• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.191-198
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• 2002

Oil-free turbo-compressor supported by compliant foil bearings which remove oil-contamination by elimination of the conventional ball bearing and oil lubrication systems is presented. Turbo-compressor makes two individual air compression with two impellers at operating speed, 39,000rpm. In this study, the rotordynamic effects caused by aerodynamic instability were investigated with variable mass flow rate. Correlation between frequencies of pressure fluctuation in two diffusers and those of excitation forces on rotor were clearly developed in aerodynamic unsteady region. Thus, these results show that it is beneficial to design high speed rotating turbomachinery considering coupling effect between aerodynamic instability and rotordynamic force.

• Journal of the Korean Applied Science and Technology
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• v.14 no.2
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• pp.49-55
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• 1997

It was tested the possibility that EPA and DHA could be separated from fish oil fatty acid ethyl ester(FAEE) in the supercritical carbon dioxide rectification method. Experiments were carried out in the 1800mm tall and temperature gradient packed rectification column at the pressure of 100bar and carbon dioxide flow rate of 52.43NL/min. Experimental results showed that this method was useful to separate the FAEE by the relative volatility of the components. The maximum attainable concentration of EPA, DHA and both of them in product were 41%, 43% and 57% respectively in this rectification column using raw fish oil feed.

• Tribology and Lubricants
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• v.25 no.4
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• pp.236-242
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• 2009

Oil viscosity is one of the important parameters for machinery condition monitoring. Basically, it is expressed as kinematic viscosity measured by capillary flow and dynamic or absolute viscosity measured by rotary shear viscometry. Recently, acoustic wave techniques appear in the market, measuring viscosity as the product of dynamic viscosity and density. For Newtonian fluids, knowledge of density allows conversion from one viscosity parameter to the other at a specific shear rate and temperature. In this work, oil samples with different chain lengths of viscosity index (VI) improvers and concentrations were examined by different viscometric techniques. Results showed that acoustic viscosity measurements give misleading results for oil samples with high molecular weight VI improvers and at low temperatures ${\leq}40^{\circ}C$.

• Journal of Drive and Control
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• v.9 no.4
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• pp.42-51
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• 2012

Variable displacement vane-type oil pumps represent one of the most innovative pump types for industrial applications, especially for engine lubrication systems. This paper deals with a modeling method for theoretical flow rate investigation of a typical variable displacement vane-type oil pump. This theoretical model is based on the pump geometric design and dynamic analyses. It can be considered as mandatory steps for a deeper understanding of the pump operation as well as for effectively implementing the pump control mechanisms to satisfy the urgent demands of engine lubrication systems. The developed pump model is finally illustrated by numerical simulations.

• Journal of the Korean Society of Safety
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• v.8 no.2
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• pp.10-15
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• 1993

In this paper, it is studied the electrostatic discharge In Insulating oil for the purpose of the technical control of the streaming electrification resulted from the interface between an insulating liquid and a solid. The streaming current increases exponentially with flow rate and In region of lower than 50［$^{\circ}C$］but decreases at higher than the same temperature. The phenomena of electrostatic discharge appear at an interface between measuring tank and insulating oil when the seven sheets of gauzes are inserted in electrification apparatus. And those of partial or surface discharge are shown when eight sheets are inserted.

• Solar Energy
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• v.20 no.1
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• pp.55-62
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• 2000

An experimental study on the stratified fluids with water and silicon oil of same volume in the cavity with upper cooling surface was carried out to investigate the flow characteristics, heat transfer through the interface of fluids, and the applications of thermal behaviors in a square cavity. The experiments were performed with variation of initial temperature and cooling surface temperature. The temperature drop of oil was faster than that of water and freezing was initiated from the interface of oil and water and propagated downward. For the water above $4^{\circ}C$, the cooling rate was faster than that below $4^{\circ}C$ and showed almost same temperature distribution but for the water that of below $4^{\circ}C$, it showed the stable stratified temperature distribution. The lower the initial temperature and the higher the cooling surface temperature was, the longer the supercooling duration.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2002.11a
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• pp.171-184
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• 2002

