• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.3
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• pp.58-64
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• 2003

Dimethyl Ether(DME) has been considered as one of the most attractive alternative fuels for compression ignition engine. Its main advantage in diesel engine application is high efficiency of diesel cycle with soot free combustion though conventional fuel injection system has to be modified due to the physical properties of DME. Experimental study of DME and conventional diesel spray employing a common-rail type fuel injection system with a 5-hole sac type injector was performed in a constant volume vessel pressurized by nitrogen gas. Spray cone angles and penetrations of the DME spray were characterized and compared with those of diesel. For evaluation of the evaporating characteristics of the DME, shadowgraphy technique employing an Ar-ion laser and an ICCD camera was adopted. Tip of the DME spray was formed in mushroom-like shape at atmospheric chamber pressure, which disappeared in higher chamber pressure. Spray tip penetration and spray cone angle of the DME became similar to those of diesel under 3MPa of chamber pressure. Higher injection pressure provided wider vapor phase area while it decreased with higher chamber pressure condition.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.1
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• pp.121-130
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• 2002

Clean stockers are being used by semiconductor and TFT-LCD manufacturers to store and buffer work in process. Since an important function of a stocker is to keep the contained material clean. The only way to keep the stored product clean is to provide constant clean airflow the product and through stocker, The airflow across the product prevent contamination from settling on the product. Up to now, stocker typically have been configured to receive their laminar airflow from fan filter units that are located on the side of the stocker This type of stocker may have such problems as complexity of structure, increment of temperature, mechanical vibration, initial investment and running cost. In this study, In order to solve the above mentioned problems, new air control system in stocker is proposed, which is to control open ratios of exits that are located on the side of the stocker without fan filter units. Open ratios of exits need to be optimized for the same quantities of airflow in each exit. In this study, static pressure regain was used for the analysis of the open ratios of exits theoretically and Blue Ridge Numerics FEM software, CFDesign, was used fur simulating airflow in stocker. As a result, Open ratios of exits important to provide constant clean airflow can be obtained by the analysis of static pressure regain and was verified by simulation results. Therefore, new air control system in stocker can be used by the semiconductor and TFT-LCD manufacturers.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1505-1509
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• 2004

A novel technique for fine particle beam focusing under the atmospheric pressure is introduced using a radiation pressure assisted aerodynamic lens. To introduce the radiation pressure in the aerodynamic focusing system, a 25 mm plano-convex lens having 2.5 mm hole at its center is used as an orifice. The particle beam width is measured for various laser power, particle size, and flow velocity. In addition, the effect of the laser characteristics on the beam focusing is evaluated comparing an Ar-Ion continuous wave laser and a pulsed Nd-YAG laser. For the pure aerodynamic focusing system, the particle beam width was decreased as increasing particle size and Reynolds number. For the particle diameter of 0.5 ${\mu}m$, the particle beam was broken due to the secondary flow at Reynolds number of 694. Using the Ar-Ion CW laser, the particle beam width becomes smaller than that of the pure aerodynamic focusing system about 16 %, 11.4 % and 9.6 % for PSL particle size of 2.5 ${\mu}m$, 1.0 ${\mu}m$, and 0.5 ${\mu}m$ respectively at the Reynolds number of 320. Particle beam width was minimized around the laser power of 0.2 W. However, as increasing the laser power higher than 0.4 W, the particle beam width was increased a little and it approached almost a constant value which is still smaller than that of the pure aerodynamic focusing system. The radiation pressure effect on the particle beam width is intensified as Reynolds number decreases or particle size increases relatively. On the other hand, using 30 Hz pulsed Nd-YAG laser, the effect of the radiation pressure on the particle beam width was not distinct unlike Ar-Ion CW laser.

• Journal of Ocean Engineering and Technology
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• v.22 no.5
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• pp.106-111
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• 2008

In this paper, study about property evaluation for the metal matrix composites fabricated by low pressure infiltration process. Aluminum alloy composite which is reinforced by Metal fiber preform was fabricated by low pressure casting process. Infiltration condition was changed the pressure infiltration time of 1 sec, 2 sec and 5 sec under a constant pressure of 0.4 MPa. The molten alloy completely infiltrated the FeCrSi metal perform regardless of the increase in the pressure acceleration time. The the porosity in the FeCrSi/AC8A composite was investigated. The porosity was reduced as the pressure acceleration time as shorter. The FeCrSi/AC8A composite was investigated the wear test for to know the relationship between Porosity and wear resistance. FeCrSi/AC8A composite at pressure acceleration time of 1sec is shown excellent wear resistance.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1664_1665
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• 2009

