hole (4) is with narrower diameter and is connected with the pressure sensor (5). This sensor is mounted on the frontal surface of the shell and via an axial channel is connected with the hole (4). At change of the angular position, the hole (4) moves on the bottom half side of the shell.

The radial force in the bearing is created by the lever-1 (6), whith a steady fulcrum. On its free

Fig. 1. Drawing of the test rig end a hole is bored for hang of different loads (7). The lever push the shell through the lever-2 (8), with fulcrum on its other end. This lever-2 has a rubber coated upper surface for greater friction, which prevents the turn of the shell from the friction moment in the bearing. The lever-2 is bind via a spoke (9) with a force sensor (10). So the tangential force on the upper surface of the shell is measured and on a scale

(depending on the geometrical sizes) can be determinated the friction moment:

9,81. .FRM F R , Nm (1)

The force F is measured in kg , the radius

0,058R , m . After correction with the lever

ratio 1,035 , we obtain:

0,55.FRM F , Nm (2)

The deformation, expressed as a radial shift of the shell toward the shaft, is measured via two

clock like micrometers (11) displaced on 90o angle toward the shaft axis. The same way is measured the deformation in 3, 4. This deformation is due to the lubricant film, and the inner shell deformation, in case with polymer cover. If we mark the deviation of both micrometers with x and y respectively ( x -

the left y - the right) toward the indications at

initial state (immobile shaft), the maximal shift at the respective speed will be:

2 2x y , (3)

and the angular position, read on the scale (12), will be:

45o arctg y x . (4)

1. shaft of the bearing; 2. outer shell – fully metal, or with inner polymer cover; 3. flexible pipe for oil supply; 4. second hole for pressure measuring; 5. sensor for pressure; 6. lever; 7. hole for hang of different loads; 8. lever 2; 9. spoke; 10.force sensor; 11.two cloch like micrometers; 12.scale; 13.adjustable DC motor; 14.control unit.

9

13

6

1112

14

1 10

2

7

3

4

5

8

11

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Copyright 2016 by Plovdiv University "Paisii Hilendarski" - Plovdiv, Bulgaria.

The added angle 45o is because of the same position of the left micrometer.

The angular position of the shell, respectively of the hole for pressure measuring, is measured on the same scale (12) in angle degrees toward the horizontal. This position is fixed by hand. Different from other rigs, in which the radial profile of the pressure is given via great number of holes and sensors 1, 3, here this is realized with only one sensor and change of its angular position.

All experiments can be carried out at different speeds of rotation, what is achieved by the controlled DC motor (13) and the respective electronic control unit (14). The angular speed is measured through counting of pulses, caused from breaking of optical beam by a disc with holes, mounted on the motors shaft and displayed in digital mode.

For the load capacity is important also the axial profile of the pressure in the bearing. For this aim, the shell is made wider than the shaft in axial direction and can be moved, so the measuring hole will be moved from the middle line to the periphery nearly the edge. This is carried out also by hand and the position is measured with a calliper. This is illustrated by fig.2, which represents a schematical side view with longitudinal section of the shell.

Fig. 2. Sectional side view of the shell The arrows shows the moving direction. Other rigs 5, 6, 7 have several holes for pressure measurement in axial direction.

3. Scientific novelty The main novelty in the developed rig is the

use of only one sensor and only one hole for the pressure measurement. In comparison with other developments 1, 3,4, which has several holes, in our opinion the priorities are:

1. Significant simplified construction; 2. More real results, because the film is not

deformed from several holes; 3. More exactly measurement because of

the possibility for graceful change of the angle, while at fixed holes this is done in steps;

4. The measurement of the axial profile of the pressure (at fixed holes is practically impossible, because they would form real a cross furrow on the inner surface, disturbing the real working conditions of the oil film).

The produced rig is shown on fig.3.

Fig. 3. Picture of the test rig The shaft diameter is 60 mm , the axial

width – 40 mm . The speed of rotation can be changed between 0 – 3000 rpm . The radial

displacements in present prototype is measured with an accuracy of 10 m and depends on choosing of

micrometers. It can be improve to 1 m . Other rigs

4 declare the same measurement precision ( 5 m ).The accuracy of the pressure measurement

depends on the sensor accuracy. In the present prototype the measurement is done with a pointer manometer.

Future improving can be made through sensors with computer outputs. The addition of sensors for the angular and axial positions will allow the profiles of the oil film pressure to be computed and plotted automatically.

2. Conclusion

The developed testing rig is a good fundament for testing of different lubricants and additives, such as different bearing covers, for example polymer one. It can be a prototype for development of an improved, computer controlled testing rig.

2

1

45

13

1. shaft of the bearing;

2. outer shell – fully metal, or with inner polymer cover;

4. second hole for pressure measuring;

5. sensor for pressure;

13.adjustable DC motor;

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Copyright 2016 by Plovdiv University "Paisii Hilendarski" - Plovdiv, Bulgaria.

References

1. Коднир Д.С., Контактная гидродинамика смазка деталей машин. М., Машиностроение, 1976.

2. Nikolakopoulos P., D. Bompos, Experimental Measurements of Journal Bearing Friction Using Mineral, Synthetic, and Bio-Based Lubricants. Lubricants 3, 2, 2015, 155-163.

3. Wada S., H. Hayashi, Hydrodynamic lubrication of journal bearings by pseudo-plastic lubricants: part 2, experimental studies. Bulletin of JSME, 14, 69, 1971, 279-286.

4. Bouyer J., M. Fillon, Experimental measurement of the friction torque on hydrodynamic plain journal bearings during start-up, Tribology International, 44, 7, 2011, 772-781.

5. Sinanoğlu C. , N. Fehmi, M. Baki Karamış, Effects of shaft surface texture on journal bearing pressure distribution, Journal of materials processing technology 168, 2 , 2005, 344-353.

6. Costa L., M. Fillon, A. S. Miranda, J. C. P. Claro, An experimental investigation of the effect of groove location and supply pressure on the THD performance of a steadily loaded journal bearing. Journal of Tribology, 122, 1, 2000, 227-232.

7. San Andres L. A., J. M. Vance, Experimental measurement of the dynamic pressure distribution in a squeeze-film bearing damper executing circular-centered orbit, ASLE transactions 30, 3, 1987, 373-383.

Contact: Anelia Mazdrakova University of Chemical Technology and Metallurgy, Department of Applied Mechanics, Sofia, Bulgaria E-mail: [email protected]

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