Approx. 200,000 bpd vacuum residue oil is produced from oil refineries in Korea. These are supplying to use asphalt, high sulfur fuel oil, and upgrading at the residue hydro-desulfurization unit. Vacuum residue oil has high energy content, however high sulfur content and high concentration of heavy metals represent improper low grade fuel. To meet growing demand for effective utilization of vacuum residue oil from refineries, recently some of the oil refinery industries in Korea, such as SK oil refinery and LG Caltex refinery, have already proceeded feasibility study to construct 435-500 MWe IGCC power plant and hydrogen production facilities. Recently, KIER(Korea Institute of Energy Research) are studing on the Vacuum Residue gasification process using an oxygen-blown entrained-flow gasifier. The experiment runs were evaluated under the reaction temperature : 1,100~1,25$0^{\circ}C$, reaction pressure : 1~6kg/$\textrm{cm}^2$G, oxygen/V.R ratio : 0.8~0.9 and steam/V.R ratio : 0.4-0.5. Experimental results show the syngas composition(CO+H$_2$) : 85~93%, syngas flow rate : 50~110Mm$^3$/hr, heating value : 2,300~3,000 ㎉/Nm$^3$, carbon conversion : 65~92, cold gas efficiency : 60~70%. Also equilibrium modeling was used to predict the vacuum residue gasification process and the predicted values were compared reasonably well with experimental data.

• Journal of Energy Engineering
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• v.12 no.1
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• pp.49-57
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• 2003

Approx. 200.000 bpd vacuum residue oil is produced from oil refineries in Korea, and is supplied to use asphalt, high sulfur fuel oil and for upgrading at the residue hydro-desulfurization unit. Vacuum residue oil has high energy content, however its high sulfur content and high concentration of heavy metals represent improper low grade fuel. To meet growing demand for effective utilization of vacuum residue oil from refineries, recently some of the oil refinery industries in Korea, such as SK oil refinery and LG Caltex refinery, have already proceeded feasibility study to construct 435~500 MWe IGCC power plant and hydrogen production facilities. Recently, KIER (Korea Institute of Energy Research) are studying on the Vacuum Residue gasification process using an oxygen-blown entrained-flow gasifier. The experiment runs were evaluated under the reaction temperature: 1.100~l,25$0^{\circ}C$, reaction pressure: 1~6 kg/$\textrm{cm}^2$G, oxygen/V.R ratio: 0.8~0.9 and steam/V.R ratio: 0.4~0.5. Experimental results show the syngas composition (CO+H$_2$): 85~93%, syngas flow rate: 50~l10 Nm$^3$/hr, heating value: 2,300~3,000 k㎈/Nm$^3$, carbon conversion: 65~92, cold gas efficiency: 60~70%. Also equilibrium modeling was used to predict the vacuum residue gasification process and the predicted values were compared reasonably well with experimental data.

• Tribology and Lubricants
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• v.37 no.4
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• pp.117-124
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• 2021

In this study, we perform a 3D CFD conjugate analysis according to the shape of the foil ramp of the air foil thrust bearing, analyze the flow characteristics inside the bearing, and compare the results corresponding to the two shapes. Air has a lower viscosity than lubricating oil. Therefore, the thrust runner of the bearing must rotate at high speed to support the load. The gap between thrust runner and foil is significantly smaller than that of the oil bearing. Hence, it is crucial to analyze the complex flow characteristics inside the bearing to predict the complex flow inside the bearing and performance of the bearing. In addition, flow characteristics may appear differently depending on the ramp shape of the bearing foil, which may affect bearing performance. In this study, we numerically analyze the main flow path of air flowing into the bearing and the secondary flow path used for cooling the bearing using the commercial CFD software ANSYS CFX and compare the flow characteristics for straight and curved foil ramp shapes. Notably, there is a difference in the speed of the flowing air according to the shape of the ramp, which affects the bearing performance.

• Journal of the Korean Society of Visualization
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• v.22 no.1
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• pp.6-17
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• 2024

This study examined the natural convection heat flow characteristics of the melting process of PCM (palm oil) inside a liquid flexitank(bag) for a cargo container. A film heating element was installed on the bottom of the container, and numerical analysis was performed under heat flux conditions of 1,000 to 4,000 W/m². As a result, the melt interface of the PCM rises to a nearly horizontal state over time. In the initial stage, conduction heat transfer dominates, but gradually waves at the cell flow and melt interfaces are formed due to natural convection heat transfer. As melting progresses, the Ra number increases parabolically, and the Nu number increases linearly and has a constant value. The Nu number rises slowly under low heat flux conditions, whereas under high heat flux conditions, the Nu number rises rapidly. As the heat flux increases, the internal temperature oscillation of the liquid phase after melting increases. However, under high heat flux conditions, excess heat exceeding the latent heat is generated, and the temperature of the molten liquid is raised, so the increase in melting rate decreases. Therefore, the appropriate heating element specification applied to a 20-ton palm oil container is 2,000 W/m².