• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.11a
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• pp.318-322
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• 1999

An analytical study about dynamic behavior of center pivot rocker arm type valve train system equipped with roller of diesel engine is developed. At first, a mathematical model for the dynamic analysis has been set up using the lumped parameter method. In that model, valve spring is divided as some mass elemehts so as to simulate spring surging, Then, how the design parameters, such as valve mass, rocker arm inertia, valve spring stiffness, and initial load on valve spring, affect valve dynamic behavior especially in the valve close area is scrutinized.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.11a
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• pp.252-259
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• 2001

Integrated condition monitoring is required to monitor effectively the machine conditions since machine failures could not be monitored accurately by any single measurement parameter. Application of various condition monitoring techniques is therefore preferred in many cases in order to diagnosis the machine condition. However it inevitably requires lots of maintenance cost and sometimes it could be proved to over-maintenance unnecessarily. This could happen especially when one measurement parameter closely correlates to another. Therefore correlation analysis of various monitoring parameters has to be performed to improve the reliability of diagnosis. In this work, Pearson correlation coefficient was used to analyze the correlation between condition monitoring parameters of an over-loaded machine system where the vibration, wear and temperature were monitored simultaneously. The result showed that Pearson correlation coefficient could be regarded as a good measure for evaluating the availability of condition monitoring technology.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.6
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• pp.34-43
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• 2002

This paper focused on the dynamic behavior of camshaft in a direct acting type valve train system. To investigate camshaft behavior, transient vibration analysis is performed by using the transfer matrix method. The camshaft is treated as a lumped mass system supported by spring and damper, From the presented analytical model, we could predict dynamic behavior of camshaft, shaft locus within bearing and bearing load. The presented model and results will be very helpful to design the optimal camshaft and valve train system.

• 유공압시스템학회:학술대회논문집
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• 2010.06a
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• pp.25-32
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• 2010

A geortor type pump is widely used in lubrication and actuator systems. Especially the pump is an essential machine element of an automotive engine to feed lubrication oil and power source of automatic transmission. A gerotor is a planar mechanism consist of a pair of rotor and circular tooth of stator assembly which forms a closed space. However, related industries do not have necessary technology to design and optimize the pump and paid royalties of gerotor profile on an advanced company. Also, gerotor profiles with setting design parameter have not been sufficiently analyzed from a theoretical view. Therefore, it is very difficult for designer to decide the specifications of the gerotor profiles, and calculation and fluctuation of flow rate is not yet confirmed. In this study, theoretical analyses and optimal design of the gerotor profiles have been performed numerical method by mathematical base. An automated design system of the tooth profile has been developed through MATLAB GUI Program considering various design parameters.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.6
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• pp.15-22
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• 2014

With a conventional positioning apparatus, it is very difficult simultaneously to achieve desired driving ranges and precision levels at the sub-micrometer level. Generally, a lead screw and friction drive have been used as servo control systems. These have large driving ranges, and high-speed positioning is feasible. In this study, we present a global servo system controlled by a laser interferometer acting as a displacement measurement sensor for achieving positioning accuracy at the sub-micrometer level.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.06a
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• pp.15-21
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• 2001

This study assesses the wear process of particle impingement erosion which is a major source of erosion among fluid power components. First, Bitter's theory was modified to simplify engineering calculations. Second, actual experiments were conducted to validate the modified equation. And the effect of concentration and size distribution of impinging particles was tested. Little deviation from the prediction of the modified equation was observed. To develop an analytical approach to the erosion mechanism, further experimental data are required to establish a correlation with other engineering parameters.

• Tribology and Lubricants
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• v.13 no.3
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• pp.1-9
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• 1997

인류가 지구상에 존재하기 이전에도 바다 속에는 오징어와 같이 자신의 힘만으로 분사 추진을 하여 움직이는 생물이 존재하였음에도 불구하고 인류는 이러한 반작용 원리를 이용한 항공용 가스터빈 엔진을 고안하는데 1900년 이상의 세월을 보내야 하였으며, 이 긴 세월 동안 많은 장치들이 고안되었다. 그러나, 실제로 이러한 원리를 사용한 현재와 같은 가스터빈 엔진의 개발은 1940년대 중반에야 가능하게 되었다. 이후 소형이면서 높은 추력을 발생시키기 위하여 많은 노력이 이루어져 왔으며, 이를 위하여 가스터빈 엔진의 주축 베어링, gearbox, seal 및 윤활 시스템 등은 더욱 큰 부담을 가질 수 밖에 없었다. 따라서, 이러한 어려움을 해결하고 보다 높은 추력을 발생시키는 가스터빈을 개발하는데 트라이볼로지의 역할이 중요하다고 할 수 있다. 가스터빈에서의 트라이볼로지의 적용 분야는 main-shift bearing, lubrication system, gearbox 및 seal등을 들 수 있으나, bearing과 lubrication을 중심으로 기술하고자 한다.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.06a
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• pp.334-339
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• 2001

The nonlinear vibration characteristics of hydrodynamic journal bearings with a circumferentially groove are analyzed numerically when the external sinusoidal disturbances are given to the rotor-bearing system continuously. Also, the cavitation algorithm implementing the Jakobsson-Floberg-Olsson boundary condition is adopted to predict cavitation regions in the fluid film more accurately than conventional analysis which uses the Reynolds condition. It is found that the difference between linear and nonlinear analysis is much more remarkable as the amplitude of external disturbance increases, and it depends upon the excitation frequency of external disturbance. It is also shown that the cavity region in the fluid film is increased as the amplitude or excitation frequency of external disturbance increases. The whirling center of the steady state orbit moves closer to the bearing center as the amplitude or the excitation frequency of the external disturbance increases because of smaller range of full film region.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.548-551
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• 2010

A 150 lbf-thrust class micro turbojet engine has been developed. The engine could be applied to power plant for small aviation vehicle such as UAV, decoy and anti-radar missile and was designed with concepts that has small size, low-cost and high performance. A prototype was manufactured and performed the ground static test and high altitude test. This paper outlines the features and layout of 150 lbf turbojet engine and also describes the design characteristics and test results of the engine and components.

• Journal of Aerospace System Engineering
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• v.1 no.4
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• pp.37-41
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• 2007

Labyrinth seal is most common way to protect the bearings installed in Reaction wheel. In spite of wide applications, no such research was found about the sealing utility of the Labyrinth seal in the condition of vacuum and high temperature. In this research, we tried to verify the utility of Labyrinth seal. Numerical analysis had been executed to predict the benefit of the Labyrinth seal and also experiments were performed to verify the utilization. Two Bearings were installed at the vacuum chamber, one was assembled with Labyrinth seal and the other was stand alone. After executing the vacuum test, it was found to be the stand alone bearing had lost more weight than the one that was assembled with the labyrinth seal. In this result, it is verified that the Labyrinth seal has useful function to preserve the lubricant that affects to the life-cycle of the Bearing.