• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.381-382
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• 2002

The Fluid film between the valve plate and the cylinder block was measured by use of a gap sensor and the mercury-cell slip ring unit under real working conditions. During the operating periods, experiments with discharge pressure, revolution speed, and valve geometry was carried out for the fluid film on the valve plate. To investigate the effect of the valve shape, we designed two valve plates each having a different shape; the first valve plate was a plane valve plate. while the second valve plate was a spherical valve plate. It was noted that these two valve plates observed different aspects of the fluid film characteristics between the cylinder block and the valve plate. The leakage flow rate and the shan torque were also investigated in order to clarify the difference between these two types of valve plates. From the results of this study. we found that the spherical valve plate estimated good fluid film patterns and performance more than the other valve plate in oil hydraulic axial piston pumps.

• Journal of Hydrogen and New Energy
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• v.31 no.1
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• pp.73-81
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• 2020

For the fault tree analysis (FTA) analysis of the packaged hydrogen filling station, the composition of the charging station was analyzed and the fault tree (FT) diagram was prepared. FT diagrams were created by dividing the causes of events into external factors and internal factors with the hydrogen event as the top event. The external factors include the effects of major disasters caused by natural disasters and external factors as OR gates. Internal factors are divided into tube tailer, compressor & storage tank, and dispenser, which are composed of mistakes in operation process and causes of accidents caused by parts leakage. In this study, the purpose was to improve the hydrogen station. The subjects of this study were domestic packaged hydrogen stations and FTA study was conducted based on the previous studies, failure mode & effect analysis (FMEA) and hazard & operability study (HAZOP). Top event as a hydrogen leaking event and constructed the flow of events based on the previous study. Refer to "Off shore and onshore reliability data 6th edition", "European Industry Reliability Data Bank", technique for human error rate prediction (THERP) for reliability data. We hope that this study will help to improve the safety and activation of the hydrogen station.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.361-361
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• 2009

KEPCO High Temperature Superconducting (HTS) cable system rated with $3\Phi$, 22.9kV, 1250A was laid in 2006, and the long term test is in progress. The HTS cable system with the cooling system has been operated below cryogenic temperature. That environment exposes the system to the thermo-mechanical stress due to the significant temperature difference, and the cooling system has moving parts for the forced circulation of the coolant. Therefore the HTS cable system experiences thermal fatigue and moving part such as liquid nitrogen pump need a regular replacement every 5000 hours Building the assessment criterion, the maintenance procedure was established and regular preventive maintenance was done; improvement of the termination structure and the replacement of the bearing of liquid nitrogen pump. Following the proper process, the reliability assessment test including He leakage detection and the stability of flow rate was performed. This paper describes the process and result of the first regular maintenance of KEPCO HTS cable system

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.4
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• pp.415-424
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• 2004

Cooling the electronic equipment is one of the major focal points of the design process and the key to successful product launch. The two-phase loop thermosyphone which is a good candidate among many available options was investigated fur cooling of the high power amplifiers. The system is composed of evaporator which contains 6 parallel cold plates, fan cooled condenser, gas-liquid separator, and interconnecting tubes. Experiments were performed for several refrigerant charging values, hs and as a experiment result, the optimum charging value fur this system was proposed. In order to optimize the system design, the operating cycle pressure and inlet/outlet temperatures of evaporator and condenser are measured and analyzed. The effect of the three parameters such as flow rate and temperature of condenser cooling air, and thermal load on the evaporator are investigated. The lower the operating pressure and the cycle temperatures are also better to prevent the leakage of the system. The system invesigated in this paper can be directly used for cooling of a real unmanned wireless communication station.

• Tribology and Lubricants
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• v.24 no.3
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• pp.140-146
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• 2008

The floating ring seal which is used in the high pressure turbo pump is frequently used in the oxidizer pump and the fuel pump of the turbo pump of the liquid propulsion rocket, because it is able to minimize clearance to decrease the leakage flow rate. But, the floating ring seal has a tendency to increase instability in decreasing eccentricity ratio. To complement this weakness, it is devised bump floating ring seal which is inserted bump in the outer surface. It has various experiment results. But the theoretical study of the bump floating ring seal didn't investigated yet. In this paper, we analyse about static characteristics of bump floating ring seal, compared previous experimental results. To analyze the characteristic of bump floating ring seal, we coupled perturbation method of floating ring seal and FEM of bump foil.

