• 동력기계공학회지
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• 제17권2호
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• pp.103-107
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• 2013

The structure of a variable liquid column oscillator(a VLCO) is analogous to that of the tuned liquid column damper used to suppress oscillatory motion in large structures like tall buildings and cargo ships. The VLCO is a system absorbing high kinetic energy of accelerated motions of multiple floating bodies in the effect of air springs occurred by installation of inner air chambers. Thus, VLCO can improve the efficiency of energy than wave energy converters of the activating object type made in Pelamis Company. In this research, the experiment was performed that a simple floating body was filled with internal fluid of same draft. The characteristics of motions were evaluated in each case of the opening or closing of the upper valves.

• 동력기계공학회지
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• 제18권3호
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• pp.36-41
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• 2014

The structure of a variable liquid column oscillator(a VLCO) is analogous to that of the tuned liquid column damper used to suppress oscillatory motion in large structures like tall buildings and cargo ships. The VLCO is a system absorbing high kinetic energy of accelerated motions of the multiple floating bodies in the effect of air springs occurred by installation of inner air chambers. Thus, VLCO can improve the efficiency of energy than wave energy converters of the activating object type made in Pelamis Company. In this research, the experiment was performed in two models of same draft. The one is that weights were filled, and the other is that water was filled. The numerical results were estimated by assuming that do not exist internal flow, and the results were compared with the results of experiments.

• 한국지하수토양환경학회지:지하수토양환경
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• 제15권6호
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• pp.37-45
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• 2010

Surfactant-enhanced ozone sparging (SEOS), an advanced version of SEAS (surfactant-enhance air sparging) was introduced in this study for the first time for removal of non-volatile contaminant from aquifer. The advantages of implementing SEAS, enhanced air saturation and expanded zone of sparging influence, are combined with the oxidative potential of ozone gas. Experiments conducted in this study were tow fold; 1-dimensional column experiments for the changes in the gas saturation and contaminant removal during sparging, and 2-dimensional box model experiment for the changes in the size of zone of influence and contaminant removal. An anionic surfactant (SDBS, sodium dodecylbenzene sulfonate) was used to control surface tension of water. Fluorescein sodium salt was used as a representative of watersoluble contaminants, for its fluorescence which is easy to detect when it disappears due to oxidative degradation. Three different gases (air, high-concentration ozone gas, and low-concentration ozone gas) were used for the sparging of 1-D column experiment, while two gases (air and low-concentration ozone gas) were used for 2-D box model experiment. When SEOS was performed for the column and box model, the air saturation and the zone of influence were improved significantly compared to air sparging without surface tension suppression, resulted in effective removal of the contaminant. Based on the experiments observations conducted in this study, SEOS was found to maintain the advantages of SEAS with further capability of oxidative degradation of non-volatile contaminants.

• 한국분무공학회지
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• 제18권1호
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• pp.35-43
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• 2013

The empirical correlations for the prediction of breakup length of liquid jet in uniform cross flow are reviewed and classified in this study. The breakup length of liquid jets in cross flow was normally discussed in terms of the distances from the nozzle exit to the column breakup location in the x and y directions, called as column fracture distance and column fracture height, respectively. The empirical correlations for the prediction of column fracture distance can be classified as constant form, momentum flux ratio form, Weber number form and other parameter form, respectively. In addition, the empirical correlations for the prediction of column fracture height can be grouped as momentum flux ratio form, Weber number form and other parameter form, respectively. It can be summarized that the breakup length of liquid jet in a cross flow is a basically function of the liquid to air momentum flux ratio. However, Weber number, liquid-to-air viscosity ratio and density ratio, Reynolds number or Ohnesorge number were incorporated in the empirical correlations depending on the investigators. It is clear that there exist the remarkable discrepancies of predicted values by the existing correlations even though many correlations have the same functional form. The possible reasons for discrepancies can be summarized as the different experimental conditions including jet operating condition and nozzle geometry, measurement and image processing techniques introduced in the experiment, difficulties in defining the breakup location etc. The evaluation of the existing empirical correlations for the prediction of breakup length of liquid jet in a uniform cross flow is required.

• 한국항공우주학회지
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• 제37권2호
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• pp.166-174
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• 2009

본 연구에서는 횡단류 아음속유동장에서 연료가 여러 분사각도를 가지고 수직 분무시 나타나는 액주영역의 궤적과 분열지점에 관한 연구를 수행하였다. 직접 사진촬영 방법과 평면레이저유도형광(PLLIF) 기법으로 정방향 분사각도의 분무에서 액주영역의 궤적식과 분열지점까지의 거리에 대한 경험식을 도출하여 기존 연구결과와 비교 분석하고 대향분사의 액주 궤적식과 분열지점까지의 거리에 대한 경험식을 도출하였다. 실험을 통하여 액주영역의 궤적과 분열지점까지의 거리는 분사차압, 공기의 유속, 인젝터 지름 크기, 분사각도에 의하여 결정됨을 확인하였다.

