• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.478-483
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• 2003

This paper describes spray characteristics of a swirl injector which is intended for use in a HCCI engine. Many optical diagnostics such as laser diffraction methods, and high speed camera photography are applied to measure the spray drop diameter and to investigate the spray development process. The effect of fuel properties on the spray characteristics was investigated using three different fuels because HCCI combustion is tolerant of the chemical composition of various fuels. From these results, the HCCI injector formed a hollow cone sheet spray rather than a liquid jet and the atomization efficiency is high for the low-pressure injector. The SMD of test injector was ranged from $15{\mu}m$ ${\mu}m$ We also found that the spray breakup characteristics were dependent on the fuel properties such as density, viscosity, and surface tension.

• 한국분무공학회지
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• 제7권3호
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• pp.1-6
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• 2002

In this study numerical and experimental study on the spray atomization characteristics of a GDI injector is performed. To carry out numerical analysis, four hybrid models that are composed of conical sheet disintegration model, LISA model, DDB model, and RT model are used. The experimental results to evaluate the prediction accuracy of hybrid models are obtained by using phase Doppler particle analyzer and spray visualization system. It is shown that the prediction accuracy of hybrid model concerning spray developing process and spray tip penetration is good for all hybrid models, but the hybrid breakup models show different prediction of accuracy in the case of local radial SMD distribution.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1522-1527
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• 2004

The purpose of this study is to investigate the effect of swirler angle and swirl chamber aspect ration of nozzle on the characteristics of single and twin spray. The performances of nozzle has been investigated by measurements of spray angle, droplet size, velocity and Weber number at a water pressure 0.4MHz. Visualization of spray was conducted to obtain the spray angle and breakup process. The spray characteristics such as droplet size and velocity were measured by Phase Doppler Anemometry(PDA). It was found that the smaller swirler angle, the larger axial velocity became. It was also shown that the larger aspect ratio, the smaller droplet diameter became.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제34회 춘계학술대회논문집
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• pp.383-389
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• 2010

적외선 흡수법을 사용하여 액체 헵탄 수직분사제트의 증기농도를 정성적으로 측정하였다. 본 연구의 목적은 모형 램젯 연소기에서 레이저를 이용한 적외선 흡수법으로 액체연료의 분열부터 기화까지의 과정을 이해하는 것이다. 실험결과로부터 헥산 증기 몰분율은 온도가 증가함에 따라 증가하였으나 연료공기 운동량비 변화에 대해서는 큰 차이가 나지 않았다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.371-377
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• 2008

In order to obtain fundamental knowledge of atomization, the three dimensional unsteady phenomenon of pinch off was numerically studied by developed method. Not only liquid shapes but also velocity distributions of numerical results were compared with corresponding experimental ones. They showed satisfactorily good agreement at least in a qualitative sense. The liquid jet shapes, the pressure and velocity distributions, and the inner flow structures were clarified through the comparisons of distinctly different flow fields due to presence or absence of surface tension. The condition of pinch off, which had close correlation with fluid acceleration at injection, was clearly specified.

• 한국추진공학회지
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• 제14권4호
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• pp.25-31
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• 2010

적외선 흡수법을 사용하여 액체 헥산 수직분사제트의 증기농도를 정성적으로 측정하였다. 본 연구의 목적은 모형 램제트 연소기에서 레이저를 이용한 적외선 흡수법으로 액체연료의 분열부터 기화까지의 과정을 이해하는 것이다. 실험결과로부터 헥산 증기 몰분율은 온도가 증가함에 따라 증가하였으나 연료 공기 운동량비 변화에 대해서는 큰 차이가 나지 않았다.

• 한국자동차공학회논문집
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• 제5권3호
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• pp.137-146
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• 1997

Spray characteristics of high pressure injectors for diesel engines have been experimentally studied with special emphasis on the effect of swirl. A constant volume chamber was rotated in order to generate a continuous swirl having the flow field of a solid body rotation, resulting in the linear dependance of the swirl number on the rotating speed of the chamber. Emulsified fuel is injected into the chamber and the developing process of fuel sprays is visualized. The fuel spray developing process in D.I. diesel engine was investigated by this liquid injection technique. The effect of swirl on the spray tip penetration is quantified through modelling. Results show that the spray tip penetration is qualitatively different for low and high pressure injections. For high pressure injection case, a good agreement is achieved between the experimental results and the modeling accounting the effect of swirl. For low pressure injection, a reasonable agreement is obtained. It is found that excessive swirl may cause adverse effect on spray dispersion during the initial combustion period since the spray can not be impinged on chamber wall.

