• Journal of Advanced Marine Engineering and Technology
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• 제26권2호
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• pp.181-191
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• 2002

Spray calculation has been studied to understand the behavior of the spray in a combustion chamber But the spray dispersion has not been predicted properly in a high velocity injection spray or a wall impaction spray. In this study the extended grazing collision model is applied to improve the problem. The gas phase is modelled by the Eulerian continuum conservation equations of mass, momentum, energy and fuel vapour fraction. The liquid phase is modelled following the discrete droplet model approach in Lagrangian form. The droplet distributions, penetration, width and gas flows are compared for the cases with or without extended model. The extended collision model makes the results better.

• 한국분무공학회지
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• 제1권2호
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• pp.66-73
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• 1996

The present study investigates experimentally the characteristics of liquid jet, which is, the spray flow in the normal direction of the air stream under the flow conditions of air velocity $110\sim125m/s$. The present study adopts with the flow visualization technique using a short duration light bulb and the image processing analyse with CCD camera. Two types of injector were used: one is a flat plate type, and the other is backward facing step type, which height are 5, 8, 10mm. Dispersion of liquid jet can be represented by gray level of CCD camera. In the upstream of liquid jet, the backward facing step shows better liquid jet penetration. However, in the downstream. mean droplet size for backward facing step injector is smaller than that for flat plate injector

• Journal of Mechanical Science and Technology
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• 제18권8호
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• pp.1271-1287
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• 2004

In this article, vapor bubble nucleation in liquid and the evaporation process of a liquid droplet at its superheat limit were discussed from the viewpoint of molecular clustering (molecular cluster model for bubble nucleation). For the vapor bubble formation, the energy barrier against bubble nucleation was estimated by the molecular interaction due to the London dispersion force. Bubble nucleation by quantum tunneling in liquid helium under negative pressure near the absolute zero temperature and bubble nucleation on cavity free micro heaters were also presented as the homogenous nucleation processes.

• 한국분무공학회지
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• 제5권4호
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• pp.12-32
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• 2000

The recent trends in numerical simulation of various spray phenomena are reviewed in this article. Major subtopics are atomization/breakup, collision/coalescence, wall collision, interfacial transfer, droplet dispersion, two-phase injection and spray combustion. Each submodel has been under continuous refinement and validation against more extensive data base by advanced laser diagnostic techniques. Most uncertainty in current spray simulations come from these physical submodels, not from excessive computational constraints.

• 한국분무공학회지
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• 제6권1호
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• pp.18-24
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• 2001

Liquid fossil fuel contaminated by water can cause trouble in the combustion processes and affect the endurance of a combustion system. Using an optical sensor to monitor the water content instantaneously in a fuel pipeline is an effective means of controlling the fuel quality in a combustion system. In two component liquid flows of oil and water, the flow pattern and characteristics of water droplets are changed with various flow conditions. Additionally, the light scattering of the optical sensor measuring the water content is also dependent on the flow patterns and droplet characteristics. Therefore, it is important to investigate the detailed behavior of water droplets in the pipeline of the fuel transportation system. In this study, the flow patterns and characteristics of water droplets in the turbulent pipe flow of two component liquids of gasoline and water were investigated using optical measurements. The dispersion of water droplets in the gasoline flow was visualized, and the size and velocity distributions of water droplets were simultaneously measured by the phase Doppler technique. The Reynolds number of the gasoline pipe flow varied in the range of $4{\times}10^{4}\;to\;1{\times}10^{3}$, and the water content varied in the range of 50 ppm to 300 ppm. The water droplets were spherical and dispersed homogeneously in all variables of this experiment. The velocity of water droplets was not dependent on the droplet size and the mean velocity of droplets was equal to that of the gasoline flow. The mean diameter of water droplets decreased and the number density increased with the Reynolds number of the gasoline flow.

• Preventive Nutrition and Food Science
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• 제21권3호
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• pp.289-295
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• 2016

