• Journal of Mechanical Science and Technology
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• v.16 no.8
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• pp.1095-1101
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• 2002

The load characteristics of engine main bearing are very important in the design of crankshaft and engine block. The stiffness of crankshaft and block, or the optimal dimension of the bearing can be determined according to the load level. This paper presents the load characteristics of engine main bearing. Two components of the main bearing load are measured during engine firing and motoring. The vertical and horizontal load components are measured by using the dynamic load cell mounted in each main bearing cap bolt. The measured main bearing loads are compared with calculated results by using the statically determinate method. The theoretical results, provided in this study, agreed well with the experimental results. The presented results are very useful for achieving optimal design of engine.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.103-104
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• 2002

The influence of the slip flow on the MEMS/MST based gas-lubricated proceeding bearing is investigated. Based on the modified Reynolds equation, the numerical analysis of the finite difference method was developed by applying the first order slip flow approximation. The numerical prediction of bearing performance provides the significant results concerning the slip flow effect in micro scale gas-lubricated proceeding bearing. The result indicates that the load-carrying capacity as well as the rotordynamic coefficients were significantly reduced due to the slip flow. Through this work, it is concluded that the slip flow effect could not be ignored in the micro gas-lubricated proceeding bearing.

• KSTLE International Journal
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• v.2 no.1
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• pp.59-64
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• 2001

A new bearing concept, the wave journal bearing, has been developed to improve the static and dynamic performance of a hydrodynamic journal bearing. This concept features a wave in bearing surface. Not only straight but also twisted wave journal bearings are investigated numerically. The performances of straight and twisted bearings are compared to a plain journal bearing over a wide range of eccentricity. The bearing load and stability characteristics are dependent on the geometric parameters such as the number of waves, the amplitude and the starting point of the wave relative to the applied load direction. The bearing performance is analyzed for various configurations and for both cases of smooth and wave member notation. The wave journal bearing, especially for the twisted one, offers better stability than the plain journal bearing under all eccentricity ratios and load orientation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.1043-1048
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• 2002

This paper considers the vibration problem of vehicle driveline which consists of two propeller shafts and the center bearing. The excessive vibration occurs at the center bearing when the vehicle starts to run. Using the kinematic constraints at the universal joint between two propeller shafts, we develop an one d.o.f model which describes the radial motion of the center bearing. We find out the vibration occurs at the specific vehicle speed corresponding to the natural frequency of the model. Comparing the simulation results with test results we also show that the vibration at low vehicle speed is caused primarily by the joint angle and secondarily by the mis-aligned yoke flange rather than by the unbalance.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.12
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• pp.929-934
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• 2002

This paper considers the vibration Problem of vehicle driveline which consists of two propeller shafts and the center bearing. The excessive vibration occurs at the center bearing when the vehicle starts to run. Using the kinematic constraints at the universal joint between two propeller shafts, we developed an one d.o.f model which describes the radial motion of the center bearing. We found out that the vibration occurs at the specific vehicle speed corresponding to the natural frequency of the model. Comparing the simulation results with test results we also show that the vibration at low vehicle speed is caused primarily by the feint angle and secondarily by the mis-aligned yoke flange rather than by the unbalance.

• International Journal of Fluid Machinery and Systems
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• v.6 no.2
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• pp.49-55
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• 2013

Water lubricated guide bearing was newly released and has been applied to actual hydro turbines with vertical shaft. As a result, they can have not only high bearing performance but environmental advantages in meeting the demand for reducing river pollution by oil leakage from oil lubricated guide bearing. The PTFE composite guide bearing was tested by experimental equipment operated under conditions similar to those of actual hydro turbines. Circumferential and axial tilting bearing segments help to improve the bearing performance and efficiency due to low friction loss in the bearing system. Furthermore, bearing cooling systems could be eliminated and maintenance periods could be extended, thus the initial investment and operating costs of the hydroelectric power plant are reduced.

• Tribology and Lubricants
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• v.27 no.2
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• pp.57-64
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• 2011

Hybrid air-foil magnetic bearing integrates two oil free bearing technologies synergetically to adopt the strengths of two bearings with minimizing their weaknesses. This paper presents bending mode vibration control of a flexible shaft supported by the hybrid air-foil magnetic bearing. An experiment set-up of a flexible shaft supported by the hybrid air-foil magnetic bearing is built. In order to verify the effectiveness of the hybrid bearing, unbalance responses of the flexible shaft supported by three different bearings: air-foil, magnetic and hybrid bearings are compared. Effect of load sharing between air-foil and magnetic bearings are investigated through changing the control gain and the rotor center position of magnetic bearing. The experimental results shows that the hybrid bearing can control the bending mode vibration of the flexible shaft effectively and an optimal performance can be achieved with an appropriate load sharing between the air-foil and the magnetic bearings.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.11a
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• pp.243-249
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• 2000

In case of the limitation of Deep RIE fabrication for Micro Gas Turbine, bearing aspect ratio is limited in very small value. The characteristics such as pressure distribution load capacity and non-linearity of a short bearing of L/D=0.083 and a conventional bearing of L/D=1.0 with coupled boundary effects are investigated far Micro Gas Tlubine bearings. The coupled efffect was analyzed by mass conservation at coupled end area. The results, increasing load capacity and non-linearity due to the coupled effect of thrust and journal bearing, are obtained and the selection of journal bearing type is discussed.

• Tribology and Lubricants
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• v.34 no.6
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• pp.300-306
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• 2018

In this study, the performance of foil thrust bearings was investigated by performing bearing take-off and load capacity tests, using an in-house designed and manufactured vertical bearing test rig. The mean take-off rotational speed and maximum load capacity of the bearing specimen were ~18,000 rpm and ~80 kPa, respectively. The vertical bearing test rig was observed to yield higher coefficients of friction and frictional torques than a horizontal bearing test rig under identical test conditions. This was a result of its structural characteristics, in that the bearing specimen is placed atop the thrust runner, which keeps it from being separated from the runner after the bearing take-off. In addition, bearing take-off was observed at a higher runner rotational speed as this structure keeps air from flowing between the top foil and runner surfaces, which requires a higher runner speed. The parallel alignment between the bearing specimen and runner surfaces can be maintained within a certain range more easily in a vertical test rig than in a horizontal test rig. Because of these advantages, Korean Industrial Standard, KS B 2060, recommends a vertical bearing test rig as the standard test device for foil thrust bearings.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.4
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• pp.47-55
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• 2008

Turbocharger has a main purpose on recycling of the exhaust gas from the engine cylinder. On the basis of the facility characteristics, the turbocharger supported on floating ring bearings has some problems such as the large volume, oil supplement for lubrication and high power loss due to high operating torque. The air foil bearing has been studied as the bearing element to be able to alternate the floating ring bearing without the problems of the floating ring bearing. In this study, the air foil bearing has 2 parts; journal and thrust bearings, and the test facility consists of the engine, exhaust and intake parts. In addiction, the specification of the turbocharger follows a small turbocharger for SUV engine. The engine speed is varied from 750 (idle rpm) to 2,500 rpm and then, the rotating speed of the turbocharger rotor is accelerated from 0 to 100,000 rpm. From those experiments, the comparison between the performances of the air foil bearing and floating ring bearing is conducted and the results show that the air foil bearing has less power loss, maximum 770 watt, than the floating ring bearing, maximum 5,110 watt. This result verifies that the air foil bearing is more efficient and able to output more power under the same condition of the input power.