• Journal of Energy Engineering
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• v.21 no.4
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• pp.398-401
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• 2012

In this Study, efficiencies of the scroll expander under development for organic Rankine cycle using engine waste heat of vehicle have been analyzed and compared with the commercial scroll expander. While operating organic Rankine cycle for analysing expander efficiencies, power of expander, inlet temperature of expander, inlet pressure of expander and the flow rate of the working fluid(refrigerant R134a) have been measured. Overall efficiency of the expander has been shown the very low level compared with the overall efficiency of the commercial expander. Especially, because the low volumetric efficiency has much effect on overall efficiency, the working fluid leakage trouble of expander has to be solved surely for improvement of the expander overall efficiency.

• Journal of the Korean Institute of Gas
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• v.16 no.4
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• pp.23-31
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• 2012

The basic understanding of gas diffusion and technology to predict the diffusion phenomena are needed to prepare against a disaster of leakage of natural gas and to design better consistent and reliable gas supply system in enclosure. The experimental results of British Gas Technology Co. are used in present study as a reference of theoretical study using CFD. The present results of 2D CFD analysis for mass flow rate of nozzle release show good agreement with experimental results within 2.6 % error. 3D CFD analysis for the characteristics of natural gas diffusion in enclosure with various ventilation patterns also gives reasonable agreement with experimental results.

• Transactions of The Korea Fluid Power Systems Society
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• v.7 no.1
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• pp.1-5
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• 2010

This paper presents the experimental results of the radial piston type oil pump with new mechanism for a metal diaphragm hydrogen compressor. Generally, metal diaphragm type hydrogen compressor systems are operated by oil hydraulic power. In this system an oil compensating pump has been demanded to compensate for a leakage oil head chamber. The metal diaphragm type hydrogen compressor consists of an oil compensating pump, commonly used hydraulic piston pump and driven by main crank shaft. The radial piston type oil compensating pump with new rolling contacted piston mechanism is developed and experimented. The developed piston element of the radial piston pump consists of piston, steel ball, return spring, two check valves, eccentric cam and ball racer. In this study, designed 4 type pistons as and orifice hole. Operating characteristics and pressure ripple characteristics are tested under no load to 60bar loaded with every 20bar increasing step and pressure ripple and flow rate are experimentally investigated.

• Fire Science and Engineering
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• v.24 no.5
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• pp.87-93
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• 2010

The fact that the smoke hinders evacuation and fire-fighting activities as well as becomes the major cause of life casualty emphasizes the importance of smoke control system. As one of the fire safety standards designed to secure the smoke safety, NFSC501A (Design Guide for Smoke Control System of Special Evacuation Stairwell and Lobby) has been proposed, preventing smoke from penetrating into the smoke-free escape route by raising the pressure of the smoke control zone higher than fire area. For model building of 20 stories, pressurization system was designed according to standard and pressure field of compartments in whole building induced by pressurization system was analyzed using the network model.

• Tribology and Lubricants
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• v.22 no.2
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• pp.105-111
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• 2006

The floating ring seal which is used in the high pressure turbo pump is frequently used in the oxidizer pump and the fuel pump of the turbo pump of the liquid propulsion rocket, because it is able to minimize clearance to decrease the leakage flow rate. Compared with contact seal, the floating ring seal has advantage of minimizing clearance without rubbing phenomenon. But, the floating ring seal has a tendency to increase instability in operating condition in the high speed region. In this research, we devised floating ring seal which is inserted bump in the outer surface in order to improve the stability in the high speed region. Through this work, we expect to improve stability of floating ring seal with increasing the direct damping coefficient of seal and decreasing the eccentricity ratio.