• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.06a
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• pp.236-242
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• 2001

In this paper the effect of bump compliance, load, and the number of pad on the lift-off speed is studied. When the load is greater and bump compliance lower, the shaft is lifted off at higher rotating speed. And when the load is applied near the center of pad, lift-off speed is lower. When the number of pad increases, the lift-off speed is higher. The lift-off characteristics can be used to lengthen the life time of the coating and design the rotating machinery supported by bump bearings.

• Tribology and Lubricants
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• v.17 no.6
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• pp.441-446
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• 2001

In this paper the effect of bump compliance, load, and the number of pad on the lift-off speed is studied. When the load is greater and bump compliance lower, the shaft is lifted off at higher rotating speed. And when the load is applied near the center of pad, lift-off speed is lower. When the number of pad increases, the lift-off speed is higher. The lift-off characteristics can be used to lengthen the lift time of the coating and design the rotating machinery supported by bump bearings.

• Tribology and Lubricants
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• v.17 no.4
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• pp.290-296
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• 2001

Lift-off means that the rotating journal surface separates from the leaf surface in an air-lubricated multi-leaf foil journal bearing. Lift-off builds up minimum film thickness which will provide load capacity between leaves and journal. In this paper an analysis of air-lubricated multi-leaf foil journal bearing was performed with effects of multi-leaf foil deflection and compressible lubrication equation simultaneously. Minimum film thickness built up versus journal speed predicts the lift off characteristics and these results will be useful in designing and selecting the proper speed of the air-lubricated multi-leaf foil journal bearing.

• 한국연소학회:학술대회논문집
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• 2004.06a
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• pp.7-14
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• 2004

The lift-off characteristics of the triple flame have been studied experimentally with various mean velocities and concentration gradients using a multi-slot burner, which can control the concentration gradient and the mean velocity independently, Lift-off height, axial maximum velocity, flame temperature, and some other characteristics were examined for methane and propane flame, It was found that minimum values of the lift-off heights exist at a certain concentration gradient for constant mean velocity, and this result implies that the propagation velocity has a maximum value at this condition, OH radical distribution was measured with LIF method and velocity variation along streamline was measured with PlV system. In addition maximum temperature along streamline was measured with CARS system. The intensity of the diffusion flame affects on the propagation velocity of triple flame in the region of very weak concentration gradient.

• Tribology and Lubricants
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• v.18 no.2
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• pp.153-159
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• 2002

This paper describes a durability characteristics of an air-lubricated bump foil journal bearing for high speed turbomachinerys at room temperature. At first, lift-off test and load capacity test were performed to understand the general characteristics of an air-lubricated bump foil Journal bearing. A 52 N weighted bump foil bearing sleeve was lilted off from a rotating Journal at about 3,000 rpm, and produced a load capacity of 500 N at an operating speed of 15,000 rpm. The next was 500 cycles lift-off test with an air-lubricated bump foil journal bearing that had a molybdenum disulfide(MoS$_2$) solid lubricant coated top foil. Data from measuring bearing torque and temperature and the observation of rubbing surfAce were included in results. Therefore the results of this work will aid in proving durability of air-lubricated bump foil journal bearings.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.11a
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• pp.212-219
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• 2001

This paper describes a durability characteristics of an air-lubricated bump foil journal bearing for high speed turbomachinerys at room temperature. At first, lift-off test and load capacity test were performed to understand the general characteristics of an air-lubricated bump foil journal bearing. A 52N weighted bump foil bearing sleeve was lifted off from a rotating journal at about 3,000rpm, and produced a load capacity of 500N at an operating speed of 15,000rpm. The next was 500 cycles lift-off test with an air-lubricated bump foil journal bearing that had a molybdenum disulfide(MoS$_2$) solid lubricant coated top foil. Data from measuring bearing torque and temperature and the observation of rubbing surface were included in results. Therefore the results of this work will aid in proving durability of air-lubricated bump foil journal bearings.

• Journal of the korean Society of Automotive Engineers
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• v.14 no.4
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• pp.50-60
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• 1992

Flame characteristics of periodic fuel jets were studied experimentally by supplying the fuel periodically using solenoid valve. Flame was observed using a high speed camera, a 35 mm camera and a cathetometer. Hot-wire ananometer was used to meature the speed of fuel flow at the nozzle exit to analyze the flow characteristics. Various types of flame characteristics such as the flame lift-off and extinction were observed for different ranges of period, duty, and flow rate, but the flame shape was not affected much by the variation in the flow rate. Decreasing duty of the pulses applied to the solenoid valve promotes lift-off and enhances premixed flame characteristics.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 1998.10a
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• pp.167-174
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• 1998

Recently several researches of high speed container ship and loading system are mainly accomplished in U.S.A. and Japan. Its shipping service is not realized but it is realized in near future. To effective use of the feature and efficiency of them, quay, loading/unloading. yard operation system, port management system and connection transport system must be well integrated and operated. Specially, loading /unloading speed of container crane is important for making effective use of them. To speed up loading/unloading system, RO-RO and LO-LO methods that are mostly exclusive system are studied on the container crane with special structure and mechanism to handle individual container or bundle of containers. In this paper these methods are shown. When new high speed loading system of container is desighed, the realistic constrains must be considered.

• Tribology and Lubricants
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• v.39 no.5
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• pp.203-211
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• 2023

This study experimentally investigates the effects of angular acceleration on the friction and wear performances of a gas foil thrust bearing (GFTB) using a typical GFTB with six pads. The outer radius of the bearing is 31.5 mm, the total bearing area is 2,041 mm² , and the bump foil and incline (ramp) height are both 500 ㎛. The newly developed GFTB test rig for measuring the friction torque and coefficient measures the axial load, drag torque, lift-off speed, and touch-down speed. The experiment is conducted for angular accelerations of 78.5, 314.2, and 328.3 rad/s² at axial loads of 5, 10, and 15 N, respectively. The test shows that the start-up friction coefficient increases with increasing axial load at the same angular acceleration, and the friction coefficient decreases with increasing angular acceleration under the same axial load. As the angular acceleration increases, the lift-off speed at the motor start-up increases, and the touch-down speed at the motor stop decreases. The wear distance of the GFTB for a single on/off cycle increases with increasing axial load at the same angular acceleration and decreases nonlinearly with increasing angular acceleration under the same axial load. The test results suggest that adjusting the rotational angular acceleration helps reduce bearing friction and wear.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.4
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• pp.152-159
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• 1999

This paper describes the rmtion characteristics of a particle in GIS under AC voltage. To measure the motion characteristics of the particle, a model gas chamber and parallel plain electrodes were designed and manufactured lift-off voltages of wire and spherical particles on the electrode were calculated and rreasured, and electric charge was calculated. By using a high speed carrera, the rmtion characteristics of various particles with aw}ied voltages, such as motion pattern, lift-off time, lift-off height, were analyzed 1be lift-off voltages were greatly affected by diarreters of wire and spherical particles. At voltage around lift-off voltage, the stand-up particle in vertical state rmved up and down between electrodes and the height of the lift-off particle was low. At voltage around breakdown voltage, the particle repeated vertical rotation a few times while they were being lifted off, and then, they were floating between the electrodes.trodes.