Many years ago, most of thermal power plants built in this country were of subcritical pressure, of medium or small size, of constant pressure operations and of drum type steam generators with circulation type boilers. But, nowadays almost all of them were of high efficiency, of supercritical pressure, of big capacity, of sliding pressure operations, and of once through type steam generator. It has such advantage as the reduction of startup duration, but it control system and operation method are very complicated. It has a big difference in operation method of turbine and boiler. The feedforward control needs to be introduced to prevent such problems as thermal shock during the transit from normal operation into bypass operation. This paper introduces the turbine control and turbine bypass control during startup of thermal power plants.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.11
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• pp.3075-3083
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• 1994

The applications of the electrical transmission line theory to the pressure propagation characteristics in the volume loaded fluid transmission line with step and impulse input wave is demonstrated in this paper. The method is based on the premise that the time response is the inverse Fourier transform of frequency spectrum of the wave which spectrum is a product of frequency spectrum of input pressure wave and system transfer function. The frequency response and transient response of step and impulse input wave in the volume loaded fluid transmission line is analysed by the Laplace transform and inverse Laplace transform with FFT numerical algorithm. The numerical solution of the distributed friction model is compared with the average friction model and the infinite product model. And the result is showed that FFT method may have major advantages for the simulation of fluid circuitary.

• Transactions of the Korean Society of Mechanical Engineers
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• v.6 no.3
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• pp.256-260
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• 1982

This paper presents the characteristics of fuel spray in a diesel engine. In this paper, in order to obtain spray droplet size in a diesel engine, water was injected into the cylinder at room temperature and pressure by injection system. Spray droplet size was measured by liquid immersion technique with a lubricant used as an immersion liquid for spray water from injection nozzle. In this experiment, single hole type throttle nozzle are used at same operating conditions, which included opening pressure of nozzle, fuel delivery, and injection speed. Sauter mean diameter decrease with the increase of injection pressure and decrease in injection nozzle diameter. The rate of spray penetration increased with increasing injection pressure and diameter of injection nozzle at the constant spray conditions.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.6
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• pp.74-79
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• 2004

The effects of change in injection pressure on spray structure have been investigated in high temperature and pressure field. To analyze the structure of evaporative diesel spray is important in speculation of mixture formation process. Also emissions of diesel engines can be controlled by the analyzed results. Therefore, this study examines the evaporating spray structure by using a constant volume vessel. The injection pressure is selected as the experimental parameter, is changed from 72 MPa to 112 MPa with a high pressure injection system(ECD-U2). The PIV(Particle Image Velocimetry) technique was used to capture flow variation of the evaporative diesel spray. A study on the mixture formation process of diesel spray was executed by the results of flow analysis in this study. Consequentially the large-scale vortex flow could be found in downstream spray and the formed vortex governs the mixture formation process in diesel spray.

• Applied Chemistry for Engineering
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• v.17 no.3
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• pp.291-295
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• 2006

The keto-enol tautomeric equilibrium constant, K, of ethyl acetoacetate in compressed and supercritical carbon dioxide was determined by using FT-IR (Fourier transform infrared) spectroscopy at three different temperatures. In order to investigate the effect of solvent density, the $CO_{2}$ pressure was systematically changed at a constant temperature. As the $CO_{2}$ density is increased, the amount of keto tautomer is increased, causing the K value to decrease. The modified lattice fluid hydrogen bonding theory has been applied to investigate the effect of density on the K.

• Applied Chemistry for Engineering
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• v.10 no.2
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• pp.324-329
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• 1999

In this work, high pressure binary phase equilibria data of carbon dioxide and isopropyl alcohol were obtained by experiment. A static type experimental apparatus was made to measure temperature, pressure and phase equilibria composition. The experimental apparatus was tested by comparing the measured phase equilibria data of the carbon dioxide-isopropyl alcohol system at $80^{\circ}C$ with those of Rodosz. The binary phase behavior data of carbon dioxide-isopropyl alcohol system were measured in range of 41 to 133 bar and at temperatures of 40, 60, 80, 100 and $120^{\circ}C$. The solubility of isopropyl alcohol increases as the temperatures increases at constant pressure. Also, these carbon dioxide-alcohol solute system have critical-mixture curves that exhibit maxima in pressure at temperatures between the critical temperatures of carbon dioxide and isopropyl alcohol. The experimental data obtained in this study were modeled using the statistical associating fluid theory(SAFT) equation of state. A good fit of the data was obtained with SAFT using two adjustable parameters for the carbon dioxide-isopropyl alcohol system.