• Journal of the Korean Vacuum Society
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• v.19 no.3
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• pp.190-198
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• 2010

Asymmetric model for plasma uniformity by Ar and $CF_4$ was modeled by the antenna structure, the diameter of chamber, and the distance between source and substrate for the development of plasma equipment for 450 mm wafer. The aspect ratio of chamber was divided by diameter, distance from substrate, and pumping port area. And we found the condition with the optimized plasma uniformity by changing the antenna structure. The drift diffusion and quasi-neutrality for simplification were used, and the ion energy function was activated for the surface recombination and etching reaction. The uniformity of plasma density on substrate surface was improved by being far of the distance between substrate wall and chamber wall, and substrate and plasma source. And when the antenna of only 2 turns was used, the plasma uniformity can improve from 20~30% to 4.7%.

• Journal of Ocean Engineering and Technology
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• v.27 no.6
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• pp.32-42
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• 2013

In this paper, a wave-induced swirl water chamber (SWC) for breakwater and wave power generation is introduced and its applicability to wave power generation in the coastal waters of Korea is investigated. The SWC type of wave power generation is a way to drive a turbine using the unidirectional swirl flow that is induced in the back of a curtain wall of a breakwater due to incident waves. The typical wave characteristics are obtained by analyzing the annual statistical wave data from KHOA (Korea Hydrographic and Oceanographic Administration). A numerical analysis is carried out on the variations in the SWC entrance height, wave height, and different installation conditions. For the numerical analysis, a commercial code, Fluent based on FVM, is used. As the entrance height decreases, the mass flow rate through the entrance is rarely changed, whereas the magnitude of the flow velocity of the smaller entrance height is greater than the other ones, which is better for the formation of an SWC swirl flow inside and the flow kinetic energy at the entrance. In cases of installation conditions where a wall is place behind and under SWC, it has been shown that the mass flow rate through the entrance is greater than that in the open condition, and sufficient flow kinetic energy is generated in the entrance for wave power generation. However, the swirl flow kinetic energy is relatively small. Thus, in the future, it is necessary to study the swirl flow generation, which is affected by the SWC shape.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.13 no.4
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• pp.263-272
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• 2001

Recently, some attempts to construct slit caisson-type breakwaters are made in Korea. Since slit caisson-type breakwaters are suitable for relatively deep sea areas, a lot of theoretical and experimental researches have been performed. In this study, the reflection characteristics of vertical slit caisson breakwaters are investigated based on the measured data in two-dimensional hydraulic model tests with irregular waves. The experiments were conducted for various cases; variation of porosity of perforated-wall, width of wave chamber, number of slits for single-and double-chamber, respectively. It is found that in the case when the wave steepness (H/L$_{s}$ ) is small, the reflection coefficients are large. The existing researches have shown that the wave reflection is minimized when the nondimensional width of wave chamber B/L is about 0.2~0.25 for the regular waves. However, for the irregular waves the reflection is lowest when $B/L_2$, is 0.13~0.15. For a same porosity condition, the wave dissipation is stronger as the width of s1it is larger. The double-chamber caisson is superior to single- chamber caisson in the wave dissipating effects.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.270-273
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• 2003

The characteristic of constant volume micro combustor was investigated experimentally. The shape of micro combustor was cylindrical and has row aspect ratio or has relatively large diameter compared with chamber height. Diameter and chamber height was varied to investigate the geometric effect of combustor on the flame propagation. Diameter of 15 mm and 7.5 mm was designed while chamber height was designed to be 1mm, 2mm, and 3mm. The effect of initial pressure was also investigated parametrically from 1bar to 3bar. The gas used in this study was stoichiometric mixture of methane and air. The maximum pressure achieved in down scaled combustors was lower than that of conventional combustor because heat loss to wall was dominant as expected. The maximum pressure responded favorably with the change of height of combustor and the initial pressure, the maximum pressure was also increased. The flame propagation was possible when the specific condition was satisfied. Although the quenching distance of stoichiometric mixture of CH4 and Air is 2.5 mm, the flame could propagate even under quenching distance as the initial pressure increased.

• Journal of Radiation Protection and Research
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• v.36 no.2
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• pp.59-63
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• 2011

It is important to reduce indirect scattered neutron beside direct neutron of chosen energy for designing a neutron-reference-field laboratory with neutron produced from a nuclear reaction by a accelerator. Therefore MCNPX simulation was performed with various conditions for obtaining such condition. At first in the original laboratory condition we calculated the direct neutron flux which was inserted in chamber (virtual chamber composed of air) of 0 degree (proton moving direction) for neutron flux measurement and the scattered neutron flux which is inserted in the chamber after scattering wall or bottom. In the result, the scattered neutron which was inserted after scattering bottom is more than that which was inserted after scattering the others. Therefore MCNPX simulation was again performed with removing the concrete bottom and with removing the concrete bottom and digging 1 m in the ground. In the result of removing concrete bottom and digging 1 m in the ground, scattered neutron which was inserted after scattering bottom became less than that which was inserted after scattering the others.