• 한국자동차공학회논문집
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• 제23권4호
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• pp.402-409
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• 2015

In this study a quasi-dimensional model is developed to predict the combustion process and emissions of a GDI engine under ultra-lean conditions. Combustion of a GDI engine condition is modeled as two simultaneous processes to consider significant fuel stratification. The first process is premixed flame propagation described as burning in a hemispherically propagating flame. The second is diffusion-controlled combustion modeled as mixing of multiple spray zones in the burned gas region. Mixing is an important factor in ultra-lean conditions leaving stratified mixture of developing sprays behind the propagating premixed flame. Sheet breakup and Hiroyasu models are applied to predict the velocity of a hollow cone spray. Validation is performed against measured pressures and NOx and CO emissions at different load and rpm conditions in the test engine.

• Macromolecular Research
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• 제10권4호
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• pp.187-193
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• 2002

Several methods have been used to synthesize polymer-clay nanocomposites. In-situ polymerization with clay belongs to a classical way to develop nano-structured materials, while melt intercalation is being recognized as another useful approach due to its versatility and environmentally benign character. In this research, we prepared polymer-clay nanocomposites based on the poly (methyl methacrylate) and organically modified montmorillonite via two-stage sonication process. According to the unique mode of power ultrasonic wave, the sonication during processing led to enhanced breakup of the clay agglomerates and reduction in size of the dispersed phase. Optimum conditions to form stable exfoliated nanocomposites were studied for various compositions and conditions. It was found that a novel attempt carried out in this study yielded further improvement in the mechanical performance of the nanocomposites compared to those produced by the conventional melt mixing process, as revealed by DMA, XRD and TEM. And rheological properties of nanocomposites were measured by ARES. As a result, sonicated PMMA-clay nanocomposites exhibits enhanced properties such as storage modulus and thermal stability than that of neat PMMA.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2018년도 학술발표회
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• pp.288-288
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• 2018

점착성 유사는 응집 현상을 겪는 유사로, 응집 현상(Flocculation Process)는 응집 과정(Aggregation Process)와 파괴 과정(Breakup Process)의 경쟁으로 이루어진다고 여겨진다. 응집 현상을 통해 점착성 유사는 물과 점착성을 띠는 작은 입자들의 덩어리인 플럭(Floc)을 형성하여 흐름 내에서는 대부분이 플럭의 형태로 이동한다. 점착성 유사의 응집 모형 중 하나인 플럭 성장모형(Floc Growth Model, FGM)은 상미분 방정식으로 시간에 따른 플럭의 크기를 계산하는 모형이다. 응집과 파괴의 평형 상태에서 평균 입경을 얻는다. 이러한 FGM은 낮은 수치 계산 비용으로 합리적인 계산 결과를 얻을 수 있으며, 유사 이동 모형 혹은 흐름 모형과의 결합이 수월한 장점을 가진다. 또한, 닫힌 계(Closed System)에서 질량이 보존되는 특징이 있다. 반면, 결정론적인 특성을 띠면서 특정 플럭 크기만을 계산하기 때문에 점착성 유사의 입도 분포에 대한 정보를 얻을 수 없다. 결정론적 특성을 띠는 FGM에 추계학적 방법을 적용함으로써 특정 확률 분포형을 가지는 플럭의 입도 분포를 얻을 수 있다. 본 연구에서는 기 개발된 추계학적 FGM과 유사 이동 모형의 결합을 통해 변화하는 유수동역학적 조건에서 플럭의 입도 분포를 산정하고자 한다. 이전의 많은 실험실 실험 결과들은 부유가 발생한 상태를 유지하면서 수행되는 것으로, 특정 난류 특성(난류 소산 매개변수)와 특정 유사 농도 조건에서의 입도 분포를 얻는다. 그러나 하구부 및 하천의 하류는 조류의 영향을 받는 구간으로, 점착성 유사의 특성을 분석하기 위해서는 변화하는 유수동역학적 특성에 관한 고려가 필수적이라 할 수 있다. 결합된 점착성 유사 입도 분포 모형은 플럭의 침강과 재부유를 고려할 수 있는 특징을 가지며, 실측자료와의 비교를 통해 입도 분포를 합리적으로 모의하는 것으로 나타난다. 본 연구에서 개발된 점착성 유사 입도 분포 모형은 나아가 비점착성 유사의 입도 분포 모형과의 결합을 통해 두 종류의 유사가 혼재하는 구간에서도 합리적인 입도분포와 유사의 이동을 모의할 수 있을 것으로 예측된다.