Curcumin is a flavonoid found in the rhizome of the turmeric plant (Curcuma longa L.) and has recently attracted interest because it has numerous biological functions and therapeutic properties. In the present study, we attempted to incorporate curcumin into medium-chain triglyceride (MCT) nanoemulsions (0.15 wt% curcumin, 10 wt% MCT oil, and 10 wt% emulsifiers) with various emulsifiers [polyoxyethylene (20) sorbitan monolaurate (Tween-20), sorbitan monooleate (SM), and soy lecithin (SL)]. The physicochemical properties of the nanoemulsions including the Ostwald ripening stability were investigated. The initial droplet size was found to be 89.08 nm for the nanoemulsion with 10 wt% Tween-20 (control), and when Tween-20 was partially replaced with SM and SL, the size decreased: 73.43 nm with 4 wt% SM+6 wt% Tween-20 and 67.68 nm with 4 wt% SL+6 wt% Tween-20 (prepared at 15,000 psi). When the nanoemulsions were stored for 28 days at room temperature, the droplet size increased as the storage time increased. The largest increase was observed for the control nanoemulsion, followed by the 4 wt% SL+6 wt% Tween-20 and 4 wt% SM+6 wt% Tween-20 systems. The Turbiscan dispersion stability results strongly supported the relationship between droplet size and storage time. The time-dependent increase in droplet size was attributed to the Ostwald ripening phenomenon. Thus, the Ostwald ripening stability of curcumin-loaded MCT nanoemulsions with Tween-20 was considerably improved by partially replacing the Tween-20 with SM or SL. In addition, curcumin may have acted as an Ostwald ripening inhibitor.

• Bulletin of the Korean Chemical Society
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• 제35권12호
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• pp.3427-3432
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• 2014

This study introduces a new method of combining Imaging Differential Optical Absorption Spectroscopy (Imaging-DOAS) data and plume dispersion formulas for power plant emissions to determine the three-dimensional structure of a dispersing pollution plume and the spatial distributions of trace gas volume mixing ratios (VMRs) under conditions of negligible water droplet and aerosol effects on radiative transfer within the plume. This novel remote-sensing method, applied to a power plant stack plume, was used to calculate the two-dimensional distributions of sulfur dioxide ($SO_2$) and nitrogen dioxide ($NO_2$) VMRs in stack emissions for the first time. High $SO_2$ VMRs were observed only near the emission source, whereas high $NO_2$ VMRs were observed at locations several hundreds of meters away from the initial emission. The results of this study demonstrate the capability of this new method as a tool for estimating plume dimensions and trace gas VMRs in power plant emissions.

• 한국가시화정보학회지
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• 제8권4호
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• pp.60-65
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• 2010

A focus is given to the breakup behavior of spray droplets issuing from a nonimpinging-type injector. The analysis has been carried out experimentally by means of the dual-mode phase Doppler anemometry (DPDA). Spray characteristic parameters in terms of axial velocity, mean diameter, velocity fluctuation, and span (width of the size distribution) of droplets are measured down the geometric axis of a nozzle orifice and on the plane normal to the spray stream with the injection pressure variations. As the injection pressure increases, the velocity and its fluctuation become higher, whereas the droplet sizes get smaller. It is also shown that the magnitudes of those parameters are smoothed out by dispersion when the droplets move downstream as well as outwardly. The atomization process is significantly influenced by the injection pressure rather than the traveling distance in the experimental condition presented.

• 한국재료학회지
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• 제29권10호
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• pp.639-646
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• 2019

Ink-jet printing is a manufacturing process technology that directly prints a digitalized design pattern onto a substrate using a fine ink jetting system. In this study, environmentally friendly yellow aqueous ceramic ink is synthesized by mixture of distilled water, yellow ceramic pigment and additives for ink-jet printing. The graft polymer, which combines electrostatic repulsion and steric hindrance mechanism, is used as a surfactant for dispersion stability of aqueous ceramic ink. Synthesized ceramic ink with graft polymer surfactant shows better dispersion stability than did ceramic ink with PAA surfactant; synthesized ink also shows desirable ink-jet printability with the formation of a single ink droplet during printability test. Finally, ceramic ink printed on glass substrate and ceramic ink with graft polymer surfactant shows a high contact angle without surface treatment on glass substrate. Consequently, it is confirmed that the ceramic ink with graft polymer surfactant can achieve high printing resolution without additional surface treatment process.

• 한국항공우주학회지
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• 제31권5호
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• pp.72-79
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• 2003

본 실험에서는 충돌형 F-O-O-F 형태인 분사기의 충돌각을 15, 20, 그리고 30도로 변화시켰으며, 혼합비(O/F 비)는 1.5부터 3.0까지 증가시키면서 분무특성을 살펴보았다. 실험결과, 분무의 가시화를 통해서 혼합비는 확산각에 큰 영향을 주지 않지만 수밀도에는 영향을 끼쳤으며, 충돌각과 환산각 사이에는 충돌각이 증가할수록 확산각이 증가하는 선형적인 실험 관계식이 있음을 알 수 있었고, 충돌각이 증가함에 따라 분무폭은 커지며. 액적들의 속도 분포와 표준편차, 그리고 SMD는 작아짐을 알 수 있었다. 또한, 액적의 크기분포를 살펴본 결과 Rosin-Rammler와 Upper-Limit 분포함수와 잘 일치하고 있음을 확인 할 수 있었다.