• 한국분무공학회지
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• 제13권3호
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• pp.117-125
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• 2008

The correlations for the prediction of maximum liquid-phase penetration in diesel spray are reviewed in this study. The existing models developed for the prediction of maximum liquid-phase penetration can be categorized as the zero-dimensional (empirical) model, the multi-dimensional model and the other model. The existing zero-dimensional model can be classified into four groups and the existing multidimensional models can be classified into three groups. The other model includes holistic hydraulic and spray model. The maximum liquid-phase penetration is mainly affected by nozzle diameter, fuel volatility, injection pressure, ambient gas pressure, ambient gas density and fuel temperature. In the case of empirical correlations incorporated with spray angle, the predicted results will be different according to the selection of correlation for spray angle. The research for the effect of boiling point temperatures on maximum liquid-phase penetration is required. In the case of multidimensional model, there exist problems of the grid and spray sub-models dependency effects.

• 한국분무공학회지
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• 제25권2호
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• pp.74-80
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• 2020

The jet in crossflow is a spray method used in the various air-breathing engine. In order to understand the spray characteristics in various environments, many prior studies have been conducted. However, there is a lack of understanding of the low-temperature liquid spray characteristics below 273 K. With this in mind, we tried to enhance the knowledge of the low-temperature liquid spray characteristics by identifying the penetration height of low-temperature ethanol. The experiment was conducted under phase pressure, and 273 K of air and 293, 263, and 233 K of ethanol was used. Shadowgraphy was employed to measure the liquid penetration, and Otsu's method was used to analyze the penetration height. The heights tend to decrease as the temperature of the liquid jet decreases. A correlation for the penetration height in the experimental conditions was derived and presented.

• 한국가구학회지
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• 제28권3호
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• pp.248-258
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• 2017

A study was carried out to observe the 1% aqueous safranine solution flow speed in longitudinal and radial directions of softwood Thuja orientalis L., diffuse-porous wood Gmelina arborea Roxb., and ring-porous wood Phellodendron amurense Rupr., Longitudinal flow was considered from bottom to top while the radial flow was considered from bark to pith directions. In radial direction, ray cells and in longitudinal direction tracheids, vessel and wood fiber were considered for the measurement of liquid penetration speed at less than 12% moisture contents(MC). The variation of penetration speed for different species was observed and the reasons behind for this variation were explored. The highest radial penetration depth was found in ray parenchyma of T. orientalis but the lowest one was found in ray parenchyma of P. amurense. The average liquid penetration depth in longitudinal trachied of T. orientalis was found the highest among all the other cells. The penetration depth in fiber of G. arborea was found the lowest among the other longitudinal cells. It was found that cell dimension and also meniscus angle of safranine solution with cell walls were the prime factors for the variation of liquid flow speed in wood. Vessel was found to facilitate prime role in longitudinal penetration for hardwood species. The penetration depth in vessel of G. arborea was found highest among all vessels. Anatomical features like ray parenchyma cell length and diameter, end-wall pits number were found also responsible fluid flow differences. Initially liquid penetration speed was high and the nit gradually decreased in an uneven rate. Liquid flow was captured via video and the penetration depths in those cells were measured. It was found that even in presence of abundant rays in hardwood species, penetration depth of liquid in radial direction of softwood species was found high. Herein the ray length, lumen area, end wall pit diameter determined the radial permeability. On the other hand, vessel and fiber structure affected the longitudinal flow of liquids. Following a go-stop-go cycle, the penetration speed of a liquid decreased over time.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.438-444
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• 2010

Crossflow에 미치는 영향을 최소화하면서 liquid Jet의 미립화 및 혼합특성을 향상시키기 위한 JICF의 분무 특성에 대해 실험적으로 연구하였다. Crossflow의 온도, 속도, 압력과 liquid Jet의 속도, 압력을 변화시키면서 crossflow와 liquid jet의 momentum ratio(q)의 변화에 따른 spray boundary (outer boundary, inner boundary)를 측정하고 실험식을 유도하여 선행연구자의 결과와 비교하였다. 특히, injector의 형상에 따른 jet penetration를 측정하여 dual orifice injector의 경우 전단 오리피스의 영향으로 후단 오리피스에서의 jet penetration은 single orifice injector 분사노즐과 비교할 때 약 18% ($L_h$=4 mm) 증가하는 것을 확인하였다.