• Ocean Systems Engineering
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• 제3권4호
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• pp.327-348
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• 2013

An Oscillating Water Column (OWC) is a relatively practical and convenient device that converts wave energy to a usable form, which is electricity. The OWC is kept inside a fixed truncated vertical cylinder, which is a hollow structure with one open end submerged in the water and with an air turbine at the top. This research adopts potential theory and Galerkin methods to solve the fluid motion inside the OWC. Using an air-water interaction model, OWC design for energy extraction from regular wave is also explored. The hydrodynamic coefficients of the scattering and radiation potentials are solved for using the Galerkin approximation. The numerical results for the free surface elevation have been verified by a series of experiments conducted in the University of New Orleans towing tank. The effect of varying geometric parameters on the response amplitude operator (RAO) of the OWC is studied and modification of the equation for evaluating the natural frequency of the OWC is made. Using the model of air-water interaction under certain wave parameters and OWC geometric parameters, a computer program is developed to calculate the energy output from the system.

• 한국분무공학회지
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• 제9권2호
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• pp.34-40
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• 2004

In a liquid-fueled ramjet engine, the insufficient mixing and evaporation result in the low combustion efficiency and combustion instability. Improving its characteristics and devising a means of fuel droplets with air may compensate these disadvantages of liquid fuel ramjet engine. The jet penetrations of various fuel injectors were measured to investigate the spray characteristics of a liquid-fueled ramjet engine under high pressure air-stream conditions. The penetrations in high pressure conditions are smaller than the values calculated from Inamura's or Lee's equations, and the jet penetrations in the high pressure conditions have a similar tendency. In the dual orifice injectors, the jet penetrations of rare orifice is rapidly increased due to the reduction of the drag, which is created by the jet column of front orifice. The jet penetration of rare orifice is increased because of the drag reduction created by the jet column of the front orifice. Because of the drag reduction formed by the column of jet, the jet penetration in the rear orifice of dual orifice injector is much larger than the jet penetrations of single orifice injector. As the distances of the orifice are increased, the jet penetrations of the rear orifice decrease.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.749-752
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• 2004

In a liquid-fueled ramjet engine, the insufficient mixing and evaporation result in the low combustion efficiency and combustion instability. Improving its spray characteristics and devising a means of mixing fuel droplets with air may compensate these disadvantages of liquid fuel ramjet engine. The jet penetrations of various fuel injectors were measured to investigate the spray characteristics of a liquid-fueled ramjet engine under high pressure air-stream conditions. The penetrations in high pressure conditions are smaller than the values calculated from Inamura's or Lee's equations, and, in the high pressure conditions, the jet penetrations are similar each other. In the dual hole injectors, the jet penetrations of rear orifice is rapidly increased due to the reduction of the drag, which is created by the jet column of front orifice. The jet penetration of rear orifice is increased because of the drag reduction created by the jet column of the front orifice. And, because of the drag reduction formed by the column of jet, the jet penetration in the rear orifice of dual hole injector is much larger than the jet penetration of single hole injector. As the distances of the orifice are increased, the jet penetrations of the rear orifice decrease.

• 한국가시화정보학회지
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• 제9권4호
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• pp.74-79
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• 2011

In this study the change of free surface vortex is represented at different times according to height of water and with or without curtain wall installation. The air volume fraction is investigated at each condition of water level and the influence about creation of vortex is analyzed. The height of sump intake is taken as 100mm and the water level is divided into 5 steps. The sump model is the TSJ model and the curtain wall is applied by HI standard of America. The results shows that the free surface vortex can be identified on the isotropic surface at air volume fraction 1%~5% and the vortices make an air column from the free surface to the sump intake and are created and destroyed repeatedly. In the higher water level, less air is absorbed into the intake pipe. After curtain wall installation, the suction rate of the air volume fraction is decreased by 6.7%. The result of the vortex motion according to time, works on a cycle.

• 분석과학
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• 제8권4호
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• pp.807-814
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• 1995

Accurate measurements of ozone precursors are required to understand the process and extent of ozone formation in rural and urban areas. Nonmethane hydrocarbons (NMHCs) have been identified as important ozone precursors. Identification and quantification of NMHCs are difficult because of the large number present and the wide molecular weight range encountered in typical air samples. A major plan of the research team of the Climate and Air Quality Taiwan Station (CATs) was the measurement of atmospheric nonmethane hydrocarbons. An analytical method has been development for the analysis of the individual nonmethane hydrocarbons in ambient air at ppb (v) and subppb(v) levels. The whole ambient air samples were collected in canisters and analyzed by GC-FID with $Al_2O_3$/KCl PLOT column. Our targeted for quantitative analysis 43 compounds that may be substantial contributors to ozone formation. The retention indices and molar response factors of some commercially available $C_2{\sim}C_{10}$ hydrocarbons were determined and used to identify and quantify air samples. A quality assurance program was instituted to ensure that good measurements were made by participating in the International Nonmethane Hydrocarbon Intercomparison Experiments (NOMHICE).