• Journal of Power System Engineering
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• v.19 no.4
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• pp.56-68
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• 2015

Liquefied petroleum gas and compressed natural gas haven been regarded as promising alternative fuels because of no smoke, and they are also clean fuel for spark-ignited engine. In spark-ignited direct-injection engine, direct injection technology can increase engine volumetric efficiency significantly and also reduce necessity of throttle valve. This study designed combustion chamber equipped with visualization system. To improve ignition probability, the study designed to help three types of impingement-walls to form mixture. In doing so, LPG CNG-air mixture could be easily formed after spray-wall impingement and ignition probability increased too. The results of this study could contribute as basic resources of spark-ignited direct injection LPG and CNG engine design and optimization extensively.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.414-414
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• 2010

KSTAR vacuum vessel has been boronized by carborane ($C_2B_{10}H_{12}$) to reduce various kinds of impurities including carbon and oxygen from the wall, since carborane is solid, non-toxic, non-explosive and is easily evaporated, while diborane ($B_2D_6$) is toxic and explosive. To find the best wall condition for the removal of contaminants before application to KSTAR, various amounts (0.3g, 0.5g, 1g) of carborane are tested in a test chamber, where filament discharge was generated in the mixture of helium and carborane with the same KSTAR target pressure (~ 5 mTorr) from base pressure (${\sim}10^-7\;Torr$). Discharge is performed by a pulse sequence mode with 3 second power on and 5 second power off. Deposited films of a-C/B:H are characterized by ellipsometery, AES and XPS, and are compared with those of KSTAR.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.237.2-237.2
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• 2010

Although oscillating water column type wave energy devices are nearing the stage of commercial exploitation, there is still much to be learnt about many facets of their hydrodynamic performance. The techniques of Computational Fluid Dynamics (CFD) are applied to simulate a wave energy conversion device in free surface such as waves. This research uses the commercially available ANSYS CFX computational fluid dynamics flow solver to model a complete oscillating water column system with savonius turbine incorporated at the rear bottom of the OWC chamber in a three dimensional numerical wave tank. The purpose of the present study is to investigate the effect of an average wave condition on the performance and internal flow of a newly developed direct drive turbine (DDT) model for wave energy conversion numerically. The effects of blade angle and front lip shape on the hydrodynamic efficiency are investigated. The results indicated that the developed models are suitable to analyze the water flow characteristics both in the chamber and in the turbine. For the turbine, the numerical results of torque were compared for the all cases. The results of the testing have also illustrated that simple changes to the front wall aperture shape can provide marked improvements in the efficiency of energy capture for OWC type devices.

• Journal of Mechanical Science and Technology
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• v.17 no.1
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• pp.146-156
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• 2003

A numerical algorithm is developed to analyze the performance of a Unit-injector (UI) System for a diesel engine. The fundamental theory of the algorithm is based on the continuity equation of fluid dynamics. The loss factors that should be seriously regarded on the continuity equation are the compressibility effect of liquid fuel, the wall friction loss in high-pressure fuel lines of the system, the kinetic energy loss of fuel in the system, and the leakage of fuel out of the control volume. For an evaluation of the developed simulation algorithm, the calculation results are compared with the experimental outputs provided by the Technical Research Center of Doowon Precision Industry Co. (DPICO) ； the maximum pressure in the plunger chamber (P$\_$p/) and total amount of fuel injected into a cylinder per cycle (Q$\_$f/) at each operational condition. The result shows that the average error rate (%) of P$\_$p/ and Q$\_$f/ are 2.90% and 4.87%, respectively, in the specified operational conditions. Hence, it can be concluded that the analytical simulation algorithm developed in this study can be reasonably applied to the performance prediction of newly designed UI system.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.359-363
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• 2011

In this paper, the characteristic of pressures had been analyzed with a series of shapes that are pressure probes used in supersonic wind tunnel. When a performance of supersonic wind tunnel is evaluated, the Mach number is calculated by using the ratio of static pressure in test section wall to total pressure in settling chamber. Also the flow condition can be visualized by schlieren system. However a number of limitations exist to measure pressure of test section due to high speed and boundary layer effect. Therefore a specific pressure probe is needed for evaluating flow condition in test section at a various of positions. In the paper, experiments were conducted in terms of some pitot probes and the results were compared and analyzed.