• 한국지반공학회논문집
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• 제32권10호
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• pp.5-15
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• 2016

본 연구에서는 소형콘의 관입저항력을 이용한 점토의 액성한계를 측정하기 위하여 카올리나이트 점토와 벤토나이트 점토의 비율을 다양하게 혼합한 점토흙에 대하여 함수비와 소형콘의 관입저항력을 조사하고 기존의 동적(Casagrande 시험법) 및 정적(Fall cone 시험법) 액성한계 시험결과와 직접 비교하였다. 비교결과 다양한 점토흙의 함수비에 따른 관입저항력 관계곡선에서 변곡점이 형성된다는 것을 파악하였으며 이 때의 함수비가 정적액성한계(Fall cone)시험법에 의한 액성한계 값과 매우 유사함을 파악하였다. 변곡점이 형성된 점에서의 소형콘의 관입저항력은 약 0.2kPa로 나타났으며 이 때 의 함수비가 점토흙의 액성한계를 나타낸다는 것을 확인하였다. 이와 같은 연구결과를 토대로 향후 점토의 액성한계를 파악하는데 본 연구에서 조사된 0.2kPa의 소형콘의 관입저항력이 유용한 지표가 될 수 있다는 사실을 파악하였다. 또한 소형콘의 관입저항력을 이용한 액성한계 시험법을 제시하였다.

• 융복합기술연구소 논문집
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• 제8권1호
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• pp.9-13
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• 2018

The purpose of this study is to investigate the liquid- and vapor-phase spray characteristics, such as spray tip penetration and spray angle using gasoline direct injection (GDI) injector with multi-hole. The vapor-phase spray was captured by the Schlieren visualization system, which consists of high-speed camera, LED lamp, concave mirrors, and knife-edge. The liquid-phase spray was visualized by Mie-scattering techniques. Both spray images of vapor- and liquid-phase were visualized under 373 K of ambient temperature, 1 bar of ambient pressure, and 100/200 bar of injection pressure. The energizing duration was fixed at 1.5 ms. From the analysis of experimental results, it revealed that the increased injection pressure induced an early vaporization due to the improvement of droplet atomization. The spray tip penetration and spray angle in vapor-phase were higher than those in liquid-phase. The difference in the spray tip penetration between vapor- and liquid-spray gradually increased with the time elapsed after the injection. Even with the spray angle characteristics, it was found that the difference between the spray angle of liquid and vapor spray gradually grew after they entered steady-state conditions.

• 한국분무공학회지
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• 제12권3호
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• pp.146-153
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• 2007

The prediction of diesel spray penetration has been the subject of several works and intensive investigations are still underway by many researchers. It is required to summarize the correlations developed before 1990 days and to introduce the correlations reported recently in the literature. The existing zero-dimensional models for the prediction of diesel fuel spray penetration can be classified as theoretical and empirical correlations. Of various correlations, the models considered in this paper were selected as based on the evaluation results of previous reviews and the recently published works in the literature. The existing theoretical correlations can be classified into seven categories and the existing empirical ones as two categories in this review. According to the review of existing models, the dominating factors for the prediction of spray tip penetration are the spray angle, discharge coefficient, pressure drop across nozzle, ambient density and orifice diameter and time after the start of injection. Especially, the definition for the measurement of spray angle is different with researchers. It is required to evaluate the existing spray tip penetration models for the very high injection pressure and other fuel sprays such as DME. It is also required to evaluate the correlations for the prediction of diesel spray penetration with the connection of liquid-phase penetration.

• 한국분무공학회지
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• 제10권1호
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• pp.35-42
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• 2005

The present study has numerically and experimentally investigated the spray behavior of liquid jet injected in subsonic cross-flow. The corresponding spray characteristics are correlated with jet operating parameters. The spray dynamics are known to be distinctly different in the three regimes: the column, the ligament and the droplet regimes. The behaviors of column, penetration and breakup of liquid jet have been studied. Numerical and physical models are base on a modified KIVA code. The primary atomization is represented by a wave model base on the KH(Kelvin-Helmholtz) instability that is generated by a high interface relative velocity between the liquid and gas flows. In odor to capture the spray trajectory, CCD camera has been utilized. Numerical and experimental results indicate that the breakup point is delayed by increasing gas momentum ratio and the penetration decreases by increasing Weber number.

• 대한기계학회논문집B
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• 제30권2호
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• pp.161-169
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• 2006

The spray characteristics of liquid jet in cross flow with variation of injection angle are numerically studied. Numerical analysis was carried out using KIVA code, which was modified to be suitable for simulating liquid jet ejected into cross flow. Wave model and Kelvin-Helmholtz(KH)/Rayleigh-Taylor(RT) hybrid model were used for the purpose of analyzing liquid column, ligament, and the breakup of droplet. Numerical results were compared with experimental data in order to verify the reliability of the physical model. Liquid jet penetration length, volume flux, droplet velocity profile and SMD were obtained. Penetration length increases as flow velocity decreases and injection velocity increases. From the bottom wall, the SMD increases as vertical distance increases. Also the SMD decreases as injection angle increases.

• 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.