• Journal of Advanced Marine Engineering and Technology
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• v.38 no.8
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• pp.961-967
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• 2014

In onshore and offshore plant engineering, a broad use of pipe system have been achieved and accordingly related technologies has been developed especially in the field of flow control valves. The aim of this study is to suggest the quadruple offset butterfly valve for bi-directional applications which show equivalent operating torque characteristics of the triple offset butterfly valve. Seat design parameters for the quadruple offset butterfly valve are determined by the proposed method utilizing both ANOVA (analysis of variance) and the orthogonal array. Through additive model considering the effect of design parameters on seating torque, mean estimation is performed and thus its optimization results are verified by design of experiment results. The insight obtained from the present study is beneficial for valve design engineers to develop reliable and integrated design of the quadruple offset butterfly valve.

• Journal of the Semiconductor & Display Technology
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• v.8 no.4
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• pp.89-94
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• 2009

The influence on a stability of thermal plasma has been investigated in an electrode structure of non-transferred plasma torch. The variations of dynamic characteristic of the arc voltage was analyzed and compared in terms of voltage character and nozzle types for both the step-shaped nozzles and magnetic-approved cylindrical nozzle. From the experimental results, an electrode gap, flow rate of arc gas, and currents are considered as major operational parameters. As conclusion, it was assured that a torch with step-shaped nozzles of magnetic-approved type produce the stable plasma jet.

• Geotechnical Engineering
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• v.13 no.5
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• pp.125-132
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• 1997

It is observed that debris mitred with a wide range of soil particles and water moves downwards like viscous fluid soon after a landslide has triggered. An Assumption can be made from the field observation that the debris flow behaves as a kind of non(non-Newtoniron) Newtonian fluid which has non linear viscosity. In this study, a series of viscosity tests are carried out to measure rheological properties of debris by using a viscometer with semples taken from a landslide site. It is proved that debris flows behave as Bingham plastic mod el of non-Newtonian fluid. This model can be used predict the movement of debris flows.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.585-588
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• 2008

Thermal mixing phenomena in a Y-type microchannel were investigated using a micro-PIV. Two inlet reservoirs of the microchannel were controlled individually so that the characteristics of thermal mixing in the channel with temperature difference were compared with those without the difference. The velocity field in the mixing process was measured using the micro-PIV system that includes an ICCD (Intensified CCD) camera. The mixing area and uniformity were also analyzed. It is observed that the flow fluctuation in spanwise direction is induced by temperature difference, which enhances mixing process in microchannels.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.6
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• pp.677-684
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• 2003

A new unipolar aerosol charger was developed by using an indirect photoelectric charging. The charger consists of two coaxial tubes, the inner UV lamp wrapped with stainless mesh and the outer Al cylinder. In this study, the effects of flow rate, particle size, and electric field were examined to search the optimal charging conditions with experimental and numerical methods. Monodisperse NaCl particles were fed into an annular space and the particles were charged by negative ions generated from Al plate exposed to the UV light. According to experimental results, the average number of elementary charge on particles increases from 2.5 to 5.5 as particle size increases from 50nm to 130nm at 2.5 L/min and 100V. The average number of elementary charge on particles was maximized at 25V as the electric potential between the stainless mesh and Al plate was varied from 0V to 400V.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1851-1856
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• 2008

A numerical program based on computational fluid dynamics has been developed to simulate characteristics of an EHD induction micropump. The ambiguity of boundary conditions was removed by adopting an equation formulated for electric potential as the dependent variable. The calculations show that the dependency of frequency agrees well with the experiments and the previous analysis. The instability, caused by backflows, is getting stronger as the channel depth increases, which is consistent with experiments. The present study reveals that it is due to the limit in the penetration depth which the electric field can affect. Despite the disadvantage of large channel depth, there is a certain optimal depth for the maximum flow rate.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.2
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• pp.258-263
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• 2011

This study is aimed at obtaining basic design data for Savonius wind turbine, available in the domestic wind environments. To the end, the flow field characteristics around the wind turbine attached with 1/4 wind shield were monitored along with numerical analysis. On the top of this, numerical analysis and experiments on the rpm of the turbine rotor were conducted. As a result, this study found that the numerical analysis results squares with the experiment results and the rpm improves by over 70%.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.6
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• pp.479-485
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• 2016

A 40 mm medium caliber gun to be equipped with ventilation holes is designed and manufactured in this study. The muffler used is composed of holes, blades, and several spaces in the tube. Accordingly, a numerical analysis is performed with computational fluid dynamics (CFD) before testing the muffler. The validity of the numerical analysis is examined by analyzing the differences between the measured data of the firing test and the results of the CFD analysis. The CFD analysis showed that the numerical analysis can be used positively in the muffler design because no difference exists between the results of the field test and the CFD analysis. The test result also indicated a noise reduction of approximately 10 dB. Moreover, the muzzle velocity is almost equivalent, regardless of the muffler.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.6
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• pp.16-23
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• 2001

Spray dispersion in high pressure diesel engines have been simulated experimentally with a special emphasis on the effect of swirl by using a liquid injection technique. A constant volume chamber was designed to be rotatable in order to generate a continuous swirl and to have the flow field closely resembling a solid body rotation. Emulsified fuel was injected into the chamber and the developing process of fuel sprays was visualized. The effect of swirl on the spray dispersion was quantified by calculating non-dimensionalized dispersion area according to the spray tip penetration length. The results show that the effect of swirl on the spray dispersion is different between short and long spray penetrations. For short range of spray tip penetration, the effect of swirl on spray dispersion is quite small. However, as the spray tip is penetrated into longer distance in spray chamber, the effect of swirl on spray dispersion becomes larger. These results can be used as a basic data for designing combustion chamber and injection system of direct injection diesel engine.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.6
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• pp.80-89
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• 2002

The flame structure and soot formation in Acetylene-Air nonpremixed jet flame are numerically analyzed. We employed two variable approach to investigate the soot formation and oxidation processes. The present soot reaction mechanism involves nucleation, surface growth, particle coagulation, and oxidation steps. The gas phase chemistry and the soot nucleation, surface growth reactions are coupled by assuming that the nucleation and soot mass growth has the certain relationship with the concentration of pyrene and acetylene. We also employed laminar flamelet model to calculate the thermo-chemical properties and the proper soot source terms from the information of detailed chemical kinetic model. The numerical and physical model used in this study successfully predict the essential features of the combustion processes and soot formation characteristics in the reaction flow field.